Synthesis of a series of fully methylated aldobiouronic acids,and β-elimination reactions of their synthetic precursors

Treatment of methyl 2,3,4-tri-O-acetyl-l-bromo-l-deoxy-α-d-glucopyranuronate severally with 2,4,6-, 2,3,6-, and 2,3,4-tri-O-methyl derivatives of methyl α-d-glucopyranoside and with methyl 4,6-O-benzylidene-3-O-methyl-α-d-glucopyranoside, in the presence of silver carbonate, afforded crystalline aldobiouronic acid derivatives in high yield. Deacetylation followed by methylation gave a series of fully methylated derivatives of laminaribiouronic, cellobiouronic, and gentiobiouronic acids, and the (1 → 2)-linked analogue. Methylation with methyl iodide and silver oxide in N,N-dimethylformamide was invariably accompanied by a small amount ofβ-elimination, with the formation of olefinic disaccharides which were also obtained by β-elimination reactions of the precursor acetates followed by methylation. Methyl 4,5-unsaturated 4-deoxyhexopyranosyluronate derivatives were the main products of the reaction, but these underwent further degradation with cleavage of the interglycosidic linkage and formation of 6-methoxycarbonyl-4-pyrone.     

The synthesis,and study of the β-elimination reaction,of di- and tri-peptides having a 3-O(2-acetamido-3,4,6-trio-O-acetyl-2-deoxy-β-D-glucopyranosyl)-L-serine residue

2-Acetamido-3,4,6-tri-O-acetyl-2-deoxy-α-D-glucopyra-nosyl chloride was condensed with the N-(benzyloxycarbonyl) derivatives of, respectively, L-seryl-glycine ethyl, L-seryl-L-alanine methyl, L-seryl-L-phenylalanine methyl, and L-seryl-L-aspartic dibenzyl esters to give (3-O-GlcpNAc-CbzN-L-Ser)-GlyOEt (8), (3-O-GlcpNAc-CbzN-L-Ser)-L-AlaOMe (9), (3-O-GlcpNAc-CbzN-L-Ser)-L-PheOMe (10), and (3-O-GlcpNAc-CbzN-L-Ser)-L-Asp(diOBzl) (11), respectively; O-(2-acetamido-3,4,6-tri-O-acetyl-β-D-glucopyranosy-l)-N-(benzyloxycarbonyl)-L-serine methyl ester was deblocked by treatment with hydrobromic acid in glacial acetic acid, followed by triethylamine, to give a glycoamino acid that was condensed with the N-(benzyloxycarbonyl) derivatives of the p-nitrophenyl ester of glycine, L-alanine, and L-proline, respectively, to give CbzNGly-(3-O)-Glcp NAc-L-SerOMe) (17), CbzN-L-Ala-(3-O-GlcpNAc-L-SerOMe), and CbzN-L-Pro-(3-O-GlcpNAc-L-SerOMe), respectively. Similarly, the glycopeptide resulting from 8 was condensed with the activated esters of glycine, L-alanine, L-phenylalanine, L-proline, and L-serine, respectively, to give CbzNGly-(3-OGlcpNAc-L-Ser)-GlyOEt, CbzN-L-Ala-(3-O-GlcpNAc-L-Ser)-GlyOEt, CbzN-L-Phe-(3-O-GlcpNAc-L-Ser)-GlyOEt, and CbzN-L-Ser-(3-O-GlcpNAc-L-Ser)-GlyOEt, respectively; that from 9, with the p-nitrophenyl esters of glycine¹,L-alanine, L-phenylalanine, L-proline, and L-leucine, respectively, to give CbzNGly-(3-O-GlcpNAc-L-Ser)-L-AlaOMe, CbzN-L-Ala(3-O-GlcpNAc-L-Ser)-L-AlaOMe, CbzN-L-Phe-(3-O-GlcpNAc-L-Ser)-L]-AlaOMe, CbzN-L-Pro-(3-O-GlcpNAc-L-Ser)-L-AlaOMe, and CbzN-L-Leu-(3-O-GlcpNAc- L-Ser)-L-AlaOMe, respectively; that from 10, with the derivatives of glycine, L-alanine, L-phenylalanine, and L-leucine, respectively, to give CbzNGly-(3-O-GlcpNAc-L-Ser)-L-PheOMe, CbzN-L-Phe-(3-O-GlcpNAc-L-Ser)-L-PheOMe, CbzN-L-Phe-(3-O-GlcpNAc-L-Ser)-L-PheOMe, and CbzN-L-Leu-(3-O-GlcpNAc-L-Ser)-L-PheOMe, respectively; and that from 11, with the derivatives of glycine, L-alanine, L-phenylalanine, L-proline, and L-leucine, respectively, to give CbzNGly-(3-O-GlcpNAc-L-Ser)-L-Asp(diOBzl), CbzN-L-Ala-(3-O-GlcpNAc-L-Ser)-L-Asp(diOBzl), CbzN-L-Phe-(3-O-GlcpNAc-L-Ser)-L-Asp(diOBzl), CbzN-L-Pro-(3-O-GlcpNAc-L-Ser)-L-Asp(diOBzl), and CbzN-L-Leu-(3-O-GlcpNAc-L-Ser)-L-Asp-(diOBzl), respectively. O-(2-Acetamido-3,4,5-tri-O-acetyl-2-deoxy-β-D-gluco-pyranosyl)-N-(benzyloxycarbonyl)- L-asparaginylglycyl-L-serine methyl ester (20) was synthesized by treating the free amine of 17 with the p-nitrophenyl ester of N-(benzyloxycarbonyl)-L-asparagine. 2-Acetamido-3,4,6-tri-O-acetyl-1-N-[N-(benzyloxycarbo-nyl)-L-aspart-1-oyl-(glycyl-L-serine methyl ester)-4-oyl]-2-deoxy-β-D-glucopyranosylamine (41) was synthesized by the condensation of 2-acetamido-3,4,6-tri-O-acetyl-1-N-[N-(benzyloxycarbo-nyl)-L-aspart-4-oyl]-2-deoxy-β-D-glucopyranosylamine with glycyl-L-serine methyl ester. Attempts to transfer the 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-D-glucopyranosyl group from the hydroxyl group of L-serine in 20 to the amido group of L-asparagine, to give 41, were unsuccessful. The β-elimination of some of the glycodi- and glycotri-peptides was studied.     

The relationship of molecular weight, and sulfate content and distribution to anticoagulant activity of heparin preparations

The crystalline intermediate 2-acetamido-6-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-D-glucopyranosyl)-3,4-di-O-acetyl-2-deoxy-β-D-glucopyranosyl azide (5), obtained by condensation of 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-D-glucopyranosyl bromide with either 2-acetamido-3,4-di-O-acetyl-2-deoxy-β-D-glucopyranosyl azide or its 6-O-triphenylmethyl derivative, was reduced in the presence of Adams' catalyst to give a disaccharide amine. Condensation with 1-benzyl N-(benzyloxycarbonyl)-L-aspartate afforded crystalline 2-acetamido-6-O-(2-acetamido-3,4 6-tri-O-acetyl-2-deoxy-β-D-glucopyranosyl)-3,4-di-O-acetyl-1-N-[1-benzyl N-(benzyloxycarbonyl)-L-aspart-4-oyl]-2-deoxy-β-D-glucopyranosylamine (9). Catalytic hydrogenation in the presence of palladium-on-charcoal was followed by saponification to give 2-acetamido-6-O-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-1-N-(L-aspart-4-oyl)-2-deoxy-β-D-glucopyranosylamine (11) in crystalline form. From the mother liquors of the reduction of 5, a further crystalline product was isolated, to which was assigned a bisglycosylamine structure (12).     

Synthesis of acetylenic sugars and uronic acids via two-carbon chain extension of d-ribose

Treatment of methyl β-d-ribofuranoside with acetone gave methyl 2,3-O-isopropylidene-β-d-ribofuranoside (1, 90%), whereas methyl α-d-ribofuranoside gave a mixture (30%) of 1 and methyl 2,3-O-isopropylidene-α-d-ribofuranoside (1a). On oxidation, 1 gave methyl 2,3-O-isopropylidene-β-d-ribo-pentodialdo-1,4-furanoside (2), whereas no similar product was obtained on oxidation of 1a. Ethynylmagnesium bromide reacted with 2 in dry tetrahydrofuran to give a 1:1 mixture (95%) of methyl 6,7-dideoxy-2,3-O-isopropylidene-β-d-allo- (3) and -α-l-talo-hept-6-ynofuranoside (4). Ozonolysis of 3 and 4 in dichloromethane gave the corresponding d-allo- and l-talo-uronic acids, characterized as their methyl esters (5 and 6) and 5-O-formyl methyl esters (5a and 6a). Ozonolysis in methanol gave a mixture of the free uronic acid and the methyl ester, and only a small proportion of the 5-O-formyl methyl ester. Malonic acid reacted with 2 to give methyl 5,6-dideoxy-2,3-O-isopropylidene-β-d-ribo-trans-hept-5-enofuranosiduronic acid (7).     

Triterpenoidal saponins of Pulsatilla koreana roots

Sixteen (1-16) triterpenoidal saponins were isolated from the roots of Pulsatilla koreana, of which four were determined as the previously unknown 23-hydroxy-3β-[(O-α-L-arabinopyranosyl)oxy]lup-20(29)-en-28-oic acid 28-O-β-D-glucopyranosyl ester (1), 23-hydroxy-3β-[(O-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosyl)oxy]lup-20(29)-en-28-oic acid 28-O-β-D-glucopyranosyl ester (2), 3β-[(O-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosyl)oxy]lup-20(29)-en-28-oic acid 28-O-β-D-glucopyranosyl-(1 → 6)-β-D-glucopyranosyl ester (3), and 3β-[(O-α-L-rhamnopyranosyl-(1 → 2)-O-[β-D-glucopyranosyl-(1 → 4)]-α-L-arabinopyranosyl)oxy]lup-20(29)-en-28-oic acid 28-O-α-L-rhamnopyranosyl-(1 → 4)-O-β-D-glucopyranosyl-(1 → 6)-β-D-glucopyranosyl ester (4), respectively, based on spectroscopic analysis. The inhibition of the lipopolysaccharide-induced nitric oxide production of sixteen isolated compounds was evaluated in RAW 264.7 cells at concentrations ranging from 1 μM to 100 μM.     

Synthesis of methyl (or propyl) 2-acetamido-2-deoxy-α-D-glucopyranoside 6-(α-D-glucopyranosyl phosphate) and derivatives for the study of the phosphoric ester linkage in the Micrococcus lysodeikticus cell-wall

Methyl 2-acetamido-3-O-allyl-2-deoxy-4-O-methyl-α-D-glucopyranoside, methyl 2-acetamido-2-deoxy-4-O-methyl-α-D-glucopyranoside, and methyl 2-acetamido-3,4-di-O-allyl-2-deoxy-α-D-glucopyranoside, prepared from methyl 2-acetamido-2-deoxy-α-D-glucopyranoside, were coupled with 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl phosphate (13), to give the phosphoric esters methyl 2-acetamido-3-O-allyl-2-deoxy-4-O-methyl-α-D-glucopyranoside 6-(2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl phosphate) (16), methyl 2-acetamido-2-deoxy-4-O-methyl-α-D-glucopyranoside 6-(2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl phosphate) (23), and methyl 2-acetamido-3,4-di-O-allyl-2-deoxy-α-D-glucopyranoside 6-(2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl phosphate) (17). Compound 13 was prepared from penta-O-acetyl-β-D-glucopyranose by the phosphoric acid procedure, or by acetylation of α-D-glucopyranosyl phosphate. Removal of the allyl groups from 16 and 17 gave 23 and methyl 2-acetamido-2-deoxy-α-D-glucopyranoside 6-(2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl phosphate) (19), respectively. O-Deacetylation of 23 gave methyl 2-acetamido-2-deoxy-4-O-methyl-α-D-glucopyranoside 6-(α-D-glucopyranosyl phosphate) (26) and O-deacetylation of 19 gave methyl 2-acetamido-2-deoxy-α-D-glucopyranoside 6-(α-D-glucopyranosyl phosphate) (24). Propyl 2-acetamido-2-deoxy-α-D-glucopyranoside 6-(α-D-glucopyranosyl phosphate) (25) was prepared by coupling 13 with allyl 2-acetamido-3,4-di-O-benzyl-2-deoxy-α-D-glucopyranoside, followed by catalytic hydrogenation of the product to give the propyl glycoside, which was then O-deacetylated. Compounds 24, 25, and 26 are being employed in structural studies of the Micrococcus lysodeikticus cell-wall.     

Chromone acyl glucosides and an ayanin glucoside from Dasiphora parvifolia

Two new chromone acyl glucosides, 5-hydroxy-7-O-(6-O-p-cis-coumaroyl-β-D-glucopyranosyl)-chromone (1) and 5-hydroxy-7-O-(6-O-p-trans-coumaroyl-β-D-glucopyranosyl)-chromone (2), and a new flavonoid glucoside, ayanin 3′-O-β-D-glucopyranoside (3) were isolated from aerial parts of Dasiphora parvifolia, together with flavonoid glycosides (4–10), catechins (11, 12), and hydrolysable tannins (13, 14). The chemical structures of these compounds were elucidated on the basis of spectroscopic data. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and the hyaluronidase inhibitory activity of these compounds were evaluated.     

Synthesis of derivatives of 3-amino-2,3-dideoxy-l-hexoses related to daunosamine (3-amino-2,3,6-trideoxy-l-lyxo-hexose)

The synthesis is described of 3-amino-2,3-dideoxy-l-arabino-hexose (10), methyl 2,3-dideoxy-3-trifluoroacetamido-α-l-lyxo-hexopyranoside (17), methyl 3-amino-2,3-dideoxy-α-l-ribo-hexopyranoside (21), methyl 2,3-dideoxy-3-trifluoroacetamido-α-l-xylo-hexopyranoside (26), and certain derivatives from methyl 4,6-O-benzylidene-2-deoxy-α-l-arabino-hexopyranoside (3). Conversion of 2-deoxy-l-arabino-hexose into 3 by modified, standard procedures, and on a large scale, gave a 75% yield.     

Preparation of some acylated 4-deoxyhex-3-enopyranosiduloses and γ-pyrone formation therefrom

Acylated 4-deoxyhex-3-enopyranosiduloses carrying benzoyl and/or acetyl groups (i.e., enolones 9, 10, and 14) were prepared by methyl sulfoxide-acetic anhydride oxidation of methyl 3,4,6-tri-O-acetyl-β-D-glucoside and of methyl 3-O-benzoyl-4,6-O-benzylidene-α-D-glucoside, the latter reaction being followed by debenzylidenation, acylation, and β-elimination of a carboxylic acid. The enolones, as well as the intermediate hexosiduloses, were readily characterized by spectral data and as their 2,4-dinitrophenylhydrazones. In basic and, less readily, in acidic medium, the enolones 9, 10, and 14 are converted into the γ-pyrone system. The mechanistic implications of these conversions are discussed.     

Isolation of phenolic constituents and characterization of antioxidant markers from sunflower (Helianthus annuus) seed extract

A new compound, benzyl alcohol β-d-apiofuranosyl-(1→6)-β-d-(4-O-caffeoyl) glucopyranoside (1), was isolated from the seed of sunflower (Helianthus annuus), together with eight known phenolic compounds: caffeic acid (2), methyl caffeoate (3), chlorogenic acid (4), 4-O-caffeoylquinic acid (5), 3-O-caffeoylquinic acid (6), methyl chlorogenate (7), 3,5-di-O-caffeoylquinic acid (8), and eriodictyol 5-O-β-d-glucoside (9). Their structures were elucidated on the basis of spectroscopic methods and chemical evidence. The antioxidative effect of the phenolic constituents from the sunflower seeds was also evaluated based on the oxygen-radical absorbance capacity (ORAC), and the fraction containing caffeic acid derivatives showed a high antioxidant potency.     

Synthesis and biological activity of O-(N-acetyl-β-muramoyl-l-alanyl-d-isoglutamine)-(1→6)-2-acylamino-2-deoxy-d-glucoses

Benzoylation of benzyl 2-acetamido-2-deoxy-4,6-O-isopropylidene-α-d-glucopyranoside, benzyl 2-deoxy-2-(dl-3-hydroxytetradecanoylamino)-4,6-O-isopropylidene-α-d-glucopyranoside, and benzyl 2-deoxy-4,6-O-isopropylidene-2-octadecanoylamino-β-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]-α-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-(methoxycarbonyl)ethyl]-β-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→6)-β-linked disaccharide derivatives 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-β-muramoyl-l-alanyl-d-isoglutamine)-(1→6)-2-acylamino-2-deoxy-d-glucoses in good yields. The immunoadjuvant activity of these compounds was examined in guinea-pigs.     

6-thio and -seleno-β-D-glucose esters of dimethylarsinous acid

Syntheses of 2-Se-(1,2,3,4-tetra-O-acetyl-β-D-glucopyranosyl)-3-N,N-dimethyl-selenopseudourea hydroiodide (3), 1,2,3,4-tetra-O-acetyl-6-S-dimethylarsino-6-thio-β-D-glucopyranose (4), 1,2,3,4-tetra-O-acetyl-6-Se-dimethylarsino-6-seleno-β-D-glucopyranose (7), 6-S-dimethylarsino-6-thio-β-D-glucopyranose (5), and 6-Se-dimethylarsino-6-seleno-β-D-glucopyranose (9) are described. Various spectral properties of the compounds are given. The relative rates of alkaline hydrolysis of 5 and 9 are compared.     

Synthesis of 2-O-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-D-mannose,and its interaction with D-mannose-specific lectins

Condensation of 3,4:5,6-di-O-isopropylidene-D-mannose dimethyl acetal with 2-methyl-(3,4,6-tri-O-acetyl- 1,2-dideoxy-α-D-glucopyrano)-[2′, 1′:4,5]-2-oxazoline in the presence of a catalytic amount of p-toluenesulfonic acid afforded crystalline 2-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-D-glucopyranosyl)-3,4:5,6-di-O-isopropylidene-D-mannose dimethyl acetal (3) in 25% yield. Catalytic deacetylation of 3 with sodium methoxide, followed by hydrolysis with dilute sulfuric acid, gave 2-O-(2-acetamido-2-deoxy-α-D-glucopyranosyl)-D-mannose (4). Treatment of 3 with boiling 0.5% methanolic hydrogen chloride under reflux gave methyl 2-O-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-α-D-mannopyranoside (5) and methyl 2-O-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-α-D-mannofuranoside (6). The inhibitory activities of 4, 5, and 6 against the hemagglutinating and mitogenic activities of Lens culinaris and Pisum sativum lectins and concanavalin A were assayed. From the results of these hapten inhibition studies, subtle differences of specificity between these D-mannose-specific lectins were confirmed.     

The stereochemistry of palladium- and platinum-catalyzed hydrogenations of nitro sugar epoxides

The catalytic hydrogenation of carbohydrate α-nitroepoxides with palladium and platinum was investigated with regard to regiospecificity and stereochemistry of ring opening, and the fate of the nitro group. 5,6-Anhydro-1,2-O-isopropylidene- 6-C-nitro-α-D-glucofuranose gave 6-amino-6-deoxy-1,2-O-isopropylidene-α-D-gluco-furanose under platinum catalysis. The methyl 2,3-anhydro-4,6-O-benzylidene-3-C- nitrohexopyranosides having the β-D-gulo (4), ?-D-allo (9), α-D-manno (13), and β-D-manno (18) configurations underwent facile, hydrogenolytic ring-opening in the presence of palladium, to give, regardless of the orientation of the oxirane ring, methyl 4,6-O-benzylidene-3-deoxy-3-C-nitro-D-hexopyranosides having an equatorial nitro group (5, 10, 14, and 19, respectively). In addition, 3-deoxy-3-oximino derivatives arose in various proportions, and two of these (from 9, and from 18) were isolated crystalline. It was shown that the oximes did not result from over-hydrogenation of the 3-deoxy-3-C-nitro glycosides produced, and it is suggested that they originated from intermediary nitronic acids. By catalysis with platinum, the oxirane rings in 4, 9, 13, and 18 were opened in the same regiospecific sense as with palladium, but notable differences were observed otherwise. Compound 4 gave the amino analog of 5, whereas 9 retained the nitro group and gave the 4,6-O-(cyclohexylmethylene) analog of 10. The α-D-manno epoxide 13 reacted with concomitant debenzylidenation, to yield methyl 3-amino-3-deoxy-α-D-altropyranoside hydrochloride, whereas the β-D-manno epoxide 18 gave the corresponding, debenzylidenated amino β-D-altroside together with the 4,6-O-(cyclohexylmethylene)-3-nitro- and -3-amino-β-D-mannosides. The results are compared with literature reports on the stereochemistry of hydrogenolysis of oxiranes, and mechanisms that may operate for the nitro derivatives are discussed.     

Nitrous acid deamination of methylated amino-oligosaccharide glycosides

G.l.c.-mass spectrometry has been used to characterize the products of N-deacetylation-nitrous acid deamination of per-O-methylated derivatives (8–11) of methyl 2-acetamido-2-deoxy-3-O-β-D-galactopyranosyl-α-D-glucopyranoside(1), methyl (2) and benzyl (3) 2-acetamido-2-deoxy-4-O-β-D-galactopyranosyl-β-D-glucopyranosides, and methyl 2-acetamido-2-deoxy-6-O-β-D-galactopyranosyl-α-D-glucopyranoside (4). 2,5-Anhydrohexoses have been converted into alditol trideuteriomethyl ethers, alditol acetates, and aldononitriles. The importance of side reactions that lead to the formation of 2-deoxy-2-C-formylpentofuranosides is discussed.     

Some observations on the selective benzoylation of maltose and its derivatives

Benzoylation of β-maltose monohydrate (2) with 10 mol. equiv. of benzoyl chloride in pyridine at ?40° gave 1,2,6-tri-O-benzoyl-4-O-(2,3,4,6-tetra-O-benzoyl-α-D-glucopyranosyl)-β-D-glucopyranose (5) in 87% yield, without the need for column chromatography. Similarly, benzoylation of 2 with 8 mol. equiv. of reagent afforded the octabenzoate 5, and the 1,2,6,2′,3′,6′-hexabenzoate 11 in 3%, 79%, and 12% yield, respectively. Methyl 2,6,2′,3′,4′,6′-hexa-O-benzoyl-β-maltoside (10) was directly isolated as a crystalline monoethanolate in 83% yield, from the reaction mixture obtained by the benzoylation of methyl β-maltoside monohydrate (8) with 8.9 mol. equiv. of reagent. Benzoylation of 8 with 7 mol. equiv. of reagent produced 10 and the 2,6,2′,3′,6′-pentabenzoate 16 in 71% and 23% yield, respectively. The order of reactivity of the hydroxyl groups in methyl 4′,6′-O-benzylidene-β-maltoside towards benzoylation is HO-2, HO-6>HO-2′ ≈ HO-3′>HO-3. Benzoylation of methyl β-cellobioside (33) with 7.9 mol. equiv. of reagent gave the heptabenzoate and the 2,6,2′,3′,4′,6′-hexabenzoate 36 in 56% and 27% yield, respectively. Compounds 5, 16, and 36 were transformed into 4-O-α-D-glucopyranosyl-D-allopyranose, methyl 4-O-α-D-galactopyranosyl-β-D-allopyranoside, and methyl 4-O-β-D-glucopyranosyl-β-D-allopyranoside, respectively, by sequential sulfonylation, nucleophilic displacement, and O-debenzoylation.     

Glycosyl esters of amino acids. V. Synthesis and properties of 1-O-acylaminoacyl-alpha- and -beta-D-glucopyranoses and 1-O-(1-beta-aspartyl)-beta-D-glucopyranose

Catalytic hydrogenation of the tetrabenzyl ethers of 1-O-acetamidoacyl- and 1-O-tert-butyloxycarbonylaminoacyl-α- and -β-D-glucopyranoses (1–6) afforded the corresponding 1-O-acylaminoacyl-D-glucopyranoses 8–13 which were fully characterised by physical methods and by conversion into the peracetylated derivatives 14–19. The α anomers of 1-O-tert-butyloxycarbonylaminoacyl-D-glucopyranoses underwent 1→2 acyl migration, and, in order to characterize the rearrangement product of 1-O-(tert-butyloxycarbonyl-L-alanyl)-α-D-glucopyranose (12α), 1,3,4,6-tetra-O-acetyl-2-O-(tert-butyloxycarbonyl-L-alanyl)-α- and -β-D-glucopyranoses (22 and 23) were synthesized by definitive methods. Initial studies of the simultaneous deprotection of the amino and hydroxyl functions were performed with D-glucose-amino acid 6-esters; catalytic hydrogenation of methyl 2,3,4-tri-O-benzyl-6-O-(N-benzyloxycarbonylglycyl)-β-D-glucopyranose (24) gave methyl 6-O-glycyl-β-D-glucopyranose (25) as the stable hydrochloride. Hydrogenolysis of the β anomer of 2,3,4,6-tetra-O-benzyl-1-O-[1-benzyl N-(benzyloxycarbonyl)-L-aspart-4-oyl]-D-glucopyranose (7) afforded 1-O-(L-β-aspartyl)-β-D-glucopyranose (27). The rates of hydrolysis of the unprotected D-glucose-amino acid 1-ester 27 in water and in 0.1M hydrochloric acid were compared with those of the D-glucose-amino acid 6-ester 25.     

Synthesis of 2,6-di(acylamino)-2,6-dideoxy-3-O-(d-2-propanoyl-l-alanyl-d-isoglutamine)-d-glucopyranoses

Five 2,6-di(acylamino)-2,6-dideoxy-3-O-(d-2-propanoyl-l-alanyl-d-isoglutamine)-d-glucopyranoses (lipophilic, muramoyl dipeptide analogs) were synthesized from benzyl 2-(benzyloxycarbonylamino)-3-O-(d-1-carboxyethyl)-2-deoxy-5,6-O-isopropylidene-β-dglucopyranoside (1). Methanesulfonylation of 3, derived from the methyl ester of 1 by O-deisopropylidenation, gave the 6-methanesulfonate (4). (Tetrahydropyran-2-yl)ation of 4 gave benzyl 2-(benzyloxycarbonylamino)-2-deoxy-3-O-[d-1-(methoxycarbonyl)ethyl]-6-O-(methylsulfonyl)-5-O-(tetrahydropyran-2-yl)-β-d- glucofuranoside, which was treated with sodium azide to give the corresponding 6-azido derivative (6). Condensation of benzyl 6-amino-2-(benzyloxycarbonyl-amino)-2,6-dideoxy-3-O-[d-1-(methoxycarbonyl)ethyl]-5-O-(tetrahydropyran-2-yl)-β-d-glucofuranoside, derived from 6 by reduction, with the activated esters of octanoic, hexadecanoic, and eicosanoic acid gave the corresponding 6-N-fatty acyl derivatives (8–10). Coupling of the 2-amino derivatives, obtained from compounds 8, 9, and 10 by catalytic reduction, with the activated esters of the fatty acids, gave the 2,6-(diacylamino)-2,6-dideoxy derivatives (11–15). Condensation of the acids, formed from 11–15 by de-esterification, with the benzyl ester of l-alanyl-d-isoglutamine, and subsequent hydrolysis, afforded benzyl 2,6-di(acylamino)-2,6-dideoxy-3-O-(d-2-propanoyl-l-alanyl-d-isoglutamine benzyl ester)-β-d-glucofuranosides. Hydrogenation of the dipeptide derivatives thus obtained gave the five lipophilic analogs of 6-amino-6-deoxymuramoyl dipeptide, respectively, in good yields.     

Chemical modification of the carbohydrate moiety in N-acetylmuramoyl-l-alanyl-d-isoglutamine,and the immunoadjuvant activity

Five carbohydrate analogs of N-acetylmuramoyl-l-alanyl-d-isoglutamine have been synthesized from benzyl 2-acetamido-2-deoxy-3-O-[d-1-(methoxycarbonyl)ethyl]-α-d-glucopyranoside (1) and the corresponding 6-O-benzoyl derivative (2). Chlorination of 1 and 2 with triphenylphosphine in carbon tetrachloride gave the 4,6-dichloro compound 3 and the 6-O-benzoyl-4-chloro compound (4), which were treated with tributyltin hydride, to yield benzyl 2-acetamido-2,4,6-trideoxy-3-O-[d-1-(methoxycarbonyl)ethyl]-α-d-xylo-hexopyranoside (6) and benzyl 2-acetamido-6-O-benzoyl-2,4-dideoxy-3-O-[d-1-(methoxycarbonyl)ethyl]-α-d-xylo-hexopyranoside (7), respectively. Methanesulfonylation of 8, derived from 7 by debenzoylation, gave the 6-methanesulfonate, which underwent displacement with azide ion to afford benzyl 2-acetamido-6-azido-2,4,6-trideoxy-3-O-[d-1-(methoxycarbonyl)ethyl]-α-d-xylo-hexopyranoside (10). Hydrolysis of the methyl ester group in compounds 3, 5 (debenzoylated 4), 6, 8, and 10 gave the corresponding free acids, which were coupled with l-alanyl-d-isoglutamine benzyl ester, to yield the dipeptide derivatives in excellent yields. Hydrogenation of the dipeptide derivatives thus obtained gave the five carbohydrate analogs of N-acetylmuramoyl-l-alanyl-d-isoglutamine, respectively, in good yields. The immunoadjuvant activity of the N-acetylmuramoyl-dipeptide analogs was examined.     

Synthesis of glycopeptides containing the amino acid sequence 17-23 of bovine pancreatic deoyxribonuclease

2-Acetamino-3,4,6-tri-O-acetly-1-N-[N-(benzyloxycarbonly-l-seryl)-l-aspart-1-oyl-(p-nitrobenzyl ester)-4-oyl]-2-deoxy-β-d-glucopyranosylamine,2-acetamido-3,4,6-tri,O-acetyl-1-N-[N-(benzyloxycarbonyl-l-seryl)-l-aspart-1-oyl-(l-alanine methyl ester)-4-oyl]-2-deoxy-β-d-glucopyranosylamine, and 2-acetamido-3,4,6-tri-O-acetyl-1-N-[N-benzyloxycarbonyl)-l-aspart-1-oyl-(l-alanyl-l-threonyl-l-leucyl-l-alanyl-l-serine p-nitrobenzyl ester)-4-oyl]-2-deoxy-β-d-glucopyranosylamine (7), which span the amino acid sequence 17-23 of bovine pancreatic deoxyribonuclease A and contain a 2-acetamido-2-deoxy-d-glucose residue, were synthesized. On treatment with lithium hydroxide, the blocked glycohexapeptide 7 gave 2-acetamido-1-N-[N-(benzyloxycarbonyl)-l-aspart-1-oyl-(l-alanyl-l-threonyl-l-leucyl-l-alanyl-l-serine)-4-oyl]-2 deoxy-β-d-glucopyranosylamine.