-continued  -continued  US 10,054,853 B2  97  98  The structure of the acid labile group R $^{6 }$in formula (e) is  not particularly limited as long as it is deprotected to  generate a hydroxyl group under the action of acid. Typical  acid labile groups are groups of acetal or ketal structure and  alkoxycarbonyl groups, with their examples being shown  below. 