American Chemical Society
ol034539o_si_001.pdf (349.4 kB)

Biomimetic Synthesis of Fused Polypyrans:  Oxacyclization Stereo- and Regioselectivity Is a Function of the Nucleophile

Download (349.4 kB)
journal contribution
posted on 2003-05-21, 00:00 authored by Fernando Bravo, Frank E. McDonald, Wade A. Neiwert, Bao Do, Kenneth I. Hardcastle
The stereoselectivity of Lewis acid-induced endo-regioselective oxacyclizations of 1,4-diepoxides is dependent upon the nature of the terminating nucleophile. For instance, the tert-butyl carbonate-substituted diepoxide of 3,6-dimethylhepta-2,5-dien-1-ol provides a cis-fused bicyclic product, whereas the N,N-dimethylcarbamate derivative affords the trans-fused diastereomer. Stereospecific and regioselective conversion of the tertiary carbamate-terminated 1,4,7-triepoxide (I) to tricyclic all-trans-fused polypyran (II) is also demonstrated.