ABSTRACT A unified approach has been developed to construct the characteristic 4a,9a‐heterocycle‐fused tetrahydrocarbazole skeleton present in various monoterpene indole alkaloids. This method hinges on a unique chiral bisphosphine BIBOP‐catalyzed asymmetric Staudinger/aza‐Wittig reaction followed by imine cyclization. Compared to conventional mono‐ and bisphosphines, BIBOP exhibits more robust performance across diverse reaction settings. Mechanistic studies revealed that BIBOP(O), the mono‐oxidized derivative of BIBOP, could also promote the asymmetric transformation with excellent enantioselectivity. Leveraging the developed method, we have accomplished a concise total synthesis of (–)‐minfiensine and a formal synthesis of (+)‐aspidophylline A. This work not only establishes a versatile platform for the synthesis of diverse monoterpene indole alkaloids but also offers a new class of organophosphine catalysts applicable to asymmetric Staudinger/aza‐Wittig reaction as well as related transformations.
Dong et al. (Wed,) studied this question.