Compounds of the formula (I) A is OH or a carbonyl group, n is 0 or 1, R is an alkyl radical having from 1 to 4 carbon atoms, in particular methyl, ethyl, n-propyl, iso -propyl, n-butyl or t-butyl; or a residue of a hydroxy carboxylic acid, in particular the residue -CH(OH)COOH, -CH(OH)CH2COOH, -CH2CH(OH)COOH or -CH(OH)CH(OH)COOH; and R' is independently selected from H or OH.
化合物的公式(I)中,A是OH或羰基,n为0或1,R是具有1至4个碳原子的烷基基团,特别是甲基、乙基、正丙基、异丙基、正丁基或叔丁基;或者是羟基
羧酸的残基,特别是残基-CH(OH)COOH,-CH(OH)CH2COOH,-CH2CH(OH)COOH或-CH(OH)CH(OH)COOH;而R'独立地选择自H或OH。