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

Glycosidation of N-acetylneuraminic acid by phase-transfer catalysis in chloroform-aqueous alkali gave several known and some new aryl α-ketosides in a short reaction time and in good yields. The 4-methylumbelliferyl α-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 α 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 μm (V. cholerae) and 96 μm (C. perfringens). © 1990.