Diastereo-, enantio-, and chemoselective sequential allylations of N,N′-alloc 3,3′-dimeric 2-oxindoles: formal total synthesis of (–)-idiospermuline

Abstract

Calycanthaceae alkaloids feature two neighboring carbon atoms that are central to their structure (quaternary stereocenters) and a long, flexible bond between them [elongated labile C3a–C3a′s bond] with impressive biological activities. Herein, we envisioned an expeditious approach to dimeric hexahydropyrrolo[2,3b]-indoline via an unprecedented catalytic asymmetric sequential allylation of N,N′-alloc 3,3′-dimeric 2-oxindoles with eventual total syntheses of naturally occurring (−)-calycanthidine and a formal total synthesis of (−)-idiospermuline.