Biomimetic Synthesis of Fused Polypyrans: Oxacyclization Stereo- and Regioselectivity Is a Function of the Nucleophile
作者:Fernando Bravo、Frank E. McDonald、Wade A. Neiwert、Bao Do、Kenneth I. Hardcastle
DOI:10.1021/ol034539o
日期:2003.6.1
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.
[反应:见正文] Lewis酸诱导的1,4-二环氧化合物的内区选择性氧杂环化的立体选择性取决于终止亲核试剂的性质。例如,3,6-二甲基庚-2,5-二烯-1-醇的碳酸叔丁酯取代的二环氧化合物提供了顺式稠合的双环产物,而N,N-二甲基氨基甲酸酯衍生物提供了反式稠合的非对映异构体。还显示了叔氨基甲酸酯封端的1,4,7-三环氧化物(I)向三环全反式稠合聚吡喃(II)的立体定向和区域选择性转化。