| 摘要 |
A process for the preparation of compound of formula (I); wherein R<1> is hydrogen, linear, branched or cyclic lower alkyl, cyclohexyl, allyl, propargyl or benzyl; R<2> is hydrogen, methyl, ethyl or propyl; or R<1> and R<2> together with the nitrogen to which they are attached form a cyclic moiety of three to eight-membered ring, with or without a hetero atom like nitrogen or oxygen; R<3> is hydrogen or lower alkyl; R<4> and R<5> are the same or different and each is a lower alkyl; comprising reacting compound of formula (II); wherein R<3>, R<4> and R<5> are as defined above, with compound of formula (III); wherein R<1>and R<2> are as defined above, in the presence of a base, and further resolving the compound of formula (I) to obtain (S)-isomer of compound of formula (I), substantially free of R-isomer. |
