CHEMISTRY OF RIBOSE AND DEOXYRIBOSE 



51 



.CH2— O, 



H-OMe 



R- 



CH2— 0. 



HO 



HO 



H-OMe — 



HO 



j^ >H-OMe 



CH2— O. 



CH2 — O, 



HyH-OMe 



HO 



H >H-OMe 



HO 



methyl 3-deoxy-/3-L-riboside (xyloside) (XLVI, R = H, D-isomer), and only traces 

 of methyl 2-deoxy-/3-L-riboside (XLV, R = H, D-isomer) were detected.^^o Change of 

 configuration at the glycosidic center had no effect in increasing the proportion of 

 the 2-deoxypentose derivative, since similar results were obtained with methyl 

 2,3-anhydro-a-L-ribopyranoside.^^'' Likewise change in the size of the lactol ring had 

 no effect on the orientation of the substituents.^*^ 



The action of halogen acids on alkyl 2,3-anhydroaldosides results in the formation 

 of an alkyl 2-halogeno- or 3-halogeno-deoxyaldoside which can readily be reduced 

 to give the corresponding alkyl 2- or 3-deoxyaldoside. Methyl 2,3-anhydro-/3-D- 

 riboside when treated with hydrobromic acid yielded mainly methyl 3-bromo-3- 

 deoxy-/3-D-xyloside (XLVI, R = Br) and only a small amount (10%) of methyl 

 2-bromo-2-deoxy-/3-D-arabinoside (XLV, R = Br). After separation of these isomers, 

 the methyl 2-bromo-2-deoxy-/3-D-arabinoside was subjected to catalytic hydrogena- 

 tion with Raney nickel in the presence of calcium hydroxide and afforded methyl 2- 

 deoxy-D-ribose. This on hydrolysis with dilute acetic acid yielded 2-deoxy-D-ribose 

 which was isolated as iV-phenyl-2-deoxy-D-ribosylamine. Allerton and Overend"* 

 showed that the action of hydrochloric acid on this anhydroriboside leads to a slightly 

 better yield (18.4%) of the methyl 2-halogeno-2-deoxy-D-arabinoside (XLV, R = 

 halogen), but these methods have no value for the large-scale synthesis of 2-deoxy-D 

 ribose. 



Attempts to convert methyl anhydroriboside directly into methyl 2-deoxyriboside 

 have not been very successful. Reaction of methyl 2,3-anhydro-^-D-riboside with 

 lithium aluminum hydride gave mainly methyl 3-deoxy-/3-D-riboside and only a 

 small amount (14%) of methyl 2-deoxy-/3-D-riboside."2 On heating methyl 2,3- 

 anhydro-/3-L-riboside at 110° in hydrogen (at 100 atmospheres) with Raney nickel 

 cleavage of the anhydro ring occurred to yield predominantly methyl 3-deoxy-/3-L- 

 riboside, accompanied by only a small amount of the 2-deoxy-isomer."'' 



Recently Allerton and Overend^^^ succeeded in directly replacing by 

 hydrogen the p-toluenesulfonyloxy (or methanesulfonyloxy) group in 



282 J. Davoll, B. Lythgoe, and S. Trippett, J. Chem. Soc. 1951, 2230. 

 ^^^ R. Allerton and W. G. Overend, J. Chem. Soc, in press. 



