Patent ID: 8206692

Claim:
A compound of formula (I) in which Y—R 1 defines a leaving group and R 1 is a C 1 -C 20 alkyl, alkenyl or alkynyl compound, optionally carrying one or more functional groups selected from hydroxy, carbonyl, carboxyl, amino, amido groups and halogen atoms, or, in which —Y—R 1 is OH or SH, and, in which: the dotted line represents a double bond, in case of which X is selected from CR 4 , and N, or the dotted line represents a single bond, in case of which X is selected from NR 4 , CR 4 R 5 , O and S, with R 4 and R 5 being, independently of each other, selected from H and C 1 -C 10 alkyl, alkenyl or alkynyl moieties.