Methyl -D-ribofuranoside

Unlike the 4,6-O-benzylidene derivatives, methyl 2,3-O-benzylidene-5-0-methyl-/ -D-ribofuranoside (99) (9) in which the acetal spans two secondary hydroxyl groups, reacts with NBS to give (48) the isomeric bromobenzoates 100 and 101. These are formed in a ratio of 2 1, and,... 

In Table I, the more stable anomer is listed first. In each of the four cases, this anomer is the Irans-C 1 -C2-aldofuranoside, having a Irons relationship of the aglycon group to the hydroxyl group at C-2. Thus, the 0-d anomers of methyl D-ribofuranoside and methyl D-xylofuranoside are listed first, even though the interactions for the latter are equal. Later in this Chapter, the effect of this conformational stability will be discussed in relation to formation of products At present, it suffices to mention that there are two factors to be considered, the C-l and C-2 interactions, and the overall interactions (C-l and C-2, C-2 and C-3, C-3 and C-4). The... 

Methyl-D-ribose has been synthesized48 starting with 2,3-isopropyli-dene-D-ribose (XL), which on methylation with silver oxide and methyl iodide gave methyl 2,3-isopropylidene-5-methyl-D-ribofuranosides (XLI), from which 5-methyl-D-ribose (XLII) was obtained by hydrolysis with... 

D-Ribose reacts rapidly at room temperature with methanol containing 1 % of hydrogen chloride, and methyl D-ribofuranoside, which may be purified by vacuum distillation, is the initial product.89 The structure of the compound was shown through methylation, hydrolysis and oxidation to 2,3,5-trimethyl-D-ribonolactone, which hydrolyzed in water at a rate characteristic of y-lactones. 

Chemical hydrolysis is a very familiar reaction for the sugar industry. However, it may generate an array of possible degradation products. For example, very low rate constants for the spontaneous hydrolysis of nonactivated methyl -D-glucopyranoside 1 have been determined at 220 °C [7], (O Fig. T). At pH > 7, the rate constants approach a constant value. On hydrolysis at pH 10 in the presence of H2 0, the results show that the reaction occurs almost exclusively by cleavage of the Cl/01 bond. The /i-anomer 1 is roughly twice as reactive as the a-anomer 2, as are also the anomeric pair of methyl D-ribofuranosides 3 and 4. Unlike the hydrolysis at pH < 7, the hydrolysis of 1 without catalysts proceeds with a negative entropy of activation. This is consistent with bimolecular attack of water on 1. 

Methyl D-ribofuranoside-boron chloride complex, prepared from methyl D-ribo-furanoside and BCI3 according to T. G. Bonner, E. J. Bourne, and S. McNally, Soc. 1962, 761, and 6-benzylthiopurine refluxed 2 hrs. in chloroform in the presence of pyridine -> 9-a-D-ribofuranosyl-6-benzylthiopurine. Y 52%. - Protection of the hydroxyl group is not necessary. a-Anomers can be obtained in fairly good yield by this method. F. e. s. Y. Furukawa, K. Imai, and M. Honjo, Tetrah. Let. 1968, 4655. 

Me, 3,5-dibenzoyl Methyl 3,5-di-O-benzoyl-2-O-methyl- -D-ribofuranoside C21H22O7 386.401... 

Scheme 7 Monofunctional donor and acceptor monomers used (EAE Ethyl allyl ether AHE Allyl hexyl ether AIG Allyl isopropylidene glycerol ACG Allyl glycerol carbonate AR Allyl-D-ribofuranoside AIR Allyl-2,3-0-isopropylidene-D-ribofuranoside ATMR Allyl-2,3,5-tri-0-methyl-D-ribofuranoside EVE Ethyl vinyl ether BVE Butyl vinyl ether HBVE 4-hydroxybutyl-vinyl ether HVE Hexyl vinyl ether VIG Vinyl isopropylidene glycerol VCG Vinyl glycerol carbonate VIR Vinyl-2,3-0-isopropylidene-D-ribofuranoside VTMR Vlnyl-2,3,5-tri-0-methyl-D-ribofuranoside DEF Diethyl fumarate DEM Diethyl maleate).

Reaction of Grignard reagents with sulphonate derivatives of methyl D-ribofuranoside leads to rearranged, branched-chain sugars as outlined in Scheme 4 anomerization of these compounds by acidic methanolysis or with Grignard reagents was also studied, the latter favouring the thermodynamically less-stable anomers. ... 

Methyl -D-ribofuranoside treated with 2 equivalents N,N-dimethylacetamide dimethyl acetal in a chlorinated hydrocarbon such as 1,1,2-trichlorethane methyl 2,3-0-[l-(dimethylamino)ethylidene]- -D-ribofuranoside (2 1 mixture of diastero-mers). Y > 90%. F. e. s. S. Hanessian and E. Moralioglu, Tetrah. Let. 1971, 813 Can. J. Chem. 50, 233 (1972). 

D-Ribose 5-phosphate is a normal metabolite in plants and animals. It was first prepared by acid hydrolysis of inosinic acid or from adenosine 5 -phosphate . It is formed enzymically from ribose and ATP . Synthesis has been carried out by phosphorylating 2,3-isopropylidene-methyl-D-ribofuranoside °. ... 

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