| 摘要 |
A compound of formula (I), or a pharmaceutically acceptable salt thereof: wherein X is -CH2O, -CH2 or -CH(CH2OR8)O where R8 is hydrogen or acyl; Y is O or S; R1 is hydroxy or amino; R2 is amino or hydrogen; R3 is hydrogen or, when X is CH2O and Y is O, R3 may be CH2OR9 where R9 is hydrogen or acyl; R4 and R5 are both hydrogen or the same C1-4 alkyl group; and R6 and R7 are independently C2-7 alkanoyloxy or benzoyloxy wherein the phenyl moiety is optionally substituted. |
