US 2020/0133122 Al  72  Apr. 30, 2020  diethylpropyl, 2-cyclopentylpropan-2-yl, 2-cyclohexylpro› pan-2-yl, 2-(bicyclo[2.2.l]heptan-2-yl)propan-2-yl, 2-(ada› mantan-1-yl)propan-2-yl,  1-ethylcyclopentyl,  1-butylcyclopentyl, 1-ethylcyclohexyl, 1-butylcyclohexyl,  l-ethyl-2-cyclopentenyl, l-ethyl-2-cyclohexenyl, 2-methyl- 2-adamantyl, and 2-ethyl-2-adamantyl. Exemplary trialkyl› silyl groups include trimethylsilyl, triethylsilyl, and dim› ethyl-tert-butylsilyl. Exemplary oxoalkyl groups include  3-oxocyclohexyl, 4-methyl-2-oxooxan-4-yl, and 5-methyl- 2-oxooxolan-5-yl. Letter x is an integer of O to  6.  [0109]  In formula (L3),  RLos  is an optionally substituted  C 1  -Cg alkyl group or an optionally substituted  CcC$_{20 }$ aryl  group. The optionally substituted alkyl group may be  straight, branched or cyclic and examples thereof include  methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert› butyl, tert-pentyl, n-pentyl, n-hexyl, cyclopentyl and cyclo› hexyl, and substituted forms of the foregoing in which some  hydrogen is substituted by hydroxyl, alkoxy, carboxyl,  alkoxycarbonyl, oxo, amino, alkylamino, cyano, mercapto,  alkylthio, sulfa or the like. Examples of the optionally  substituted aryl groups include phenyl, methylphenyl, naph› thyl, anthryl, phenanthryl, and pyrenyl, and substituted  forms of the foregoing in which some hydrogen is substi› tuted by hydroxyl, alkoxy, carboxyl, alkoxycarbonyl, oxo,  amino, alkylamino, cyano, mercapto, alkylthio, sulfa or the  like. Letter y is equal to O or 1, z is an integer ofO to 3, and  2y+z is equal to 2 or 3.  [0110]  In formula (L4),  RL $^{06 }$is an optionally substituted  C 1  -Cg alkyl group or an optionally substituted C 6 -C 20  aryl  group. Examples of the alkyl and aryl groups are the same  as exemplified for  RL0 5 •  [0111]  RL 07  to RL 16  are each independently hydrogen or an  optionally substituted C 1  -C 15  monovalent hydrocarbon  group.  Suitable hydrocarbon groups  include  straight,  branched or cyclic alkyl groups such as methyl, ethyl,  propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-pentyl,  n-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, cyclopentyl,  cyclohexy I, cyclopenty lmethy I, cyclopenty lethy I, cyclopen› ty lbuty l, cyclohexylmethyl, cyclohexylethyl and cyclohex› ylbutyl, and substituted forms of the foregoing in which  some hydrogen is substituted by hydroxyl, alkoxy, carboxyl,  alkoxycarbonyl, oxo, amino, alkylamino, cyano, mercapto,  alkylthio, sulfa or the like.Alternatively, two ofRL 07  to RL 16  may bond together to form a ring with the carbon atom to  which they are attached (for example, a pair of RL 07  and  RLOg’ RLo7 and  RLo9,  RLo7 and  RLio,  RLog and  RLio, RLo9  and  RLI 0 ,  RL 11  and RL 12 , RL 13  and RL 14 , or a similar pair form  a ring). Each of RL 07  to RL 16  represents a divalent C 1  -C 15  hydrocarbon group when they form a ring, examples of  which are the ones exemplified above for the monovalent  hydrocarbon groups, with one hydrogen atom being elimi› nated. Two of RL 07  to RL 16  which are attached to vicinal  carbon atoms may bond together directly to form a double  bond (for example, a pair ofRL 07  and  RL 09 , RL $^{09 }$and  RLI 5 ,  RL 13  and  RLI 5 ,  RL 14  and RL 15 , or a similar pair).  [0112]  Of the acid labile groups having formula (Ll), the  straight and branched ones are exemplified by the following  groups, but not limited thereto.  [0113]  Of the acid labile groups having formula (Ll ), the  cyclic ones are, for example, tetrahydrofuran-2-yl, 2-meth› yltetrahydrofuran-2-yl, tetrahydropyran-2-yl, and 2-methyl› tetrahydropyran-2-yl.  [0114]  Examples of the acid labile group having formula  (L2) include tert-butoxycarbonyl, tert-butoxycarbonylm› ethyl,  tert-pentyloxycarbonyl,  tert-pentyloxycarbonylm› ethyl, 1, 1-diethylpropyloxycarbonyl, 1, 1-diethylpropyloxy› carbonylmethyl,  1-ethylcyclopentyloxycarbonyl,  1-ethy lcyclopenty loxycarbony lmethy I, 1-ethy 1-2-cyclopen› tenyloxycarbonyl,  1-ethy 1-2-cyclopenteny loxycarbony !m› ethyl, 1-ethoxyethoxycarbonylmethyl, 2-tetrahydropyrany› loxycarbonylmethyl,  and  2-tetrahydrofuranyloxycarbonylmethyl groups.  [0115]  Examples of the acid labile group having formula  (L3) include 1-methylcyclopentyl, 1-ethylcyclopentyl, 1-n› propylcyclopentyl, 1-isopropylcyclopentyl, 1-n-butylcyclo› pentyl,  1-sec-butylcyclopentyl,  1-cyclohexylcyclopentyl,  1-( 4-methoxy-n-butyl)cyclopentyl,  1-methylcyclohexyl,  1-ethy lcyclohexy I, 3-methy 1-1-cyclopenten-3-y I, 3-ethy 1-1- cyclopenten-3-y l, 3-methyl-1-cyclohexen-3-yl, and 3-ethyl› l-cyclohexen-3-yl groups.  [0116]  Of the acid labile groups having formula (L4),  groups having the following formulas (L4-1) to (L4-4) are  preferred. 