【摘 要】
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The biosynthetic cationic polyene cyclizations of acyclic precursors squalene and (3S)-2,3-oxidosqualene lead to a vast array of known tricyclic,tetracyclic and pentacyclic natural products.2 In parti
【机 构】
：
Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, P.R. Ch
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The biosynthetic cationic polyene cyclizations of acyclic precursors squalene and (3S)-2,3-oxidosqualene lead to a vast array of known tricyclic,tetracyclic and pentacyclic natural products.2 In particular,lanosterol is biosynthesized in a single,economical and effective step from (3S)-2,3-oxidosqualene by a single 83-kDa enzyme.The impressive part about this reaction is the ability of the reaction to produce four rings complex structure in a single step with the formation of highly substituted carbon-carbon bonds,8 stereogenic centers and 1 out of 128 possible isomers.In addition,this reaction is carried out in aqueous media,a reaction media considered taboo for organic chemists.Our group has reported the first intermolecular acetal-initiated polyene cyclization (Schemes 1).1 Using this method,a wide variety of natural products has been constructed.We have also shown the feasibility of carrying out epoxide initiated polyene cyclization in aqueous media using a water-tolerant Lewis acid discovered in our lab (Scheme 2).2 We have also reported the first aziridine initiated polyene cyclization (Scheme 2).2 Recently,we have also discovered a new asymmetric ketone ester initiated polyene cyclization,leading to complex polycyclic structures in high enantioselectivies.3
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