PHASE-TRANSFER-CATALYZED SYNTHESIS OF ARYL α-KETOSIDES OF N-ACETYLNEURAMINIC ACID. A 2-METHYLFLUORAN-6-YL GLYCOSIDE OF N-ACETYLNEURAMINIC ACID, 2-METHYL-6-(5-ACETAMIDO-3,5-DIDEOXY-α-D-glycero-D-galacto-NONULOPYRANOSYLONIC ACID)XANTHENE-9-SPIRO-1'-ISOBENZOFURAN-3'-ONE, A NEW SUBSTRATE..

Article abstract of DOI:10.1016/0008-6215(90)84104-3

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 70percent.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-methylbenzoyl) benzoic acid and 3-fluorophenol.The α configuration was ascertained by 400-MHz 1H-NMR 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 K_m values of 82 μM (V. cholerae) and 96 μM (C. perfringens).