Formal intramolecular [5 + 2] photocycloaddition reactions of maleimides: a novel approach to the CDE ring skeleton of (-)-cephalotaxine.
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. Reaction: see text.
Booker-Milburn
K I
KI
School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K. k.booker-milburn@bristol.ac.uk
Dudin
L F
LF
Anson
C E
CE
Guile
S D
SD
D000972:Antineoplastic Agents, Phytogenic / Q000138:chemical synthesis* / Q000737:chemistry; D006248:Harringtonines / Q000138:chemical synthesis* / Q000737:chemistry; D000077863:Homoharringtonine; D008301:Maleimides / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D010777:Photochemistry; D018515:Plant Leaves / Q000737:chemistry; D010946:Plants, Medicinal / Q000737:chemistry
D000972:Antineoplastic Agents, Phytogenic; D006248:Harringtonines; D008301:Maleimides; D000077863:Homoharringtonine