D-Lyxose

Of the eight stereoisomeric aldopentoses Figure 25 2 shows the Fischer projections of the d enantiomers (d ribose d arabinose d xylose and D lyxose) Likewise Figure 25 2 gives the Fischer projections of the eight D aldohexoses... 

Which of the other three n aldopentoses gives the same aldaric acid as D-lyxose ... 

D-glyceraldehyde) D-Erythrose D-Lyxose D-Xylose D-Arabinose D-Ribose D>Galactose D-Mannose D-Glucose... 

D-Lyxose Heart muscle. A constituent of a lyxoflavin isolated from human heart muscle. ... 

D-Lyxose yielded a D-lyxosyl chloride 2,3,4-tri(chlorosulfate) which, on treatment with chloride ion, led to a dichlorodideoxy compound, most probably 2,4-dichloro-2,4-dideoxy-L-arabinose.353 D-Glucose gave a compound presumed to be 4,6-dichloro-4,6-dideoxy-a,/3-D-galactosyl chloride 2,3-di(chlorosulfate),360 and D-xylose afforded a monochloromonodeoxy derivative formulated, on indirect evidence, as 4-chloro-4-deoxy-L-arabinopyranosyl chloride 2,3-di(chlorosulfate).360 3,4-Dichloro-3,4-dideoxy-/3-D-ribopyranosyl chloride 2-(chlorosulfate) was the major, and 4-chloro-4-deoxy-a-D-xylopyranosyl chloride 2,3-di(chlorosulfate) the minor, product from the reaction of L-arabinose with sulfuryl chloride at room temperature for 24 hours.357,361 It has been established that, on reaction with sulfuryl chloride at low temperature, crystalline a-D-xylopyranose and /3-D-lyxopyranose afford, respectively, the 2,4,6-tri(chlorosul-fate)s of /3-D-xylopyranosyl chloride and a-D-lyxopyranosyl chloride,362 363 confirming that substitution at C-l occurs by an Sn2 process on a l-(chlorosulfuric) ester intermediate. 

Kristallisierte Mercaptale von D-Ribose, von D-Lyxose und Derivate des Galactose-und Glucose-dibenzyl-mercaptals, by E. Hardegger, E. Schreier, and Z. El Heweihi, Helv. Chim. Acta, 33 (1950) 1159-1164. 

In the pentose series, attack has also been observed to occur mainly from the less-hindered side of the double bond, as in the addition of trifluoro(fluoroxy)methane to di-O-acetyl-D-arabinal. Trifluoromethyl 3,4-di-0-acetyl-2-deoxy-2-fluoro-/3-D-arabinopyranoside and 3,4-di-0-acetyl-2-deoxy-2-fluoro-/J-D-arabinopyranosyl fluoride were obtained,72,74 together with a very small proportion of 3,4-di-0-acetyl-2-deoxy-2-fluoro-a-D-ribopyranosyl fluoride.74 With di-O-acetyl-D-xylal, however, the lyxose derivatives were mainly obtained.72,73 The suggestion has been made73 that the greater conformational mobility of pentopyranoses results in a preponderance of the C d) conformer of the D-lyxose derivatives,72,73 such that F-l and CFsO-l are axially disposed. For further reactions of unsaturated carbohydrates with tri-fluoro(fluoroxy)methane, see Section 11,9. 

The L-lyxose derivative was prepared from the anti-adduct 13a of 3-phenylpropanal as outlined below, and the absolute configuration was determined by comparison with the optical rotation of an authentic sample(lO) derived from D-lyxose. 

This enzyme [EC 5.3.1.7] catalyzes the interconversion of D-mannose and D-fructose. Both D-lyxose and D-rham-nose can act as substrates as well. 

Lysyl-tRNA phosphatidylglycerol transferase, LYSYLTRANSFERASE a-LYTIC PROTEINASE CHYMOTRYPSIN CATALYTIC TRIAD D-Lyxose,... 

SCHEME 2. Richardson s unsuccessful attempted oxidative degradation of a D-lyxose diethylsulfonyl dithioacetal possessing a fused acetal (1959). 

The oxime of D-lyxose has not been prepared, but L-rhamnose oxime (XX) with ithe same spatial configuration about carbon atoms 2, 3 and 4 reacts in an open-chain form when submitted to mild acetylation, and gives only the nitrile this reactivity is confirmed when the oxime is submitted to mild propionylation, for only the hexapropionyl-aWe%do-L-rhamnose oxime is produced and that in high yield. As already mentioned, the oximes of D-mannose (XXI), and D-gala-L- reawno-heptose (XXII),having the same configuration as rhamnose about carbon atoms 2, 3 and 4, react in a similar manner. 

D-Lyxose diacetamide. Ammonia-silver oxide.y Ten grams of pentaaoetyl-n-galactononitrile was dissolved in 30 ml. of ethanol, and a solution of silver oxide (from 5 g. of silver nitrate) in 50 ml. of 30 % ammonia added. After two days at room temperature, the precipitated silver cyanide was removed by filtration and the solution evaporated in vacuo at 40° imtil all ammonia was eliminated. The residue was diluted with water and the soluble silver eliminated by treatment with hydrogen sulfide and filtration. The filtrate was treated with decolorizing carbon, filtered and evaporated to dryness. When the residue crystallized, it was suspended in warm ethanol and filtered yield, 2.5 g. (40%). After recrystallization from 60% ethanol, the product had a melting point of 230-231°. 

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. 

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