Ribopyranose

Figure 5. Partial 100 MHz P.M.R. Spectrum of l,2,3,4-tetra-0-acetyl-f3-i>-ribopyranose (8) in acetone-d6 solution.

In addition to the above mentioned 4J couplings, we have now observed several examples of couplings across five bonds—i.e. 5J. For example, the ribopyranose derivative (13) shows a coupling of ca. 0.1 Hz between Hx and H4. Further examples occur in the spectrum of 2,3,4-tri-0-acetyl-l,6-anhydro-/ -D-glucopyranose (12), where Ji,4 = ca. 0.1 Hz and J2,5 = 0.5 Hz. Whether it is significant that these couplings all occur between equatorially oriented protons must await further studies. 

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... 

Fig. 5.6. PFT 1 1H NMR spectra of D-ribose, 22.63 MHz. 1 g/2 mL D20, temperature 30 C, accumulation of 2000 pulse interferograms (6 K data points), 90 pulses, pulse interval 6 s, 2500 Hz, the numbers of the signals refer to the numbering of the C atoms. A quantitative evaluation of the spectrum gave 62% of /j-ribopyranosc (P (i), 20.3% of a-ribopyranose (Pa). 11.6% of /1-ribo-furanose (Ffi) and 6.1 % of a-ribofuranose (Fa) [132b],...

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