摘 要: | Thephotocycloadditionofmethyl2,4-dioxopentanoate1toalkenesorconjugatedolefins2regioselectivelygavethecycloadduct3(Schemel).ThisreactioncouldconvenientlybeusedtoconstructthebasicframeworkofvariousnatUraIlyoccutringchamigran-tyPespirosesquiterPenes,suchasa-chamigrene",6-chamigrene:=,andaseriesofrelatedhaIogenatedderivativesd.The(i)-Q-Chamigrene-3-onewasanewmemberofthisfamilyandwasrecentlyisolatedfromMarchantiapolymorPha".whichpossessedthestrUctUreofasyntheticintermediate,1-methoxycarbonyl-5,…
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