Stereoselective Synthesis Of Functionalized Quaternary Stereocenters Naturally Occurring Tetronic Acids And R R L Factor

Stereoselective Synthesis of Functionalized Quaternary Stereocenters, Naturally Occurring Tetronic Acids and (-)-(R,R)-L-factor

Studies on the Stereoselective Synthesis of Functionalized Quaternary Stereocenters and E-3-(arylmethylidene)-5-(alkyl/aryl)-2(3H)-Furanones

An enantioselective synthesis of isolated acyclic quaternary stereocenters was achieved using metal-catalyzed Gosteli-Claisen rearrangements of allyl vinyl ethers. A concise synthesis of 2-t-butoxycarbonyl allyl vinyl ethers by regioselective Petasis methylenation and stereoselective Suzuki-Miyaura cross-coupling reactions of iodoallyl t-butyl oxalates was developed. Ethers with a terminally unsubstituted vinyl group and a terminally disubstituted allyl portion are readily accessible by this method. In addition to the metal-catalyzed Gosteli-Claisen rearrangements, organocatalytic variant of the Gosteli-Claisen rearrangement was investigated. A modular synthesis of several new, chiral cyclic phosphoramide-based, thioureas, formamidines and thiosemicarbazides was developed and these phosphoramides were examined for their ability to catalyze the Gosteli-Claisen rearrangement of a selected allyl vinyl ether. A variety of E-3-(arylidene)-5-(alkyl/aryl)-2(3H)-furanones were synthesized by employing regioselctive addition of -aryl acrylic acids with iodoacetylenes and subsequent intramolecular Heck reaction of Z-acyloxy iodo alkenes. The approach was applied in a formal synthesis of the naturally occurring kinase inhibitor BE-23372M.

Stereoselective Synthesis