Fucose isolation

The primary cell walls of most higher plant species contain XGs of the XXXG type, which bear trisaccharide side chains (8) on the backbone [247]. The seeds of many plants contain XXXG-type XGs, in which about 30% of the xylose units possess a /3-D-Galp residue attached to position 2. Several plant species produce XGs that lack fucose and galactose, and have a-L-Ara/ attached to 0-2 of some of the Xylp side-chains, such as XG isolated from olive fruit [262] and soybean (Glycine maxima) meal [263]. However, a-L-Ara/ residues occur also 2-linked directly to some of the Glcp residues of the backbone [154]. 

Relative molar ratios (calculated on the basis of 1 residue of 3,4-linked fucose) of methyl ethers characteristic for RG-II in the preparations isolated from fruit-derived products... 

The latter was isolated in the form of fully methylated methyl fuco-side, i. e., methyl 2,3,4-trimethyl-a-L-fucoside (XLVII), a compound previously obtained from methylated gum tragacanth.128 The recognition of this particular derivative indicates that the n-fucose residues in part at least must constitute end groups linked glycosidically to the rest of the molecule. The same compound128 was isolated by methylation and... 

In fact, other studies have shown that TMSOTf catalyzes the glycosylation of a silylated acceptor with a silylated hemiacetal donor [49]. Nudel man s procedure was applied to the synthesis [1-glucuronide 30, isolated in 57% yield. Kiyoi and Kondo have applied the TMSOTf activation protocol to protected L-fucose hemiacetal donors for glycopeptide synthesis and obtained glycopeptide fragment 31 in 74% yield (a p, 20 1) [50], Posner and Bull have developed a procedure that uses excess TMSOTf in the presence of molecular sieves (SYLOSIV A4) to synthesize various l.l -linked disaccharides such as the galactopyranose dimer 32 [51,52]. 

From his time at the Squibb research laboratories, he was interested in the chemistry of antibiotics, and in this area, he elucidated the partial structure of curamycin, an antibiotic produced by Streptomyces curacoi. From curamycin, he isolated and characterized the new natural sugar derivatives D-curacose (4-O-methyl-D-fucose), curacin [4-0-(dichlo-roisoeveminyl)-2,6-dideoxy-D-araW/io-hexose], and curamycose (2,6-di-O-methyl-D-mannose). 

A cyclic hexaacetyl oxime (XII) was also isolated by mild acetylation of D-galactose oxime and by treatment with sodium acetate and acetic anhydride. A cyclic aldoxime acetate (XIII) was also obtained by Voto6ek from D-fucose oxime, and by Restelli de Labriola and Deulofeu ... 

D-Fucose (Rhodeose). Voto6ek obtained tetraacetyl-D-fucononitrile in 25% yield by treating D-fucose oxime with sodium acetate-acetic anhydride. The nitrile, degraded with ammonia and silver oxide, yielded 5-desoxy-D-lyxose diacetamide in 40% yield. The diacetamide compound was hydrolyzed with 5% hydrochloric acid and the 5-desoxy-D-lyxose was obtained in solution and characterized as the p-bromo-phenylosazone. Hydrolysis of the diacetamide compound with 6 N sulfuric acid was realized by Voto6ek and Valentin and the 5-desoxy-D-lyxose was isolated as a sirup. 

Enzymic reactions with D-galactose oxidase or L-fucose isomerase were used for identification of the monosaccharide isolated after degradation of the esters. 

A disaccharide derivative (42) of more conventional structure has also been isolated from hen oviduct.177 Its structure was confirmed by its conversion into L-fucose and uridine 5 -(2-acetamido-2-deoxy-a-D-glucopyranosyl pyrophosphate) after treatment with a-L-fucosi-dase. Mild, acidic hydrolysis of the ester 42 produces a disaccharide whose structure was confirmed by periodate oxidation. Human milk and colostrum,178 or milk and colostrum of pig,128 are also sources of... 

In addition, the isolation of 4(5)-ethylimidazole (23) from the reactions of L-rhamnose (see Table VI), L-fucose (6-deoxy-L-galactose), and 3-deoxy-L-glyceraldehyde (see Table IX) with aqueous ammonia, led Komoto and Tsuchida39 to believe that the 2-oxobutanal forming the 4(5)-ethylimidazole (23) arose from an aldol reaction of the 3-deoxy-L-glyceraldehyde (formed by dealdolization in the cases of L-rhamnose and L-fucose) with formaldehyde, with subsequent loss of water from the 4-deoxytetrose so formed. 

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