A stereoselective synthesis of protected N-glycosyl oxazolines has been developed from available acylated sugar 1,2-O-acetonides using intramolecular Ritter-like reactions. New N-α- and β-D-pentofuranosyl, α-D-hexofuranosyl oxazolines as valuable intermediates for preparation of diverse N-glycosides were obtained by BF3.OEt2-KHF2 or BF3.OEt2-promoted reactions of pentofuranose and hexafuranose acetonide derivatives with nitriles. When selectively acylated D-xylo- or ribofuranoses were employed in the reactions, N-α-pentofuranosyl oxazolines were prepared in good yields. A mechanism for the formation of glycosyl oxazolines was proposed. A series of oxazoline derivatives were evaluated for their antiproliferative activity on three human cancer cell lines (MCF-7, Hela and K562). 折りたたむ

A stereoselective synthesis of N-glycosyl amides was studied from available N-glycosyl oxazolines prepared by Ritter-like reactions of protected sugar acetonides. Hydrolysis reactions of the protected pentofuranosyl and hexafuranosyl oxazolines, as precursors of glycosyl amine derivatives, were carried out in the presence of silica gel in chloroform to give N-α- and β-glycosyl amides in good yields after column chromatography on silica gel. Access to selectively blocked N-α-xylo-, -ribo-, β-arabino-furanosyl, α-glyco-, α-allo-furanosyl, α- and β-galactopyranosyl amides (twelve examples) useful for preparing modified N-glycosides was accomplished through a mild hydrolysis of sugar oxazolines with 2-alkyl substituents in acidic and neutral conditions. To further explore the scope of the BF3.Et2O-mediated approach developed for N-furanosyl oxazolines, a stereoselective synthesis of protected N-α-hexopyranosyl oxazoline was fulfilled in a high yield from d-galactopyranose diacetonide derivative. The Ritter-like promoted reaction between D-arabinose and benzonitrile afforded 2-phenyl-β-d-arabinofurano-(1,2-d)-2-oxazoline as the main product. In acetonitrile the BF3.Et2O-KHF2-assisted reactions of unprotected native sugars were found to result in the formation of mixtures of N-furanosyl and pyranosyl acetamides. 折りたたむ