Glycosides for testing glycosidases: vinyl, 1-ethoxyethyl, and 1-ethoxybut-3-enyl D-glucopyranosides

The reaction of ethyl vinyl ether and 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranose (1) in the presence of Hg(OAc)2 and toluene-p-sulphonic acid as catalysts yielded the acetylated vinyl, 1-ethoxyethyl, and 1-ethoxybut-3-enyl glycosides in varying proportions. Crystalline 1-ethoxybut-3-enyl 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranoside (2), vinyl 2,3,4,6-tetra-O-acetyl-alpha-D-glucopyranoside (3), and 1-ethoxyethyl 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranoside (4) were isolated by chromatography. Compound 4 was also prepared by the reaction of 1 with cold acetaldehyde diethyl acetal containing a trace of acetic acid, and its alpha anomer (5) by the reaction of 1 with boiling acetaldehyde diethyl acetal containing a trace of acetic acid. Each deacetylated D-glucoside was cleaved by the corresponding D-glucosidase, to yield D-glucose and either acetaldehyde (from deacetylated 3--5) or but-3-enal (from deacetylated 2).