Regio- and stereoselective reduction of bicyclic imides for the asymmetric synthesis of highly substituted pyrrolidines

Article abstract of DOI:10.1016/S0040-4020(01)90230-3

1,3-dipolar cycloaddition of N-phenylmaleimide with azomethine ylides generated from α-aminonitrile or α-aminoester oxazolidines gave bicyclic imides, which were reduced regio- and stereoselectively to hydroxylactams. In the aminonitrile series, reduction with NaBH₄/CeCl₃ at low temperature gave a single hydroxylactam in high yield. In the aminoester series the regioselectivity was more dependent on the structure, and other conditions (LiBEt₃H) were found to obtain a single hydroxylactam which corresponds to a reverse regiochemistry when compared with the aminonitrile series.