0-D-Ribopyranose

CnHi (BrN204 D-Ribopyranose (p-bromophenyl)hydrazone RIBBRP 31 367... 

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 Michaelis-Arbuzov reaction of methyl 5-deoxy-5-iodo-2,3-0-isopropylidene-/ -D-ribofuranoside38 (43) with diethyl ethylphosphonite gave,35 in 80% yield, the 5-C-[(ethoxy)ethylphosphinyl] derivative which, on treatment with SDMA and then mineral acid, yielded (30%) 5-deoxy-5-C-[(RS)-ethylphosphinyl]-D-ribopyranose (44) as a mixture of diastereoisomers. These compounds showed no mutarotation in methanol during 24 h. Upon treatment with acetic anhydride-pyridine, the product, 44, was converted (90% yield) into a syrup, presumably consisting of four diastereoisomers of the peracetate 45, separation of which was not attempted. Treatment of 45 with sodium methoxide in methanol regenerated 44 quantitatively. 

T etra-O-acety l-5-deoxy-5-C- (ethylphosphinyl)-D-ribopyranose Tri-0-acetyl-5-deoxy-3-0-methyl-D-xylopy- syrup -24 C 36... 

T etra-O-acetyl- a, p-D-ribopyranose T etra-O-acetyl- a, -D-arabinopy ranose Tetra-0-acetyl-a,( -D-xylopyranose Tetra-O-acetyl-a -D-lyxopy ranose... 

Figure 9. The low-field portion of the 220 MHz NMR spectrum of fi-D-ribopyranose tetraacetate in acetone-d6 at 20, —60, —70, —84°C...

Exercise 20-5 Make a sawhorse drawing of what you believe to be the favored conformations of a- and /3-d -ribopyranose and of a- and /3-d-idopyranose. 

A-6. A wedge-and-dash representation of a form of ribose (called /3-D-ribopyranose) is shown here. Draw the most stable chair conformation of this substance. 

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