group, L1 represents a bond or a substituted or unsubstituted alkylene group, provided that when L1 is a bond, at least one of R12, R13, R14, R15 and R16 is --S--R18 or --SO--R18, R17 represents a hydrogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted acyl group, and Y1 represents a hydrogen atom or a substituted carbonyl group represented by the following form