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Antifertility agents. 38. Effect of the side chain and its position on the activity of 3,4-diarylchromans.

In a study of the effect of the substituent on the receptor binding affinity (RBA), estrogenicity, and antiimplantation (AI) activity in trans-3,4-diarylchromans, it has been found that demethylation of trans-2, 2-dimethyl-3-phenyl-4-[p-(beta-pyrrolidinoethoxy)phenyl]-7-methoxychroman (centchroman, 1) to the corresponding 7-hydroxy compound (7) results in a 20-fold increase in RBA (112%) without any appreciable change in AI activity. On the other hand, absence of the pyrrolidinoethyl group from the 4-phenyl residue (6) leads to a drop in both RBA and AI activity. A chain length of two to three carbon atoms and a pyrrolidino ring appear to be necessary for activity in these compounds. It has been found that while the trans isomers with the tertiary aminoalkoxy side chain in the para position of the 4-phenyl radical were the most active, in the corresponding cis-chromans and chromenes, analogues with this chain in the meta position were most active; the ortho substituted compounds of all these series were inactive. In 3-phenyl-substituted compounds, the trans isomer carrying the p-hydroxy substituent (33) was found to be the most active; the corresponding pyrrolidinoethyl ether (13) showed a lower order of activity. The implication of these observations on the mapping of the different subsites on the receptor has been discussed.