Total Synthesis, Revised Structure, and Biological Evaluation of Elgonene B and Analogues.

Herein, we report the first total synthesis of elgonene B and its congeners, thus resulting in a revision of the configuration at the C-6 carbon of the originally proposed structure of elgonene B. This synthetic approach demonstrates the utility of several important reactions such as the chiral oxazaborolidinium ion-catalyzed Diels-Alder reaction, Ando's Horner-Wadsworth-Emmons olefination, and the intermolecular Nozaki-Hiyama-Kishi reaction as key steps. Additionally, the study explores the cytotoxic and antibacterial activities of elgonene B and its congeners (1-4).

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.