D-Ribose derivatives

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... 

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%... 

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... 

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.

A tungsten-catalyzed cycloisomerization of the D-ribose-derived alkynyl alcohol 181 provides a 6-endo-dig cyclization route to 3,4-dihydropyrans. Excellent endo-modc selectivity, and hence minimal tetrahydrofuran production is... 

Since D-ribose derivatives of amines occur naturally in ribonucleic acids, vitamin B12, and in cozymase and are used in the isolation of D-ribose as well as in the synthesis of vitamin B2, they have attracted much attention and are currently under active investigation in a number of laboratories. As mentioned earlier, the ribonucleic acids and their component parts have been well reviewed elsewhere 4 in the following discussion the syntheses of the nucleosides will be discussed only insofar as they illustrate methods of forming N-ribosides. 

D-ribose derivatives such as 5-benzoyl-D-ribose,152 5-benzyl-D-ribose90 and D-ribose 5-phosphate.127... 

An example of highly selective formation of both anomers is given in Scheme 4.55 [580]. As illustrated, treatment of the D-ribose derivative 272 with KO Bu, followed by the addition of the triflate 274, gave the -linked disaccharide 275. On the other hand, NaH-assisted reaction of the hemiacetal 276 with a bulky protecting group and the same triflate afforded the a-linked compound... 

A variant of this process was used to achieve a chain extension at C5 of a pentose derivative, allowing the construction of the oxahydrinden part of avermectins [59,156]. As shown in Scheme 11.49, the D-ribose derived aldehyde 217 was treated with ( )-trimethylcrotylsilane in the presence of BF3-Et20 [157]. This produced a mixture of three isomers in an 8.9 1.1 1.0 ratio, from which compound 218 was isolated in a yield of 78%. The subsequent steps allowed deoxygenation of the sugar ring to give the diol 219. This compound was, in turn, transformed into the... 

SCHEME 13.111 Jung s total syntheses of 2,3-deoxy-3-substituted D-ribose derivatives. 

The octosyl acids are isolated from Streptomyces cacaoi they are part of a broader group of polyoxin antifungal nucleosides [349]. Danishefsky and co-workers [350] have reported a total synthesis of octosyl acid A featuring the hetero-Diels-Alder addition of ( )-l-methoxy-3-(trimethylsilyloxy)butadiene to a protected D-ribose-derived aldehyde. 

Matsuura, N., Yashiki, Y, Nakashima, S., Maeda, M., and Sasaki, S., A shortcut and stereoselective synthesis of l-P-alkyl-2-deoxy-D-ribose derivatives via Wittig-Horner-Emmons reaction. Heterocycles, 51, 975, 1999. 

Benzoate participation by way of six-membered orthoester ions can be visualized, but it was not realized in work reported by Hughes and Speak-man. The D-ribose derivative (81), with tetrabutylammonium benzoate... 

Starting with methyl 3-acetamido-3-deoxy-2,4-di-0-(methylsulfonyl)-/3-L-xylopyranoside (96), Baker and Schaub" > > were able to obtain the D-ribose derivative (98) after prolonged refluxing. When the solvolysis of (96) was conducted in refluxing 95% ethanol, an intermediate was formed which was assumed to be the L-lyxose derivative (97) this could be converted into (98) by further reaction with sodium acetate in 2-methoxy-... 

Direct heteroarylation of the acyclic D-ribose derivative 226 with the maleimide phosphorus ylides 197 gave the corresponding 3-(alditol-l-ylidene)pyrroles 227 (69MI7) (Scheme 49). 

Recently, Bertolini and Frigerio reported an improved method. Their preparation of 199 is performed by coupling of 5-deoxy-D-ribose derivative with silylated fluoropyrimidine in the presence of Lewis acid at subzero temperature in inert organic solvent. The one-pot reaction of 177 with chlorotrimethylsilane and hexamethyldisilazane in methylene chloride, followed by coupling with l, 2, 3 -tria-cetyl-5 -deoxy-D-ribose gives pure 2, 3 -diacetyl-5 -deoxy-5-fiuorouridine 201 in 90% yield (Scheme 12.39). 

Addition of trifluoromethyltrimethylsilane to l,2-0-isopropylidene-5-0-Tbdms-a-D-er f/iro-pentofuranos-3-ulose (prepared from D-xylose) afforded the corresponding 3-C-trifluoromethyl-ribose derivative 33. After de-silylation at 0-3 (NaOMe/MeOH) and radical-induced deoxygenation, the 3-deoxy-3-C-trifluoro-methyl-D-ribose derivative 34 was formed. D-Glucose was also used as starting material. ... 

The aziridinium-fused furanoside 221 was prepared from D-ribose derivative 220, and thence elaborated to acyclic aziridine 222 and compound 223, which are both 3,4-disubstituted L-glutamates (Scheme 16). [2+2] Cycloadditions of sugar vinyl ethers 224 and 225 to tosylcyanide followed by reduction with RedAl afforded the P-lactams 226 and 227. These were elaborated to the tricyclic systems 228 and 229. ... 

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