Synthesis of Two New Chromogenic Glycosides of 4-nitrocatechol - α-D-N-acetylmannopyranosaminide and α-L-rhamnopyranoside, as Substrates for Exoglycosidases

The peracetates of N-acetyl-D-mannosamine and L-rhamnose were reacted with 4-nitrocatechol in a Helferich glycosylation, by using BF3 center dot OBu2 as chemical promotor. The synthesized glycosides were purified by column chromatography on silica gel or by crystallization from ethanol and then characterized chemically, chromatographically and by H-1 and C-13 NMR spectroscopy. Both synthetic glycosides were hydrolyzed by an enzymatic extract of snail, Helix pomatia.