Ribofuranoside, methyl 2,3-isopropylidene

Ribofuranoside, methyl /8-D-, 280 —, methyl 4-acetamido-4-deoxy-/3-D-, 185 —, methyl 5-0-acetyl-2,3-anhydro-j8-D-, 0X0 reaction with, 108 —, methyl 5-(adenin-l-yl)-5-deoxy-2,3-0-isopropylidene- 8-D-, 141 —, methyl 2,3-anhydro-/3-D-, 108 —, methyl 2,3-anhydro- 8-L-, 277 —, methyl 5-deoxy-2,3-0-isopropylidene-5-[(purin-6-yl)amino]-/3-D-, 141 —, methyl 5-deoxy-5-[9-(tetrahydropyran-2-yl)purin-6-yl]amino-2,3-di-0-p-tol-ylsulfonyl-/3-D-, 141... 

Methyl 5-deoxy-2,3-0-isopropylidene l3-T>-erythro-pent-4-enofurano-side (43). A solution of methyl 5-deoxy-5-iodo-2,3-0-isopropylidene-/ -D-ribofuranoside (42) (30) (1.0 grams) in pyridine (10 ml.) was shaken for 7 hours at room temperature with anhydrous silver fluoride (1.5 grams). Isolation of the product as described previously afforded the 4-ene (43) as a sirup (414 mg., 70%) which distilled at 40°C. (bath) at 0.1 mm. G.l.c. showed the presence of a major component (95%) together with 5% of another component which was not investigated. [ ]D21 + 26.3° (c, 2.3). Anal Calcd. for C9H1404 C, 58.05 H, 7.6. Found C, 57.9 H, 7.7. 

Difluoro compounds have been prepared by treatment of carbonyl compounds with DAST. These are methyl 5-deoxy-5,5-difluoro-2,3,-0-isopropylidene-)S-D-ribofuranoside, 6-deoxy-6,6-difluoro-1,2 3,4-di-0-isopropylidene-a-D-galactopyranose, methyl 2-deoxy-2,2-difluoro-... 

Mlotkowska, B., Tropp, B.E., and Engel, R., The preparation of methyl 5-deoxy-5-(dihydroxyphosphinoyl)hydroxymethyl-2,3-0-isopropylidene-fS-D-ribofuranoside, a precursor to a hydroxymethylene analog of D-ribose 5-phosphate, Carbohydr. Res., 117, 95, 1985. 

Transformation of chiral nitrones into enantiomer enriched a-chiral N -hydroxylamines and their derivatives, has been successfully employed in the enantioselective synthesis of (+ )-(R)- and (—)-(S)-zileuton (216). An expeditious synthesis of thymine polyoxin C (347), based on the stereocontrolled addition of 2-lithiofuran (a masked carboxylate group) to the A-benzyl nitrone derived from methyl 2,3-O-isopropylidene-dialdo-D-ribofuranoside, is described (Scheme 2.151) (194). 

Potassium fluoride in 1,2-ethanediol has further been used, as, for example, in the preparation of 5-deoxy-5-fluoro-D-ribose from methyl 2,3-0-isopropylidene-5-0-(methylsulfonyl)-a-D-ribofuranoside,87 and of 6-deoxy-6-fluoro-D-glucose from methyl 6-O-p-tolylsulfoiiyl-a-D-glucopyranoside.77 In one study of primary fluorinations with potas-... 

Primary alcohol groups in several protected ribo-, fructo- and glucofuranoses including 2,3,4-tri-O-benzoyl-D-glucose, 1,2-isopropylidene-D-xylo-furanose, 2,3 4,5-di-0-isopropylid-ene-D-fructopyranose, methyl 2,3-O-isopropylidene-P-D-ribofuranoside, l,2-0-isopropylidene-3,5-0-benzylidene-D-glucofuranose and... 

The reaction of 2,3-0-isopropylidene-5-0-mesyl-D-lyxofuranose (8) with sodium methoxide proceeds similarly. The main product, methyl 2,3-0-isopropylidene-y3-L-ribofuranoside (10), is formed (with its an-omer) by opening of the furanose ring, elimination of the primary, 5-methanesulfonate anion (inversion not observable) by 0-4 alkoxide ion to form epoxide 9, and attack at C-l by methoxide to form an 0-1 alkoxide ion which attacks C-4 with inversion. Some attack at C-5 gives minor proportions of methyl 2,3-0-isopropylidene-/3-i>lyxo-pyranoside and its anomer (11). The formation of l,5-anhydro-2,3-0-isopropylidene-/J-D-lyxofuranose (l,4-anhydro-2,3-0-isopropylidene-/3-D-lyxopyranose), 12, occurs to only a minor extent55,56 (see Scheme 2). 

The deamination of the pentoside methyl 4-amino-4-deoxy-2,3-0-isopropylidene-a-D-lyxofuranoside paralleled that of the mannopy-ranoside 39a in that substitution (with inversion) and ring contraction occurred to give a-D-Iyxopyranoside (60%) and /B-l.-ribofuranoside (40%) derivatives as products.1243 In contrast, there was no ring... 

Montgomery and Hewson144 have described yet another synthesis for this class of deoxy sugars. Treatment of methyl 2,3-0-isopropylidene-5-0-(p-nitrophenylsulfonyl)-/J-D-ribofuranoside with sodium cyanide in IV,AT-dimethylformamide afforded the corresponding 5-cyano-5-deoxy derivative... 

Methyl-D-ribose has been synthesized48 starting with 2,3-isopropyli-dene-D-ribose (XL), which on methylation with silver oxide and methyl iodide gave methyl 2,3-isopropylidene-5-methyl-D-ribofuranosides (XLI), from which 5-methyl-D-ribose (XLII) was obtained by hydrolysis with... 

One of the earliest reported preparations of the requisite glycosidation precursor 5-deoxy-l,2,3-tri-0-acetyl-p-D-ribofuranoside (17) was published by Kissman and Baker in 1957.23 D-Ribose was heated at reflux in a methanol/acetone mixture in the presence of concentrated HCI to provide methyl 2,3-O-isopropylidene-D-ribofuranosidc (21), which was in turn converted to the corresponding 5-O-mesyl ribofuranoside 22 with methanesulfonyl chloride in pyridine in 63% yield. The sulfonate moiety of 22 was then displaced with sodium iodide in refluxing DMF to provide 5-deoxy-5-iodo derivative 23 in 76% yield on a multigram scale. Reductive dehalogenation of 23 was accomplished under heterogeneous catalytic hydrogenation conditions to provide the reduced 2,3-0-protected intermediate 24 in 56% yield, which was subjected to hydrolysis conditions in... 

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). 

Anderson, Goodman, and Baker employed an O-(methoxycarbonyl) protecting group in an analogous manner for their synthesis of methyl 2,3-anhydro-D-ribofuranoside (XLV). Treatment of 1,2-0-isopropylidene-D-xylofuranose (XLI) with methyl chloroformate in pyridine gave, by preferential esterification of the least-hindered alcohol group (at C5), predominantly 1,2-0-isopropylidene-5-0-(methoxycarbonyl)-D-xylofuranose (XLII) a small proportion of the 3,5-di-0-(methoxycarbonyl) derivative was separated by fractional recrystallization. Subsequently, the C3-hydroxyl was esterified with tosyl chloride, and the resulting 3-0-tosyl ester XLIII... 

D-Ribofuranoside Benzyl 2,3-O-isopropylidene-5-O-benzyl- Methyl 2,3-O-isopropyIidene-5-ehloro-5-deoxy- ... 

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