Methyl-a-D-ribopyranoside

C16H20O5S2 Methyl 4,6-0-benzylidene-2-deoxy-3-0-[(methylthio)thio-carbonyl]-a-D-ribopyranoside (MBDRIP)88... 

C6H12O3S2 0.25 H20 Methyl 1,5-dithio-a-D-ribopyranoside, tetartohydrate MDTRPY20 32 358... 

A similar reaction of methyl P-D-ribopyranoside (5) with P(NMe2)3 in dioxane gave 2,3,4-bicyclophosphite of P-methyl-D-ribopyranoside, 6a in 90% yield. It was sulfurated and selenated to give the corresponding thiophosphate 6b and selenophosphate 6c in 89 and 81% yields, respectively. Oxidation of 6a with hydrogen peroxide gave cyclic phosphate 6d (92%), whereas its hydrolysis in aqueous... 

Many other glycosides have been subjected to selective chlorination with sulfuryl chloride. Methyl /3-L-arabinopyranoside afforded methyl 4-chloro-4-deoxy-a-D-xylopyranoside 2,3-di(chlorosulfate) in 29% yield, whereas the a-L anomer gave357 methyl 3,4-dichloro-3,4-dideoxy-/3-i)-ribopyranoside 2-(chlorosulfate) (30%). Methyl /3-d-ribopyranoside was converted into methyl 3,4-dichloro-3,4-dideoxy-a-L-arabinopyranoside through the action of pyridine hydrochloride on its 2,3,4-tri(chlorosulfate).358 Methyl a-D-lyxopyranoside gave only the 2,3,4-tri(chlorosulfate),353 as would be expected from the disposition of its hydroxyl groups, similar to that in the rhamno- and manno-pyranosides. Methyl a-D-altropyranoside was transformed into the 6-chloro-6-deoxy 2,3,4-tri(chlorosulfate) derivative in 80% yield.353... 

The other two known examples of intramolecular H-bonds within a monosaccharide unit in the crystalline state occur in two thio-sugars, methyl-l-thio and methyl-1,5-dithio-a-D-ribopyranoside (40) (illustrated in Figure 3). As far as we know, these are the first examples of syn-diaxial O-H O bonding in a cyclic carbohydrate in the solid state. It is not certain now, whether any particular significance should be associated with the fact that these are thio sugars. 

An amorphous 2,3,4-tribenzoyl-D-ribose has been reported as a product of the hydrolysis of aniline D-ribopyranoside tribenzoate29 as well as of the hydrolysis of tribenzoyl-/3-D-ribopyranosyl bromide with moist acetone in the presence of silver carbonate.110 In the latter case the structure of the product was demonstrated through methylation to the known methyl /9-D-ribopyranoside tribenzoate. Recently Ness, Fletcher and Hudson111 have succeeded in obtaining a 2,3,4-tribenzoyl-D-ribose in crystalline form. 

In the presence of an acid acceptor the intermediate ion XLV may react directly with a methoxyl ion to give a methyl 1,2-orthobenzoate such as XLVI. Experiment showed that while reaction of the a-D-bromide (XL) with methanol in the presence of silver carbonate gave the levorotatory methyl /3-D-ribopyranoside tribenzoate (XLII) in good... 

Fig. 13.9. An example of intramolecular hydrogen bonding in the crystal structure of methyl 1-thio-a-D-ribopyranoside. The infinite 0(2)H 0(4)H 0(3)H 0(2)H chains form a double ribbon linking the molecules. The -S-CH3 group is omitted for clarity [MTRIBP10]...

METRBP10. Methyl 5-thio-a-D-ribopyranoside (absolute configuration) (C6H1204S). Girling... 

Brom-isopropyloxy- -ethylester E14a/3, 27 (H Br) Brom-methoxy- -tert.-butylester E14a/3, 25 (H - Br) 2,3,5-Tri-deoxy-a-D-ribopyranosid Methyl-2-brom-4-0-methyl-E14a/3, 805 (En + N-Br—Der./ H3C OH)... 

Methyl 4-deoxy-4-(dimethoxyphosphinyl)-2,3-0-isopropylidene-a-D-ribopyranoside [(47 )-22] obtained in this manner in 30% overall yield is then reduced with sodium dihydrobis(2-methoxyethoxy)aluminate (SDMA) to 4-deoxy-2,3-0-isopropylidene-4-phosphino-/3-D-ribopy-ranoside (23), which on subsequent hydrolysis, oxidation, treatment with diazomethane and acetic anhydride gives a diastereomeric mixture of phosphasugar tetraacetates 24/25/26 in 12 6 5 ratio50. 

O-p-tolylsulfonyl-a-D-xylopyranoside (197), obtainable therefrom, was transformed by sodium acetate in N,N-dimethylformamide into methyl 4-acetamido-4-deoxy-a-D-ribopyranoside (198a) by inversion at C-3. The )S-D anomer of 198 is obtainable from methyl 2,3-0-isopropylidene-4-O-p-tolylsulfonyl-a-L-lyxopyranoside by inversion at C-4 to the corresponding 4-azido-4-deoxy-D-Wbo compound. ... 

For synthesis of nucleosides, methyl 4-acetamido-2,3-di-0-benzoyl-4-deoxy-a-D-ribopyranoside (198c), obtained from 198a, was trans-formed by acetolysis into 4-acetamido-l,5-di-0-acetyl-2,3-di-0-benzoyl-4-deoxy-D-ribofuranose (199b). Either with preliminary treatment with hydrogen chloride in acetyl chloride, or directly, in the presence of titanium tetrachloride, 199b gave with chloromercuri-(6-... 

Similar reactions of 2-methanesulfonic esters with sodiiun methoxide have been described by Fletcher and coworkers 1,3,5-tri-0-benzoyl-2-0-(methylsulfonyl)-a-D-ribose afforded methyl a-D-arabinopyranoside. From l,3,5-tri-0-benzoyl-2-0-(methylsul-fonyl)-/8-D-arabinose, a mixture of methyl /3-D-ribofuranoside and methyl /3-D-ribopyranoside was obtained, whereas only the latter glycoside was isolated when 2-0-(methylsulfonyl)-l,3,5-tri-0-(p-nitrobenzoyl)-)8-D-arabinose was the starting material. 

P2,2,2i Z = 4 Dx = 1.479 R = 0.07 for 660 intensities. The conformation is C4, with three axially attached hydroxyl groups, two of which, O-2-H and O-4-H, are linked by an intramolecular hydrogen-bond. Similar intramolecular hydrogen-bonding has been observed in the crystal structures of methyl 1-thio-a-D-ribopyranoside and methyl 1,5-dithio-a-D-ribopyranoside.13 This is the same crystal structure as that given in a preliminary report,14 which did not include the atomic parameters. 

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