A Novel Process Of Free Radical Cyclization

It is utmost important to develop biochemical and chemical methods of synthesizing cyclic structures due to their prevalence in the biologically important natural products. The controlled cyclization strategy can be diversely applied to the syntheses of cyclic natural products.We progress the research to efficiently control the mode of cascade cyclization of isoprenoid chain molecules, which can be used in the synthesis of various natural products. The research used radical cyclization condition to control the mode of cyclization of isoprenoid chain molecules. This method utilizes oxidative free radical cyclization ofβ-keto ester with Mn(OAc)3·2H2O to form the bicyclic products.β-keto esters can be used for Mn(III)-based oxidative cyclization at 20℃or slightly above.We found a novel cyclization reaction, in which oxygen radical was involved to give a bicyclic compound in a highly stereoselective manner. The mechanism was already proposed based on the isolated reaction intermediates with different substrates under various reaction conditions. We further apply it to variously substituted starting materials.It is expected that the new radical cyclization can be more efficiently used in the synthesis of various kinds of natural products.