Ribo-pyranoside

The reaction of p-D-ribopyranose tetraacetate (63) with methanethiol and zinc chloride gave 32), after deacetylation, methyl 1-thio-p-D-ribo-pyranoside (64), methyl 1,5-dithio-p-D-ribopyranoside (72, R=H), 4-S-methyl-4-thio-L-lyxose dimethyl dithioacetal (77, R=H), and a small... 

The reaction of /3-D-ribopyranose tetrabenzoate with hydrogen bromide in glacial acetic acid solution has recently been reinvestigated by Ness, Fletcher and Hudson111 and a new, crystalline tribenzoyl-D-ribopyranosyl bromide, isomeric with that previously known, obtained in 5% yield. In contrast to the major product of the reaction, the new halide proved to have a dextrorotation of [a]20D + 78° in chloroform and, since it reacted readily with methanol to give methyl 0-D-ribo-pyranoside tribenzoate (XLII), it was concluded that it is tribenzoyl-... 

Methyl 1-thio-a-D-ribo-pyranoside (X-ray data) 0(2)H 0(4) 2.09 142 MTRIBP10... 

By tritylation studies, Bredereck "- established the presence of a free primary hydroxyl group and a furanose ring in the n-ribose portion of certain nucleosides. This proof is quite conclusive because of comparative experiments with n-glucopyranosyltheophylline, whose primary hydroxyl group easily forms a trityl ether, and with methyl n-ribo-pyranoside which, in the absence of a primary hydroxyl group, is not tritylated under ordinary conditions. ... 

The 3-thioacetate 17 has been obtained by opening of the cyclic sulfamidate 16, which was formed on exposure of the cis-vicinal hydroxy acetamide 15 to 1,T-sulfonyldiimidazole. Regioselective opening of benzyl 2,3-anhydro-a-D-ribo-pyranoside gave access to benzyl 3-(phenylthio)-a-D-xyloside (18). The 3-thio-and 6-thio-analogues 20 and 21, respectively, of amiprilose (19), have been synthesized by standard methods.3,6-Thio-anhydro-D-glucose derivatives 24... 

Me glycoside, i,2,4-tri-Ac Methyl 3-acet-amido-2,4-di-0-acetyl-3-deoxy-a-D-ribo-pyranoside C12H19NO7 289.285 Mp 116-117°. [a] +93.7 (c, 1.6 in CHCI3). 

Me glycoside, 3,4-isopropylidene Methyl 2-C-formyl-3,4AA-isopropylidene-p-D-ribo-pyranoside [35522-72-6]... 

Details have appeared on the behaviour of methyl 2,3-0-isopropylidene-4-0-toluene-p-sulphonyl-a-D-lyxo- and -P-L-ribo-pyranoside towards nucleophiles (see Vol. 8, p. 53). The dithiepane derivatives (127) and (128) were formed via the intermediate (126), resulting from sulphur migration, when the mesylate (125) was treated with sodium azide in warm DMF ° (see also Chapter 15). The reactions of... 

Singlet oxygen adducts of 1-acyl-1,2-dihydropyridines have been utilized for the stereoselective synthesis of 5-amino-5-deoxy-DL-lyxo- and ribo-pyranosides ( piperidinoses ) by the route outlined in Scheme 5. A new procedure for... 

The elfects of substitution at position on hydrolysis of NAD " analogues, in both the ara series (six points) and the ribo series (five points), gave values of Pi of —6.7 and —7.0, respectively (Figure 3.8). These values are lower than those observed for spontaneous hydrolysis of 2,4-dinitrophenyl pyranosides (Table 3.1), suggesting slightly different mechanisms (see Section 3.6). 

There has been substantial activity in the synthesis of 3-amino-2,3,6-trideoxy-hexoses and their di-A-methyl derivatives as a result of their wide occurrence in antibiotics. In a paper of substantial proportions, Bartner et alP have synthesized by standard reactions all four possible methyl 2,3,6-dideoxy-3-dimethylamino-a-D-hexopyranosides (and some /3-anomers) as well as the corresponding L-ribo isomer (L-megosaminide). Syntheses have been reported for D-ristosamine (3-amino-2,3,6-trideoxy-D-rz7 o-hexose) from methyl 2-deoxy-D-amfcmo-hexo-pyranoside and of the isomeric 3-amino-2,3,6-trideoxy-L-Jcy/o-hexose (1) from methyl 2,6-dideoxy-L- mZ>mo-hexopyranoside, using standard sequences involving azidej displacement of sulphonate esters for introducing the nitrogen. 

Reduction of the a-keto-oxiran (269) with sodium borohydride yielded methyl 2,3-anhydro-j3-L-ribo- and -a-o-lyxo-pyranosides in the ratio of 3 2. 3-Deoxy-D-cry/Ar<7-hexosulose has been shown to be less stable than normal carbohydrates and to polymerize within the range 100—200 °C. The poly-... 

Deoxy and Branched-Chain Sugars.- Methyl 7-deoxy-0-D-glycero-D-qalacto-heptopyranoside and methyl 7-deoxy-a-L-qlycero-D-galacto-hepto-pyranoside,derivatives of 1,2-0-isopropylidene-3-C-pyridin-2-yl-0-D-psicopyranose, ° methyl 4,6-bis-O-(p-chloroben-zoyl)-2,3-dideoxy-3-C-(methoxycarbonylmethyl)-g-D-ribo-hexopyran-oside, and ethyl 4,6-di-0-acetyl-2,3-dideoxy-45 -dihydro-3 -phenyl-g-D-manno-hexopyranosid [2,3-d]isoxazole. ... 

Thiem [29] found that methyl 3,4-di-O-acetyl-D-glucuronal 38 adopts almost exclusively an inverted H4 (d) half-chair conformation. A 60 40 mixture of a-D-ma no-pyranoside 39 [in a flattened (d) boat conformation] and fi-D-gluco pyranoside 40 was obtained when 38 was treated with cyclohexanol and A-iodosuccinimide in acetone (Scheme 9). Other methyl glycuronals h-ribo, u-lyxo and h-xylo) adopt the usual conformation with an equatorial methoxycarbonyl... 

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