Heptose, formation

Bonsignore, a., Pontremoli, S., Fornaini, G. and Gra23, E. (1957) Non-oxidative heptose formation in enzyme preparations of rat liver. Italian J. Biochem. VI, 227-238. 

Phase 3. Formation activation and modification of a putative NDP-heptose. We suggest that the heptose moiety is derived from erfo-heptulose-7-phos-phate, which is the universal source for heptoses in all organisms having a functional pentosephosphate cycle. Also, for C-7 cyclitols (e.g., valien-amine) or for secondary metabolic sugar units with longer C chains, such as octoses (e.g., lincosamine, or the octose unit in APR, see Section 2.2.4.2), this seems to be the preferred precursor in actinomycete pathways. ... 

Formation of a possible precursor of 9, namely, o-glycero-D-manno-heptose 7-phosphate, from D-sedoheptulose 7-phosphate was demonstrated in Salmonella typhimurium.238... 

S. J. Angyal and T. Q. Tran, Conformational analysis in carbohydrate chemistry. 5. Formation of glycosidic anhydrides from heptoses, Can. J. Chem., 59 (1981) 379-383. 

L. C. Stewart and N. K. Richtmyer, Formation of 1,6- and 1,7-anhydro-D-g7ycero-fi-D-gw/o-heptopyranose from D-glycero-fi-D-gulo-heptoses in acid solution, J. Am. Chem. Soc., 77 (1955) 424-427. 

In our syntheses of Salmonella structures [10,13,19,21], the heptose derivative 1 was used as a precursor for all of the heptose residues found in the target molecules. An acceptor precursor for later formation of the (1 —> 7)-linkage was obtained by regioselective silylation of the primary hydroxyl group followed by benzoylation of OH-6 (Scheme 3). Van Boom et al. postpone the oxidation step... 

The reported yields in these ketose preparations range from less than 10% to around 50%. Nevertheless, this is the method of choice for preparing certain ketoses, especially where the starting aldose can be sacrificed. For some unknown reason, the best yields have consistently been obtained in the formation of D- Zwco-heptulose from D-j/Zj/cero-D-j/aZo-heptose. The procedure of Pratt, Richtmyer, and Hudson for preparation of this substance is given here. 

The tetraglycosyl phosphate repeating-unit polymer of the extracellular polysaccharide of Campylobacter lari strain ATCC 3521 contains 6-deoxy-L-gM/o-heptose (55) in a-pyranosyl form. The identity of this constituent was established by comparison with synthetic 6-deoxy-L-gn/oheptose, with substantiation of the L-enantiomeric configuration through formation of chiral glycosides.259... 

The synthesis of 7-deoxy-L-g/ cero-D-g/Mco-heptose (19), an inhibitor of gluco-kinase and glucose 6-phosphatase, from 1,2-0-isopropylidene-D-glucuronolac-tone derivative 18 is shown in Scheme 5. The 2 -0-cyclohexylcarbamoyl disaccharide 20 (see Chapter 3 for formation) was readily converted to the corresponding xanthate which was deoxygenated with tributyltin hydride to the 2 -deoxy disaccharide 21. Radical deoxygenation with tributyltin hydride has also been use to prepare l, 6 -dideoxysucrose from the corresponding l, 6 -ditriflate. ... 

Epimerization at the third carbon or formation of ketoses that have a carbonyl group at carbon 3 may take place. These reactions explain the formation of D-psicose from D-glucose (85) D-gluco-heptulose from D-glycero-D- aZa-heptose (86), the interconversions of D-sorbose and D-galactose (78),... 

The formation of colored products by the reaction of sugars and phenols in the presence of strong acids has been mentioned previously as a qualitative test for carbohydrates. Carbazole or anthrone may be used instead of a phenol. Methods employing orcinol (3,5-dihydroxy toluene) and carbazole have been described in detail 31). Dische 32) described a modified carbazole reaction for determining ketohexoses, ketopentoses, trioses, and glycolic aldehyde as well as a method for determining heptoses. 

Reaction of 2-amino-2-deoxy-D-glucose hydrochloride with potassium qranate yields a mixture from which, after acetylation, the fused urea derivative (20) and the heterocycle (21) were isolated 2-deoxy-2-ureido-D-glucose is postulated as an intermediate in the formation of both products. Reaction of 2-amino-2-deoxy-D-g/ycere>-L-g/Mco-heptose with cyanamide gave the fused guanidine salt (22) acetylation of the crude reaction product provided both the fused urea derivative (23) and the heterocycle (24). ... 

Reaction of 3-acetamido-3-deoxy-4,5 6,7-di-0-isopropylidene-2-0-methyl-a/dle/i> dlo-D-g/yccro-D-gfl/flcro-heptose with [ethoxy(ethoxycarbonyl)methylene]-triphenyl-phosphorane, followed by an ethoxymercuration-demercuration reaction and acid hydrolysis resulted in the formation of the ethyl esters of 4-0-methyl-N-acetylneuraminic acid and 4-0-methyl-4-epi-N-acetylneuraminic acid (Beau et al. 1978). By oxymercuration of ethyl 5-acetamido-3,5-dideoxy-2-0-ethyl-4-0-methyl-D-g/jcero-D-ga/acto-non-2-enonate with mercury(II) trifluoroacetate, followed by borohydride-demercuration, 4-0-methyl-N-acetylneuraminic acid ethyl (3-glycoside was obtained (Beau et al. 1980). 4-0-Methyl-N-acetylneuraminic acid has been used in metabolism studies, as reported by Beau and Schauer (1980). Using tritiated sodiumborohydride, the corresponding 4-0-methyl-N-acetyl-[3-3H]neuraminic acid was obtained (Beau and Schauer 1980). 

KDO has chemical properties similar to those of neuraminic acid as it has a carboxylate group, a 3-deoxy group, and a similar biosynthesis (see Chapter 10). The monosaccharide composition, sequence, and linkages, along with the position of attachment of phosphate and ethanolamine pyrophosphate substituted onto the heptose residues of the core polysaccharide have been determined [53-58] and are shown in Fig. 9.16C. The fatty acids in the lipopolysaccharide participate in the formation of a lipid bilayer for the outer membrane. The carbohydrate is hydrophilic and is located on the outer faces of the lipid bilayer membrane. The O-antigen polysaccharides and other capsular polysaccharides are attached to position-4 of the next to last monosaccharide residue, a-D-glucopyranose of the core polysaccharide. 

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