Graham R. Woolard

Structural studies on a glucuronoarabinoxylan from the husk of sorghum grain

Abstract Polysaccharide H-3 is composed of L -arabinose, D -xylose, glucuronic acid, and 4-O-methylglucuronic acid in the molar ratios of 15:18:2:1. The polysaccharide contains a primary chain of α- D -(1→4)-linked D -xylopyranose residues. The identification of 2-O-(glucopyranosyluronic acid)- D -xylose and 2-O-(4-O-methylglucopyranosyluronic acid)- D -xylose revealed that the acid residues are bonded through O-2 of some D -xylopyranose moieties. Most of the L -arabinofuranose residues occur as nonreducing end-groups, attached through O-3, and in some cases through both O-2 and O-3, of certain D -xylose residues. Some L -arabinofuranose residues are substituted at O-2 or O-3. P.m.r. spectroscopy suggested that most of the L -arabinose units are α-linked.

A hemicellulosic β-D-glucan from the endosperm of sorghum grain☆

Abstract A hemicellulosic β- D -glucan of d.p. ≈26 has been isolated from the endosperm of sorghum grain. Methylation analysis, partial hydrolysis with acid, and periodateoxidation studies showed that the glucan is linear and has both (1 → 3)- and (1 → 4)-linked D -glucopyranose residues in the ratio of 3:2. The low, positive, specific rotation and chromium trioxide oxidation studies indicated that the D -glucose residues are β-linked.

A heteroxylan from the husk of Sorghum grain

Polysaccharide H-1 from the husk of Sorghum bicolor contains xylose, arabinose, glucose, galactose, glucuronic acid and 4-O-methylglucuronic ac

Conformational analysis of 1,2:3,4-di-O-isopropylidene-α-d-galacto-octopyranose derivatives: a 1H- and 13C-N.M.R.-spectral and x-ray comparative study

Abstract The pyranoid conformations of 7-acetamido-6,7,8-trideoxy-1,2:3,4-di- O -isopropylidene- d - glycero -α- d - galacto -octopyranose ( 3 ) and 7-acetamido-7,8-dideoxy-1,2:3,4-di- O -isopropylidene- l - threo -α- d - galacto -octopyranose ( 4 ) in solution have been determined by calculation of the dihedral angles from the vicinal, proton-proton coupling-constants, using three modifications of the Karplus equation. Of these, only the equation 3 J (HCCH)(φ)  (7.48  0.74 -ΣδE x )  (2.03  0.17 ΣE x )cos φ + (4.60  0.23 ΣδE x )cos 2φ + 0.06 (Σ ± ΔE x )sin φ + 0.62 (Σ ± ΔE x )sin 2φ indicates that the pyranoid part of 3 and 4 has the ° S 2 conformation, very slightly distorted towards ° H 5 , in agreement with the conformations determined for the crystalline state. Analysis of the 1 H-n.m.r. data for a series of 1,2:3,4-di- O -isopropyl-idene-α- d - galacto -octopyranose derivatives shows that the pyranoid parts of these compounds adopt the same conformation as that found for 3 and 4 .

Synthesis and crystal structures of 7-acetamido-7,8-di-deoxy-1,2:3,4-di-O-isopropylidene-β-L-threo-Dgalacto-octopyanose and 7-acetamido-6-O-acetyl-7,8-dideoxy-1,2:3,4-di-O-isopropylidene-α-D-erythro-D-galacto-octopyranose

Abstract 7-Acetamido-7,8-dideoxy-1,2:3,4-di- O -isopropylidene-α- D -erythro- ( 14 ) and -threo- and -β- L -erythro- and -threo- ( 17 ) octopyranose, intermediates for the synthesis of analogs of the antibiotic lincomycin, have been synthesized from a mixture of 7,8-dideoxy-7-C-nitro-octoses prepared from D -galactose. O -Acetylation of 14 gave the 6-acetate ( 18 ). The configurations of C-6 and C-7 in compounds 17 and 18 were determined by X-ray crystallography. The crystals of compound 17 are monoclinic, space group C2, with Z  4, in a unit cell of dimensions a  1.825(1) nm, b  947(1) pm, and c  1.123(1) nm. The crystals of compound 18 are orthorhombic, space group P2 1 2 1 2 1 , with Z  12, in a unit cell of dimensions a  2.814(2) nm, b  1.302(1) nm, and c  1.713(1) nm.

Structural studies on the water-soluble gums from the endosperm of sorghum grain

Abstract Purification by Bio-Gel P-100 chromatography of the cold-water-soluble gum from the endosperm of sorghum grain gave an electrophoretically homogeneous d -glucan. This polysaccharide (glucan A) had [α] d 20 + 88° and d.p. 23. Methylation analysis and periodate-oxidation studies indicated that glucan A has both (1→4)- and (1→6)-linked d -glucopyranose residues, in the ratio of 2:1. On average, three d -glucose residues per molecule of glucan A are branched. Chromium trioxide oxidation analysis of glucan A indicated a preponderance of α- d -glucosidic linkages. P.m.r. spectroscopy of permethylated glucan A showed the presence of α- and β-linkages in the ratio of 4:1. Purification of the hot-water-soluble gum by Bio-Gel P-100 chromatography gave glucan B, having [α] d 20 + 134° and d.p. 20. Structural studies showed glucan B to be similar to glucan A, differing in the ratio of (1→4)- to (1→6)-linkages; glucan B has these d -glucosidic linkages in the ratio of 6:1.

Synthesis and crystal structure of 7-acetamido-6,7,8-trideoxy-1,2:3,4-Di-O-isopropylidene-α-d-glycero-d-galacto-octo-pyranose

Abstract 7-Acetamido-6,7,8-trideoxy-1,2:3,4-di- O -isopropylidene-α- d - and -β- l - glycero - d - galacto -octopyranoses (8) and (9) , intermediates for the synthesis of analogs of the antibiotic lincomycin, have been synthesized from cis -6,7,8-trideoxy-1,2:3,4-di- O -isopropylidine-7- C -nitro-α- d - galacto -oct-6-enose (4) . The configuration of C-7 in compound 8 was determined by X-ray crystallagraphy. The crystals are orthorhombic, space group P 2 1 ,2 1 2 1 with Z4, in a unit cell of dimensions a2.457(1) nm, b 1.380(1) nm, and c 526(1) pm. The conformation of compound 8 in the solid state is °S 2 , slightly distorted towards ° H 5 .

DMSO-soluble hemicelluloses from the husk of Sorghum grain

Abstract The chlorite holotellulose from the grain husk of Sorghum bicolor was extracted with DMSO and the hemicellulosic material separated into water-solu

Structural studies on three hemicellulose B fractions from the husk of sorghum grain

Abstract Hemicelluloses H-4, H-8, and H-9 each contains L -arabinose, D -xylose, D -galactose, D -glucose, glucuronic acid, and 4- O -methylglucuronic acid. The degrees of polymerization of these polysaccharides are 993 (H-4), 2,380 (H-8), and 851 (H-9). These polysaccharides have backbones of β-(1→4)-linked D -xylopyranosyl residues to which are attached side chains of L -Arabinofuranosyl or glucosyluronic acid groups. L -Arabinofuranosyl groups are attached at O-3, or O-2 and O-3, of certain D -xylopyranose residues. Glucosyluronic acid side-chains are attached to the primary xylan chain at O-2 of some D -xylose residues. Hemicelluloses H-4, H-8, and H-9 differ from one another in their degree of branching.

A stereospecific synthesis of l-dendroketose derivatives

Abstract The 3,4-O- and 1,2:3,4-di-O-isopropylidene derivatives (7 and 8) of l -dendroketose [4-C-(hydroxymethyl)- l -glycero-pentulose] (1) have been synthesized stereo-specifically from 4-C-(hydroxymethyl)-1,2:3,4-di-O-isopropylidene- l -erythro-pentitol (2).