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

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[2,3<i>b</i>]-indoline <i>via</i> an unprecedented catalytic asymmetric sequential allylation of <i>N</i>,<i>N</i>'-alloc 3,3'-dimeric 2-oxindoles with eventual total syntheses of naturally occurring (-)-calycanthidine and a formal total synthesis of (-)-idiospermuline.