Stereoselective synthesis of four possible isomers of streptopyrrolidine

The synthesis of (4R,5R)-streptopyrrolidine (1), (4S,5R)-streptopyrrolidine (2) (4R,5S)-streptopyrrolidine (3) and (4S,5S)-streptopyrrolidine (4) have been achieved in a concise and highly efficient manner via a highly stereoselective aldol type reaction with the trimethylsilyl enolate of ethyl acetate and Lewis acid mediated lactamization as the key reactions in ≈42% yield over six steps starting from D-phenylalanine and L-phenylalanine, respectively. The absolute configuration of the natural product was shown to be (4S,5S) by comparing its spectral and analytical data with the reported values.