R0 is hydrogen, or an aliphatic, cycloaliphatic or aromatic radical containing from 1 to 9 carbon atoms, or OR2, or ##STR28## R1 is hydrogen or an aliphatic, cycloaliphatic or aromatic radical containing from 1 to 9 carbon atoms, or R3 O R4, or ##STR29{HEAD ~ ## R2} is {TAIL ~ hydrogen}, or an aliphatic, cycloaliphatic or aromatic radical having from 1 to 9 carbon atoms, or R3 