A process for preparing S type 2-substituted hydroxy-2-indolidinyl-butyric ester compound \x9bII!: ##STR1## wherein R.sup.o is residue of nitrogen-containing fused heterocyclic carboxylic acid having absolute configuration of "R"(in which the nitrogen atom is protected), R.sup.1 and R.sup.2 are lower alkyl group, and E is ester residue, which is useful as an intermediate for preparing camptothecin derivatives having antitumor activities, which comprises 2-ethylating 2-substituted hydroxy-2-indolidinylacetic ester compound \x9bI!: ##STR2## wherein the symbols are as defined above.
一种制备S型2-取代羟基-2-
吲哚丁酸酯化合物的方法\x9bII!:##STR1##其中R.sup.o是氮杂
环羧酸的残基,具有“R”的绝对构型(其中氮原子被保护),R.sup.1和R.sup.2是较低的烷基基团,E是酯基团,可用作制备具有抗肿瘤活性的
紫杉醇衍
生物的中间体,包括对2-取代羟基-2-
吲哚丁酸乙酯化合物进行乙酰化的步骤\x9bI!:##STR2##其中符号如上定义。