Friedel-Crafts and modified Vorbrüggen ribosylation. A short synthesis of aryl and heteroaryl-C-nucleosides

A direct coupling of aryl donor and tetra-O-acetylribose in the presence of Lewis acid led to β-C-nucleosides in good yields. In contrast, for deactivated electron-poor aromatics, a modified Vorbrüggen ribosylation reaction was investigated and successfully applied in the case of 2-trimethylsilyl-thiazole.     

Synthesis of C-Nucleoside Analogues： 2-[2-（Hydroxymethyl）-1, 3-dioxolan-5-yl]1, 3-thiazole-4-carboxamide and 2-[2-（Mercaptometh-yl）-1, 3-dioxolan-5-yl] 1, 3-thiazole-4-carboxamide

Novel C-nucleosides of tiazofurin analogue (2-[2-(hydroxymethyl)-1,3-dioxolan-5-yl] 1,3-thiazole-4-carboxamide) and its thiol-substituted derivative (2-[2-(mercaptomethyl)-1,3-dioxolan-5-yl] 1, 3-thiazole-4-carboxamide) were synthesized from methyl acrylate through a multistep procedure. Their structures were confirmed by IR, ^1HNMR, ^13CNMR and elemental analysis.     

Alkynyl-2-deoxy-d-riboses, a cornucopia for the generation of families of C-nucleosides

This study focuses on the preparation of some 1-alkynyl-2-deoxy-d-riboses and their application to the generation of C-nucleosides analogues. Examples are provided in which the alkyne functionality took part in alkylation or cycloaddition reactions. A discussion of the protecting group used is provided.     

One-pot Amberlite IR-120 Catalysed Synthesis of Glycosyl Dihydropyridones

Summary. The one-pot reaction of β-glycosyl amino acids with β-ketoesters in the presence of Amberlite IR-120 resin and 4 ? molecular sieve in refluxing toluene resulted in the respective dihydropyridones in fair to good yields. Present address: Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi-221005, India.     

Dye-sensitized photooxygenation of sugar-furans as synthetic strategy for novel C-nucleosides and functionalized exo-glycals

The methylene blue-sensitized photooxygenation of β-ribofuranosyl furan 1e followed by in situ Et₂S treatment afforded the conformationally stable β-ribofuranoside 4e almost quantitatively. The latter was converted to pyridazine C-nucleoside 6e by cyclization with NH₂NH₂ and to pyrazoline 7e through a 1,3-dipolar cycloaddition with diazomethane. Attempts to epoxidize the double bond failed both by dimethyldioxirane (DMDO), which left 4e unchanged, and by NEt₃/t-BuOOH or NaOO-t-Bu which respectively afforded the new and unexpected exo-glycals E,Z-8e and the novel furan derivative 9.     

Chiroptical Assignment of the Anomeric Configuration of 4-(α,β-D-lyxopyranosyl)- and 4-(α,β-D-lyxofuranosyl)-2-phenyl-2H-1,2,3-Triazole C-Nucleoside Anomeric Pairs: Extension of the CD Triazole Rule

The circular dichroism of the anomeric 4-(α,β-D-lyxopyranosyl)- and 4-(α,β-D-lyxofuranosyl)-2-phenyl-2H-1,2,3-triazole C-nucleoside analogs obtained by acid-catalyzed dehydrative cyclization of 4-(D-galacto-pentitol-1-yl)-2-phenyl-2H-1,2,3-triazole analog was studied. A correlation between the sign of the Cotton effect at the maximal UV absorption and the absolute configuration of the anomeric carbon atom was obtained and used for their anomeric configuration assignment. This correlation supports the CD triazole rule for anomeric assignment and is in accord with the assignment obtained by NMR spectral studies.