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PubMed1986

The outer membrane of Pseudomonas aeruginosa is a barrier against the penetration of disaccharides.

The outer membrane of Pseudomonas aeruginosa acted as a barrier against the penetration of di- (Mr, 342), tri- (Mr, 504) and tetrasaccharides (Mr, 666), whereas the membrane allowed the penetration of pentose (Mr, 150) and methylhexoses (Mr, 194) into the periplasm. When the intact cells of P. aeruginosa were treated with 600 mosM saccharides of various sizes and observed under an electron microscope, saccharides of Mr larger than 342 caused the extensive shrinking of the outer membrane. Whereas the cells treated with the saccharides of Mr less than 194 or with sucrose in the presence of EDTA showed plasmolysis. Determination of the extent of saccharide penetration into the periplasm of the cells treated with 600 mosM sodium chloride or with 600 mosM saccharides of various sizes showed that only pentose and hexoses, so far examined, were penetrable but di-, tri- and tetrasaccharides were impenetrable.

Disaccharides↗
PubMed1987

A convenient synthetic route to the disaccharide repeating-unit of peptidoglycan.

Glycosylation of the readily accessible benzyl 2-acetamido-6-O-benzyl-2-deoxy-3-O-[(R)-1-(methoxycarbonyl)ethyl]-alpha- D- glucopyranoside with 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl chloride (2), using the silver triflate method in the absence of a base, afforded 65-70% of the fully protected [beta-D-GlcNPhth-(1----4)-MurNAc] methyl ester derivative 4, the structure of which was ascertained on the basis of 500-MHz 1H-n.m.r. data. 2,2'-Dideoxy-2,2'-diphthalimido-beta,beta-trehalose hexa-acetate was a by-product. Removal of the Phth group from 4, followed by acetylation, yielded 90% of the acetylated 1,6-di-O-benzyl derivative 5, which, on saponification and catalytic hydrogenation, afforded 2-acetamido-4-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-3-O-[(R)-1- carboxyethyl]-2-deoxy-D-glucopyranose. Similarly, 5 was converted into the acetylated methyl ester derivative, which, on selective removal of the methyl ester group, gave benzyl 2-acetamido-4-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-beta-D- glucopyranosyl)-6-O-benzyl-3-O-[(R)-1-carboxyethyl]-2-deoxy-alpha-D- glucopyranoside. An alternative route for the preparation of 2 is described.

Carbohydrate Conformation↗
PubMed1989

Synthesis of disaccharide fragments of dermatan sulfate.

Condensation of crystalline methyl 2-azido-4,6-O-benzylidene-2-deoxy-beta-D-galactopyranoside with methyl (2,3,4-tri-O-acetyl-alpha-L-idopyranosyl bromide)uronate in dichloromethane, in the presence of silver triflate and molecular sieve, provided 54% of methyl 2-azido-4,6-O-benzylidene-2-deoxy-3-O-(methyl 2,3,4-tri-O-acetyl-alpha-L-idopyranosyluronate)-beta-D-galactopyranoside . The use of methyl (2,3,4-tri-O-acetyl-alpha-L-idopyranosyl trichloroacetimidate)uronate as glycosyl donor, in the presence of trimethylsilyl triflate, improved the yield to 68%. Regioselective opening of the benzylidene group with sodium cyanoborohydride followed successively by O-sulfation with the sulfur trioxide-trimethylamine complex, saponification, catalytic hydrogenolysis and selective N-acetylation gave the disodium salt of methyl 2-acetamido-2-deoxy-3-O-(alpha-L-idopyranosyluronic acid)-4-O-sulfo-beta-D-galactopyranoside. Condensation of methyl 2-azido-4,6-O-benzylidene-2-deoxy-beta-D-galactopyranoside with methyl (2,3,4-tri-O-acetyl-alpha-D-glucopyranosyl bromide)uronate in dichloromethane, in the presence of silver triflate and molecular sieve, gave methyl 2-azido-4,6-O-benzylidene-2-deoxy-3-O-(methyl 2,3,4-tri-O-acetyl-beta-D-glucopyranosyluronate)-beta-D-galactopryano side in 85% yield. The sequence already described then gave the disodium salt of methyl 2-acetamido-2-deoxy-3-O-(beta-D-glucopyranosyluronic acid)-4-O-sulfo-beta-D-galactopyranoside.

Carbohydrate Sequence↗
PubMed1990

Synthesis of disaccharide methyl glycosides related to the polysaccharide from Klebsiella serotype 40 and a study of their inhibition in the precipitin reaction.

The methyl glycosides of alpha-D-Manp-(1----4)-alpha-L-Rhap (3), alpha-L-Rhap-(1----3)-beta-D-Galp (4), beta-L-Rhap-(1----3)-beta-D-Galp (5), beta-D-Galp-(1----2)-alpha-L-Rhap (6), and beta-D-GlcpA-(1----2)-alpha-L-Rhap (7) have been synthesised and their inhibition reactions in the Klebsiella serotype 40 immune system have been studied. The results obtained accord with only one of two structures proposed for the repeating unit of the K40 antigen.

Carbohydrate Sequence↗
PubMed1990

Synthesis of alpha-Kdo-(2----4)-Kdo disaccharide derivatives and their conjugation with a protected form of GLA-60, a biologically active analog of a lipid A subunit.

A variety of the protected O-[(3-deoxy-alpha-D-manno-2-octulopyranosyl)onic acid]-(2----4)-3-deoxy-D-manno-2-octulosonic acid [alpha-Kdo-2(2----4)-Kdo] derivatives have been synthesized starting from methyl [2-(trimethylsilyl)ethyl 4,5,7,8-tetra-O-acetyl-3-deoxy-alpha-D-manno-2-octulopyranosid] onate. Some of these were conjugated with a protected form of a bacterial lipid A subunit-analog (GLA-60) having beneficial immunopharmacological activity, namely benzyl 2-[(3R)-3-(benzyloxy-methoxy)tetradecanamido]-2-deoxy-4-O- (diphenoxyphosphinyl)3-O-[(3R)-3-tetradecanoyloxytetradecanoyl+ ++]-beta -D-glucopyranoside.

Carbohydrate Sequence↗