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Examples of the acid labile groups of formula (L2) include tert-butoxycarbonyl, tert-butoxycarbonylmethyl, tert-amy- loxycarbony I, tert-amy loxycarbony !methyl, 1, 1-diethy lpro- py loxycarbony I, 1, 1-diethy lpropyloxycarbony lmethy I, 1-ethylcyclopentyloxycarbonyl, 1-ethylcyclopentyloxycar› bonylmethyl, l-ethyl-2-cyclopentenyloxycarbonyl, l-ethyl- 2-cyclopenteny loxycarbony lmethy I, 1-ethoxyethoxycarbon- y lmethy I, 2-tetrahydropyrany loxycarbony !methyl, and 2-tetrahydrofuranyloxycarbonylmethyl groups. 

Examples of the acid labile groups of formula (L3) include 1-methylcyclopentyl, 1-ethylcyclopentyl, 1-n-propylcyclo- pentyl, 1-isopropylcyclopentyl, 1-n-butylcyclopentyl, 1-sec› buty lcyclopenty I, 1-cyclohexy lcyclopenty I, 1-( 4-methoxy› buty l)cyclopentyl, l-(bicyclo[2.2.1 ]heptan-2-yl) cyclopentyl, l-(7-oxabicyclo[2.2.1 ]heptan-2-yl)cyclopentyl, 1-methylcyclohexyl, 1-ethylcyclohexyl, l-methyl-2-cyclo- penteny I, 1-ethy 1-2-cyclopenteny I, 1-methy 1-2-cyclohex› eny l, and l-ethyl-2-cyclohexenyl groups. 

Of the acid labile groups having formula (L4), groups having the following formulas (L4-1) to (L4-4) are preferred. 

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In formulas (L4-1) to (L4-4), the broken line denotes a bonding site and direction. RL 41 is each independently a monovalent hydrocarbon group, typically a straight, branched or cyclic C$_{1 }$-C$_{10 }$alkyl group, such as methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl and cyclohexyl. 

For formulas (L4-1) to (L4-4), there can exist enantiomers and diastereomers. Each of formulae (L4-1) to (L4-4) collec› tively represents all such stereoisomers. Such stereoisomers may be used alone or in admixture. 

For example, the general formula (L4-3) represents one or a mixture of two selected from groups having the following general formulas (L4-3-l) and (L4-3-2). 

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Similarly, the general formula (L4-4) represents one or a mixture of two or more selected from groups having the following general formulas (L4-4-1) to (L4-4-4). 

