Ribose derivatives, preparation

Angier and Marsico followed the course of alkylation first. The 7-dimethylamino-5-methylmercapto derivative reacted with dimethyl sulfate in an alkaline medium to yield a mixture of the 2- and 3-methyl derivatives. The reaction of the 7-diraethylamino derivative with ethyl iodide in an alkaline medium led to a mixture of all three possible monoethyl derivatives. The position of the alkyl group in all these substances was defined by comparing the UV spectra with derivatives prepared by a straightforward synthesis. After reacting the mercuric salts with tri-0-benzoylribofuranosyl chloride, they demonstrated the ribose residue to be bound in position 2. The same structure was shown to be valid for the derivative prepared by Andrews and Barber. ... 

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... 

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... 

C-Nucleosides. The first step in a new synthesis of C-nucleosides involves reaction of ethoxycarbonylethylidenetriphenylphosphoranc with the 2,3-di-O-isopropylidene-D-ri-bose derivative 1 to give the acyclic product 2. On treatment with C6H5SeCl, 2 gives a single cyclic ribose derivative (3), shown to be the 3-anomer by the conversion shown here to a derivative (6) of showdomycin. In addition, several other 1 p-substituted 1-deoxyribose derivatives were prepared. 

Walker et al. have described by tliis method a seven-step synthesis of 4-thio-2-deox-y-i3-eri f/7ro-pentosc (37) from 2-dcoxy-D-erir/ira-pentosc via dithioacetals 35 and 36, involving inversion at C-4 by Mitsunobu reaction and final cyclization of the dithioacetal, accompanied by further inversion at C-4. Secrist et al.- have synthesized 39 from the ribose derivative 38 using the same method. Similarly, Imbach et al. have prepared 1,4-dithio-D-ribofuranosides 39 from L-lyxose and from D-ribose,and 1,4-dithio-L-lyxofuranosides 40 from D-ribose. Mackenzie... 

With respect to 1,3-dipolar cycloadditions, several approaches have been utilized in the preparation of C-glycosides. As shown in Scheme 6.5.4, Kozikowski, et al.,18 effected the reaction of the ribose-derived nitrile oxide with the olefin, shown. The reaction provided a 70% yield of the isoxazoline glycoside with no deleterious effects on the configuration at the anomeric center. 

In attempts to prepare the 2-benzyl-2-phenylhydrazone (29) of 3,5-di-O-benzoyl-2-deoxy-n-eryribose derivative), the unsaturated hydrazone (30) was obtained. ... 

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. ... 

S. An efficient synthesis of enantiomeric ribonucleic acids from D-glucose. Helv. Chim. Acta 1997, SO 2286—2314). The protected enantiomeric cytidine was produced in 94% yield by the above reaction. After adjusting protecting groups, solid-phase oligonucleotide synthesis methods (Section 25.7) were used with this compound and the other three nucleotide monomers (also derived from L-ribose) for preparation of the unnatural RNA enantiomer. See also Vorbriiggen, H. Ruh-Pohlenz, C., Handbook of Nucleoside SynlhestsTy Wiley Hoboken, NJ, 2001. 

Deoxy-3-C-hydroxymethyl-DL-lyxose and ribose derivatives have been synthesized from 2-methyl-3-furoic acid by a procedure analogous to that used for preparing DL-apiose from 3-furoic acid (see Vol. 7, p. 115). L-My-carose (5) has also been prepared from non-carbohydrate precursors by the... 

The four nucleosides of RNA have been prepared with 13C labels at either C-1 or C-2, for use in nmr studies,by condensation with an appropriately-labelled D-ribose derivative. Label at C-1 was introduced by a Kiliani reaction, and at C-2 by molybdate-catalysed rearrangement of 1-13C-... 

The D-ribose derivative (98) was converted into the C-glycosides (99) and (100) via the 2- and E-alkenes as indicated in Scheme 40, the former product being used to prepare the 2,7-anhydride (loi). In a related study the effects of different groups and electrophiles on the electrophilic ring closure of compound (102) and related substances to a- and -furanoid and pyranoid products were examined. ... 

The synthesis of pyrazofurin A (the 4-hydroxy analogue of (17)) and its a-anomer pyrazofurin B by a Wittig condensation on a ribose derivative is mentioned in Chapter 3 (ref. 183). Further references to antibiotic C-nucleosides occur in Chapter 18. C-Nucleosides of indoles have been prepared by glycosylation using ribosyl chloride derivatives. ... 

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