There are described compounds of the formula
in which R' is hydrogen or C1-6 alkyl, R2 is hydrogen, C1-6 alkyl or C3-6 alkenyl, R3 is hydrogen or C1-6 alkyl, R4 is hydrogen or an N-protecting group, n is 2, 3, 4 or 5, and X is oxygen, sulphur or -CH2-, provided that when X is -CH2- n is 0; and salts thereof. The compounds in which R4 is hydrogen have pharmaceutical activity.
所述化合物的
化学式为
其中 R' 是氢或 C1-6 烷基,R2 是氢、C1-6 烷基或 C3-6 烯基,R3 是氢或 C1-6 烷基,R4 是氢或 N-保护基团,n 是 2、3、4 或 5,X 是氧、
硫或 -
CH2-,条件是当 X 是 - - 时 n 为 0;及其盐类。其中 R4 为氢的化合物具有药物活性。