Ribose derivatives

Barker and Lock71 have hydrolyzed a tetramethyl-di-D-ribose anhydride (p. 173) and adduced evidence to show that the product (not isolated) was 2,3-dimethyl-D-ribose. 

A 5-benzyl-D-ribose has been prepared by Kenner, Taylor and Todd,90 who etherified the methyl 2,3-isopropylidene-D-ribofuranoside (XXI) of Levene and Stiller91 with benzyl chloride to obtain methyl 2,3-iso-propylidene-5-benzyl-D-ribofuranoside (XXII), which was subsequently hydrolyzed to give amorphous 5-benzyl-D-ribose (XXIII). The structure of this ether was confirmed through acetylation to its triacetate (XXIV), hydrogenolysis to 1,2,3-triacetyl-D-ribofuranose (XXV) and further acetylation to the known, crystalline tetraacetyl-D-ribofuranose (XXVI). 

Bredereck, Kothnig and Berger26 obtained a crystalline monotrityl-D-ribose through direct tritylation of the free sugar in pyridine solution for four days at 37°. In view of the known selectivity of trityl chloride 

The acetylation of D-ribose in pyridine solution at low or ordinary temperatures leads to the formation of a crystalline tetraacetate melting at 110° and showing [ ]26D — 54.3° in chloroform.56-14 The ring structure of this substance is retained on conversion to triacetyl-D-ribosyl bromide since the latter compound may be reconverted to it by treatment with silver acetate.66 While indirect evidence early indicated94 that the bromide as well as the tetraacetate possessed a pyranose structure the question was not settled unequivocally until the bromide was used in the synthesis of nucleosides which were known to be pyranosides through quantitative periodate oxidation.95 While the configuration of the crystalline tetraacetate at carbon one will not be known with certainty until its anomer is obtained, the compound may provisionally be considered jS-D-ribopyranose tetraacetate because of its strong levorotation. 

Zinner98 has studied the acetylation of D-ribose in pyridine solution with acetic anhydride at various temperatures. At 0° the pyranose tetraacetate is the sole product, but as the temperature at which acetylation is carried out is increased, the furanose isomer is also formed, the proportions of the two isomers formed at 100° being nearly equal. These findings parallel the earlier work by Schlubach and Prochownick99 in the D-galactose series. Zinner also observed that the acetylation of D-ribose with sodium acetate and acetic anhydride at higher temperatures gives rise to the furanose tetraacetate. 

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Notice that the eclipsed conformation of d ribose derived directly from the Fischer pro jection does not have its C 4 hydroxyl group properly oriented for furanose ring forma tion We must redraw it m a conformation that permits the five membered cyclic hemi acetal to form This is accomplished by rotation about the C(3)—C(4) bond taking care that the configuration at C 4 is not changed... 

The synthesis of pentose-2,4-diphosphate referred to above gave the best yields of a ribose derivative. Thus, the search for an effective synthesis leading to necessary starting materials such as glycol aldehyde phosphate (GAP) was important Krishnamurthy et al. (1999, 2000) reported new synthetic routes to GAP glycol aldehyde is allowed to react with amidotriphosphate (AmTP) in dilute aqueous solution. The triphosphate derivative is formed from trimetaphosphate and NH4OH. 

According to Muller (1990) this aldehyde can give ribose-2,4-diphosphate in the presence of formaldehyde via a two-step, base-catalysed reaction. This reaction provides a route to ribose derivatives, and thus to the nucleic acids. 

Figure 1.39 The formation of an N-glycosidic bond links the base unit of nucleic acids to the associated ribose derivative.

A substantial improvement was reported by D. M. Brown and coworkers,156 who used the more readily hydrolyzable tert-butyl pyrimidine derivative (222) in a condensation reaction with the aldehydo-D-ribose derivative 223. Acid hydrolysis of the epimeric mixture (224) gave pseudouridine and its a anomer in 18 and 8%... 

NAD+ is a substrate for pertussis toxin, allowing the transfer of an ADP-ribose derivatives to G-proteins. Ruoho used [125I]-iodoazidophenylpropionyl-NAD+... 

Reaction of nitromethane and monosaccharide-derived dialdehydes is a useful tool that has been broadly used for the preparation of nitro and amino sugars, and carbocycles.30 Dialdehydes can easily be obtained by oxidative cleavage of conveniently protected monosaccharides with sodium periodate. Their subsequent Henry reaction with a nitroalkene, commonly nitromethane, usually gives isomeric mixtures that require the isolation of the major isomer.31 Thus, treatment of the D-ribose derivative 27 with sodium periodate gave dialdehyde 28, which was subjected to a Henry reaction with nitromethane, to afford nitrosugar 29 as an epimeric mixture (Scheme 11).32... 

The synthesis of the antibiotic showdomycin, starting from a ribose derivative, is illus-trative." ... 

Nature has exploited ribose derivatives for a number of cmcially significant biochemicals. Many of these contain a heterocyclic base attached to the P-anomeric position of o-ribofuranose, and are termed nucleosides. Adenosine, guanosine, cytidine, and uridine are fundamental components of ribonucleic acids (RNA see Section 14.1),... 

Total Synthesis of D- and L-AUose, D- and L-Talose and of D- and L-Ribose Derivatives... 

L-Ribose is quite rare and the only practical method for its preparation is the transformation of L-arabinose by the method of Austin and HumoUer (4 steps, 9.5 % overall yield). L-Ribose has also been derived from, 2,3-<9-isopropylidene-L-glyceraldehyde, (5 steps, 12 %) after separation from a mixture containing L-arabinose. In Scheme 7 we summarize our total syntheses of D- and L-ribose derivatives using the " naked sugars" 32 and 38, respectively." Ketone 138 (Scheme 4) was oxidized into the corresponding lactone (-)-158 with MCPBA in 98 % yield. Treatment with anhydrous methanol, 2,2-dimethoxypropane and a small amount of methanesulfonic acid afforded the methyl 5-deoxy-D-allonate (-)-I59... 

The known adduct (385) of furan and vinylene carbonate, previously used for the synthesis of some cyclitols,256,257 has been transformed into DL-ribose derivatives. After hydroxylation of 385 and subsequent formation of the isopropylidene derivative, the carbonate group was removed by treatment with barium hydroxide, and the resulting diol was cleaved by oxidation with permanganate. Dicarboxyl-ic acid 386 gave, upon treatment with acetic anhydride, cyclic anhydride 387. The reaction of 387 with azidotrimethylsilane produced... 

DNA contains thymine (Thy) rather than uracil. The deoxyribose derivatives are thymidine (dThd or dT) and thymidine 5 -phosphate. The ribose derivatives of thymine are the nucleoside ribosylthymidine (Thd) and ribosylthy-midine 5 -phosphate (Thd-5 -P). 

Micheel220 obtained 5-deoxy-L-arabinose and -D-ribose derivatives by the oxidation of L-rhamnal and 6-deoxy-D-allal derivatives, respectively, with ozone. 

Table IV, which briefly summarizes the material described in previous sub-sections, shows the total of the different monosaccharide components identified in bacterial polysaccharides, and our present knowledge about their activated forms. It may be seen that identification of the activated forms has been achieved for only approximately half of the monosaccharides known to be involved. The most striking gap in the information available is the lack of data about the activated forms of D-ribose-derived monosaccharides and of most of the D-fructose-derived aldoses having configurations other than gluco, galacto, and manno.

It has been known for many years (15-24) that venom exonuclease is capable of hydrolyzing both DNA and RNA. Gray and Lane (56) showed that naturally occurring 2 -0-methyl-substituted ribose derivatives are also hydrolyzed, even though the rate of hydrolysis is slower than with the unsubstituted ribose. Interestingly, the 2 -0-methylated derivatives are totally resistant to 5 -nucleotidase (57, 58). 

Phosphate-containing carbohydrates that are stable, such as the 5 -phosphate of the ribose derivatives of oligonucleotides, may be targeted for modification using a carbodiimide-facilitated reaction (Section 4.3). The water-soluble carbodiimide EDC can react with the phosphate groups to form highly reactive phospho-ester intermediates. These intermediates can react with amine- or hydrazide-containing molecules to form stable phosphoramidate bonds. 

Y. S. Choi, B. W. Kang, R. Lu, M. Osawa, K. Hattori, T. Yoshida, T. Mimura, Y. Kaneko, H. Nakashima, N. Yamamoto, and T. Uryu, Synthesis of sulfated deoxy-ribofuranans having selective anti-AIDS virus activity by ring-opening copolymerization of 1,4-anhydro ribose derivatives, Polym. J. (Tokyo), 29 (1997) 374-379. 

The known allylic alcohol 9 derived from protected dimethyl tartrate is exposed to Sharpless asymmetric epoxidation conditions with (-)-diethyl D-tartrate. The reaction yields exclusively the anti epoxide 10 in 77 % yield. In contrast to the above mentioned epoxidation of the ribose derived allylic alcohol, in this case epoxidation of 9 with MCPBA at 0 °C resulted in a 65 35 mixture of syn/anti diastereomers. The Sharpless epoxidation of primary and secondary allylic alcohols discovered in 1980 is a powerful reagent-controlled reaction.12 The use of titanium(IV) tetraisopropoxide as catalyst, tert-butylhydro-peroxide as oxidant, and an enantiopure dialkyl tartrate as chiral auxiliary accomplishes the epoxidation of allylic alcohols with excellent stereoselectivity. If the reaction is kept absolutely dry, catalytic amounts of the dialkyl tartrate(titanium)(IV) complex are sufficient. 

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