| abstract |
S-substituted 2-substituted hydrides, useful as intermediates for preparing camptothecin derivatives having antitumor activity, including 2-ethylation of 2-substituted hydroxy-2-indolidinylacetic acid ester compound 1 Process for preparing oxy-2-indolidinylbutyric acid ester compound (2):n n n n n n n n n n Wherein R 0 is a residue of the nitrogen-containing fused heterocyclic carboxylic acid of the absolute configuration "R", wherein the nitrogen atom is protected, R 1 and R 2 are lower alkyl groups, and E is an ester residue. ,n n n n n n n n n n [Symbols are the same as the above definition]. |