The Convergent Synthesis of Polyether Ionophore Antibiotics: An Approach to the Synthesis of the Monensin Tetrahydropyran-Bis(tetrahydrofuran) via the Ester Enolate Claisen Rearrangement and Reductive Decarboxylation

Article abstract of DOI:10.1021/ja00297a039

The monensin tetrahydropyran equivalent 22 is prepared from D-fructose and then joined to the monensin bis(tetrahydrofuran) equivalent 24a via the ester enolate Claisen rearrangement.Methodology for the radical induced, reductive decarboxylation of the resulting acid 26a is described.Anomeric stabilization of the intermediate tetrahydrofuran-2-yl radical is an important factor in the stereochemical outcome of this process.Reduction of 1-chloro-2,3-O-isopropylidene furanoid and pyranoid carbohydrate derivatives with lithium di-tert-butylbiphenyl affords the corresponding glycals in high yield.