Ribitol

The liquid began to crystallize on standing, but after several months time crystallization appeared to stop and the crystalline material (2 g.) was removed. The latter proved to be identical with the D,L-arabitol pentaacetate obtained above, the total yield of which was approximately equal to that of the liquid which did not crystallize. 

This liquid was hydrolyzed under conditions similar to those employed with D,L-arabitol pentaacetate and yielded a sirup which crystallized spontaneously on standing, or immediately if seeded with ribitol. The crude product melted at 96-104° upon recrystaUization from ethanol the melting point and mixed melting point with an authentic sample of ribitol was 

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Fig. 1. Stmctures of the tetritols (a) erythritol, (b) D-threitol, and (c) L-threitol and the pentitols (d) ribitol, (e) D-arabinitol, (f) L-arabinitol, and (g) xyhtol.

D,L-Arahinitol can be prepared by the action of hydrogen peroxide in the presence of formic acid on divinyl carbinol (36) and, together with ribitol (Fig. ld),fromD,L-erythron-4-pentyne-l,2,3-triol,HOCH2CHOHCHOHC=CH (37). 

Sweetness is often an important characteristic of sugar alcohols in food and pharmaceutical applications. The property of sweetness is measured in a variety of ways and has a corresponding variability in ratings (218). Based on one or more test methods, erythritol and xyfitol are similar to or sweeter than sucrose (218,219). Sorbitol is about 60% as sweet as sucrose, and mannitol, D-arabinitol, ribitol, maltitol, isomalt, and lactitol are generally comparable to sorbitol (see Sweeteners). 

Teichoic acids (16) are bacterial polymers in which alditols, glycerol, or ribitol are joined through the primary hydroxyl groups via phosphate diester linkages. 

Adonitol (Ribitol) [488-81-3] M 152.2, m 102 . Crystallise from EtOH by addition of diethyl ether. Adrenalin see epinephrine. 

D-Glucitol D-Mannitol D-Xylitol D-Glycerol myo- Inositol D-Ribitol... 

FIGURE 9.25 Teichoic acids are covalently linked to the peptidoglycan of Grampositive bacteria. These polymers of (a, b) glycerol phosphate or (c) ribitol phosphate are linked by phosphodiester bonds. 

Ribitol teichoic acid from Bacillus subHUs... 

Riboflavin, or vitamin B2, is a constituent and precursor of both riboflavin 5 -phosphate, also known as flavin mononucleotide (FMN), and flavin adenine dinucleotide (FAD). The name riboflavin is a synthesis of the names for the molecule s component parts, ribitol and flavin. The structures of riboflavin. 

In fact, it has been found (52) that in unbuffered solution, at room temperature, authentic 2-deoxy ribose 5-phosphate reduces more than 4 molar equivalents of periodate, but. that there is no noticeable slowing down of the reaction rate after the reduction of the first molar equivalent. This may be owing to the fact that only the aldehydo form (76) of 2-deoxy ribose 5-phosphate has a free vicinal diol group as the acyclic 2-deoxy ribitol 5-phosphate reduces one molar equivalent of periodate quite fast (58), it is probable that the time-curve of periodate uptake by the phosphorylated sugar reflects the rate of formation of the aldehyde form from the furanose form. 

The unknown phosphate ester had the same electrophoretic mobility as 2-deoxy ribitol 5-phosphate and it seemed reasonable to expect that in the conditions used (0.1 M pyridinium acetate buffer of pH 5) 2-deoxy ribitol-4- and -5-phosphates would behave similarly therefore it was considered probable that the unknown phosphate ester is 2-deoxy ribitol 4-phosphate, resulting from the reduction of the periodate resistant 2-deoxy ribose 4-phosphate. However, the possibility that both 2-deoxy ribitol 4-phosphate and 2-deoxy erythritol 3-phosphate (formed from... 

On catalytic hydrogenation over a platinum catalyst, ribose (Problem 9.57) is converted into ribitol. Is ribitol optically active or inactive Explain. 

R = H 3.5-Q-benzylidene-l-deoxy-2-C-phenyl-D-arabinitol yield 77% d.r. (39/40) 100 0 40 R = TBDMS 3,5-0-benzylidene-4-0-tert-butyldimethylsilvl-t-deoxy-2-C-phenyl-D-ribitol yield 89% d.r. (39/40) 0 100... 

Poly[(p-D-ribofuranosyl-5-0-yl)(1-deoxy-D-ribitol-1-C,5-0-diyl)(oxidophosphoryl)]... 

CN 1 -deoxy-1 -[3,4-dihydro-7,8-dimethyl-2,4-dioxobenzo[g]pteridin-10(27/)-yl]-D-ribitol... 

Several of the intracellular teichoic acids are polymers of glycerol phosphate or ribitol phosphate. An unusual teichoic acid, composed of d-mannitol phosphate, and with pyruvic acid linked as an acetal to 0-4 and 0-5, has been isolated from Brevibacterium iodinum. ... 

Like the polymethylene hydrocarbons, acyclic carbohydrates and alditols tend to adopt the planar, zigzag conformation wherein all of the carbon atoms lie in the same plane. " However, non-bonded interactions between parallel hydroxyl groups in the 1,3 positions (sy/i-axial interaction) are the most highly destabilizing, and, in xylitol and ribitol, this... 

Fig. 1.3 A, glycerol teichoic acid B, ribitol teichoic acid G, 3-10 glycosyl Ala, D-alanyl.

Flavins — These are isoalloxazine derivatives methylated at Cg and C-j, with substituents at Ng The most important flavin, riboflavin, has a ribityl gronp (derived from ribitol) at Ng. 

The rate-limiting step in the absorption of those compounds that readily penetrate the intestinal membrane (i.e., have a large permeability coefficient) may be the rate at which blood perfuses the intestine. However, absorption will be independent of blood flow for those compounds that are poorly permeable. Extensive studies have illustrated this concept in rats [106,107]. The absorption rate of tritiated water, which is rapidly absorbed from the intestine, is dependent on intestinal blood flow, but a poorly absorbed compound, such as ribitol, penetrates the intestine at a rate independent of blood flow. In between these two extremes are a variety of intermediate compounds whose absorption rate is dependent on blood flow at low flow rates but independent of blood flow at higher flow rates. By altering blood flow to the intestine of the dog, as blood flow decreased the rate of sulfaethidole absorption also decreased [108]. These relationships are illustrated in Fig. 16. 

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