Biomimetic synthesis of fused polypyrans: oxacyclization stereo- and regioselectivity is a function of the nucleophile.
[reaction: see text] 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.
Bravo
Fernando
F
Department of Chemistry, Emory University, 1515 Pierce Drive, Atlanta, Georgia 30322, USA.
McDonald
Frank E
FE
Neiwert
Wade A
WA
Do
Bao
B
Hardcastle
Kenneth I
KI
D032701:Biomimetics; D003500:Cyclization; D004852:Epoxy Compounds / Q000737:chemistry; D008958:Models, Molecular; D011714:Pyrans / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
D004852:Epoxy Compounds; D011714:Pyrans