L-Ribose

Synthesis of Some Phosphates of 2-Deoxy-L-ribose," R. Allerton, W. G. Overend, and M. Stacey, Chem. Ind. (London), (1952) 952-953. 

Streptose is the first branched-chain sugar to have been identified as a component of a biological compound produced by a microorganism. This dicarbonyl sugar is known only in its derivatives. The chemistry of streptose and streptomycin has been lucidly reviewed by Lemieux and Wolfrom.1 In this article, it was noted that streptose must be either 5-deoxy-3-C -formyl-L-ribose or 5-deoxy-3-C-formyl-L-lyxose. Since then, the presence of the latter configuration (XXXIV) has been definitely established by Wolfrom and DeWalt,66 who found that N-acetyltetrahydrostreptobi-... 

In an attempt to synthesize 2-desoxy-L-ribose, Mukherjee and Todd68 treated methyl 2,3-anhydro-jS-L-ribopyranoside (LXXII) with sodium thiomethoxide and then reduced the amorphous product. The sulfur-free sirup thus obtained was inert to the action of periodate and is therefore methyl 3-desoxy-/3-L-riboside (ayn., methyl 3-desoxy-/3-L-xyloside) (LXXIV) rather than the desired 2-desoxy derivative. The methylthio intermediate (LXXIII) was consequently a 3-methylthio-L-xylose derivative rather than a 2-methylthio-L-arabinose compound. The presence of a trace of the latter, however, is not wholly excluded since the sirupy desoxypentoside (LXXIV) gave a feeble green coloration in the Keller-Kiliani test, a reaction generally accepted as being specific for 2-desoxy-sugars. 

The legioselectivity of electrophilic additions of the C=C double bond in 7-oxabicyclo[2.2.1]hept-5-en-2-yl (7-oxanorbom-5-en-2-yl) derivatives depends on the nature of the substituents at C(2). The adducts so-obtained can be transformed into the corresponding 5,6-disubstituted 7-oxanorboman-2-ones, which can be mono-substituted at C(3) stereoselectively, giving products with the same stereochemical information as hexoses. Thus, optically pure 7-oxanorbom-5-en-2-yl derivatives can be viewed as "naked sugars" Applications to the total, asymmetric syntheses of L-daunosamine, 2-deoxy-L-fucose, D- and L-aUose, D- and L-talose, D- and L-ribose,... 

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... 

D- and L-Ribose are synthesized starting from 2,3-0-isopropylidene-D-and L-glyceraldehyde, respectively, by the application of this reaction (2). 

The synthesis of L-ribose required two significant innovations for its completion. The first was an efficient synthesis of diisopropyl (chloromethyl)boronate (1) via the in situ preparation of (chloromethyl)lithium by addition of butyllithium to a mixture of chloroiodomethane and triisopropyl borate in THF at — 78°C 18. 

The overall yield in the three-carbon chain extension of 2 to 6 is 37%. However, chain extension of 4 in the usual way failed, and only a 36% yield was obtained in the one-step conversion of 6 to 7. Further conversion of 7 to L-ribose is straightforward and essentially quantitative. 

The utility of these metallated 2-allyloxybenzimidazoles was demonstrated further through a synthesis of both d- and L-ribose (81CL1005). The allylcadmium derivative (551) reacted with 2,3-O-isopropylidene-D- and -L-glyceraldehyde to form the corresponding ribo-5-hexenitols (554) with high regio- and stereo-selectivity. Conversion of these products through their oxiranes to d- and L-ribose (557) required only a few additional manipulations as shown in Scheme 122. 

The exo/endo (99 1) adducts are of 90-92% optical purity. The enantiomeric bicyclic ketones can be transformed into carbohydrates in a few, stereochemically well-defined steps. In this way, derivatives of d- and L-ribose [38], L-allose, L-talose, and such [39] have been obtained. 

Deoxy-D-ribose, AE75 2-Deoxy-L-ribose, AE76 Di-N-acetamide, AD07 Diacetic acid diselenide, AC90 Diacetone alcohol, AI00 2-Diacetoxymethyl-5-ni trofuran,... 

It is well known that if there is over-hydrolysis in the Feulgen test, the intensity of the color developed is much reduced. Lately, renewed interest in this effect has led to several interpretations being forwarded.69 81 82 The work of Stacey and his coworkers on the properties and reactions of desoxy-pentoses and -hexoses and in particular of 2-desoxy-D- and -L-ribose, indicates that over-hydrolysis of the nucleic acid not only brings it into a more diffusible form, but also changes the desoxypentose... 

A series of similar changes was observed on treatment of 2-desoxy-D-galactose with ethanolic hydrogen chloride and it was possible to prepare ethyl 2-desoxy-a/8-D-galactofuranoside and ethyl 2-desoxy-aj8-D-galacto-pyranoside. Essentially similar results were observed with desoxy-pentoses, and the methyl glyco-furanosides and -pyranosides of 2-desoxy-L-ribose were prepared.141... 

When 2-desoxy-L-ribose was treated with one percent methanolic hydrogen chloride it afforded a methyl 2-desoxyriboside mixture which was separated into crystalline a- and /3-isomers (A and B, respectively). If 0.1 percent methanolic hydrogen chloride was used, then a third methyl 2-desoxypentoside (C) was obtained. The glycoside C was much... 

Eclipsed conformation of L-ribose is oriented properly for ring closure. 

Of the two chair conformations of jS-L-ribose, the one with the greater number of equatorial substituents is more stable. 

Y. Chong and C. K. Chu, Efficient synthesis of 2-deoxy-L-eryt/fro-pentose (2-deoxy-L-ribose) from L-arabinose, Carbohydr. Res., 337 (2002) 397 102. 

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