J.S. Brimacombe

The oxidation of some carbohydrate derivatives, using acid anhydride-methyl sulphoxide mixtures and the pfitzner-moffatt reagent. Facile synthesis of 3-acetamido-3-deoxy-D-glucose and 3-amino-3-deoxy-D-xylose

Examples are provided which further demonstrate the value of the Pfitzner-Moffatt reagent and acid anhydride-methyl sulphoxide mixtures as oxidants in carbohydrate chemistry. Convenient and stereospecific syntheses of 3-acetamido-3-deoxy-D-glucose and 3-amino-3-deoxy-D-xylose have been developed from 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose.

Nucleophilic displacement reactions in carbohydrates: The formation of 1,4-anhydro-6-deoxy-2,3-O-isopropylidene-β-l-talopyranose (1,5-anhydro-6-deoxy-2,3-O-isopropylidene-α-l-talofuranose)

Abstract The action of sodium methoxide in methanol on 2,3- O -isopropylidene-4- O -methanesulphonyl- l -rhamnopyranose rapidly yields 1,4-anhydro-6-deoxy-2,3- O -isopropylidene-β- l -talopyranose(1,5-anhydro-6-deoxy-2,3- O -isopropylidene-α- l -talofuranose) as the sole product. The structure is assigned on the basis of chemical and n.m.r. evidence. The anhydro sugar is also obtained by similar treatment of 6-deoxy-2,3- O -isopropylidene-5- O -methanesulphonyl- d -allofuranose, prepared from benzyl 6-deoxy-2,3- O -isopropylidene-β- d -allofuranoside.

The addition of dichloromethylene to unsaturated sugars

Abstract Addition of dichloromethylene to 3,4,6-tri- O -methyl- d -glucal gave a single product that was tentatively identified, by stereochemical considerations as, 1,5-anhydro-2-deoxy-1,2- C -(dichloromethylene)-3,4,6-tri- O -methyl- d - glycero - d - ido -heptitol(1), and was characterised, after demethylation, as the tribenzoate 3 . 3-Deoxy-1,2:5,6-di- O - isopropylidene-α- d - erythro -hex-3-enofuranose reacted with dichloromethylene to give 3-deoxy-3,4- C -(dichloromethylene)-1,2:5,6-di- O -isopropylidene-α- d -galactofuranose ( 6 ), which was then converted by mild hydrolysis with acid into the 1,2- O -isopropylidene derivative ( 8 ). Reduction of compound 1 and 6 with lithium aluminium hydride gave the corresponding cyclopropyl derivatives, 4 and 7, respectively.

A synthesis of chromose D and an improved synthesis of chromose A

Abstract The structure of chromose D, a sugar component of the antitumour substance chromomycin A 3 , has been confirmed as 3- O -acetyl-2,6-dideoxy- D - lyxo -hexose by synthesis. The corresponding 4- O -acetate has been synthesised for reference purposes. An improved synthesis of chromose A is described.

Purification of pneumococcus types II and V polysaccharides

Abstract DEAE Sephadex has been shown to afford separation of Type V Pneumococcus specific polysaccharide, C-substance, and other components, when alcohol fractionation or detergent precipitation were only partially effective. Dissociable complex formation between Type II polysaccharide and nucleic acid has been demonstrated on the same column. Sephadex G-200 can be used to remove nucleic acid impurities from Type II Pneumococcus polysaccharide.

The acetonation of D-talose

Abstract The acetonation of α- D -talopyranose in the presence of anhydrous copper(II) sulphate and sulphuric acid has been re-examined, and the major products have been shown to be 2,3:5,6-di-O-isopropylidene-α- D -talofuranose (1, 28%) and 1,2:5,6-di-O-isopropylidene-β- D -talofuranose (2, 10%). These structures were allocated primarily on the basis of mass spectrometry and nuclear magnetic resonance spectroscopy. Oxidation of diacetal 1 with acetic anhydride in methyl sulphoxide gave 2,3:5,6-di-O-isopropylidene- D -talono-1,4-lactone (4). 1,2:5,6-Di-O-isopropylidene-3-O-toluene-p-sulphonyl-β- D -talofuranose (3) was obtained on sulphonylation of diacetal 2.

A re-examination of the acetonation of an equilibrium mixture of d-altrose and 1,6-anhydro-β-d-altropyranose and a synthesis of 1,2:5,6-di-O-isopropylidene-β-d-mannofuranose

Abstract Acid-catalysed acetonation of an equilibrium mixture of d -altrose and 1,6-anhydro-β- d -altropyranose was shown by g.l.c. to yield 1,6-anhydro-3,4- O -isopropylidene-β- d -altropyranose ( 6 , 60%), 1,2:5,6-di- O -isopropylidene-β- d -altrofuranose ( 2 , 23%), and 1,2:3,4-di- O -isopropylidene-β- d -altropyranose ( 4 , 17%). Evidence is presented in support of the structure 4 for the latter diacetal which has been obtained in crystalline form. Oxidation of the diacetal 2 with acetic anhydride-methyl sulphoxide afforded 1,2:5,6-di- O -isopropylidene-β- d - arabino -hexofuranos-3-ulose (14) , which was reduced stereospecifically, with sodium borohydride, to 1,2:5,6-di- O -isopropylidene-β- d -mannofuranose (15) .

Structural studies on the capsular polysaccharide of pneumococcus Type V

Abstract Further details of the structure of the capsular polysaccharide (SV) of Pneumococcus Type V have been elucidated by methylation studies and by oxidation with periodate. It is proposed that the polysaccharide contains multiple residues of 2-acetamido-2,6-dideoxy-3- O -( D glucopyranosyluronic acid)- L -galactose, to which are attached residues of D -glucose and 2-acetamido-2,6-dideoxy- L -talose N -acetyl- L - pneumosamine). Residues of 2-acetamido-2,6-dideoxy- L -galactose N -acetyl- L -fucosamine) constitute branch points, and pneumosamine residues are present mainly as non-reducing end-groups. The majority of the D -glucose and D -glucuronic acid residues are 1,4- and 1,2-linked, respectively. The immunochemistry of SV is reviewed in the light of these findings.

Nucleophilic displacement reactions in carbohydrates

Abstract The solvolysis of methyl 6- O -methanesulphonyl-2,3-di- O -methyl-β- d -galactoyranoside ( 8 ) in boiling 50% aqueous methanol, in the presence of sodium acetate afforded three products which were identified as methyl 3,6-anhydro-2- O -methyl-β- d -galactopyranoside ( 9 ), methyl 2,3,6-tri- O -methyl-β- d -galactopyranoside ( 12 ), and methyl 2,3-di- O -methyl-β- d -galactopyranoside ( 7 ). Anhydro-sugar 9 is considered to result from attack of solvent on an oxonium-ion intermediate 14 , formed as a consequence of methoxy-group participation in displacement of the sulphonic ester group, while compounds 7 and 12 may result either from solvent attack upon the oxonium ion or from a solvent-assisted displacement of the sulphonic ester group.

Graded, acid hydrolysis of some O-isopropylidene derivatives (including β-erythro-ketals) of carbohydrates

Abstract Evidence is presented which supports the sequence β- erythro > α for ketal stability in the graded, acid hydrolysis of 3,5:6,7-di- O -isopropylidene- D - glycero - D - gulo -heptono-1,4-lactone ( 1 ), 1,2:3,5-di- O -isopropylidene- L - glycero - L - gulo -heptitol monohydrate ( 2 ), and 1,2:3,5-di- O -isopropylidene- L -gulitol ( 3 ).