Tryptamine Derivatives Disarm Colistin Resistance in\nPolymyxin-Resistant Gram-negative Bacteria
The last three decades have seen a dwindling number of novel antibiotic classes approved for clinical use and a concurrent increase in levels of antibiotic resistance, necessitating alternative methods to combat the rise of multi-drug resistant bacteria. A promising strategy employs antibiotic adjuvants, non-toxic molecules that disarm antibiotic resistance. When co-dosed with antibiotics, these compounds restore antibiotic efficacy in drug-resistant strains. Herein we identify derivatives of tryptamine, a ubiquitous biochemical scaffold containing an indole ring system, capable of disarming colistin resistance in the Gram-negative bacterial pathogens Acinetobacter baumannii, Klebsiella pneumoniae, and Escherichia coli while having no inherent bacterial toxicity. Resistance was overcome in strains carrying endogenous chromosomally-encoded colistin resistance machinery, as well as resistance conferred by the mobile colistin resistance \xe2\x80\x93 1 (mcr-1) plasmid-borne gene. These compounds restore a colistin minimum inhibitory concentration (MIC) below the Clinical Laboratory Sciences Institute (CLSI) breakpoint in all resistant strains.
Introduction<!>Results and Discussion<!>General Biological Assay Methods:<!>Single Compound MIC Determination via Broth Microdilution:<!>Antibiotic Resensitization MIC Determination via Broth Microdilution:<!>Bacterial Growth Curve:<!>BacLight Cell Permeability Assay:<!>Ovine Erythrocyte Lysis Assay:<!>General Synthetic Methods:<!>General Procedure for Condensing Primary Amines with\n2,2,2-trichloroacetylpyrroles:<!>General Procedure for Synthesis of 3-(2-nitrovinyl) indoles:<!>General Procedure for N-alkylation of Indole:<!>General Procedure for the Reduction of N-alkylated 3-nitrovinyl\nIndoles:<!>General Procedure for the Coupling of Carboxylic Acids to Primary Amines\nusing PyBOP:<!>N-(2-(1H-indol-3-yl)ethyl)-4,5-dichloro-1H-pyrrole-2-carboxamide (1):<!>N-(2-(1H-indol-3-yl)ethyl)-4,5-dibromo-1H-pyrrole-2-carboxamide\n(2):<!>N-(2-(1H-indol-3-yl)ethyl)-4-bromo-1H-pyrrole-2-carboxamide\n(3):<!>N-(2-(1H-indol-3-yl)ethyl)-4-bromo-1-methyl-1H-pyrrole-2-carboxamide\n(4):<!>N-(2-(1H-indol-3-yl)ethyl)-1-methyl-1H-pyrrole-2-carboxamide\n(5):<!>N-(2-(1H-indol-3-yl)ethyl)-1H-pyrrole-2-carboxamide\n(6):<!>2,2,2-trichloro-1-(4,5-dibromo-1H-pyrrol-2-yl)ethan-1-one\n(7):<!>N-((1H-indol-3-yl)methyl)-4,5-dibromo-1H-pyrrole-2-carboxamide\n(8):<!>4,5-dibromo-N-(2-(1-butyl-1H-indol-3-yl)ethyl)-1H-pyrrole-2-carboxamide\n(9):<!>N-(2-(1H-imidazol-4-yl)ethyl)-4,5-dibromo-1H-pyrrole-2-carboxamide\n(10):<!>N-benzyl-4,5-dibromo-1H-pyrrole-2-carboxamide\n(11):<!>4,5-dibromo-N-(2-(pyridin-2-yl)ethyl)-1H-pyrrole-2-carboxamide\n(12):<!>4,5-dibromo-N-(2,3-dihydro-1H-inden-2-yl)-1H-pyrrole-2-carboxamide\n(13):<!>N-((1H-indol-2-yl)methyl)-4,5-dibromo-1H-pyrrole-2-carboxamide\n(14):<!>N-((1H-indol-6-yl)methyl)-4,5-dibromo-1H-pyrrole-2-carboxamide\n(15):<!>4,5-dibromo-N-(2-(5-hydroxy-1H-indol-3-yl)ethyl)-1H-pyrrole-2-carboxamide\n(16):<!>4,5-dibromo-N-(2-(5-methoxy-1H-indol-3-yl)ethyl)-1H-pyrrole-2-carboxamide\n(17):<!>2-(benzo[b]thiophen-3-yl)ethan-1-amine (18):<!>N-(2-(benzo[b]thiophen-3-yl)ethyl)-4,5-dibromo-1H-pyrrole-2-carboxamide\n(19):<!>(E)-6-fluoro-3-(2-nitrovinyl)-1H-indole\n(20):<!>(E)-7-methyl-3-(2-nitrovinyl)-1H-indole\n(21):<!>2-(6-fluoro-1H-indol-3-yl)ethan-1-amine (22):<!>2-(7-methyl-1H-indol-3-yl)ethan-1-amine (23):<!>4,5-dibromo-N-(2-(6-fluoro-1H-indol-3-yl)ethyl)-1H-pyrrole-2-carboxamide\n(24):<!>4,5-dibromo-N-(2-(7-methyl-1H-indol-3-yl)ethyl)-1H-pyrrole-2-carboxamide\n(25):<!>1-methyl-1H-indole (26a):<!>1-butyl-1H-indole (26b):<!>1-benzyl-1H-indole (26c):<!>(E)-1-methyl-3-(2-nitrovinyl)-1H-indole\n(27a):<!>(E)-1-butyl-3-(2-nitrovinyl)-1H-indole\n(27b):<!>(E)-1-benzyl-3-(2-nitrovinyl)-1H-indole\n(27c):<!>(E)-7-methyl-3-(2-nitrovinyl)-1H-indole\n(28a):<!>2-(1-butyl-1H-indol-3-yl)ethan-1-amine (28b):<!>2-(1-benzyl-1H-indol-3-yl)ethan-1-amine (28c):<!>4,5-dibromo-N-(2-(1-methyl-1H-indol-3-yl)ethyl)-1H-pyrrole-2-carboxamide\n(29a):<!>4,5-dibromo-N-(2-(1-butyl-1H-indol-3-yl)ethyl)-1H-pyrrole-2-carboxamide\n(29b):<!>N-(2-(1-benzyl-1H-indol-3-yl)ethyl)-4,5-dibromo-1H-pyrrole-2-carboxamide\n(29c):<!>N-(2-(1H-indol-3-yl)ethyl)thiophene-2-carboxamide\n(30):<!>N-(2-(1H-indol-3-yl)ethyl)-4-chloro-1H-pyrrole-2-carboxamide\n(31):<!>N-(2-(1H-indol-3-yl)ethyl)-4,5-dibromofuran-2-carboxamide\n(32):<!>N-(2-(1H-indol-3-yl)ethyl)-4,5-dibromothiophene-2-carboxamide\n(33):<!>N-(2-(1H-indol-3-yl)ethyl)-5-bromofuran-2-carboxamide\n(34):<!>N-(2-(1H-indol-3-yl)ethyl)-3-bromothiophene-2-carboxamide\n(35):<!>N-(2-(1H-indol-3-yl)ethyl)-5,6-dibromopicolinamide\n(36):<!>N-(2-(1H-indol-3-yl)ethyl)-6-bromopicolinamide\n(37):<!>N-(2-(1H-indol-3-yl)ethyl)-5-bromonicotinamide\n(38):<!>N-(2-(1H-indol-3-yl)ethyl)picolinamide\n(39):<!>2,2,2-trichloro-1-(4,5-dibromo-1-methyl-1H-pyrrol-2-yl)ethan-1-one\n(40a):<!>2,2,2-trichloro-1-(4,5-dibromo-1-butyl-1H-pyrrol-2-yl)ethan-1-one\n(40b):<!>2,2,2-trichloro-1-(4,5-dibromo-1-butyl-1H-pyrrol-2-yl)ethan-1-one\n(40c):<!>N-(2-(1H-indol-3-yl)ethyl)-4,5-dibromo-1-methyl-1H-pyrrole-2-carboxamide\n(41a):<!>N-(2-(1H-indol-3-yl)ethyl)-4,5-dibromo-1-butyl-1H-pyrrole-2-carboxamide\n(41b):<!>N-(2-(1H-indol-3-yl)ethyl)-1-benzyl-4,5-dibromo-1H-pyrrole-2-carboxamide\n(41c):<!>2,2,2-trichloro-1-(4,5-diiodo-1H-pyrrol-2-yl)ethan-1-one\n(42):<!>2,2,2-trichloro-1-(4-iodo-1H-pyrrol-2-yl)ethan-1-one\n(43):<!>N-(2-(1H-indol-3-yl)ethyl)-4,5-diiodo-1H-pyrrole-2-carboxamide\n(44):<!>N-(2-(1H-indol-3-yl)ethyl)-4-iodo-1H-pyrrole-2-carboxamide\n(45):<!>N-((1H-indol-3-yl)methyl)-6-bromopicolinamide\n(46):<!>N-((1H-indol-3-yl)methyl)-4,5-diiodo-1H-pyrrole-2-carboxamide\n(47):
<p>The proliferation of antibiotic resistant bacteria threatens a collapse of
modern medicine. As multi-drug resistant (MDR) bacterial strains continue to grow in
both strength and number while the antibiotic clinical arsenal remains stagnate, a
"Post-Antibiotic World" has become increasingly tangible. Antibiotic
resistant infections currently claim more than 700,000 lives world-wide each
year.1 These infections are
most often caused by one or more of the ESKAPE pathogens
(Enterococcus
faecium,
Staphylococcus aureus,
Klebsiella pneumoniae,
Acinetobacter baumannii,
Pseudomonas aeruginosa, and
Enterobacter
species). Efforts to combat these six agents have been met with limited success, as
only two novel antibiotic classes, lipopeptides and oxazolidinones, have been
deployed clinically in the last two decades. Both are active only against
Gram-positive bacteria, and offer a transient solution as bacterial resistance to
each has been documented.2 Given
the lack of treatment options to combat MDR Gram-negative bacteria, colistin
(polymyxin E), a decades-old cationic polypeptide, has reemerged as salvage therapy
for MDR Gram-negative bacterial infections despite causing severe
nephrotoxicity.3 This
"last resort" antibiotic is not exempt from resistance development, as
numerous primary clinical isolates have shown resistance that far exceeds the
Clinical Laboratory Standards Institute (CLSI) breakpoint for safe and effective
treatment.4</p><p>Colistin elicits bacterial cell lysis by displacing divalent cations chelated
by phosphate moieties on lipid A, a component of lipopolysaccharide (LPS), which
destabilizes the outer membrane leading to envelope rupture and cell
death.5 Bacteria become
resistant to colistin by modifying lipid A in a number of ways, including
modification of the phosphate group with positively charged residues. Addition of
aminoarabinose, galactosamine, and phosphoethanolamine residues to the terminal
phosphate moieties of lipid A, the membrane anchor of lipopolysaccharide (LPS) has
been documented.6 These
modifications all impart decreased electrostatic attraction toward the polycationic
polymyxin, leading to drug resistance. This resistance mechanism is typically
evolved under intense selection pressure, comes at a fitness cost, and is controlled
and encoded by endogenous genomic material.7 The latter of the three modifications, however, can also be
acquired from the mobile colistin resistance – 1
(mcr-1) or related genes. These compact, plasmid-borne
transcripts can be rapidly disseminated amongst pathogenic bacteria.8 While mcr-1 was
first identified in China, several additional mcr gene variants
(mcr-1–8) have since been found in bacteria across the
globe.9</p><p>Antibiotic adjuvant therapy offers an alternative to novel antibiotic
discovery by targeting non-essential bacterial systems and restoring susceptibility
to a given antibiotic in a concurrent treatment strategy. Our research group has
demonstrated diverse modulation of bacterial behavior using compounds derived from
and inspired by marine natural products. Among these active compounds, a
2-aminoimidazole (2-AI) or 2-aminobenzimidazole (2-ABI) moiety has been a key
component of the adjuvant scaffold in previous reports.10, 11
Herein, we expand the breadth of active scaffolds and report that tryptamine, a
well-established biogenic amine and component of the amino acid tryptophan, serves
as a synthetic platform for novel, non-toxic small molecules that successfully
disarm colistin resistance, and report a lead molecule active against multiple
colistin-resistant (colR) strains.</p><!><p>In a previous report from our group, a comprehensive screening of our
in-house library identified that compound 1 (Figure 1) disarms colistin resistance in Gram-negative
strains carrying the mcr-1 gene.12 When dosed at 60 Î¼M, 1
returned up to a 32-fold reduction in the colistin minimum inhibitory concentration
(MIC) against five engineered mcr-1 colR Gram-negative
strains.13 This compound
was one of six tryptamine derivatives (1–6, Figure 1) of the natural product oroidin first prepared in
a previous report from our group aimed toward discovery of anti-biofilm agents
against P. aeruginosa.14 Interestingly, biofilm dispersion or inhibition activity
was not noted for any of these six molecules. When we screened the remaining five
compounds from this original study (2-6) for synergy with
colistin in four colR Gram-negative strains, two that harbor
chromosomally encoded resistance (A. baumannii 4106, K.
pneumoniae B9), and two transfected with the mcr-1
gene contained in a plasmid vector (A. baumannii ATCC
17978+mcr−1, and E. coli
ATCC 25922+mcr−1) (Table 1), we found consensus activity in the molecule
subset. Of these, compound 2 was consistently twice as active as
1 and returned MICs below the CLSI breakpoint (4 Î¼g/mL) and
thus became our lead molecule and the subject of a structure activity relationship
(SAR) study.</p><p>With lead compound 2 in hand, we envisioned an SAR strategy that
focused on dividing the molecule along the amide bond and launching two separate
diversification campaigns, one focused on the indole head group and carbon linker,
and the other on the brominated carboxypyrrole tail (Figure 1). As each of the thirty-three analogs were synthesized, their
activity with colistin was determined in the same four Gram-negative colR
strains used previously (Table 2).
Interestingly, all analogs synthesized in this study showed no antimicrobial
activity in monotherapy (MIC = >200 Î¼M) and were initially tested at
60 Î¼M when co-dosed with colistin. We synthesized a panel of analogs with a
variety of changes to the head group scaffold via condensing 7 with
commercially available amines under basic conditions (Scheme 1).14 The
two-carbon linker of 2 was first both shortened and lengthened using
1H-indole-3-methanamine and homotryptamine as reactive amines
to afford compounds 8 and 9 respectively, both of which
showed increased activity over 2 in several strains. Reactions with
histamine, benzylamine, 2-pyridineethanamine, and 2-aminoindane yielded compounds
10, 11, 12, and 13,
respectively, all of which were inactive. We moved the tail group from the 3-
position to the 2- position of the indole ring (14) via reaction with
1H-indole-2-methanamine, and moved it to the 6- position
(15) using 1H-indole-6-methanamine as the amine
source. Both 14 and 15 were roughly equipotent with
2. Using this same methodology, we then employed both
5-hydroxytryptamine and 5-methoxytryptamine to afford the corresponding indole ring
substitution in final products 16 and 17, which were both
upwards of eight-fold less active than 2.</p><p>Further modifications to the head group required preparation of derivatized
amines (Scheme 2). We first sought to
substitute benzothiophene for indole. Starting from commercially available
benzo[b]thiophene-3-acetonitrile, reduction with
SmI2 gave the corresponding ethylamine 18,15 which was then condensed with
7 to give 19, a product with greatly reduced (32 fold)
activity compared to 2. To access additional substitutions of the
indole ring, synthesis of substituted tryptamine precursors was necessary due to
either lack of commercial availability or cost. Briefly, a nitrovinyl group was
appended to the 3-position of the appropriately substituted indole via an
addition-elimination reaction with 1-(dimethylamino)-2-nitroethylene (DMANE) in
trifluoroacetic acid and dichloromethane. The nitroalkenes were then reduced with
lithium aluminum hydride at room temperature to give the corresponding tryptamine
derivatives.16 Starting
from 6-fluoroindole and 7-methylindole, this route gave both 6-fluorotryptamine
(22) and 7-methyltryptamine (23), which were each
condensed with 7 to afford 24 and 25 in three
steps overall. This same route also proved useful to access
N-alkylated analogs of 2. N-methyl,
N-butyl, and N-benzyl indole
(26a-c) were each accessed by N-alkylating with
the appropriate alkyl halide, and were then converted to the nitroalkene
intermediate (27a-c) and finally reduced to the tryptamine derivative
(28a-c). Each was then condensed with 7 to afford
29a-c.</p><p>From the biological data, we see that in general, an indole ring is required
for activity though its orientation with respect to the aliphatic linker is
flexible, as is the case for the overall length of the aliphatic linker itself.
Substitutions about the indole ring are well tolerated in some cases but do not
return increases in activity over the original lead 2, while indole
N-alkylation renders a complete loss of activity.</p><p>Turning our attention to the pyrrole tail moiety, tryptamine was either
directly reacted with commercially available acid chlorides, or coupled with
commercially available carboxylic acids through activation with PyBOP, to access
compounds 30–39 (Scheme 3,
biological data given in Table 3). These
compounds offer diversification of the 4,5-dibromopyrrole with multiple five and six
membered heterocycles with varying halide substituents, and revealed that alteration
of the 4,5-dibromopyrrole moiety is deleterious for activity with few exceptions.
Isolated activity was seen with 37 in K. pneumoniae
B9, returning a colistin MIC of 1 Î¼g/mL (1024 fold reduction) when dosed at
60 Î¼M, while remaining inactive in other Gram-negative strains.</p><p>Mirroring efforts towards the indole N-alkylated analogs
29a-c, we accessed N-alkylated
derivatives of the 4,5-dibromopyrrole moiety, namely N-methyl,
N-butyl, and N-benzyl analogs of
7. Each of these derivatives was condensed with tryptamine to
afford compounds 41a-c (Scheme 4). We observed diminished biological activity with increased
steric bulk. To further explore the impact that halogenation patterns of the pyrrole
tail had upon activity, the 4,5-diiodopyrrole analog 44 was synthesized
from 7 (Scheme 4). Iodination of
the 2-trichloroacetyl pyrrole using molecular iodine and silver trifluoroacetate
generated the 4,5-diiodinated pyrrole along with the 4-iodopyrrole as a side product
as an inseparable mixture.17
Condensation of this mixture with tryptamine gave both the 4,5-diiodoinated product
44, as well as the 4-iodinated 45, which were readily
isolated on silica gel. Both 44 and 45 were most effective
in K. pneumoniae B9 and returned a 2048 fold reduction in colistin
MIC when dosed at 60 Î¼M.</p><p>Preliminary screening showed promising results for compounds 8,
37, and 44 (MIC fold-reduction of >512 in any
tested strain, Tables 2 and 3) and thus we elected to combine successful alterations
on both sides of the amide bond (Scheme 4).
Coupling 1H-indole-3-methanamine with 6-bromopicolinic acid
delivered 46, a shortened analog of 37. We also generated
47, the analogous shortened derivative of 44 via
condensation of 1H-indole-3-methanamine with the corresponding
4,5-diiodopyrrole to afford 47. Compound 46 had modest
activity (32-fold MIC colistin reduction) against two strains (A.
baumannii 4106, K. pneumoniae B9), while compound
47 was completely inactive (Table
3). All analogs having with equal or greater activity compared to
2 in any of the four test strains were then taken forward for
further testing. These criteria eliminated twenty-three analogs and identified a
cohort of nine molecules of interest (8, 9,
14, 15, 24, 25,
37, 44, and 45.)</p><p>These nine compounds were then subjected to further screening with nine
additional bacterial strains: five primary clinical isolates that harbor
chromosomally-encoded colistin resistance (A. baumannii 3941,
A. baumannii 3942, A. baumannii 4112,
K. pneumoniae A5, and K. pneumoniae C3) as
well as the mcr-1 parent strains without plasmid (A.
baumannii ATCC 17978, and E. coli ATCC 25922) and two
other colistin sensitive strains (A. baumannii 5075 and K.
pneumoniae ATCC BAA 2146). These results are tabulated in Table 4.</p><p>This second round of screening established that all molecules were
efficacious in colR primary clinical isolates of A.
baumannii and K. pneumoniae, and identified
8 as the most active colistin modulator, in some cases returning a
2048-fold reduction in colistin MIC and a four-fold increase in activity compared to
the original lead molecule 2. A subsequent dose-response study with
8 (Table 5) showed
concentration-dependent activity in two Gram-negative clinical isolates (A.
baumannii 3942, K. pneumoniae C3). To explore
potential aggregate effects, this same experiment was repeated supplementing
Cation-Adjusted Mueller Hinton Broth (CAMHB) with 0.001% Triton X100. No significant
changes in colistin MIC were observed in the presence of detergent (Table S1, Supporting Information).
Additionally, growth curves were constructed for A. baumannii 3942
treated with 60 Î¼M 8, (Figure S1) which showed that
8 did not perturb bacterial proliferation. To identify changes in
membrane permeability, the BacLight cell viability assay was used. This duplex
colorimetric fluorescence screen offers quantized detection of potential increases
in cell permeability caused by xenobiotics. The ratio of nucleic-acid bound STYO-9
(green-fluorescent), which readily crosses healthy cellular membranes, to the
redfluorescence of propidium iodide, which only enters cells with compromised
cellular envelopes, is determined by scanning the distinct emission wavelengths of
the two dyes. In endotoxin-free water dosed with 60 Î¼M 8,
membrane permeability was increased by a factor of 1.9 in A.
baumannii 3942 and of 1.5 in K. pneumoniae C3 compared
to untreated controls. Conversely, no significant change in cell permeability was
detected in either strain treated with the inactive compound 29b at the
same concentration. In a separate assay, neither 8 nor 29b
lysed red blood cells (<1%) when dosed in phosphate-buffered saline (PBS) at
100 Î¼M.</p><p>In conclusion, we have presented the synthesis of thirty-three analogs of a
tryptamine-based lead-molecule previously observed to suppress colistin resistance.
This diverse panel allowed for preliminary relationships between structure and
activity to be uncovered indicating that there are rigid constraints on the scaffold
to retain suppression of colistin resistance. The indole head group is necessary for
activity, and neither substitution about the ring nor N-alkylation
enhance efficacy. We further saw that deviation from the 4,5-dibromopyrrole to other
five and six membered heterocycles greatly reduced activity. These molecules are
non-toxic to bacteria, each having an MIC >200 Î¼M in all strains that
were studied. Based on activity, this panel of thirty-three analogs was narrowed to
nine compounds for further screening against an additional nine bacterial strains.
This second round of screening revealed that while they had unremarkable activity in
colistin-sensitive strains, they were effective in both colR primary
clinical isolates of A. baumannii and K.
pneumoniae, as well as strains transfected with the
mcr-1 gene, and returned sub-breakpoint colistin MICs, in some
cases as low as 0.25 Î¼g/mL.</p><p>In the end, shortening the aliphatic linker by one carbon accessed compound
8 with fourfold greater activity than the parent molecule. In
subsequent studies we observed dose-dependent activity of 8, and when
given as monotherapy, it caused no abnormalities in bacterial growth and did not
lyse red blood cells. Currently, the mechanism-of-action of this family of compounds
is unknown. Previous reports from our research group have disclosed colistin
adjuvants containing a 2-AI heterocycle reversed lipid A modification leading to
re-sensitization to colisin. These tryptamine-based adjuvants, however, do not
reverse lipid A modification, thus appear to act via a novel mechanism. In all, this
study identified several scaffolds that can be tasked in future probes of colistin
resistance pathways and potentially new leads for further SAR studies while
concurrent in vivo investigations are pursued.</p><!><p>All antibiotics, media, and other biological reagents were purchased
from commercial sources and used without further purification. Compounds
synthesized in this study were dosed from DMSO stocks.</p><!><p>This procedure follows the guidelines set by the Clinical Laboratory
Sciences Institute.4 Bacteria
were cultured for 4 to 6 hours in Cation-Adjusted Mueller-Hinton Broth (CAMHB)
and subcultured to 5 ×105 CFU/mL in fresh CAMHB. For each
compound to be tested, a 1 mL aliquot of subculture was taken and dosed with
compound to a final concentration of 200 Î¼M. Samples were then dispensed
(200 Î¼L) into the first row of a 96-well microtiter plate in which
subsequent wells were prefilled with 100 Î¼L of subculture. 100 Î¼L
of dosed subculture was then serially diluted a total of 6 times in each
subsequent row of the plate save for the last row which served as a control.
Plates were then sealed and incubated stationary at 37°C. After 18 hours,
the plates were removed and MIC values were recorded. All compounds tested had a
purity of >95%.</p><!><p>This procedure was adapted from the guidelines set by the Clinical
Laboratory Sciences Institute.4
Bacteria were cultured for 4 to 6 hours in Cation-Adjusted Mueller-Hinton Broth
(CAMHB) and subcultured to 5 ×105 CFU/mL in fresh CAMHB. For
each compound to be tested, a 5 mL aliquot of subculture was taken and dosed
with adjuvant to a set concentration. A 1 mL aliquot of each dosed subculture
was collected and dosed with antibiotic to a set concentration. Co-dosed
aliquots were then dispensed (200 Î¼L) into the first row of a 96-well
microtiter plate in which subsequent wells were prefilled with 100 Î¼L of
the corresponding dosed subculture. 100 Î¼L of co-dosed subculture was
then serially diluted a total of 6 times in each subsequent row of the plate
save the last row as a control to afford serial dilution of the antibiotic while
holding a constant concentration of adjuvant. Plates were then sealed and
incubated stationary at 37°C. After 18 hours, the plates were removed and
MIC values were recorded. All compounds tested had a purity of >95%.</p><!><p>Bacteria were cultured overnight in CAMHB and subcultured to 5 ×
105 CFU/mL in fresh CAMHB. The subculture was then transferred to
culture tubes in 5 mL aliquots, which were dosed with adjuvant to a set
concentration, save one aliquot as a control. All subcultures were then
incubated at 37°C with shaking. At 2, 4, 6, 8, and 24 hours, 100
Î¼L samples of each culture was serially diluted in 900 Î¼L aliquots
of CAMHB for a total of 5 to 7 times. 100 Î¼L of each dilution point were
plated on nutrient agar and incubated stationary overnight. The total number of
bacterial colonies on each plate was recorded.</p><!><p>Bacteria were cultured overnight in CAMHB at 37°C and diluted
1:10 in fresh CAMHB and grown for an additional 4 hours to an OD600
of ~0.3. Cultures were centrifuged at 10,000 g for 15 mins, supernatants
were discarded, and cell pellets were washed once with sterile water and
resuspended in 1/10th the original volume in sterile water or water
dosed with compounds. Suspensions were incubated for 1 hour at 37°C with
shaking and centrifuged at 10,000 g for 15 mins, washed with sterile water and
resuspended in sterile water supplemented with 1:1 SYTO-9 and propidium iodide
(3 Î¼L/mL, from Invitrogen BacLight Kit). 100 Î¼L of each test
condition were added to a 96 well plate which was covered and allowed to stand
at room temperature. After 15 mins, the plate was read at 530 nm and 645 nm
(excitation 485 nm). The ratio of green to red fluorescence was calculated as a
percentage of the control.</p><!><p>Hemolysis assays were performed on mechanically difibrinated sheep blood
(Hemostat Labs: DSB100). Difibrinated blood (1.5 mL) was placed into a
microcentrifuge tube and centrifuged for 10 min at 10,000 rpm. The supernatant
was then removed and then the cells were resuspended in 1 mL of
phosphate-buffered saline (PBS). The suspension was centrifuged, the supernatant
was removed and cells were resuspended two additional times in PBS. The final
cell suspension was then diluted 10-fold in PBS dosed with test compounds from
DMSO stock solutions. DMSO was used as a negative control and a zero hemolysis
marker. Triton X100 (1%) was used as a positive control serving as the 100%
lysis marker. Samples were incubated at 37°C with shaking. After one
hour, the samples were centrifuged for 10 min at 10,000 rpm. The supernatant was
diluted 1:40 in distilled water. The absorbance of the supernatant at 540 nm was
then measured with a UV spectrometer.</p><!><p>All reagents used for chemical synthesis were purchased from commercial
sources and used without further purification. Flash chromatography was
performed using 60Å mesh silica gel (Sorbtech, Norcross, GA). Both
1H (300 and 400 MHz) and 13C NMR (75 MHz and 100 Mhz)
spectra were collected on Varian Mercury spectrometers at 25°C.
Ultraviolet spectra were obtained from a Genesys 10 Scanning UV/Vis
spectrophotometer (Î»max in nm). Infrared spectra were obtained
on a solid-phase FT-IR-4100 spectrophotometer (Î½max in
cm−1). High-resolution mass spectra were obtained by the
NCSU Molecular Education, Technology, and Research Innovation Center (METRIC).
All NMR spectra are available in this article's supplemental information
document. The purity of all reported compounds was determined to be greater than
or equal to 95% both by NMR spectra and subsequent liquid chromatography UV/Vis
trace analysis.</p><!><p>This method was adapted from methods described by Richards et
al.14 One equivalent
of the appropriate 2,2,2-trichloroacetylpyrrole was combined with 2 equivalents
of the appropriate primary amine along with 3 equivalents of anhydrous potassium
carbonate and dissolved in 4 mLs of anhydrous dimethylformamide (DMF) under
argon and stirred for 18 hours. The reaction was poured into 75 mLs EtOAc and 25
mLs of deionized water, the aqueous layer was discarded and the organic was
further washed thrice with water, twice with 25 mLs 1N HCl, and once with 25 mLs
brine. The organic layer was then dried with anhydrous magnesium sulfate and
evaporated under reduced pressure. The crude solid was purified by flash
chromatography (5–20% EtOAc/Hexanes) to yield the final products.</p><!><p>This procedure was adapted from the methods described by
Holloway.16 The
corresponding indole (0.9 equiv) was dissolved in 4 mLs anhydrous
dichloromethane (DCM) under argon and stirred for 15 mins at RT. In a separate
flask, N,N-dimethyl-2-nitroethen-1-amine
(DMANE) (1 equiv) was dissolved in 3 mLs trifluoroacetic acid (TFA) and stirred
for 15 mins at RT. The solution of indole in DCM was added dropwise to the
stirring solution of TFA and stirred for an additional 30 mins at RT. The
reaction was quenched with the addition of water (10 mLs) and was poured into 25
mLs water and extracted three times with 25 mLs DCM. The organic layers were
combined and dried with anhydrous magnesium sulfate and evaporated under reduced
pressure. The resulted crude solid was recrystallized from chloroform to give
the products with no further purification necessary.</p><!><p>Indole (1 g, 8.54 mmols) was dissolved in 15mLs DMF and cooled to
0°C under argon. Sodium hydride (410 mg, 10.2 mmols) was added in
portions to the solution which was then stirred at 0°C for 30 mins. Two
equivalents of the appropriate alkyl halide were then added to the solution
which was allowed to warm to RT for 18 hours. The reaction was poured into 75
mLs EtOAc and 25 mLs of deionized water, the aqueous layer was discarded and the
organic was further washed thrice with water, twice with 25mLs 1N HCl, and once
with 25 mLs brine. The organic layer was then dried with anhydrous magnesium
sulfate and evaporated under reduced pressure. The crude solid was purified by
flash chromatography (5–20% EtOAc/Hexanes) to yield the final
products.</p><!><p>This procedure was adapted from the methods described by
Muratore.18 The
corresponding N-alkylated 3-nitrovinyl indole was dissolved in 15 mLs anhydrous
tetrahydrofuran (THF) and cooled to −78°C for 20 mins. A 2.4M
solution (5 mLs) of lithium aluminum hydride (LAH) in THF) was added dropwise to
the stirring solution which was then allowed to come to room temperature for 18
hours. The stirring solution was then cooled to 0°C and the following
solutions were added dropwise in sequence: 0.86 mL of water, 0.86 mL of 15% aq.
NaOH, and finally, 2.2 mL of deionized water. After 30 mins, magnesium sulfate
was added to the slurry which was subsequently filtered through a pad of celite
and washed twice with 20 mLs DCM. The organics were evaporated under reduced
pressure and the crude amine was taken to further transformations with no
further purification.</p><!><p>The corresponding carboxylic acid (1 equiv),
benzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate (PyBOP) (1
equiv), and triethylamine (TEA) (3 equiv) were dissolved in anhydrous DMF under
argon and stirred for 15 mins at RT. The appropriate primary amine (2 equiv) was
then added in one portion and the reaction was allowed to stir for 18 hours at
RT and then poured into 75 mLs EtOAc and 25 mLs deionized water. The aqueous
layer was discarded and the organic layer was washed twice with water (25 mLs)
and once with brine (25 mLs). The organic layer was dried with magnesium sulfate
and evaporated under reduced pressure. The crude solids were purified by flash
chromatography (5–20% EtOAc/Hexanes) to afford pure products.</p><!><p>Compound was synthesized using the methods previously reported by
Richards et al. Spectral data were consistent with previous
reports.14</p><!><p>Compound was synthesized using the methods previously reported by
Richards et al. Spectral data were consistent with previous
reports.14</p><!><p>Compound was synthesized using the methods previously reported by
Richards et al. Spectral data were consistent with previous
reports.14</p><!><p>Compound was synthesized using the methods previously reported by
Richards et al. Spectral data were consistent with previous
reports.14</p><!><p>Compound was synthesized using the methods previously reported by
Richards et al. Spectral data were consistent with previous
reports.14</p><!><p>Compound was synthesized using the methods previously reported by
Richards et al. Spectral data were consistent with previous
reports.14</p><!><p>Compound was synthesized using the methods previously reported by
Richards et al. Spectral data were consistent with previous
reports.14</p><!><p>Compound was synthesized using the general procedure for condensing
primary amines with 2,2,2-trichloroacetyl pyrroles with
(1H-indol-3-yl)methanamine (323 mg, 2.14 mmols) and
7 (396 mg, 1.07 mmols) as condensation partners to afford
8 as a tan solid (372 mg, 77%). 1H NMR (400 MHz,
DMSO-d6) Î´ 12.69 (s, 1H), 10.94 (s, 1H),
8.41 (s, 1H), 7.60 (d, J = 7.9 Hz, 1H), 7.36 (d,
J = 8.1 Hz, 1H), 7.28 (s, 1H), 7.07 (t, J
= 7.5 Hz, 1H), 7.01 – 6.88 (m, 2H), 4.57 (d, J = 5.5 Hz,
2H); 13C NMR (101 MHz, dmso) Î´ 158.54, 136.20, 128.26, 126.46,
123.82, 121.20, 118.81, 118.56, 112.71, 112.25, 111.44, 104.21, 97.86, 33.91
ppm; UV (Î»max nm) 288; IR vmax
(cm−1) 3392, 1504, 804, 749, 492; HRMS (ESI) calcd for
C14H11Br2N3O
[M+H]− 393.9196, found 393.9192.</p><!><p>Compound was synthesized using the general procedure for condensing
primary amines with 2,2,2-trichloroacetyl pyrroles with
(1H-indol-3-yl)propylamine (150 mg, 0.86 mmols) and
7 (287 mg, 0.78 mmols) as condensation partners to afford
9 as a tan solid (186 mg, 38%). 1H NMR (400 MHz,
DMSO-d6) Î´ 12.70 (s, 1H), 8.26 (s, 1H),
7.58 (d, J = 7.8 Hz, 1H), 7.39 (d, J = 8.1 Hz,
1H), 7.16 (s, 1H), 7.14 – 7.07 (m, 1H), 7.05 – 6.96 (m, 1H), 6.92
(s, 1H), 4.07 (t, J = 6.5 Hz, 2H), 3.62 – 3.39 (m, 2H),
2.91 (t, J = 6.9 Hz, 2H), 1.82 – 1.49 (m, 2H), 1.19 (dd,
J = 14.7, 7.3 Hz, 2H), 0.84 (t, J = 7.2
Hz, 3H); 13C NMR (101 MHz, acetone) Î´ 160.09, 137.48, 129.43,
129.00, 126.97, 122.00, 119.62, 119.26, 113.08, 113.05, 112.35, 110.34, 99.44,
46.24, 40.79, 33.20, 26.21, 20.74, 14.01 ppm; UV (Î»max nm)
296; IR vmax (cm−1) 3117, 1611,
1557, 742, 492; HRMS (ESI) calcd for
C19H21Br2N3O
[M+H]− 463.9978, found 463.9976.</p><!><p>Compound was synthesized using the methods previously reported by
Richards et al. Spectral data were consistent with previous
reports.14</p><!><p>Compound was synthesized using the general procedure for condensing
primary amines with 2,2,2-trichloroacetyl pyrroles with benzylamine (89
Î¼L, 0.81 mmols) and 7 (300 mg, 0.81 mmols) as condensation
partners to afford 11 as a white solid (162 mg, 56%). 1H
NMR (300 MHz, DMSO-d6) Î´ 12.73 (s, 1H), 8.68
(s, 1H), 7.40 – 7.17 (m, 5H), 6.98 (d, J = 2.8 Hz, 1H),
4.42 (d, J = 5.8 Hz, 2H); 13C NMR (75 MHz, dmso)
Î´ 158.93, 139.51, 128.36, 128.06, 127.21, 126.86, 112.73, 104.78, 97.92,
41.99 ppm; UV (Î»max nm) 286; IR
vmax (cm−1) 3187, 1602, 1558,
1232, 711; HRMS (ESI) calcd for
C12H10Br2N2O
[M+H]− 354.9087, found 354.9088.</p><!><p>Compound was synthesized using the general procedure for condensing
primary amines with 2,2,2-trichloroacetyl pyrroles with
2-(pyridin-2-yl)ethan-1-amine (97 Î¼L, 0.81 mmols) and 7 (300
mg, 0.81 mmols) as condensation partners to afford 12 as a white
solid (97 mg, 32%). 1H NMR (300 MHz,
DMSO-d6) Î´ 12.67 (s, 1H), 8.50 (d,
J = 6.4 Hz, 1H), 8.23 (t, J = 5.4 Hz, 1H),
7.69 (td, J = 7.6, 1.9 Hz, 1H), 7.23 (dd, J =
14.0, 7.2 Hz, 2H), 6.87 (s, 1H), 3.56 (q, J = 6.7 Hz, 2H), 2.95
(t, J = 7.3 Hz, 2H); 13C NMR (101 MHz, dmso)
Î´ 159.05, 158.91, 149.11, 136.55, 128.25, 123.23, 121.60, 112.49, 104.52,
97.84, 38.65, 37.50 ppm; UV (Î»max nm) 288; IR
vmax (cm−1) 3108, 1626, 1566,
1327, 765; HRMS (ESI) calcd for
C12H11Br2N3O
[M+H]− 369.9196, found 369.9197.</p><!><p>Compound was synthesized using the general procedure for condensing
primary amines with 2,2,2-trichloroacetyl pyrroles with 2-aminoindane (211
Î¼L, 1.62 mmols) and 7 (300 mg, 0.81 mmols) as condensation
partners to afford 13 as a gray solid (102 mg, 33%). 1H
NMR (300 MHz, DMSO-d6) Î´ 12.68 (s, 1H), 8.29
(d, J = 6.2 Hz, 1H), 7.20 (d, J = 20.0 Hz,
4H), 6.99 (s, 1H), 4.85 – 4.38 (m, 1H), 3.22 (dd, J =
16.3, 7.3 Hz, 2H), 2.88 (dd, J = 16.0, 5.5 Hz, 2H);
13C NMR (101 MHz, dmso) Î´ 158.80, 141.22, 128.21, 126.46,
124.52, 112.97, 104.50, 97.84, 50.12, 39.07 ppm; UV (Î»max nm)
288; IR vmax (cm−1) 3133, 1635,
1503, 811, 740; HRMS (ESI) calcd for
C14H12Br2N2O
[M+H]− 380.9243, found 380.9245.</p><!><p>Compound was synthesized using the general procedure for condensing
primary amines with 2,2,2-trichloroacetyl pyrroles with
(1H-indol-2-yl)methanamine (237 mg, 1.62 mmols) and
7 (300 mg, 0.81 mmols) as condensation partners to afford
14 as a yellow solid (239 mg, 74%). 1H NMR (300 MHz,
DMSO-d6) Î´ 12.76 (s, 1H), 10.96 (s, 1H),
8.64 (s, 1H), 7.45 (d, J = 7.7 Hz, 1H), 7.33 (d,
J = 8.2 Hz, 1H), 7.07 – 6.99 (m, 2H), 6.98 –
6.89 (m, 1H), 6.28 (s, 1H), 4.57 (s, 2H); 13C NMR (101 MHz, dmso)
Î´ 158.98, 137.01, 136.18, 128.08, 127.98, 120.72, 119.60, 118.92, 113.08,
111.14, 104.82, 99.20, 98.01, 36.25 ppm; UV (Î»max nm) 294; IR
vmax (cm−1) 3314, 1685, 1521,
1229, 684; HRMS (ESI) calcd for C15H14ClN3O
[M+H]− 393.9196, found 393.9198.</p><!><p>Compound was synthesized using the general procedure for condensing
primary amines with 2,2,2-trichloroacetyl pyrroles with
(1H-indol-6-yl)methanamine (236 mg, 1.62 mmols) and
7 (300 mg, 0.81 mmols) as condensation partners to afford
14 as a white solid (268 mg, 83%). 1H NMR (300 MHz,
DMSO-d6) Î´ 12.73 (s, 1H), 11.01 (s, 1H),
8.66 (s, 1H), 7.47 (d, J = 8.1 Hz, 1H), 7.30 (s, 2H), 7.00 (s,
1H), 6.94 (d, J = 9.0 Hz, 1H), 6.38 (s, 1H), 4.51 (d,
J = 5.9 Hz, 2H); 13C NMR (101 MHz, dmso)
Î´ 158.85, 136.06, 132.19, 128.30, 126.64, 125.30, 119.90, 118.85, 112.73,
110.00, 104.68, 100.94, 97.97, 42.54 ppm; UV (Î»max nm) 292; IR
vmax (cm−1) 3403, 1637, 1512,
867, 769; HRMS (ESI) calcd for C15H14ClN3O
[M+H]− 393.9196, found 393.9198.</p><!><p>Compound was synthesized using the general procedure for condensing
primary amines with 2,2,2-trichloroacetyl pyrroles with one exception: final
product was purified by flash chromatograpy (0.5 – 5% MeOH-NH3/DCM) in
lieu of EtOAc/Hexanes. 5-hydroxytryptamine (117 mg, 0.54 mmols) and
7 (200 mg, 0.54 mmols) were condensed to afford 16
as a tan solid (48 mg, 21%). 1H NMR (400 MHz,
DMSO-d6) Î´ 12.68 (s, 1H), 10.50 (s, 1H),
8.61 (s, 1H), 8.25 (s, 1H), 7.13 (d, J = 8.5 Hz, 1H), 7.06 (s,
1H), 6.93 (s, 1H), 6.87 (s, 1H), 6.61 (d, J = 8.6 Hz, 1H), 3.53
– 3.42 (m, 2H), 2.82 (t, J = 7.0 Hz, 2H); 13C
NMR (101 MHz, dmso) Î´ 158.86, 150.24, 130.85, 128.44, 127.93, 123.16,
112.46, 111.73, 111.35, 110.79, 104.40, 102.29, 97.83, 39.44, 25.46 ppm; UV
(Î»max nm) 296; IR vmax
(cm−1) 3161, 1569, 1178, 829, 614; HRMS (ESI) calcd for
C15H13Br2N3O2
[M+H]− 423.9301, found 423.9304.</p><!><p>Compound was synthesized using the general procedure for condensing
primary amines with 2,2,2-trichloroacetyl pyrroles with 5-methoxytryptamine (318
mg, 1.62 mmols) and 7 (300 mg, 0.81 mmols) as condensation partners
to afford 14 as a pink solid (207 mg, 58%). 1H NMR (300
MHz, DMSO-d6) Î´ 12.69 (s, 1H), 10.66 (s, 1H),
8.26 (s, 1H), 7.22 (d, J = 8.6 Hz, 1H), 7.12 (s, 1H), 7.04 (s,
1H), 6.91 (s, 1H), 6.71 (d, J = 8.7 Hz, 1H), 3.53 – 3.39
(m, 2H), 2.87 (t, J = 7.1 Hz, 2H); 13C NMR (101 MHz,
dmso) Î´ 158.94, 153.04, 131.43, 128.46, 127.65, 123.43, 112.50, 112.09,
111.69, 111.18, 104.42, 100.16, 97.85, 55.28, 39.72, 25.35 ppm; UV
(Î»max nm) 296; IR vmax
(cm−1) 3340, 1606, 1467, 1167, 923; HRMS (ESI) calcd for
C16H15Br2N3O2
[M+H]− 437.9458, found 437.9460.</p><!><p>Compound was synthesized using the methods previously reported by
Szostak. Spectral data were consistent with previous reports.15</p><!><p>Compound was synthesized using the general procedure for condensing
primary amines with 2,2,2-trichloroacetyl pyrroles with 18 (100 mg,
0.56 mmols) and 7 (209 mg, 0.56 mmols) as condensation partners to
afford 19 as a yellow solid (105 mg, 44%). 1H NMR (300
MHz, DMSO-d6) Î´ 12.71 (s, 1H), 8.35 (s, 1H),
7.95 (dd, J = 16.0, 7.2 Hz, 2H), 7.48 (s, 1H), 7.45 –
7.33 (m, 2H), 6.89 (s, 1H), 3.54 (q, J = 6.8 Hz, 2H), 3.05 (t,
J = 7.2 Hz, 2H); 13C NMR (101 MHz, dmso)
Î´ 159.03, 139.73, 138.81, 133.73, 128.24, 124.35, 124.11, 122.98, 122.86,
121.77, 112.52, 104.59, 97.85, 38.50, 28.34 ppm; UV (Î»max nm)
286; IR vmax (cm−1) 3410, 3117,
2921, 1629, 739; HRMS (ESI) calcd for
C15H12Br2N2OS
[M+H]− 424.8964, found 424.8969.</p><!><p>Compound was synthesized using the methods previously reported by
Muratore. Spectral data were consistent with previous reports.18</p><!><p>Compound was synthesized using the general procedure for synthesis of
3-(2-nitrovinyl) indoles with 7-methyl indole (800 mg, 6.09 mmols) as the
starting material to afford 21 as an orange solid (730 mg, 59%).
1H NMR (400 MHz, DMSO-d6) Î´
12.22 (s, 1H), 8.35 (d, J = 13.4 Hz, 1H), 8.19 (d,
J = 2.7 Hz, 1H), 7.93 (d, J = 13.4 Hz,
1H), 7.68 (d, J = 7.8 Hz, 1H), 7.07 (t, J =
7.5 Hz, 1H), 7.00 (d, J = 7.1 Hz, 1H), 2.44 (s, 3H);
13C NMR (101 MHz, dmso) Î´ 137.17, 135.99, 134.82, 131.02,
124.53, 123.99, 122.21, 122.09, 117.98, 108.68, 16.62 ppm; UV
(Î»max nm) 396; IR vmax
(cm−1) 3104, 1609, 1521, 1201, 793; HRMS (ESI) calcd for
C11H10N2O2
[M+H]− 201.0669, found 201.0669.</p><!><p>Compound was synthesized using the methods previously reported by
Muratore and taken to the next reaction without further purification.18</p><!><p>Compound was synthesized using the methods previously reported by Blough
and taken on to the next reaction without further purification.19</p><!><p>Compound was synthesized using the general procedure for condensing
primary amines with 2,2,2-trichloroacetyl pyrroles with 22 (204 mg,
1.14 mmols) and 7 (300 mg, 0.81 mmols) as condensation partners to
afford 24 as a brown solid (129 mg, 37%). 1H NMR (300
MHz, Chloroform-d) Î´ 11.25 (s, 1H), 8.11 (s, 1H), 7.50
(dd, J = 8.6, 5.3 Hz, 1H), 7.09 – 7.00 (m, 2H), 6.90
(td, J = 9.1, 2.1 Hz, 1H), 6.37 (s, 1H), 5.97 (s, 1H), 3.76 (q,
J = 6.4 Hz, 2H), 3.03 (t, J = 6.5 Hz, 2H);
13C NMR (101 MHz, cd3od) Î´ 161.64, 159.89,
137.95, 128.85, 125.40, 123.79, 120.13, 114.21, 113.48, 108.09, 105.88, 99.94,
98.19, 41.34, 26.33 ppm; UV (Î»max nm) 288; IR
vmax (cm−1) 2924, 1613, 1556,
1454, 799; HRMS (ESI) calcd for
C15H12Br2FN3O
[M+H]− 425.9258, found 425.9262.</p><!><p>Compound was synthesized using the general procedure for condensing
primary amines with 2,2,2-trichloroacetyl pyrroles with 23 (201 mg,
1.14 mmols) and 7 (300 mg, 0.81 mmols) as condensation partners to
afford 25 as a tan solid (141 mg, 41%). 1H NMR (400 MHz,
DMSO-d6) Î´ 12.70 (s, 1H), 10.79 (s, 1H),
8.27 (s, 1H), 7.40 (d, J = 7.4 Hz, 1H), 7.15 (s, 1H), 6.93 (s,
1H), 6.88 (t, J = 9.1 Hz, 2H), 3.50 (q, J =
6.3 Hz, 2H), 2.91 (t, J = 7.2 Hz, 2H), 2.44 (s, 3H);
13C NMR (101 MHz, dmso) Î´ 158.85, 135.79, 128.42, 126.92,
122.39, 121.45, 120.46, 118.49, 115.90, 112.43, 112.19, 104.34, 97.79, 39.57,
25.42, 16.79 ppm; UV (Î»max nm) 286; IR
vmax (cm−1) 3392, 3085, 1559,
777, 448; HRMS (ESI) calcd for
C16H15Br2N3O
[M+H]− 421.9509, found 421.9514.</p><!><p>Compound was synthesized via the general procedure for N-alkylation of
indole with methyl iodide as the electrophile. Spectral data were consistent
with previous reports.20</p><!><p>Compound was synthesized via the general procedure for N-alkylation of
indole with butyl iodide (4.84 mLs, 42.7 mmols) as the electrophile to afford
26b as a yellow oil (1.36 g, 92%). 1H NMR (400 MHz,
Chloroform-d) Î´ 7.90 (d, J = 8.5
Hz, 1H), 7.57 (d, J = 8.2 Hz, 1H), 7.46 (t, J
= 7.6 Hz, 1H), 7.37 (t, J = 7.4 Hz, 1H), 7.28 (d,
J = 3.1 Hz, 1H), 6.74 (d, J = 3.1 Hz, 1H),
4.27 (t, J = 7.1 Hz, 2H), 2.01 (p, J = 7.2 Hz,
2H), 1.59 – 1.51 (m, 2H), 1.17 (t, J = 7.4 Hz, 3H);
13C NMR (101 MHz, cdcl3) Î´ 136.08, 128.71,
127.79, 121.34, 120.99, 119.22, 109.44, 100.92, 46.06, 32.37, 20.22, 13.75 ppm;
UV (Î»max nm) 298; IR vmax
(cm−1) 2928, 1510, 1313, 734, 425; HRMS (ESI) calcd for
C12H15N [M+H]+ 174.1277, found
174.1277.</p><!><p>Compound was synthesized using the methods previously reported by Yu.
Spectral data were consistent with previous reports.21</p><!><p>Compound was synthesized using the general procedure for synthesis of
3-(2-nitrovinyl) indoles with 26a (536 mg, 4.08 mmols) as the
starting material to afford 27a as an orange solid (115 mg, 14%).
1H NMR (400 MHz, DMSO-d6) Î´
8.34 (d, J = 13.4 Hz, 1H), 8.16 (s, 1H), 8.03 – 7.89 (m,
2H), 7.56 (d, J = 8.0 Hz, 1H), 7.33 (t, J =
7.6 Hz, 1H), 7.27 (t, J = 7.5 Hz, 1H), 3.84 (s, 3H);
13C NMR (101 MHz, dmso) Î´ 139.48, 138.27, 134.20, 131.00,
125.06, 123.42, 122.24, 120.69, 111.26, 107.25, 33.33 ppm; UV
(Î»max nm) 394; IR vmax
(cm−1) 2918, 1614, 1296, 948, 740; HRMS (ESI) calcd for
C11H10N2O2
[M+H]− 201.0669, found 201.0672</p><!><p>Compound was synthesized using the general procedure for synthesis of
3-(2-nitrovinyl) indoles with 26b (1.21 g, 6.98 mmols) as the
starting material to afford 27b as a brown oil (545 mg, 32%).
1H NMR (400 MHz, Chloroform-d) Î´ 8.26 (d,
J = 14.6 Hz, 1H), 7.78 – 7.71 (m, 2H), 7.55 (s, 1H),
7.44 (d, J = 7.9 Hz, 1H), 7.40 – 7.35 (m, 1H), 7.35
– 7.29 (m, 1H), 4.14 (t, J = 7.1 Hz, 2H), 1.84 (dq,
J = 12.5, 5.7, 5.0 Hz, 2H), 1.37 (h, J =
7.3 Hz, 2H), 0.98 (t, J = 7.4 Hz, 3H); 13C NMR (101
MHz, cdcl3) Î´ 137.74, 136.29, 133.63, 131.51, 125.51, 123.67,
122.32, 120.58, 110.83, 107.91, 46.75, 31.67, 19.96, 13.54 ppm; UV
(Î»max nm) 394; IR vmax
(cm−1) 2929, 1615, 1294, 1174, 740; HRMS (ESI) calcd for
C14H16N2O2 [M+H]+
245.1284, found 245.1285.</p><!><p>Compound was synthesized using the general procedure for synthesis of
3-(2-nitrovinyl) indoles with 26c (770 mg, 3.71 mmols) as the
starting material to afford 27c as an orange solid (390 mg, 38%).
1H NMR (400 MHz, Chloroform-d) Î´ 8.23 (d,
J = 13.4 Hz, 1H), 7.75 (d, J = 13.3 Hz,
2H), 7.53 (s, 1H), 7.37 (td, J = 14.0, 12.6, 9.3 Hz, 5H), 7.19
(d, J = 6.0 Hz, 2H), 5.33 (s, 2H); 13C NMR (101 MHz,
cdcl3) Î´ 137.99, 136.27, 135.38, 133.43, 132.14, 129.11,
128.39, 127.17, 125.68, 124.04, 122.63, 120.72, 111.19, 108.55, 50.73 ppm; UV
(Î»max nm) 394; IR vmax
(cm−1) 3105, 1616, 1488, 1247, 701; HRMS (ESI) calcd for
C17H14N2O2 [M+H] 277.0982, found
277.0982.</p><!><p>Compound was synthesized using the general procedure for the reduction
of N-alkylated 3-nitrovinyl indoles and taken to the next reaction without
further purification.</p><!><p>Compound was synthesized using the general procedure for the reduction
of N-alkylated 3-nitrovinyl indoles and taken to the next reaction without
further purification.</p><!><p>Compound was synthesized using the general procedure for the reduction
of N-alkylated 3-nitrovinyl indoles and taken to the next reaction without
further purification.</p><!><p>Compound was synthesized using the general procedure for condensing
primary amines with 2,2,2-trichloroacetyl pyrroles with 28a (330
mg, 1.89 mmols) and 7 (701 mg, 1.89 mmols) as condensation partners
to afford 29a as a white solid (476 mg, 59%). 1H NMR
(400 MHz, DMSO-d6) Î´ 12.75 (s, 1H), 8.33 (s,
1H), 7.60 (d, J = 7.8 Hz, 1H), 7.35 (d, J =
8.1 Hz, 1H), 7.21 – 7.07 (m, 2H), 7.08 – 6.91 (m, 2H), 3.70 (s,
3H), 3.58 – 3.44 (m, 2H), 2.94 (t, J = 6.4 Hz, 2H);
13C NMR (101 MHz, dmso) Î´ 158.99, 136.70, 128.45, 127.62,
127.13, 121.17, 118.59, 118.43, 112.57, 111.22, 109.60, 104.48, 97.92, 39.77,
32.26, 25.28 ppm; UV (Î»max nm) 298; IR
vmax (cm−1) 3113, 1639, 1516,
824, 736; HRMS (ESI) calcd for
C16H15Br2N3O
[M+H]− 421.9509, found 421.9521.</p><!><p>Compound was synthesized using the general procedure for condensing
primary amines with 2,2,2-trichloroacetyl pyrroles with 28b (204
mg, 0.95 mmols) and 7 (350 mg, 0.95 mmols) as condensation partners
to afford 29b as a tan solid (168 mg, 38%). 1H NMR (400
MHz, DMSO-d6) Î´ 12.70 (s, 1H), 8.26 (s, 1H),
7.58 (d, J = 7.8 Hz, 1H), 7.39 (d, J = 8.1 Hz,
1H), 7.16 (s, 1H), 7.14 – 7.07 (m, 1H), 7.05 – 6.96 (m, 1H), 6.92
(s, 1H), 4.07 (t, J = 6.5 Hz, 2H), 3.62 – 3.39 (m, 2H),
2.91 (t, J = 6.9 Hz, 2H), 1.82 – 1.49 (m, 2H), 1.19 (dd,
J = 14.7, 7.3 Hz, 2H), 0.84 (t, J = 7.2
Hz, 3H); 13C NMR (101 MHz, acetone) Î´ 160.09, 137.48, 129.43,
129.00, 126.97, 122.00, 119.62, 119.26, 113.08, 113.05, 112.35, 110.34, 99.44,
46.24, 40.79, 33.20, 26.21, 20.74, 14.01 ppm; UV (Î»max nm)
296; IR vmax (cm−1) 3111, 1638,
1506, 745, 494; HRMS (ESI) calcd for
C19H21Br2N3O
[M+H]− 463.9978, found 463.9976.</p><!><p>Compound was synthesized using the general procedure for condensing
primary amines with 2,2,2-trichloroacetyl pyrroles with 28c (400
mg, 1.59 mmols) and 7 (300 mg, 0.81 mmols) as condensation partners
to afford 29c as a tan solid (117 mg, 15%). 1H NMR (300
MHz, DMSO-d6) Î´ 12.69 (s, 1H), 8.25 (s, 1H),
7.60 (d, J = 7.8 Hz, 1H), 7.40 (d, J = 8.1 Hz,
1H), 7.32 (s, 1H), 7.24 (t, J = 8.0 Hz, 3H), 7.16 (d,
J = 7.7 Hz, 2H), 7.12 – 7.05 (m, 1H), 7.03 –
6.97 (m, 1H), 6.90 (s, 1H), 5.35 (s, 2H), 3.54 – 3.46 (m, 2H), 2.92 (t,
J = 7.3 Hz, 2H); 13C NMR (101 MHz, dmso)
Î´ 158.91, 138.40, 136.10, 128.51, 128.40, 127.86, 127.26, 127.04, 126.75,
121.28, 118.74, 118.63, 112.44, 111.71, 110.11, 104.43, 97.84, 48.94, 39.43,
25.16 ppm; UV (Î»max nm) 290; IR
vmax (cm−1) 3109, 1638, 824,
746, 490; HRMS (ESI) calcd for
C22H19Br2N3O
[M+H]− 497.9822, found 497.9821.</p><!><p>Tryptamine (152 mg, 0.984 mmols) and TEA (0.13 mLs, 0.984 mmols) were
dissolved in 3 mLs anhydrous DCM and stirred for 10 mins at RT. To the stirring
solution was added thiophene-2-carbonyl chloride (100 Î¼L, 0.984 mmols)
dropwise over five minutes. The reaction was stirred for an additional hour at
RT and then poured into 75 mLs EtOAc and 25 mLs of deionized water, the aqueous
layer was discarded and the organic was further washed thrice with water, twice
with 25mLs 1N HCl, and once with 25 mLs brine. The organic layer was then dried
with anhydrous magnesium sulfate and evaporated under reduced pressure. The
crude solid was purified by flash chromatography (5–20% EtOAc/Hexanes) to
afford 30 as a brown solid (192 mg, 80%).1H NMR (300
MHz, DMSO-d6) Î´ 10.83 (s, 1H), 8.65 (s, 1H),
7.74 (d, J = 4.0 Hz, 2H), 7.58 (d, J = 7.8 Hz,
1H), 7.34 (d, J = 8.0 Hz, 1H), 7.18 (s, 1H), 7.16 – 7.11
(m, 1H), 7.07 (t, J = 7.4 Hz, 1H), 6.98 (t, J
= 7.3 Hz, 1H), 3.57 – 3.47 (q, 2H), 2.94 (t, J = 7.5 Hz,
2H); 13C NMR (101 MHz, cd3od) Î´ 164.44, 140.40,
138.12, 131.36, 129.42, 128.78, 128.68, 123.41, 122.31, 119.60, 119.34, 113.30,
112.21, 42.03, 26.38 ppm; UV (Î»max nm) 292; IR
vmax (cm−1) 3401, 1551, 741,
717, 504; HRMS (ESI) calcd for C15H14N2OS
[M+H]+ 271.0899, found 271.0899.</p><!><p>Compound was synthesized using the general procedure for condensing
primary amines with 2,2,2-trichloroacetyl pyrroles with tryptamine (81 mg, 0.41
mmols) and
2,2,2-trichloro-1-(4-chloro-1H-pyrrol-2-yl)ethan-1-one (50 mg,
0.20 mmols) as condensation partners to afford 31 as a tan solid
(46 mg, 79%). 1H NMR (300 MHz, DMSO-d6)
Î´ 11.76 (s, 1H), 10.82 (s, 1H), 8.24 (s, 1H), 7.58 (d, J
= 7.8 Hz, 1H), 7.34 (d, J = 8.0 Hz, 1H), 7.17 (s, 1H), 7.07 (t,
J = 7.5 Hz, 1H), 7.03 – 6.92 (m, 2H), 6.77 (s, 1H),
3.49 (q, J = 6.8 Hz, 2H), 2.91 (t, J = 7.3 Hz,
2H); 13C NMR (101 MHz, cd3od) Î´ 162.67, 138.08,
128.72, 126.77, 123.39, 122.31, 120.07, 119.58, 119.31, 113.71, 113.31, 112.19,
110.69, 41.45, 26.50 ppm; UV (Î»max nm) 288; R
vmax (cm−1) 2922, 1610, 1516,
1454, 740; HRMS (ESI) calcd for C15H14ClN3O
[M+H]− 286.0752, found 286.0752.</p><!><p>Compound was synthesized using the general procedure for coupling
carboxylic acids to primary amines using PyBOP. Tryptamine (712 mg, 4.44 mmols)
and 4,5-dibromofuran-2-carboxylic acid (400 mg, 1.48 mmols) were coupled to
afford 32 as a white solid (290 mg, 48%). 1H NMR (400
MHz, Chloroform-d) Î´ 8.51 (s, 1H), 7.62 (d,
J = 7.8 Hz, 1H), 7.38 (d, J = 8.1 Hz, 1H),
7.22 (t, J = 7.2 Hz, 1H), 7.14 (t, J = 7.4 Hz,
1H), 7.10 (s, 1H), 7.02 (d, J = 1.8 Hz, 1H), 6.59 (s, 1H), 3.74
(q, J = 6.7 Hz, 2H), 3.06 (t, J = 6.8 Hz, 2H);
13C NMR (101 MHz, cdcl3) Î´ 156.64, 149.34,
136.51, 127.24, 125.21, 122.28, 122.22, 119.52, 118.61, 118.53, 112.40, 111.45,
104.32, 39.85, 25.37 ppm; UV (Î»max nm) 286; IR
vmax (cm−1) 3286, 1643, 1479,
978, 738; HRMS (ESI) calcd for
C15H12Br2N2O2
[M+H]+ 410.9338, found 410.9329.</p><!><p>Compound was synthesized using the general procedure for coupling
carboxylic acids to primary amines using PyBOP. Tryptamine (672 mg, 4.19 mmols)
and 4,5-dibromothiophene-2-carboxylic acid (400 mg, 1.39 mmols) were coupled to
afford 33 as a white solid (387 mg, 65%). 1H NMR (400
MHz, DMSO-d6) Î´ 10.83 (s, 1H), 8.80 (s, 1H),
7.76 (s, 1H), 7.55 (d, J = 7.8 Hz, 1H), 7.35 (d,
J = 8.0 Hz, 1H), 7.17 (s, 1H), 7.07 (t, J
= 7.5 Hz, 1H), 6.98 (t, J = 7.4 Hz, 1H), 3.51 (q,
J = 6.7 Hz, 2H), 2.94 (t, J = 7.3 Hz, 2H);
13C NMR (101 MHz, dmso) Î´ 159.17, 141.61, 136.26, 129.95,
127.20, 122.74, 120.95, 118.27, 118.20, 116.21, 113.72, 111.54, 111.41, 40.22,
25.00 ppm; UV (Î»max nm) 294; IR
vmax (cm−1) 3285, 2921, 1620,
1540, 738; HRMS (ESI) calcd for
C15H12Br2N2OS
[M+H]− 424.8964, found 424.8966.</p><!><p>Compound was synthesized using the general procedure for coupling
carboxylic acids to primary amines using PyBOP with modifications to the
purification procedure. Tryptamine (671 mg, 4.19 mmols) and
5-bromofuran-2-carboxylic acid (400 mg, 2.09 mmols) were coupled under standard
conditions. In lieu of flash chromatography, the crude product was
recrystallized from chloroform to afford 34 as a white solid (202
mg, 29%). 1H NMR (400 MHz, DMSO-d6)
Î´ 10.82 (s, 1H), 8.57 (s, 1H), 7.57 (d, J = 7.9 Hz, 1H),
7.34 (d, J = 7.6 Hz, 1H), 7.20 – 7.16 (m, 1H), 7.12 (d,
J = 3.5 Hz, 1H), 7.06 (t, J = 7.5 Hz, 1H),
6.98 (t, J = 7.4 Hz, 1H), 6.74 (dd, J = 3.5,
1.1 Hz, 1H), 3.49 (q, J = 6.7 Hz, 2H), 2.92 (t,
J = 7.5 Hz, 2H); 13C NMR (101 MHz, dmso)
Î´ 156.60, 149.95, 136.23, 127.22, 124.10, 122.60, 120.92, 118.26, 118.21,
115.57, 113.91, 111.66, 111.36, 39.45, 25.16 ppm; UV (Î»max nm)
286; IR vmax (cm−1) 3385, 1596,
1120, 797, 582; HRMS (ESI) calcd for
C15H13BrN2O2
[M+H]− 331.0087, found 331.0090.</p><!><p>Compound was synthesized using the general procedure for coupling
carboxylic acids to primary amines using PyBOP with modifications to the
purification procedure. Tryptamine (619 mg, 3.86 mmols) and
3-bromothiophene-2-carboxylic acid (400 mg, 1.93 mmols) were coupled under
standard conditions. Flash chromatography (1% MeOH-NH3/DCM) followed by
trituration of the solid in diethyl ether gave 35 as a white solid
(249 mg, 36%). 1H NMR (400 MHz, DMSO-d6)
Î´ 10.84 (s, 1H), 8.20 (s, 1H), 7.79 (d, J = 5.2 Hz, 1H),
7.59 (d, J = 7.8 Hz, 1H), 7.34 (d, J = 8.1 Hz,
1H), 7.21 (d, J = 2.3 Hz, 1H), 7.17 (d, J =
5.2 Hz, 1H), 7.11 – 7.03 (m, 1H), 6.99 (td, J = 7.5,
7.1, 1.0 Hz, 1H), 3.60 – 3.46 (m, 2H), 2.95 (t, J = 7.4
Hz, 2H); 13C NMR (101 MHz, dmso) Î´ 160.12, 136.29, 133.67,
131.61, 129.74, 127.20, 122.87, 120.98, 118.33, 118.28, 111.48, 111.40, 109.48,
40.31, 24.94 ppm; UV (Î»max nm) 290; IR
vmax (cm−1) 3275, 1605, 1536,
729, 544; HRMS (ESI) calcd for C15H13BrN2OS
[M+H]− 346.9859, found 346.9863.</p><!><p>Compound was synthesized using the general procedure for coupling
carboxylic acids to primary amines using PyBOP. Tryptamine (684 mg, 4.27 mmols)
and 5,6-dibromopicolinic acid (400 mg, 1.42 mmols) were coupled to afford
36 as a white solid (274 mg, 46%). 1H NMR (400 MHz,
DMSO-d6) Î´ 10.84 (s, 1H), 8.86 (s, 1H),
8.36 (d, J = 8.1 Hz, 1H), 7.93 (d, J = 8.1 Hz,
1H), 7.62 (d, J = 7.7 Hz, 1H), 7.34 (d, J =
8.0 Hz, 1H), 7.18 (s, 1H), 7.06 (t, J = 7.5 Hz, 1H), 6.98 (t,
J = 7.4 Hz, 1H), 3.57 (q, J = 6.7 Hz, 2H),
3.02 – 2.89 (m, 2H); 13C NMR (101 MHz, dmso) δ 161.89,
149.71, 143.70, 141.51, 136.26, 127.22, 126.05, 122.69, 122.60, 120.95, 118.39,
118.23, 111.65, 111.36, 39.99, 25.14 ppm; UV (Î»max nm) 288; IR
vmax (cm−1) 3256, 1672, 1524,
1339, 744; HRMS (ESI) calcd for
C16H13Br2N3O [M+H]+
421.9498, found 421.9493.</p><!><p>Compound was synthesized using the general procedure for coupling
carboxylic acids to primary amines using PyBOP. Tryptamine (476 mg, 2.97 mmols)
and 6-bromopicolinic acid (300 mg, 1.49 mmols) were coupled to afford
37 as a white solid (251 mg, 49%). 1H NMR (400 MHz,
DMSO-d6) Î´ 10.83 (s, 1H), 8.81 (s, 1H),
8.06 (d, J = 7.5 Hz, 1H), 7.94 (t, J = 7.7 Hz,
1H), 7.85 (d, J = 7.9 Hz, 1H), 7.63 (d, J =
7.8 Hz, 1H), 7.34 (d, J = 8.6 Hz, 1H), 7.19 (s, 1H), 7.07 (t,
J = 7.5 Hz, 1H), 6.98 (t, J = 7.4 Hz, 1H),
3.59 (q, J = 6.7 Hz, 2H), 2.96 (t, J = 7.5 Hz,
2H); 13C NMR (75 MHz, acetone) Î´ 163.21, 152.64, 141.30,
141.03, 137.58, 131.43, 128.50, 123.17, 122.14, 122.04, 119.45, 119.40, 113.20,
112.10, 40.96, 29.84, 26.28 ppm; UV (Î»max nm) 290; IR
vmax (cm−1) 3372, 1666, 1552,
1408, 746; HRMS (ESI) calcd for C16H14BrN3O
[M+H]+ 344.0393, found 344.0391.</p><!><p>Tryptamine (581 mg, 3.63 mmols) and trimethylamine (762 Î¼L, 5.44
mmols) were dissolved in anhydrous DMF under argon and stirred for 15 mins and
5-bromonicotinoyl chloride (400 mg, 1.81 mmols) was added in a single portion.
The reaction was allowed to stir at RT for 2 hours and was then poured into 75
mLs EtOAc / 25 mLs deionized water. The aqueous layer was discarded and the
organic layer was washed twice with water (25 mLs) and once with brine (25 mLs).
The organic layer was dried with anhydrous magnesium sulfate and evaporated
under reduced pressure. The crude solid was triturated in diethyl ether to
afford pure 38 as a tan solid (372 mg, 60%). 1H NMR (400
MHz, DMSO-d6) Î´ 10.85 (s, 1H), 8.96 (s, 1H),
8.92 (s, 1H), 8.85 (s, 1H), 8.40 (s, 1H), 7.57 (d, J = 7.8 Hz,
1H), 7.34 (d, J = 8.1 Hz, 1H), 7.20 (s, 1H), 7.07 (t,
J = 7.5 Hz, 1H), 6.98 (t, J = 7.4 Hz, 1H),
3.55 (q, J = 6.7 Hz, 2H), 2.96 (t, J = 7.3 Hz,
2H); 13C NMR (101 MHz, dmso) Î´ 163.70, 152.81, 147.44, 137.69,
136.69, 132.14, 127.69, 123.21, 121.38, 120.48, 118.69, 118.66, 112.10, 111.86,
40.84, 25.37 ppm; UV (Î»max nm) 286; IR
vmax (cm−1) 3392, 1628, 1545,
739, 692; HRMS (ESI) calcd for C16H14BrN3O
[M+H]− 342.0247, found 342.0248.</p><!><p>Compound was synthesized using the general procedure for coupling
carboxylic acids to primary amines using PyBOP. Tryptamine (1.56 g, 9.74 mmols)
and picolinic acid (400 mg, 3.25 mmols) were coupled to afford 39
as a tan solid (475 mg, 55%). 1H NMR (300 MHz,
Chloroform-d) Î´ 8.74 (s, 1H), 8.49 (d,
J = 4.7 Hz, 1H), 8.36 – 8.27 (m, 1H), 8.24 (d,
J = 7.8 Hz, 1H), 7.85 – 7.74 (m, 1H), 7.68 (d,
J = 7.7 Hz, 1H), 7.36 (dd, J = 7.5, 4.9
Hz, 2H), 7.24 – 7.17 (m, 1H), 7.17 – 7.08 (m, 1H), 7.03 (s, 1H),
3.85 (q, J = 7.0 Hz, 2H), 3.12 (t, J = 7.0 Hz,
2H); 13C NMR (75 MHz, cdcl3) Î´ 164.51, 149.87,
148.08, 137.35, 136.49, 127.32, 126.13, 122.27, 122.11, 121.93, 119.22, 118.72,
112.67, 111.37, 39.86, 25.55 ppm; UV (Î»max nm) 286; IR
vmax (cm−1) 3244, 1662, 1522,
1430, 747; HRMS (ESI) calcd for C16H15N3O
[M+H]+ 266.1287, found 266.1282.</p><!><p>Compound was synthesized using the methods previously reported by
Richards. Spectral data were consistent with previous reports.14</p><!><p>7 (500 mg, 1.35 mmols) was dissolved in 15 mLs DMF and cooled to
0°C under argon. Sodium hydride (59 mg, 1.48 mmols) was added in portions
to the solution which was then stirred at 0°C for 30 mins. Butyl iodide
(460 Î¼L, 4.05 mmols) was then added to the solution and stirred at RT for
18 hours. The reaction was poured into 75 mLs EtOAc and 25 mLs of deionized
water, the aqueous layer was discarded and the organic was further washed thrice
with water, twice with 25 mLs 1N HCl, and once with 25 mLs brine. The organic
layer was then dried with anhydrous magnesium sulfate and evaporated under
reduced pressure. The crude solid was purified by flash chromatography
(5–20% EtOAc/Hexanes) to afford 40b as a brown oil (299 mg,
52%). 1H NMR (300 MHz, Chloroform-d) Î´ 7.58
(s, 1H), 4.60 – 4.30 (m, 2H), 1.68 (p, J = 7.6 Hz, 2H),
1.39 (dt, J = 14.9, 7.4 Hz, 2H), 1.02 – 0.93 (m, 3H);
13C NMR (101 MHz, cdcl3) Î´ 171.25, 125.09,
122.64, 119.02, 100.45, 95.57, 50.00, 32.33, 19.87, 13.83 ppm; UV
(Î»max nm) 324; IR vmax
(cm−1) 2959, 1675, 1360, 830, 683; HRMS (ESI) calcd for
C10H10Br2Cl3NO
[M+H]− 421.8122, found 421.8130.</p><!><p>Compound was synthesized using the methods previously reported by
Richards. Spectral data were consistent with previous reports.14</p><!><p>Compound was synthesized using the methods previously reported by
Richards. Spectral data were consistent with previous reports.14</p><!><p>Compound was synthesized using the general procedure for condensing
primary amines with 2,2,2-trichloroacetyl pyrroles with tryptamine (179 mg, 1.11
mmols) and 40b (238 mg, 0.56 mmols) as condensation partners to
afford 41b as a tan solid (176 mg, 68%). 1H NMR (400
MHz, DMSO-d6) Î´ 10.83 (s, 1H), 8.34 (s, 1H),
7.56 (d, J = 7.8 Hz, 1H), 7.36 (d, J = 8.0 Hz,
1H), 7.18 (s, 1H), 7.08 (t, J = 7.5 Hz, 1H), 7.03 – 6.92
(m, 2H), 4.42 (t, J = 7.3 Hz, 2H), 3.49 (q, J
= 6.8 Hz, 2H), 2.93 (t, J = 7.3 Hz, 2H), 1.59 (p,
J = 7.6 Hz, 2H), 1.25 (dq, J = 14.3, 7.1
Hz, 2H), 0.86 (s, 3H); 13C NMR (75 MHz, cdcl3) Î´
160.45, 136.43, 127.25, 127.18, 122.21, 122.16, 119.43, 118.58, 113.74, 112.50,
111.41, 110.53, 98.01, 48.03, 39.83, 33.00, 25.30, 19.73, 13.77 ppm; UV
(Î»max nm) 286; IR vmax
(cm−1) 3281, 1630, 1421, 807, 736; HRMS (ESI) calcd for
C19H21Br2N3O
[M+H]− 463.9978, found 463.9980.</p><!><p>Compound was synthesized using the general procedure for condensing
primary amines with 2,2,2-trichloroacetyl pyrroles with tryptamine (170 mg, 1.06
mmols) and 40c (245 mg, 0.53 mmols) as condensation partners to
afford 41c as a tan solid (143 mg, 53%). 1H NMR (300
MHz, DMSO-d6) Î´ 10.80 (s, 1H), 8.42 (s, 1H),
7.52 (d, J = 7.9 Hz, 1H), 7.29 (dt, J = 14.8,
8.4 Hz, 4H), 7.04 (dq, J = 21.3, 7.3 Hz, 6H), 5.76 (s, 2H),
3.46 – 3.39 (m, 2H), 2.86 (t, J = 7.2 Hz, 2H);
13C NMR (101 MHz, dmso) Î´ 159.65, 137.66, 136.25, 128.53,
128.53, 128.07, 127.24, 127.18, 126.35, 122.70, 120.95, 118.27, 114.55, 111.72,
111.41, 110.35, 97.90, 50.07, 39.73, 25.10 ppm; UV (Î»max nm)
290; IR vmax (cm−1) 3398, 1626,
1327, 772, 692; HRMS (ESI) calcd for
C22H19Br2N3O
[M+H]− 497.9822, found 497.9827.</p><!><p>Compound was synthesized using the methods previously reported by Essa.
Spectral data were consistent with previous reports.17</p><!><p>Compound was synthesized using the methods previously reported by Essa
and was isolated as a side product in this procedure along with the major
product 42. Spectral data were consistent with previous
reports.17</p><!><p>Compound was synthesized using the general procedure for condensing
primary amines with 2,2,2-trichloroacetyl pyrroles with tryptamine (376 mg, 2.34
mmols) and 42 (545 mg, 1.17 mmols) as condensation partners to
afford 44 as a white solid (121 mg, 21%). 1H NMR (400
MHz, DMSO-d6) Î´ 12.32 (s, 1H), 10.81 (s, 1H),
8.19 (s, 1H), 7.57 (d, J = 7.8 Hz, 1H), 7.34 (d,
J = 8.0 Hz, 1H), 7.15 (s, 1H), 7.06 (t, J
= 7.5 Hz, 1H), 6.97 (t, J = 7.3 Hz, 1H), 6.90 (s, 1H), 3.48 (q,
J = 6.5 Hz, 2H), 2.90 (t, J = 7.2 Hz, 2H);
13C NMR (101 MHz, cd3od) Î´ 161.37, 138.12,
133.82, 128.74, 123.44, 122.30, 119.85, 119.58, 119.31, 113.29, 112.20, 82.15,
76.24, 41.46, 26.46 ppm; UV (Î»max nm) 288; IR
vmax (cm−1) 3556, 2396, 1597,
1451, 747; HRMS (ESI) calcd for
C15H13I2N3O
[M+H]− 503.9075, found 503.9075.</p><!><p>Compound was synthesized using the general procedure for condensing
primary amines with 2,2,2-trichloroacetyl pyrroles with tryptamine (516 mg, 3.22
mmols) and 43 (545 mg, 1.61 mmols) as condensation
partners to afford 45 as a tan solid (172 mg, 28%). 1H
NMR (400 MHz, DMSO-d6) Î´ 11.80 (s, 1H), 10.81
(s, 1H), 8.22 (s, 1H), 7.58 (d, J = 7.8 Hz, 1H), 7.35 (d,
J = 8.8 Hz, 1H), 7.17 (s, 1H), 7.07 (t, J
= 7.5 Hz, 1H), 7.03 – 6.94 (m, 2H), 6.91 (s, 1H), 3.50 (q,
J = 6.6 Hz, 2H), 2.92 (t, J = 7.4 Hz, 2H);
13C NMR (101 MHz, cd3od) Î´ 162.28, 138.06,
129.08, 128.71, 127.78, 123.39, 122.29, 119.58, 119.30, 118.13, 113.30, 112.18,
60.99, 41.44, 26.49 ppm; UV (Î»max nm) 284; IR
vmax (cm−1) 3341, 1633, 1548,
752, 592; HRMS (ESI) calcd for C15H14IN3O
[M+H]− 378.0108, found 378.0108.</p><!><p>Compound was synthesized using the general procedure for coupling
carboxylic acids to primary amines using PyBOP.
(1H-indol-3-yl)methanamine (362 mg, 2.47 mmols) and
6-bromopicolinic acid (250 mg, 1.24 mmols) were coupled to afford
46 as a red solid (22 mg, 6.9%). 1H NMR (400 MHz,
DMSO-d6) Î´ 10.95 (s, 1H), 8.82 (s, 1H),
8.08 (d, J = 7.5 Hz, 1H), 7.93 (t, J = 7.9 Hz,
1H), 7.82 (d, J = 7.9 Hz, 1H), 7.67 (d, J =
7.9 Hz, 1H), 7.35 (d, J = 8.2 Hz, 1H), 7.31 (s, 1H), 7.07 (t,
J = 7.5 Hz, 1H), 6.97 (t, J = 7.5 Hz, 1H),
4.64 (d, J = 6.0 Hz, 2H); 13C NMR (101 MHz,
cdcl3) Î´ 162.75, 151.07, 140.61, 139.68, 136.48, 130.72,
126.64, 123.64, 122.39, 121.38, 119.88, 118.93, 112.26, 111.48, 35.16 ppm; UV
(Î»max nm) 286; IR vmax
(cm−1) 3434, 1665, 1515, 759, 492; HRMS (ESI) calcd for
C15H12BrN3O [M+Na]+ 352.0056,
found 352.0049.</p><!><p>Compound was synthesized using the general procedure for condensing
primary amines with 2,2,2-trichloroacetyl pyrroles with
(1H-indol-3-yl)methanamine (182 mg, 1.25 mmols) and
42 (290 mg, 0.62 mmols) as condensation partners to afford
47 as a pink solid (146 mg, 48%). 1H NMR (400 MHz,
DMSO-d6) Î´ 12.31 (s, 1H), 10.92 (s, 1H),
8.31 (s, 1H), 7.59 (d, J = 7.8 Hz, 1H), 7.35 (d,
J = 8.1 Hz, 1H), 7.27 (s, 1H), 7.07 (t, J
= 7.5 Hz, 1H), 6.96 (t, J = 7.5 Hz, 1H), 6.92 (s, 1H), 4.55 (d,
J = 5.3 Hz, 2H) 13C NMR (101 MHz, dmso) Î´
158.25, 136.31, 132.93, 126.47, 123.89, 121.13, 118.74, 118.50, 118.24, 112.31,
111.41, 83.00, 76.03, 33.94 ppm; UV (Î»max nm) 290; IR
vmax (cm−1) 3386, 3145, 1643,
1543, 809; HRMS (ESI) calcd for
C14H11I2N3O
[M+H]− 489.8918, found 489.8915.</p>