Crystal and molecular structure of methyl l-glycero-α-d-manno-heptopyranoside, and synthesis of 1→7 linked l-glycero-d-manno-heptobiose and its methyl α-glycoside

Abstract

Graphical abstract

Large‐Scale Synthesis of Crystalline 1,2,3,4,6,7‐Hexa‐O‐acetyl‐L‐glycero‐α‐D‐manno‐heptopyranose

“…A two-step strategy based on initial formation of methyl heptoside 14 and a concomitant acetylation/acetolysis step turned out to be more reliable. Fischer-type glycosylation of 1 with MeOH (with DOWEX™ 50 H + resin at reflux overnight) has been reported before and delivers high proportions of the methyl pyranosides 14 23a. Alternatively, the same transformation was achieved conveniently, more rapidly and with substantially less catalyst in a continuous-flow process.…”

“…Fischer-type glycosylation of 1 with MeOH (with DOWEX™ 50 H + resin at reflux overnight) has been reported before and delivers high proportions of the methyl pyranosides 14 . 23a Alternatively, the same transformation was achieved conveniently, more rapidly and with substantially less catalyst in a continuous-flow process. A standard Vapourtec system with a heated column reactor filled with QP-SA beads was used to optimise the reaction conditions (see the Supporting Information).…”

“…Preparation of Methyl Heptosides 14: 23a The crude heptose 1 (<121.5 mmol) was taken up in MeOH (500 mL); a small amount of a white fine precipitate was filtered off (filter paper). A 5 mL aliquot was pumped through the reactor (QP-SA, 15 g) at 90 °C with 1 mL min –1 flow rate and the product stream was analysed by TLC, showing a peak of material at 25–30 min and no material eluting before 20 min.…”

“…The spectroscopic data ( 1 H NMR) were consistent with the literature. 23a A small sample (0.98 g) was stored; the rest was subjected to the acetylation/acetolysis step to afford 16a .…”

A new look at acid catalyzed deacetylation of carbohydrates: A regioselective synthesis and reactivity of 2-O-acetyl aryl glycopyranosides

“…Thus, 2-O-acetyl gluco-and galactopyranosyl building blocks can find application in oligosaccharide synthesis. To remove acetyl groups from carbohydrate moiety base-catalyzed methods such as Zemplen [17] or similar [18,19,20] procedures are commonly used. Acidic catalysis is applied only in the case of selective removal of acetyl group in the presence of benzoyl [21] or other ester groups [22,23,24,25].…”