A compound having formula (2): ##STR1## wherein R represents hydrogen, a straight or branched C.sub.1-10 alkyl group, a C.sub.7-11 aralkyl group or a C.sub.2-10 carboacyl group and m stands for 1 to 5.
化合物
化学式为(2): ##STR1## 其中R代表氢、直链或支链C.sub.1-10烷基、C.sub.7-11芳基烷基或C.sub.2-10羰基烷基,m代表1至5。