Partial acetolysis

Fig. 18.—C-l Regions of 13C-N.m.r. Spectra of a,)3-D-Mannopyranans from Pichia pastoris (A) and Citeromyces matritensis (B), and Those of Oligosaccharides Formed by Partial Acetolysis (C and D, Respectively). (Solvent, DjO temperature, 70° chemical shifts expressed as 8C, relative to external tetramethylsilane.)...

Partial-acetolysis studies conducted on yeast D-mannopyranans containing (l- 6)-linked a-D-mannopyranosyl main-chains revealed a large variety of side-chain structures, as represented by oligosaccharides isolated from the acetolyzate (see Table III). Following purification by cellulose-column chromatography, the oligosaccharides were identified by their typical, 13C-n.m.r. spectra.85... 

Oligosaccharide Fragments Obtained Following Partial Acetolysis of Mannans Having (1— 6)-Linked a-D-Mannopyranosyl Main-Chains... 

SCHEME 7. Oligosaccharides obtained after partial acetolysis of a complex sulfated galactan from Grateloupia divaricata.253... 

A. I. Usov and V. V. Barbakadze, Polysaccharides of algae. 27. Partial acetolysis of the sulfated galactan from the red seaweed Grateloupia divaricata Okam, Sow J. Bioorg. Chem., 4 (1978) 814-820(English translation from Bioorg. Khim., 4 (1978) 1107-1115). 

A branched mannan extracted from the cells of the yeast Tricho-sporon aculeatum also contains a-D-(l- 2)- and a-D-(l— 6)-link-ages (see Table III). Partial acetolysis gives rise to a (I— 2)-linked mannohexaose this represents a maximum of five consecutive a-D-(I- 2)-linkages in the mannan. 

The great use of acetolysis in polysaccharide chemistry is in degradation of the polysaccharides, imder mild conditions, to oligosaccharide per-acetates. More-drastic conditions afford monosaccharide peracetates, including those of the aldehydo forms of the sugars. " The many oligosaccharides obtained from the partial acetolysis of various polysaccharides are excellently documented in a book by Bailey, and the reader searching for particular examples is referred thereto. 

Synthesis from o-xylose A construction of the AB ring has also been achieved from D-xylose (Scheme 5). D-Xylose was reacted with ethanethiol followed by treatment with formaldehyde to afford the dithioacetal 35, which underwent partial acetolysis of the... 

Partial acetolysis of bis(2, 4, 6-tribromophenyl) trichlorophosphorane affords bis(2, 4, 6-tribromophenyl) phosphorochloridate which, in the presence of... 

Another common method, that of preparation of a 6-D-galactofur-anosyl mannose by partial hydrolysis or by partial acetolysis, is impractical since such a glycosidic linkage is relatively labile. 

The methylation data is very complex, 2,3,4,6-tetra-O-methylmannitol acetate (25%), 2,3,5,6-tetra-07methylgalactitol acetate (9%), and 3,4,6-tri-O-methylmannitol acetate (17%) being detected as major components. Also agreeing with the 13( data was the formation, following partial acetolysis, of a (1—>2) -linked trisaccharide containing a-D-mannopyranosyl units. 

Isol. from partial acetolysate of X-carra-geenan. Constit. of the products obt. by partial acetolysis of the algae galactans from Aeodes ulvoidea and Pachymenia carnosa. Constit. of the repeating unit of Klebsiella antigens. 

Reducing disaccharide. Isol. from the partial acetolysis of xanthan gum from Xanthomonas campestris. 

The most widely distributed polysaccharide on earth is cellulose, which is built up in plants as a skeletal compound. Cellulose is depolymerized by acetol-ysis, that is, by treatment with a mixture of acetic acid anhydride and sulfuric acid. The y0-glucopyranose residues in cellulose are linked in 1-4-position. Figure 3.247 shows the chromatogram of an aqueous solution of -(l-4)-linked D-glucans, which was obtained by Koizumi et al. [236] after partial acetolysis of cellulose and subsequent deacetylation in 0.15 mol/L NaOH. Oligomers up to DP28 were detected. 

Fig. 3-188. Separation of jS-(1.4)-linked D-glucans after partial acetolysis of cellulose. - Separator column CarboPac PAl eluant (A) 0.15 mol/L NaOH, (B) 0.15 mol/L NaOH + 0.5 mol/L NaOAc gradient linear, 20% B to 50% B in 10 min, then to 60% B in 20 min flow rate 1 mL/min detection see Fig. 3-182 injection 50 pL of a 0.3% aqueous solution of the acetolysate (taken from [185]).

A useful halide was encountered by Hudson and co-workers 29) in the partial acetolysis of methyl tri-0-acetyl-/8-D-arabinopyranoside and was shown to have the structure R—CH(OMe)Cl. It was obtainable in two forms and its halogen was replaceable by methoxyl and acetoxyl groups. Other and more general methods for preparing these halides were devised by Wolfrom and co-workers 84) and the products were utilized in the preparation of acetals and thioacetals, as shown below 85),... 

A nearest-neighbour analysis of the products of partial acetolysis of S. cerevisiae mannan has been carried out in an attempt to learn whether the side-chains are in ordered or in random sequences. The results suggested that the... 

The structure of one of the carbohydrate moieties of an a-amylase from a Rhizopus species has been determined. Six o-mannosyl residues and a 2-acetamido-2-deoxy-D-gIucosyl residue were released on digestion of a glyco-peptide in turn with a-o-mannosidase and -D-2-acetamido-2-deoxyglucosidase. The structure (5) was proposed on the basis of the results of enzymic hydrolysis, methylation, partial acetolysis, and Smith degradation. 

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