Conversion of amylose into a (1-4)-2-amino-2-deoxy-alpha-D-glucopyranuronan and its 2-N-sulfo derivative, a heparin analog

By a modification of a previously established reaction-sequence involving successive oxidation with methyl sulfoxide-acetic anhydride, oximation, and reduction with lithium aluminum hydride, 6-O-tritylamylose (1) was converted into a 6-O-tritylated (1→4)-α-D-linked glucan (3) containing 2-amino-2-deoxy-D-glucose residues and some O-(methylthio)methyl groups. Removal of the ether groups from this product gave a 2-aminated amylose (4) of degree of substitution (d.s.) by amine of 0.54 that underwent cleavage by fungal alpha-amylase to give oligosaccharides containing amino sugar residues. N-Trifluoroacetylation of 3 followed by removal of the ether groups, oxidation at C-6 with oxygen-platinum, and removal of the N-substituent, gave a (1 →4)-2-amino-2-deoxy-α-D-glucopyranuronan 7 having d.s. by amine of up to 0.65, and by carboxyl, of 0.46. Sulfation of this product with sulfur trioxide-pyridine and then with chlorosulfonic acid-pyridine gave a (1→4)-2-deoxy-2-sulfoamino-α-D-glucopyranuronan, isolated as its sodium salt 8, which showed appreciable blood-anticoagulant activity.     

The synthesis of oligosaccharide-asparagine compounds. V. O- -D-mannopyranosyl-(1 leads to 6)-O-(2-acetamido-2-deoxy- -D-glucopyranosyl)-(1 leads to 4)-2-acetamido-N-(L-aspart-4-oyl)-2-deoxy- -D-glucopyranosylamine

O-α-d-Mannopyranosyl-(1→6)-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-(1→4)-2-acetamido-N-(l-aspart-4-oyl)-2-deoxy-β-d-glucopyranosylamine (12), used in the synthesis of glycopeptides and as a reference compound in the structure elucidation of glycoproteins, was synthesized via condensation of 2,3,4,6-tetra-O-acetyl-α-d-mannopyranosyl bromide with 2-acetamido-4-O-(2-acetamido-3-O-acetyl-2-deoxy-β-d-glucopyranosyl)-3,6-di-O-acetyl-2-deoxy-β-d-glucopyranosyl azide (5) to give the intermediate, trisaccharide azide 7. [Compound 5 was obtained from the known 2-acetamido-4-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-d-glucopyranosyl)-3,6-di-O-acetyl-2-deoxy-β-d-glucopyranosyl azide by de-O-acetylation, condensation with benzaldehyde, acetylation, and removal of the benzylidene group.] The trisaccharide azide 6 was then acetylated, and the acetate reduced in the presence of Adams' catalyst. The resulting amine was condensed with 1-benzyl N-(benzyloxycarbonyl)-l-aspartate, and the O-acetyl, N-(benzyloxycarbonyl), and benzyl protective groups were removed, to give the title compound.     

Synthese der T-antigenen trisaccharide O-β-d-galactopyranosyl-(1→3)-O-(2-acetamido-2-desoxy-α-d-galactopyranosyl)-(1→6)-d-galactopyranose und O-β-d-galactopyranosyl-(1→3)-O-(2-acetamido-2-desoxy-α-d-galactopyranosyl)-(1→6)-d-glucopyranose und deren anknüpfung an proteine

The synthesis of the trisaccharides O-β-d-galactopyranosyl-(1→3)-O-(2-acetamido-2-deoxy-α-d-galactopyranosyl)-(1→6)-d-galactopyranose (15) and O-β-d-galactopyranosyl-(1→3)-O-(2-acetamido-2-deoxy-α-d-galactopyranosyl)-(1→6)-d-glucopyranose (27) is described and the synthesis of α-d-glycosides by reaction of 3,4,6-tri-O-acetyl-2-azido-2-deoxy-β-d-galactopyranosyl chloride with highly reactive hydroxyl groups is discussed. The trisaccharide 27 was coupled with serum albumin by formation of an imine intermediate and reduced to an amine, to yield a synthetic T-antigen. A similar coupling of 15 was unsuccessful.     

Conversion of amylose into a (1→4)-2-amino-2-deoxy-α-D-glucopyranuronan and its 2-N-sulfo derivative, a heparin analog

By a modification of a previously established reaction-sequence involving successive oxidation with methyl sulfoxide-acetic anhydride, oximation, and reduction with lithium aluminum hydride, 6-O-tritylamylose (1) was converted into a 6-O-tritylated (1→4)-α-D-linked glucan (3) containing 2-amino-2-deoxy-D-glucose residues and some O-(methylthio)methyl groups. Removal of the ether groups from this product gave a 2-aminated amylose (4) of degree of substitution (d.s.) by amine of 0.54 that underwent cleavage by fungal alpha-amylase to give oligosaccharides containing amino sugar residues. N-Trifluoroacetylation of 3 followed by removal of the ether groups, oxidation at C-6 with oxygen-platinum, and removal of the N-substituent, gave a (1 →4)-2-amino-2-deoxy-α-D-glucopyranuronan 7 having d.s. by amine of up to 0.65, and by carboxyl, of 0.46. Sulfation of this product with sulfur trioxide-pyridine and then with chlorosulfonic acid-pyridine gave a (1→4)-2-deoxy-2-sulfoamino-α-D-glucopyranuronan, isolated as its sodium salt 8, which showed appreciable blood-anticoagulant activity.     

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.     

Interactions glycanne-protéine. Synthése des 4-méthylombelliféryl-(2-acétamido-2-désoxy-β-D-glucopyranoside), -DI-N-acétyl-β-chitobioside et -tri-N-acétyl-β-chitotrioside. Interaction de ces osides avec le lysozyme

4-Methylumbelliferyl 2-acetamido-2-deoxy-β-D-glucopyranoside, 2-acetamido-4-O-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-2-deoxy-β-D-glucopyranoside (di-N-acetyl-β-chitobioside), and O-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-(1→4)-O-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-(1→4)-2-acetamido-2-deoxy-β-D-glucopyranoside (tri-N-acetyl-β-chitotrioside) were obtained in good yield from the corresponding peracetylated glycosyl chlorides by condensation with the sodium salt of 4-methylumbelliferone in N,N-dimethylformamide. The trisaccharide glycoside is hydrolyzed by lysozyme and is, therefore, a convenient substrate for this enzyme; the 4-methylumbelliferone produced can be determined by the increase of the fluorescence intensity at 442 nm. The intensity of the fluorescence of 4-methylumbelliferyl tri-N-acetyl-β-chitotrioside is enhanced upon binding with lysozyme without modification of the position of the absorption maximum. The binding constant and the rate of hydrolysis of the trisaccharide glycoside by lysozyme are higher than those obtained with p-nitrophenyl tri-N-acetyl-β-chitotrioside.     

Unusual properties of glycuronans [poly(glycosyluronic) compounds]

2-Methyl-[3,6-di-O-acetyl-2-deoxy-4-O-(2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl)-α-d-glucopyrano]-[2,1-d]-2-oxazoline (4) was prepared from 2-acetamido-3,6-di-O-acetyl-2-deoxy-4-O-(2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl)-α-d- glucopyranosyl chloride. Condensation of 3,4:5,6-di-O-isopropylidene-d-mannose dimethyl acetal with 4 in the presence of a catalytic amount of p-toluenesulfonic acid afforded O-(2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl)-(1 → 4)-O-(2-acetamido-3,6-di-O-acetyl-2-deoxy-β-d-glucopyranosyl)-(1 → 2)-3,4:5,6-di-O-isopropylidene-d-mannose dimethyl acetal (6) in 8.6% yield. Catalytic deacetylation of 6 with sodium methoxide, followed by hydrolysis with dilute sulfuric acid, gave O-β-d-galactopyranosyl-(1 → 4)-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-(1 → 2)-d-mannose (7). The inhibitory activities of 7 and related sugars against the hemagglutinating activities of various lectins were assayed, and 7 was found to be a good inhibitor against Phaseolus vulgaris hemagglutinin.     

Stereoselectivity of glycosylation with derivatives of 2-azido-2-deoxy-d-galactopyranose. The synthesis of a determinant oligosaccharide related to blood-group a (type 1)

The stereoselective glycosylation of a model alcohol (cyclohexanol) by derivatives of 2-azido-2-deoxy-d-galactopyranose was studied under various conditions. 2-Azido-3,4,6-tri-O-benzyl-2-deoxy-β-d-galactopyranosyl chloride (9) was found to be the most efficient glycosylating agent for the synthesis of oligosaccharides containing 2-acetamido-2-deoxy-α-d-galactopyranose residues, and gave a tetrasaccharide, which is a determinant of the blood-group A (Type 1), i.e., O-α-l-fucopyranosyl-(1→2)-[O-2-acetamido-2-deoxy-α-d- galactopyranosyl-(1→3)]-O-β-d-galactopyranosyl-(1→3)-2-acetamido-2-deoxy-d-glucose, and its trisaccharide fragment, O-2-acetamido-2-deoxy-α-d-galactopyranosyl-(1→3)-O-β-d-galactopyranosyl-(1→3)-2-acetamido-2-deoxy-d-glucose. In the course of this synthesis, the determinant trisaccharide related to the H blood-group, i.e., O-α-l-fucopyranosyl-(1→2)-O-β-d-galactopyranosyl-(1→3)-2-acetamido-2- deoxy-d-glucose, was also obtained.     

The attachment of poly(ribitol phosphate) to lipoteichoic acid carrier

2-Acetamido-3,4,6-tri-O-acetyl-1-N-[N-(benzyloxycarbonyl)-L-aspart-1-oyl-(L-leucyl-L-threonyl-N²-tosyl-L-lysine p-nitrobenzyl ester)-4-oyl]-2-deoxy-β-D-glucopyranosylamine (21) and 2-acetamido-3,4,6-tri-O-acetyl-1-N-[N-(benzyloxycarbonyl)-L-aspart-1-oyl-(L-leucyl-L-threonyl-N²-tosyl-L-lysine p-nitrobenzyl ester)-4-oyl]-2-deoxy-β-D-glucopyranosylamine (22), 2-acetamido-3,4,6-tri-O-acetyl-1-N-[N-(benzyloxycarbonyl)-L-aspart-1-oyl-(glycine ethyl 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-(phenylalanine methyl ester)-4-oyl]-2-deoxy-β-D-glucopyranosylamine were synthesized by condensation of 2-acetamido-3,4,6-tri-O-acetyl-1-N-[N-(benzyloxycarbonyl)-L-aspart-4-oyl]-2-deoxy-β-D-glucopyranosylamine with the appropriate protected amino acids and tri- and tetra-peptides. The amino acid sequences of 21 and 22 correspond to the protected amino acid sequences 34–37 and 34–38 of ribonuclease B that are adjacent to the carbohydrate-protein linkage.     

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.     

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-β-muramoyl-l-alanyl-d-isoglutamine)-(1→4)-2-acetamido-2-deoxy-d-glucose, and the other, O-(2-acetamido-2-deoxy-β-d-glucosyl)-(1→4)-N-acetyl-muramoyl-l-alanyl-d-isoglutamine, have been synthesized. Some carbohydrate analogs, such as O-(N-acetyl-β-muramoyl-l-alanyl-d-isoglutamine)- (1→4)-N-acetylmuramoyl-l-alanyl-d-isoglutamine, O-β-d-glucosyl-(1→4)-N-acetylmuramoyl-l-alanyl-d-isoglutamine, and O-(6-acetamido-6-deoxy-β-d-glucosyl)-(1→4)-N-acetylmuramoyl-l-alanyl-d-isoglutamine, were also synthesized. Their immunoadjuvant activities were examined in guinea-pigs.     

Conversion of a 2-(N-nitroso)acetamido hexose into a five-carbon, acetylenic sugar derivative

Dinitrogen tetraoxide was used to convert 2-acetamido-1,3,4,6-tetra-O-acetyl-2-deoxy-β-D-glucopyranose (1) in high yield into the syrupy N-nitroso derivative 2, and benzyl 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-D-glucopyranose (6) into the crystalline N-nitroso analog 7. The N-nitroso derivative 2 in acetonitrile underwent photolysis by pyrex-filtered, u.v. light to regenerate the starting acetamide 1 in high yield; spontaneous decomposition of 2 afforded β-D-glucopyranose pentaacetate (3) and other products. In ethereal solution, compound 2 reacted with potassium hydroxide in isopropyl alcohol with loss of the 2-substituent and C-1, to give a C₅ acetylene, 1,2-dideoxy-D-erythro-pent-1-ynitol, isolated in high yield as its triacetate 4 and characterized by conversion into the known, crystalline 1,2-dideoxy-3-O-(3,5- dinitrobenzoyl)-4,5-O-isopropylidene-D-erythro-pent-1-ynitol (5).     

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).     

Receptors for glucocorticoids in lung tissue

Gas chromatography-mass spectrometric identification of partially methylated aminosugars has been developed: (a) various kinds of O-methylated 2-deoxy-2-(N-methyl)-acetamidohexitols were prepared from partially O-(1-methoxy)-ethylated 2-deoxy-2-acetamidohexoses, and their gas chromatography-mass spectrometric patterns were determined; (b) permethylated glycolipids gave a satisfactory yield of 2-deoxy-2-N-methyl-amidohexoses by acetolysis with 0.5 n sulfuric acid in 95% acetic acid, followed by aqueous hydrolysis; (c) the resulting partially methylated aminosugars and neutral sugars were analyzed after borohydride reduction and acetylation according to the procedure of Lindberg and associates (Björndal, Lindberg and Svennson, 1967; Björndal, Hellerqvist, Lindberg and Svensson, 1970).This method was successfully applied to analysis of aminosugar linkages in blood group B-active ceramide pentasaccharide from rabbit erythrocytes and in Forssman antigen of equine spleen. The structure of blood group B-active glycolipid of rabbit erythrocyte was found to be Galα1 → 3Galβ1 → 4G1cNAcβ1 → 3Ga11 → 4Glc → Cer, and that of Forssman antigen to be GaNAcα1 → 3GalNAcβ1 → 3Galα1 → 4Ga11 → 4Glc → Cer.     

Preparation of acetylenic sugar derivatives by way of 2-(N-nitroso)acetamido sugars

N-Nitrosation with dinitrogen tetraoxide was used to convert 2-acetamido-1,3,4,6-tetra-O-acetyl-2-deoxy-α-D-glucopyranose (1) and 2-acetamido-1,3,4,6-tetra-O-acetyl-2-deoxy-β-D-galactopyranose (4) in high yield into the N-nitroso derivatives 2 and 5, respectively. Similarly, 3-acetamido-1,2,4,6-tetra-O-acetyl-3-deoxy-β-D-glucopyranose (12) and methyl 2-acetamido-3,4,5,6-tetra-O-acetyl-2-deoxy-D-gluconate (15) gave their respective, crystalline N-nitroso derivatives 13 and 16. Various other 2-acetamido sugar derivatives were likewise nitrosated. In ethereal solution, compounds 2 and 16 reacted with potassium hydroxide in isopropyl alcohol to give the C₅ acetylene, 1,2-dideoxy-D-erythro-pent-1-ynitol, isolated as the known triacetate 3. By the same procedure, the galacto derivative 5 was converted in high yield into the 3-epimeric C₅ acetylene, 1,2-dideoxy-D-threo-pent-1-ynitol, isolated as its triacetate 6 and characterized by conversion into the known, crystalline 1,2-dideoxy-3-O-(3,5-dinitrobenzoyl)-4,5-O-isopropylidene-D-threo-pent-1-ynitol (7).     

Studies on the interconversion of 2,3'-anhydro-1-β-D-xylofuranosyluracil and 2,2'-anhydro-1-β-D-arabinofuranosyluracil

2,3'-Anhydro-1-β-D-xylofuranosyluracil (10) is converted, reversibly, into 2,2'-anhydro-1-β-D-arabinofuranosyluracil (1) in the presence of sodium tert-butoxide. The reaction probably involves 2',3'-anhydrouridine as an intermediate and equilibrium is strongly in favour of 1. The behaviour of 1 and 10 towards sodium hydroxide and sodium methoxide is described. Reaction of 3-azido-3-deoxy-2,5-di-O-p-nitrobenzoyl-β-D-xylofuranosyl chloride with monochloromercuri-4-ethoxy-2(lH)-pyrimidinone afforded crystalline 1-(3-azido-3-deoxy-2,5-di-O-p-nitrobenzoyl-β-D-xylofura-nosyl)uracil (24) in 57% yield. Alkaline methanolysis of 24 gave crystalline 1-(3-azido-3-deoxy-β-D-xylofuranosyl)uracil, which yielded 1-(3-amino-3-deoxy-β-D-xylofuranosyl)uracil (27) on hydrogenation. Deamination of 27 with nitrous acid gave mainly uracil (55%) and not the epoxide 5 or compounds derived from it.     

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.     

Equimolar oxymercuration of D-glucal triacetate with mercuric perchlorate and its application to the synthesis of 2′-deoxy disaccharides

A search for appropriate reaction conditions for the equimolar methoxymercuration of D-glucal triacetate was made by using various mercuric salts, bases, and reaction solvents. Under optimum conditions with mercuric perchlorate, sym-collidine, and acetonitrile, D-glucal triacetate underwent methoxymercuration with an equimolar amount of methanol to afford methyl 3,4,6-tri-O-acetyl-2-deoxy-2-perchloratomercuri-β-D-glucopyranoside (1, 26%) and its α-D-manno isomer (2, 49%). Equimolar oxymercuration of D-glucal triacetate with partially protected sugars, followed by subsequent demercuration of the products with sodium borohydride, afforded α- and β-linked 2′-deoxy disaccharide derivatives in moderate yields. The partially protected sugars used were 1,2,3,4-tetra-O-acetyl-β-D-glucopyranose and 1,2:3,4-di-O-isopropylidene-α-D-galactopyranose, and the corresponding products were O-(3,4,6-tri-O-acetyl-2-deoxy-α-D-arabino-hexopyranosyl)-(1→6)-1,2,3,4-tetra-O-acetyl-D-glucopyranose(4, 23%) and its β-linked isomer (5, 11%) from the former, and O-(3,4,6-tri-O-acetyl-2-deoxy-α-D-arabino-hexapyranosyl)-(1→6)-1,2:3,4-di- O-isopropylidene-α-D-galactopyranose (9, 29%) and its β-linked isomer (10, 10%) from the latter. Deacetylation of these 2′-deoxy disaccharides was effected with methanolic sodium methoxide, but deacetonation was unsuccessful owing to simultaneous cleavage of the glycosidic linkage.     

Synthesis,properties, and reactions of α- and β-D-glucopyranosyl esters of some tripeptides

The 2,3,4,6-tetra-O-benzyl-1-O-(N-benzyloxycarbonyltripeptidyl)-D-glucopyranoses 1, 8, and 13 were synthesised from 2,3,4,6-tetra-O-benzyl-α-D-glucopyranose and the active esters of the appropriate N-protected tripeptides (Gly-Gly-Gly-, L-Phe-Gly-Gly-, and Gly-Gly-L-Phe-) in the presence of imidazole; the anomeric mixtures were resolved and the α and β anomers characterised. The β anomer of 13, containing the L and D enantiomers (ratio ≈ 3:1) of Gly-Gly-Phe- as the aglycon, could be resolved by column chromatography into the pure isomeric forms. Catalytic hydrogenolysis of the β anomers, in the presence and absence of a strong acid, yielded the free 1-esters 2β, 9β, and 14β, which were characterised as the monooxalate or trifluoroacetate salts and as free bases. Similarly, the α anomers afforded 2α, 9α, and 14α, whereas omission of the strong acid led to accompanying 1→2 acyl migration, to give the 2-O-acyl derivatives. All of the compounds prepared were converted into the N-acetyl and/or peracetylated derivatives. The 1-esters 2β and 9β, both in the charged and uncharged form, and the trifluoroacetate salt of 14β, are susceptible to cleavage by β-D-glucosidase; the enzyme had no effect on the uncharged form of 14β. This difference between 14β and its salt is discussed in conformational terms.     

β-Elimination of 2-O-(4-O-methyl-α-d-glucopyranosyluronic acid)-d-xylose with methylsulphinyl carbanion and hydrolysis of the hex-4-enopyranosiduronic linkage

On treatment with m sodium methylsulphinylmethanide at 25°, 2-O-(4-O-methyl-α-d-glucopyranosyluronic acid)-d-xylose (1) was rapidly degraded by β-elimination, to form 2-O-(4-deoxy-β-l-threo-hex-4-enopyranosyluronic acid)-d-xylose (2). The kinetics of hydrolysis of 1 and 2 in 0.5m sulphuric acid have been studied. Compound 2 was hydrolysed 70 times faster than 1. Compared with the rate coefficients of other related compounds, 2 was hydrolysed at approximately the same rate as 2-O-(4-O-methyl-α-d-glucopyranosyl)-d-xylose, 3.5 times more slowly than xylobiose, and twice as fast as the xylosidic bond in O-(4-O-methyl-α-d-glucopyranosyluronic acid)-(1→2)-O-β-d-xylopyranosyl-(1→4)-d-xylose.