D-Ribopyranosides, methyl

C7H14Oe Methyl 2-C-(hydroxymethyl)-/ -D-ribopyranoside [methyl / -D-hamameloside] (MHAMEL)850... 

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)... 

Alkyl a- and p-hexopyranosides with protected primary hydroxyl groups were, as a rule, selectively acetylated at 0-2 and 0-3, respectively, by vinyl acetate and Pseudomonas cepacia lipase the effects of variations in the size and hydrophobi-city of the anomeric and primary substituents on the regioselectivity of these reactions have been discussed in terms of enzyme-substrate binding. Methyl P-D-ribopyranoside, methyl P-D-arabinopyranoside, methyl P-D-xylopyranoside, and methyl-a-L-rhamnopyranoside were all acetylated at 0-4 by lipases from... 

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... 

CeHjjOjjS Methyl 5-thio-/ -D-ribopyranoside (R)-S-oxide TRPROX 43 371... 

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... 

Scheme 3 Synthesis of 2,3,4-bicyclophosphite of P-methyl-d-ribopyranoside, 6a and its selected...

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 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... 

---