S TYPE 2-SUBSTITUTED HYDROXY-2-INDOLIDINYLBUTYRIC ESTER COMPOUNDS AND PROCESS FOR PREPARATION THEREOF

摘要

The present invention is directed to a process for preparing S type 2-substituted hydroxy-2-indolidinylbutyric ester compound ¢II!: (see fig. II) wherein R0 is a residue of nitrogen-containing fused heterocyclic carboxylic aci d having absolute configuration of "R" (in which the nitrogen atom is protected), R1 and R2 are lower alkyl groups, and E is an ester residue. The compound of the present invention is useful as an intermediate for preparing camptothecin derivatives having antitumor activities, which comprises 2-ethylating 2-substitu ted hydroxy-2-indolidinylacetic ester compound ¢I!: (see fig. I) wherein R0, R1, R2 and E are as defined above.