Patent ID: 8283481

Claim:
A compound of formula (I): wherein: R 1 is —SR 10 , —O—C(O)—R 11 , —NR 12 R 13 , where R 10 is a C 1-8 -alkyl group or a phenyl group unsubstituted or substituted by a C 1-4 -alkyl group, R 11 is a thiophenenyl, furanyl or pyrrolyl group, R 12 is H or a C 1-4 -alkyl group and R 13 is a C 1-8 -alkyl group or a phenyl group unsubstituted or substituted by a C 1-4 -alkyl group; R 2 is H or a C 1-4 -alkyl group; R 3 and R 4 are independently H or C 1-4 -alkyl groups; R 5 and R 6 are independently H, OH or OR 14 , or taken together are ═O, where R 14 is a protecting group; R 7 is H or a C 1-4 -alkyl group; and, R 8 is H, R 9 is OH and R 15 is H, or R 15 is H and R 8 and R 9 taken together are —O—, or R 9 is OH and R 8 and R 15 taken together form a bond; and, R 18 and R 19 are both H, or R 18 and R 19 taken together form a bond, or a plant physiologically acceptable salt thereof.