Ribose crystalline form

If only one, or none, of the forms is known in the crystalline state, polarimetry does not yield any useful results. It was not even certain, for example, before the advent of n.m.r. spectroscopy, whether the one known crystalline form of D-ribose is the a- or the / -pyranose its muta-rotational change is small, but complex.5... 

An amorphous 2,3,4-tribenzoyl-D-ribose has been reported as a product of the hydrolysis of aniline D-ribopyranoside tribenzoate29 as well as of the hydrolysis of tribenzoyl-/3-D-ribopyranosyl bromide with moist acetone in the presence of silver carbonate.110 In the latter case the structure of the product was demonstrated through methylation to the known methyl /9-D-ribopyranoside tribenzoate. Recently Ness, Fletcher and Hudson111 have succeeded in obtaining a 2,3,4-tribenzoyl-D-ribose in crystalline form. 

The only known crystalline form of D-ribose is /3-D-ribopyranose, but in solution the a and /3 anomers of both pyranose and furanose forms occur. 

A description of an amplification procedure based on the different solubility of the D-enantiomer and that of the corresponding d, L-racemate of ribonucleosides follows. When the melting points and solubilities of crystalline d, L-ribonucleosides and the pure D-ribonucleoside were determined, it was found that solution-based amplification of a slight ee of D-cytidine and D-adenosine, in a mixture with the d, L-racemates, is sufficiently large to produce solutions with at least 99% ee of the D-enantiomer (Breslow et al. 2010 and references cited therein). The 96% excess of D-uridine could also be sufficient to allow for the selection of the d isomer in solution under prebiotic conditions. In contrast, d, L-ribose itself forms a solid solution and d, l-guanosine a conglomerate (Breslow et al. 2010). This work is based on the mechanism for the amplification of fluctuations in racemic mixtures of the corresponding compounds (Morowitz 1969). 

The existence of a very active, widely distributed nucleoside diphosphate kinase has been demonstrated repeatedly (see Chapter 4 and reference S5). This enzyme has been prepared in crystalline form from yeast (36), and Mourad and Parks (37) have isolated the enzyme in high purification from human erythrocytes. The latter enzyme reacts with nucleoside di-and triphosphates which contain either ribose or deoxyribose and any of the natural purine or pyrimidine bases, including thymine. 

The transketolase enzyme of Racker el obtained in crystalline form from baker s yeast, catalyzes the cleavage of ribulose-5-phosphate, with the formation of D-glyceraldehyde-3-phosphate upon the addition of an acceptor aldehyde, such as ribose-5-phosphate or glycolaldehyde. The reaction of hydroxypyruvate with D-glyceraldehyde-3-phosphate as acceptor aldehyde leads to the decarboxylation of the hydroxypyruvate with the formation of ribulose-5-phosphate. The transketolase enzyme was demonstrated to have a requirement for thiamine pyrophosphate. ... 

ADENOSINE. [CAS 58-61-7]. An important nucleoside composed of adenine and ribose. White, crystalline, odorless powder, mild, saline, or bitter taste, Mp 229C, quite soluble in hot water, practically insoluble in alcohol. Formed by isolation following hydrolysis of yeast nucleic acid. The upper portion of Structure 1 represents the adenine moiety, and the lower portion of the pentose, D-ribose. 

A new synthetic approach to D-ribose has recently been made by Sowden.43 In this procedure 4,6-benzylidene-D-glucose (X) was reduced catalytically to 4,6-benzylidene-D-glucitol (XI) which was then oxidized with sodium metaperiodate to 2,4-benzylidene-D-erythrose (XII). Condensation of this latter compound with nitromethane gave a mixture of epimeric, crystalline, substituted C-nitro alcohols, 3,5-benzylidene-1-desoxy-l-nitro-D-arabitol and 3,5-benzylidene-l-desoxy-l-nitro-D-ribitol (XIII). After separation, the appropriate isomer was hydrolyzed to 1-nitro-l-desoxy-D-ribitol (XIV) which, in the form of its sodium salt was decomposed directly to D-ribose (XV), isolated as its benzylphenyl-hydrazone. This synthesis is of interest in that it may be used to obtain D-ribose labeled at carbon 1 with C.14... 

While the melting points of the aniline glycosides, the so-called anilides, are too variable for identification purposes, the partially etherified sugars form anilides which have reliable melting points and such anilides are widely used for identification purposes. Sirupy 2,3,5-trimethyl-D-ribose, for instance, has been converted into a crystalline anilide,89 presumably aniline 2,3,5-trimethyl-D-ribofuranoside. An investigation of the configuration and properties of such derivatives would seem highly desirable. 

Acetylated nitroolefins have been prepared in similar fashion from D-erythrose,80 D-arabinose, D-ribose and D-glucose. The ease with which the acetylated nitroolefins usually crystallize is exemplified by the experience with D-glucose. Here, the product, D- lwco-pentaacetoxy-1-nitroheptene-1, was obtained in the crystalline state from a sirupy mixture containing approximately twenty times the nitroolefin s weight of other acetylated carbohydrate material, formed from the original... 

It was in 1910 that Levene and Jacobs first applied the classical cyanohydrin synthesis to o-ribose (I), a five carbon atom aldehyde sugar (aldopentose) which had become more readily available through their earlier research on nucleic acids. Two new aldohexoses were thus obtained in sirupy form, and characterized by suitable crystalline derivatives. To one of these sugars was given the name allose, with configuration V, because it should be oxidizable readily to allomucic acid (VIII). The latter is an optically inactive, dibasic acid, described by... 

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