ASYMMETRIC INDUCTION IN THE VINYLOGOUS AMIDE PHOTOCYCLOADDITION REACTION - A FORMAL SYNTHESIS OF VINDOROSINE

The application of the intramolecular vinylogous amide photocycloaddition/retro-Mannich fragmentation/Mannich closure sequence to a formal synthesis of vindorosine, 6, starting from L-tryptophan, is described. The synthesis of 7, which has been converted to vindorosine by Buchi, in 14 steps (7% overall yield from L-tryptophan) in homochiral form attests to the efficiency of this photochemical approach to the synthesis of the aspidosperma alkaloids, and demonstrates the exceedingly high levels of asymmetric induction which are possible via the intramolecular [2 + 2]photocycloaddition reaction of vinylogous amides. © 1990, American Chemical Society. All rights reserved.