Formal Intramolecular [5 + 2] Photocycloaddition Reactions of Maleimides: A Novel Approach to the CDE Ring Skeleton of (−)-Cephalotaxine
作者:Kevin I. Booker-Milburn、Leo F. Dudin、Christopher E. Anson、Simon D. Guile
DOI:10.1021/ol016411h
日期:2001.9.1
A concise approach to the cephalotaxine CDE ring skeleton based on the intramolecular formal [5 + 2] photocycloaddition of cyclopentenyl-substituted maleimides is described. An investigation of the diastereoselectivity afforded by various protected alkoxy groups demonstrated that the best selectivity (3.5:1) was afforded by the free hydroxyl group, strongly suggesting a hydrogen-bonded excited state