. . "and R2 are as defined above; --(CHOR1)(CH2 R6) wherein R1 is as defined above and R6 is a halogen preferably fluorine, chlorine, iodine or bromine; --CH2 R6 wherein R6 is as defined above; --CH2 O--CO--R4 wherein R4 is as defined above; or --CHR9 OH wherein R9 is (C1-C5)-alkyl; with the proviso that when R1 is hydrogen and R3 is --(CHOH)(CH2 OH), R2 cannot be methyl, n-butyl or benzyl and that whe" . .