Octoses

The same scheme may be extended to the octoses, e.g., in the correlation of D-manno-L-manno-octose (whose configuration is proved by its reduction to an optically inactive meso octitol)27 and the L-rhamno-... 

Figure 2.25. Biosynthetic gene clusters for APR and HYG-B. D octose synthase, transfer, modification (APR), P 8 Glycosyltransfer/modifica-tion (APR), D HYG-specific genes all other colors see Figure 2.9.

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. ... 

Figure 2.25. Biosynthetic gene clusters for APR and HYG-B. P octose synthase, transfer,...

Treatment of the dichloromethyl derivative 472 with sodium cyanide gave290 an almost quantitative yield of the epimeric nitriles (480, 481). The mixture could not he separated by chromatographic methods, but differences in reactivity of the stereoisomers towards methanolic hydrogen chloride allowed isolation of only one ester, namely, 482 the trails cyanide underwent ready conversion into the methyl ester, whereas the cis compound gave a rather complicated mixture of products, with amide 483 being identified as the major component. Reduction of the ester group in 482, followed hydrolysis of the dichloromethyl group, afforded DL-t/ireo-DL- Y/o-octose, characterized as the heptaacetate, and identified as threo-ido-octito by comparison with an authentic sample. 

Later, pillaroside was also synthesized by reaction of 250a with388 48c and with141 50. y-Octose (29) was also synthesized by introduction of a C-vinyl group into the corresponding glycos-4-ulose.388... 

An interesting variation of the cyanohydrin synthesis is based on the application of the Strecker reaction 118], or an appropriate modification of it, to protected dialdo sugars to give glycosyl a-aminonitriles, with good levels of diastereoselectivity (ds > 90%) [19]. This approach was employed for a formal synthesis of the amino octose lincosamine from... 

See also J. S. Brimacombe, R. Hanna, A. K. M. S. Kabir, F. Bennett, and I. D. Taylor, Higher-carbon sugars. Part 1. The synthesis of some octose sugars via the osmylation of unsaturated precursors, J. Chem. Soc. Perkin Trans. 1, p. 815 (1986). 

S. Jeganaihan and P. Vogel, Highly stereoselective total syntheses of octoses and derivatives, J. Org. Chem. 56 1133 (1991) P. Vogel, D. Fattori.F. Gasparini, and C. Le Drian, Optically pure 7-oxabicyclo[2.2.1]hept-5-en-2-yl derivatives ( naked sugars ) as new chirons, Synlett. p. 173 (1990). 

Octoses.1 A new route to octoses involves catalytic osmylation (7, 256-257) of allylic alcohols derived from a hexose by Wittig olefination to introduce two... 

The simple sugars, or monosaccharides, are the building blocks of carbohydrate chemistry. They are polyhydroxy aldehydes or ketones with five, six, seven, or eight carbon atoms that are classified appropriately as pentoses, hexoses, heptoses, or octoses, respectively. They can be designated by more... 

A. Sonesson and E. Jantzen, The branched-chain octose yersiniose A is a lipopolysaccharide constituent of Legionella micdadei and Legionella maceachernii, J. Microbiol. Methods, 15 (1992) 241-248. 

D-Gala-irffoZo-octose oxime, IV, 124 heptaacetate, IV, 124 octaacetate, IV, 150 D-Gala-L-ffluco-heptitol, I, 9, 11 and heptaacetate, I, 35 L-Gala-D-gluco-heptitol, I, 14 and heptaacetate, I, 35 L-Gala-D-gfuco-heptonic acid, 7-desoxy-, I, 30... 

D-Gluco-D-j/ola-decose, I, 29 d-G1u co- L-jala-octitol, I, 20, 22 and octaacetate, I, 35 D-Gluco-L-0o2a-octose, I, 20, 22 Gluco-ffulo-heptitol, and heptaacetate, I, 9, 34, 35... 

D-Gluco-L-talo-octitol, I, 22 and octaacetate, I, 35 D-Gluco-L-tolo-octose, I, 22 [Pg.363]

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