. . . "; a cycloalkylcarbonyloxy group having a carbon number of 6-9, a benzoyloxy group, or an (alkyl having a carbon number of 1-12)-substituted benzoyloxy group (in this regard, when R9 is a hydrogen atom or a methyl group, R7 or R9 in a formula (II) mentioned later does not represent a hydroxy group or an alkanoiloxi group having a carbon number of 1-25); or each pair of substituents R2 and R3, R3 an" . .