Alkyl/Glycosyl Sulfoxides as Radical Precursors and Their Use in the Synthesis of Pyridine Derivatives**

Abstract

We report here the use of simple and readily available alkyl sulfoxides as precursors to radicals and their application in the preparation of pyridine derivatives. We show that alkyl sulfoxides, N-methoxy pyridinium salts and fluoride anions form electron donoracceptor (EDA) complexes in solution, which, upon visible light irradiation, undergo a radical chain process to afford various pyridine derivatives smoothly. This reaction displays broad scope with respect to both sulfoxides and N-methoxy pyridiniums. The synthetic versatility of sulfoxides as a handle in chemistry adds to their power as radical precursors. Glycosyl sulfoxides are converted to the corresponding pyridyl C-glycosides with high stereoselectivities. Computational and experimental studies provide insights into the reaction mechanism.

Palladium catalyzed decarboxylative β-C-glycosylation of glycals with oxazol-5-(4H)-ones as acceptors

“…3 Studies have revealed that compared to O - or N -glycosidic linkages, the C -surrogates possess higher metabolic stability, thereby enhancing their physicochemical and pharmacological properties. 4 Indeed, the therapeutic uses of a large variety of C -glycoside natural products as well as drug candidates have been established, 5 including C -glycosyl amino acid analogues and the derived glycopeptides. 6…”