Enantioselective synthesis of intermediate used in preparation of physostigmine

PURPOSE: To effectively obtain an enantiomer useful for preparation of (+)- physostigmine with a high optical purity in high yield by treating a enantiomer- contg. mixture of specified alkylated oxyindole under specified conditions. CONSTITUTION: A mixture containing first and second enantiomers of alkylated oxyindoles selected from formula I or II (R is methyl, ethyl or benzyl), wherein the first enantiomer exists more than the second enantiomer, is treated with a suitable recrystallizing solvent such as methanol to dissolve selectively the first enantiomer existing much, and form a soln. and precipitates of the mixture contg. at least the second enantiomer. The soln. is separated from the precipitates to obtain the objective enantiomer. COPYRIGHT: (C)1994,JPO