Synthesis of 4-O-β-D-Glucopyranosyl-L-rhamnopyranose

Abstract

4-0-(P-D-Glucopyranosyl)-L-rhamnose (scillabiose) has been synthesized in 55% y~eld by condensation of 2,3,4,6-tetra-0-acetyl-a-D-glucopyranosyl bromide with methyl 2.3-0-isopropylidene-a-L-rhamnopyranoside using mercuric cyanide in acetonitrile (Helferich reaction). The disaccharide and the derived alditol are both syrups but each forms a crystalline peracetate. A convenient synthesis of I-deoxy-D-erythritol is described.4-0-(P-D-Glucopyrannosyle)-L-rhamnose (scillabiose) a ete synthetise avec un rendement de 55% par reaction du a-D-tetracetylbromoglucose avec le methyl 2,3-0-isopropylidene-a-L-rhamnopyrannoside en utilisant le cyanure de mercure dans I'acetonitrile (reaction de Helferich). Le disaccharide et I'alditol correspondant son; sirops mais chacun donne un peracetate crystallin. Une nouvelle synthtse de 1-deoxy-D-erythritol est decrite.Canadian Journal of Chemistry, 50. 3373 (1972) L-Rhamnose is widely distributed in nature and is commonly found as a constituent of plant gums (I), plant glycosides (2), and in bacterial polysaccharides (3). Despite this, no disaccharide having L-rhamnose as the aglycone has been synthesized (4) with the exception of. Such disaccharides are invaluable not only for the identification of fragments obtained in structural studies but also for the determination of immunodominant groups in polysaccharides which have antigenic activity (6). The aldobiouronic acid 4-0-(8-D-glucopyranosyluronic acid)-L-rhamnose has been isolated from hydrolyzates of Acrosiphonia centralis (7), Ulva lactuca (8), and Klebsiella K9 capsular polysaccharide (9). In the first two cases this acid has been characterized after reduction to the neutral disaccharide.The synthesis of 4-0-(8-D-glucopyranosy1)-Lrhamnose (scillabiose) described here was originally undertaken mainly as a model study for the subsequent synthesis of the D-manno-analog (3) but since the related aldobiouronic acid has now been identified as a component of Klebsiella type K9 capsular polysaccharide the preparation of this disaccharide is related to our studies on these bacteria. Scillabiose was first isolated from the glycosides scillarin A and glucoscilliphaeoside obtained from Scilla maritima (2, 10) and its identification as 4-0-(P-D-glucopyranosy1)-L-rhamnose was subsequently established (1 1, 12).Methyl 2,3-0-isopropylidene-a-L-rhamnopyranoside (3) was prepared most conveniently from methyl a-L-rhamnopyranoside (1) by reaction with acetone in the presence of cation exchange resin (1 3-16) and was purified through the crystalline 4-acetate (2). Condensation of this intermediate with 2,3,4,6-tetra-0-acetyl-cr-D-glucopyranosyl bromide using mercuric cyanide in acetonitrile (17) gave methyl 4-0-(2,3,4,6-tetra-0-acetyl-p-D-glucopyranosy1)-2,3-0-isopropylidene-a-L-rhamnopyranoside (5) as a crystalline product (yield 80%).Initial attempts to prepare scillabiose heptaacetate (7) by direct acetolysis of 5 under several different conditions gave only very poor yields (1 573 of 7. This was eventually explained by the fact that direct a...

Synthesis of 4-O-β-D-Galactopyranosyl-L-rhamnopyranose

“…General methods and experimental procedures are essentially as described previously (2). Melting points were taken between glass slides on a Fisher-Johns apparatua and are uncorrected.…”

“…Nuclear magnetic resonance spectra were recorded on a Varian XL-100 instrument using tetramethylsilane as internal standard except as noted. Gas-liquid partition chromatography was carried out on an F and M 720 instr~~nient at a gas flow rate of 60 ml min using columns: Deacetylation of 5 (0.80 g) gave 6 (0.40 g) as a syrup were visualized using silver nitrate in acetone for nonwhich showed only one spot on paper chromatography reducing compounds (12) and p-anisidine spray (13) of the volume of acetone) or as previously reported (2). Found: C, 43.78; H, 7.37.…”

“…Hence, the synthesis of a series of disaccharides with L-rhamnose linked through position 4 as the aglycon, was undertaken (2)(3)(4)(5)(6). We now report the synthesis of another member of this series, namely, 4-0-P-D-galactopyranosyl-~Irhamnose (6).…”

“…The disaccharide described here ( 6 ) has been found as part of the structure of the capsule of Klrbsiella K-type 47 (7). The rationale for such syntheses and detailed experimental procedures for many of the steps have already been given (2). Since this work has been completed and reported (8) an additional synthesis of 6 has been published (9).…”

“…Since this work has been completed and reported (8) an additional synthesis of 6 has been published (9). Crystalline 2,3,4,6-tetra-0-acetyl-cr-D-galactopyranosyl bromide (I), prepared by the method of Fletcher (lo), was condensed with methyl 2,3-0-isopropylidene-r-L-rhan~nopyranoside (2) in acetonitrile using mercuric cyanide. Methyl…”