Spacer-modified oligosaccharides with basic anchoring groups are inhibitors for endo-glycanases: Porcine pancreatic alpha-amylase as model enzyme

By coupling methyl 2,3,6-tri-O-acetyl-4-O-(5-azido-6-p-tolylsulfonyloxyhexyl)-α-d-glucopyranoside with 2-benzoylthioethyl 2,3,4,6-tetra-O-acetyl-α-d-glucopyranoside, a spacer-modified disaccharide derivative, methyl 4-O-(5-azido-9-α-d-glucopyranosyloxy-7-thianonyl)-α-d-glucopyranoside, was obtained and then enzymatically glucosylated to yield the spacer-modified tri- and tetra-saccharide methyl 4-O-(5-azido-9-α-maltosyloxy-7-thianonyl)-α-d-glucopyranoside and methyl 4-O-(5-azido-9-α-maltotriosyloxy-7-thianonyl)-α-d-glucopyranoside, respectively, the extended spacer spanning the length of two (1 → 4)-linked pyranosyl units. The corresponding amines methyl 4-O-(5-amino-9-α-d-glucopyranosyloxy-7-thianonyl)-α-d-glucopyranoside, methyl 4-O-(5-amino-9-α-maltosyloxy-7-thianonyl)-α-d-glucopyranoside and methyl 4-O-(5-amino-9-α-maltotriosyloxy-7-thianonyl)-α-d-glucopyranoside, obtained by catalytic reduction, carry the basic functionality in a spacer position to allow ionic interaction with a catalytically active acidic group in porcine pancreatic alpha-amylase (PPA). Optimal inhibition of enzymic activity is by methyl 4-O-(5-amino-9-α-maltosyloxy-7-thianonyl)-α-d-glucopyranoside where three of the five subsites are occupied by glucosyl units and the spacer spanning the remaining subsites positions the amino group near the catalytic site.