| abstract |
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)CH 2 COOH, -CH 2 CH(OH)COOH or -CH(OH)CH(OH)COOH; and R' is independently selected from H or OH. |