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Abstract

The aldehyde 2 prepared from [5-(2,3-O-isopropylidene-β-D-erythrofuranosyl)-2-methylfuran-3-yl]methanol (1) was converted to E,Z-oximes 3, 4 and imine derivative 5 by the reaction with hydroxylamine and pyridin-2-yl amine, respectively. The Knoevenagel reaction with malonic acid afforded exclusively the 3-substituted acrylic acid 6 while corresponding Hantzsch 1,4-dihydropyridines 7 and 8 were obtained by the reaction of aldehyde 2 with ethyl acetoacetate or acetylacetone and ammonia. 3,5-Dicyano-1,4-dihydropyridine derivative 9 was isolated only in forms of hydrates after the reaction of aldehyde 2 with 3-aminocrotonitrile. 1,4-Dihydropyridines 7 and 9 were aromatized to corresponding pyridines 10 and 11. Isoxazoles 12, 13 and isoxazolines 14, 15 were prepared by 1,3-cycloaddition of appropriate dienophiles to a nitrile oxide generated from aldoximes 3, 4. Ferricyanide oxidation of 1-{[5-(2,3-O-isopropylidene-β-D-erythrofuranosyl)-2-methylfuran-3-yl]methyl}pyridinium chloride (17a), -3-methylpyridinium chloride (19a) and the corresponding isoquinolinium chloride 21a gave optically active pyridin-2(1H)-ones 22, 23 and 2H-isoquinolone derivative 24 while the procedure with 2-methylpyridinium salt 18a and 4-methylpyridinium salt 20a led to complex mixtures of products. Reaction of 2,4,6-triphenylpyrylium perchlorate with furanoid amine 26 afforded a mixture of major 2,4,6-triphenylpyridine, minor pyridinium perchlorate 25 and primary alcohol 1. The absolute configuration of the studied compounds has been confirmed by X-ray analysis of the Schiff base 5.

Keywords: Furans; 1,4-Dihydropyridines; Isoxazoles; Pyridin-2(1H)-ones; Ferricyanide oxidation; Gabriel synthesis; Schiff bases; X-Ray diffraction; Absolute configuration.