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In formula (A-2), RL$^{31 }$and RL $^{32 }$are hydrogen or straight, branched or cyclic alkyl groups of 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms. Exemplary alkyl groups include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, cyclopentyl, cyclohexyl, 2-ethylhexyl, and n-oc- tyl. RL $^{33 }$is a monovalent hydrocarbon group ofl to 18 carbon atoms, preferably 1 to 10 carbon atoms, which may contain a heteroatom such as oxygen, examples of which include straight, branched or cyclic alkyl groups and substituted forms of such alky I groups in which some hydrogen atoms are replaced by hydroxyl, alkoxy, oxo, amino, alkylamino or the like. Illustrative examples of the substituted alkyl groups are shown below. 

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A pair ofRL$^{31 }$and RL 32 , RL$^{31 }$and RL 33 , or RL $^{32 }$and RL 33 may bond together to form a ring with the carbon and oxygen atoms to which they are attached. Each ofRL 31 , RL $^{32 }$and RL 33 is a straight or branched alkylene group of 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms when they form a ring, while the ring preferably has 3 to 10 carbon atoms, more preferably 4 to 10 carbon atoms. 

Examples of the acid labile groups of formula (A-1) include tert-butoxycarbony I, tert-butoxycarbony lmethy I, tert-amy loxycarbonyl, tert-amy loxycarbonylmethy I, 1, 1-di› ethylpropy loxycarbony I, 1, 1-diethy lpropy loxycarbonylm› ethyl, 1-ethylcyclopentyloxycarbonyl, 1-ethylcyclopenty- loxycarbony !methyl, 1-ethy 1-2-cyclopenteny loxycarbony I, 1-ethy 1-2-cyclopenteny loxycarbonylmethyl, 1-ethoxy› ethoxycarbony lmethy l, 2-tetrahydropyranyloxycarbonyl› methyl, and 2-tetrahydrofuranyloxycarbonylmethyl groups. 

Also included are substituent groups having the formulae (A-1)-1 to (A-1)-10. 

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Herein RL$^{37 }$is each independently a straight, branched or cyclic C$_{1 }$-C$_{10 }$alkyl group orC$_{6}$-C$_{20 }$aryl group. RL$^{33 }$is hydro› gen or a straight, branched or cyclic C$_{1 }$-C$_{10 }$alkyl group. RL 39 is each independently a straight, branched or cyclic C$_{2}$-C$_{10 }$ alkyl group or C$_{6}$-C$_{20 }$aryl group. Al is an integer of Oto 6. 

Of the acid labile groups of formula (A-2), the straight and branched ones are exemplified by the following groups hav› ing formulae (A-2)-1 to (A-2)-35. 

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-continued 

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