A general, convenient synthesis of the repeating, disaccharide—dipeptide unit of the bacterial, cell-wall peptidoglycan by the oxazoline method

Concise and efficient synthesis of 2-acetamido-2-deoxy-beta-D-hexopyranosides of diverse aminosugars from 2-acetamido-2-deoxy-beta-D-glucose

The furanose acetonide derivative 1 is readily prepared from 2-acetamido-2-deoxy-D-glucose on a large scale without the need for chromatography. Mesylation of 1 provides an efficient, concise, synthetic route to rare 2-acetamido-2-deoxy-beta-D-hexopyranosides (2 and 3) via the corresponding methyl 2-acetamido-2-deoxy-3-O-methanesulfonyl-beta-D-glucopyranoside and subsequent inversion of configuration by direct displacement or formation of a 3,4-epoxide. Opening of this epoxide by azide provided a direct route to methyl 2-acetamido-4-amino-2,4,6-trideoxy-beta-D-gulopyranoside 4. Benzylation of 1 followed by ring expansion to the glucopyranoside, deoxygenation at C-6, and subsequent displacement of a C-4 triflate permitted the synthesis of methyl 2-acetamido-4-amino-2,4,6-trideoxy-beta-D-galactopyranoside 5. Methyl 2-acetamido-2-deoxy-beta-D-glucopyranoside available from 1 in quantitative yield was readily converted to methyl 2-acetamido-2-deoxy-beta-D-galactopyranoside 6 (>60%) by inversion of configuration at C-4. Introduction of a lactyl substituent at C-3 of oxazoline 1 also provides a facile synthesis of the biologically important muramic acid beta-glycoside 7. An interesting reaction to convert 2-acetamido-2-deoxyhexopyranosides to the corresponding 2-deoxy-2-tetrazole is also reported.

Synthesis of an orthogonally protected precursor to the glycan repeating unit of the bacterial cell wall

[reaction: see text]. A synthesis of stereochemically pure and orthogonally protected N-acetyl-(2-deoxy-2-aminoglucopyranosyl)-beta-[1,4]-N-acetylmuramyl (NAG-NAM) monopeptide (2), the glycopeptide core of lipid II and of the bacterial cell wall repeating unit, is reported.

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.

Synthesis and immunoadjuvant activities of the repeating, disaccharide-dipeptide unit of the bacterial, cell-wall peptidoglycan and of some carbohydrate analogs

The repeating disaccharide-dipeptide units of the bacterial, cell-wall peptidoglycan, one being O-(N-acetyl-beta-muramoyl-L-alanyl-D-isoglutamine)-(1 leads to 4)-2-acetamido-2-deoxy-D-glucose, and the other, O-(2-acetamido-2-deoxy-beta-D-glucosyl)-(1 leads to 4)-N-acetyl-muramoyl-L-alanyl-D-isoglutamine, have been synthesized. Some carbohydrate analogs, such as O-(N-acetyl-beta-muramoyl-L-alanyl-D-isoglutamine)-(1 leads to 4)-N-acetylmuramoyl-L-alanyl-D-isoglutamine, O-beta-D-glucosyl-(1 leads to 4)-N-acetylmuramoyl-L-alanyl-D-isoglutamine, and O-(6-acetamido-6-deoxy-beta-D-glucosyl)-(1 leads to 4)-N-acetylmuramoyl-L-alanyl-D-isoglutamine, were also synthesized. Their immunoadjuvant activities were examined in guinea-pigs.

Synthesis and biological activity of O-N-acetyl-beta-muramoyl-L-alanyl-D-isoglutamine)-(1 leads to 6)-2-acylamino-2-deoxy-D-glucoses

Benzoylation of benzyl 2-acetamido-2-deoxy-4,6-O-isopropylidene-alpha-D-glucopyranoside, benzyl 2-deoxy-2-(DL-3-hydroxytetradecanoylamino)-4,6-O-isopropylidene-alpha-D-glucopyranoside, and benzyl 2-deoxy-4,6-O-isopropylidene-2-octadecanoylamino-beta-D-glucopyranoside, with subsequent hydrolysis of the 4,6-O-isopropylidene group, gave the corresponding 3-O-benzoyl derivatives (4, 5, and 7). Hydrogenation of benzyl 2-acetamido-4,6-di-O-acetyl-2-deoxy-3-O-[D-1-(methoxycarbonyl)ethyl]-alpha-D-glucopyranoside, followed by chlorination, gave a product that was treated with mercuric actate to yield 2-acetamido-1,4,6-tri-O-acetyl-2-deoxy-3-O-[D-1-(methoxy-carbonyl)ethyl]-beta-D -glucopyranose (11). Treatment of 11 with ferric chloride afforded the oxazoline derivative, which was condensed with 4, 5, and 7 to give the (1 goes to 6)-beta-linked disaccharide derivative 13, 15, and 17. Hydrolysis of the methyl ester group in the compounds derived from 13, 15, and 17 by 4-O-acetylation gave the corresponding free acids, which were coupled with L-alanyl-D-isoglutamine benzyl ester, to yield the dipeptide derivatives 19-21 in excellent yields. Hydrolysis of 19-21, followed by hydrogenation, gave the respective O-(N-acetyl-beta-muramoyl-L-alanyl-D-isoglutamine)-(1 goes to 6)-2-acylamino-2-deoxy-D-glucoses in good yields. The immuno-adjuvant activity of these compounds was examined in guinea-pigs.