Biomimetic Cyclization of Enamide-Containing Polyenes as a New Route to Azapolycycles.
Enamide 4 was studied for its effectiveness as a polyene precursor in biomimetic cyclizations. While most conventional Lewis acids were poor cyclization promoters, FeCl(3).6H(2)O initiated the conversion of 4 into tricycles 6 and 7 in excellent yield. The two isomeric products result from the cyclization of intermediate aldehyde 5 by either a chair or boat B-ring transition state. These results suggest that enamides may be incorporated into polyene precursors for the construction of larger azapolycycles such as azasteroids.
Sen
Stephanie E.
SE
Department of Chemistry, Indiana University-Purdue University at Indianapolis (IUPUI), 402 North Blackford Street, Indianapolis, Indiana 46202.
Roach
Steven L.
SL