合成路线1

In a related procedure, aldehyde (XLVI) was condensed with triphenylmethanesulfenamide (LIV), producing the S-trityl sulfenimine (LV). Aldol-type condensation of (LV) with the silyloxy pyrrole (XLIX) gave rise to a diastereoisomeric mixture of adducts from which the desired isomer (LVI) was isolated as the major compound. Diastereoselectivity was increased using triflic acid as the condensation catalyst. Conjugate addition to (LVI) of propenylmagnesium bromide in the presence of CuBr yielded (LVII). Conversion of pyrrolidinone (LVII) to the cyano pyrrolidine (LVIII) was accomplished by the same sequence as above. Then, acidic cleavage of the tritylsulfanyl group of (LVIII), followed by N-acetylation, furnished the intermediate (XXXVII), which was finally processed as in the preceding methods.