Studies on 3-epimeric l-2-hexulose phenylosazones. Structure and anomeric configuration of the 3,6-anhydro-osazone derivatives obtained from l-xylo- and l-lyxo-2-hexulose phenylosazone

Studies on the dehydrative cyclization of epimeric 4-(L-xylo and L-lyxo-tetritol-1-yl)-2-phenyl-2H-1,2,3-triazoles. Circular dichroism and NMR assignment of the formed anomericC-nucleoside L-threofuranosyl triazole analogs

Dehydrative cyclization of epimeric 4-(L-xylo- and L-lyxo-tetritol-1-yl)-2-phenyl-2H-1,2,3-triazoles afforded the anomeric alpha and beta-L-threofuranosyl analogs. The anomeric configuration of the formed anomeric C-nucleoside analogs was determined by circular dichroism and NMR spectroscopy.

Acid-catalyzed dehydrative cyclization of 4-(D-galacto -pentitol-1-yl)-2-phenyl-2H-1,2,3-triazole. synthesis and anomeric configuration of D-lyxo-C-nucleoside analogs

Dehydration of 4-(D-galacto-pentitol-1-yl)-2-phenyl-2H-1,2,3-triazole with 20% methanolic sulfuric acid afforded the anomeric pairs of nucleosides, 4-(alpha-D-lyxopyranosyl)-2-phenyl-2H-1,2,3-triazole (major component) and its beta-anomer, as well as 4-(alpha-D-lyxofuranosyl)-2H-1,2,3-triazole and its beta-anomer. The four anomeric C-nucleosides were separated by chromatography, and their structure and anomeric configuration were determined by periodate oxidation, acylation, and NMR spectroscopy as well as mass spectrometry. The anomeric assignment from optical rotation was not in agreement with final structure assignment and represented a violation of the Hudson isorotation rules. NOE studies and X-ray diffraction measurements confirmed the anomeric configuration.

Studies on epimeric D-xylo-and D-lyxo-tetritol-1-yl-2-phenyl-2H-1,2,3-triazoles. Synthesis and anomeric configuration of 4-(alpha-and beta-D-threofuranosyl)-2-phenyl-2H-1,2,3-triazole C-nucleoside analogs

Treatment of 4-(D-xylo-tetritol-1-yl)-2-phenyl-2H-1,2,3-triazole (1) with one mole equivalent of tosyl chloride in pyridine solution, afforded the C-nucleoside analog; 4-(beta-D-threofuranosyl)-2-phenyl-2H-1,2,3-triazole (2) in 55% yield, as well as the byproduct 4-(4-chloro-4-deoxy-D-xylo-tetritol-1-yl)-2-phenyl-2H-1,2,3-triazo le (4). Treatment of the epimeric 4-(D-lyxo-tetritol-1-yl)-2-phenyl-2H-1,2,3-triazole (6) with tosyl chloride in pyridine solution afforded the anomeric C-nucleoside analog; 4-(alpha-D-threofuranosyl)-2-phenyl-2H-1,2,3-triazole (7) in 29% yield, as well as the byproduct 4-(4-chloro-4-deoxy-D-lyxo-tetritol-1-yl)-2-phenyl-2H-1,2,3- triazole (9). Similar treatment of 1 and 6 with trifluoromethanesulfonyl chloride in pyridine solution afforded 2 and 7, respectively. The structure and anomeric configuration of these compounds were determined by acetylation, NMR, NOE, and circular dichroism spectroscopy, as well as mass spectrometry.