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Communication | Special issue | Vol 35, No. 1, 1993, pp.93-97
Published online, 1st January, 1970
DOI: 10.3987/COM-92-S35
General Routes to 4-Oxo-4H-pyrano[2,3-b]pyridine-3-carboxylates and Related Compounds: Synthesis of the Oxygen and Sulfur Isosteres of Nalidixic Acid

Stuart W. McCombie,* Sue-Ing Lin, and Jayaram R. Tagat

*Chemical Research, Schering-Plogh Research Institute, DDF 2015 Galloping Hill Road, Kenilworth, NJ 07033-0539, U.S.A.

Abstract

lmidazolides of 2-hydroxy- and 2-mercaptonicotinic acids with LiCH2CO2Bu-t gave ketoesters which were cyclised with MeOCH=NMe2+ MeOSO3- and i-Pr2NEt or with (RCO)2O-NEt3-DMAP to the title 2-H or 2-R bicyclic esters; the corresponding 3-methylsulfonyl and 3-phosphonate analogs were similarly prepared. The 2-unsubstituted 4-oxopyranopyridine-3-carboxylates were unstable at physiological pH, whereas the thio analogs were stable.