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[摘要]：The total synthesis of the natural stilbene (+)-schweinfurthin G (I) has been accomplished through a sequence based on an efficient cationic cascade cyclization. This cascade process is initiated by Lewis acid promoted ring opening of an epoxide and terminated through a novel reaction with a phenolic oxygen "protected" as its MOM ether. Several Lewis acids have been examd. for their ability to induce this new reaction, and BF3譋t2O was found to be the most effective. The only major byproduct under these conditions was one where the expected secondary alc. was found as its MOM ether deriv. While this byproduct could be converted to the original target compd. through hydrolysis, it also could be employed as a protected alc. to allow prepn. of a benzylic phosphonate without dehydration of the secondary alc. The resulting phosphonate was employed in a Horner-Wadsworth-Emmons condensation with an aldehyde representing the right half of the target compds., an approach complementary to previous studies based on condensation of a right-half phosphonate and a left-half aldehyde. |
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