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2,3-O-Isopropylidene-~-ribose has been converted stereoselectively into 3( 5)-( P-~-ribofuranosyl)pyrazole 11, a precursor for the C-nucleoside antibiotics pyrazofurin and fonnycin.Since the isolation of the C-nucleoside antibiotics, there has been considerable interest in synthetic approaches to these compounds, including in particular the pyrazole C-nucleosides formycin 1 and pyrazofurin 2.' Previous work in one of our HO OHHO OH 1 2

General Syntheses of Ethyl 2-Ulosonates and 3-Deoxy-Dmanno-oct-2-ulosonic Acid from Carbohydrate Lactones with 1-Ethoxyvinyllithium. -Sugar lactones (I) react with 1-ethoxyvinyllithium (II) to afford a diastereomeric mixture of the corresponding hemiacetals (III) which can be efficiently converted to ethyl 2-ulosonates (IV) by ozonolysis. Application of the strategy to the pyranonolactone (V) allows the synthesis of 3-deoxy-D-manno-oct-2-ulosonic acid (KDO) (VIII), an essential constituent of lipopolysaccharides and exopolysaccharides found in cell surface of Gramnegative bacteria. -(JIANG, S.; RYCROFT, A. D.; SINGH, G.; WANG, X.

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