Stereoselective synthesis of 2,3,4-trisubstituted tetrahydrofurans and a general approach to a total synthesis of (-)-indolizidine195B and related indolizidines

Tetrahydrofuran containing natural products have been the subject of many studies due to their biological activities. Our laboratory has developed a highly stereoselective general method of preparation of substituted tetrahydrofurans. The stereoselective synthesis of trisubstituted tetrahydrofurans from benzyl diazoacetate and α-alkyl-β-benzyloxyaldehydes or α-alkyl-β-(triethylsilyl)oxyaldehydes is described.; Indolizidine type alkaloids have been attractive synthetic targets due to their biological activity. There have been a few reported syntheses of indolizidine (−)-19513, (−)-223A, (−)-239A, and myrmicarin (−)-237A recently isolated from African ant Myrmicaria eumenoides . However, all of the syntheses to date require rather dramatic changes in synthetic strategies and starting materials to prepare other indolizidines. The primary research has been an enantioselective synthesis of indolizidine (−)-195B, (−)-223A, (−)-239A, and myrmicarin (−)-237A from a common intermediate using a general method.