title: Phase-transfer-catalyzed synthesis of aryl alpha-ketosides of N-acetylneuraminic acid. A 2-methylfluoran-6-yl glycoside of N-acetylneuraminic acid, 2-methyl-6-(5-acetamido-3,5-dideoxy-alpha-D-glycero-D-galacto- nonulopyranosylonic acid)xanthene-9-spiro-1'-isobenzofuran-3'-one, a new substrate for neuraminidase assay.
abstract: Glycosidation of N-acetylneuraminic acid by phase-transfer catalysis in chloroform-aqueous alkali gave several known and some new aryl alpha-ketosides in a short reaction time and in good yields. The 4-methylumbelliferyl alpha-ketoside, the standard substrate for neuraminidase, was prepared in a yield of up to 70%. New Neu5Ac ketosides were prepared with fluorescein and the fluorescein analog, 2-methyl-6-hydroxyfluoran (2-methyl-6-hydroxyxanthene-9-spiro-1'-isobenzofuran-3'-one) as aglycons, the latter being synthesized from 2-(2-hydroxy-5-methyl-benzoyl) benzoic acid and 3-fluorophenol. The alpha configuration was ascertained by 400-MHz 1H-n.m.r. spectroscopy and by cleavage of the ketosides with neuraminidases from Vibrio cholerae and Clostridium perfringens. The enzymic hydrolysis of the 2-methylfluoran-6-yl ketoside gave Km values of 82 microM (V. cholerae) and 96 microM (C. perfringens).
authors.affiliation: Biochemie, Universität des Saarlandes, Saarbrücken, F.R.G.
authors.forename: J
authors.initials: J
authors.lastname: Rothermel
authors.forename: H
authors.initials: H
authors.lastname: Faillard
mesh_terms: D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002384:Catalysis; D055598:Chemical Phenomena; D002621:Chemistry; D019793:Fluorescein; D005452:Fluoresceins / Q000138:chemical synthesis* / Q000378:metabolism; D006868:Hydrolysis; D008969:Molecular Sequence Data; D019158:N-Acetylneuraminic Acid; D009439:Neuraminidase / Q000378:metabolism*; D012794:Sialic Acids / Q000138:chemical synthesis* / Q000378:metabolism
chemical_list: D005452:Fluoresceins; D012794:Sialic Acids; C064236:2-methyl-6-(5-acetamido-3,5-dideoxy-alpha-glycero-galacto-nonulopyranosylonic acid)xanthene-9-spiro-1'-isobenzofuran-3'-one; C064237:6-hydroxy-2-methylfluoran; D009439:Neuraminidase; D019158:N-Acetylneuraminic Acid; D019793:Fluorescein