R12 is a hydrogen atom, an alkanoyl group having 2 to 6 carbon atoms unsubstituted or substituted with 1 to 3 group(s) selected from ???a halogen atom, and an amino group unsubstituted or substituted with 1 or 2 alkyl group(s) having 1 to 6 carbon atom(s)???, a vinylcarbonyl group, an alkyl group having 1 to 6 carbon atom(s), a cyclic alkyl group having 3 to 6 carbon atoms, or ???an aryl group, or