CHEMISTRY OF RIBOSE AND DEOXYRIBOSE 39 



rate. However, Levene and his co-workers'^^- -'- were able to isolate a crys- 

 talline dibrucine salt of a ribose phosphate (not identical with the known 

 ribose-5-phosphate) from a hydrolysate of xanthylic acid. The xanthylic 

 acid was obtained by treatment of guanylic acid with nitrous acid: after 

 deamination the sugar-base linkage is found to be more labile. Reduction 

 of the ribose phosphate yielded an optically inactive ribitol phosphate,-'^ 

 considered to be ribitol-3-phosphate, derived from ribose-3-phosphate. This 

 structural proof makes no account for possible migration of the phosphate 

 group during any of the experimental operations. Deamination of adenosine- 

 3'-phosphate to the corresponding inosinic acid, followed by hydrolysis, 

 also yields some ribose-3-phosphate.-'^ 



By methanolysis of yeast nucleic acid, Levene and Harris-'^ obtained a 

 crude sample of a methyl D-ribopyranoside-3-phosphate. Exhaustive meth- 

 ylation and subsequent dephosphorylation afforded methyl 2,4-di-O- 

 methyl-D-riboside, which on successive hydrolysis and catalytic reduction 

 yielded 2,4-di-O-methyl-D-ribitol. Although this compound is a meso 

 structure and would be expected to be optically inactive, the product did 

 exhibit some optical activity, and it was shown that the crude methyl d- 

 ribopyranoside-3-phosphate was contaminated with a furanoside isomer 

 which gave rise to optically active 2 , 5-di-O-methyl-D-ribitol as an impurity 

 in the 2 , 4-di-O-methyl derivative. 



LePage and Umbreit-'^ have prepared ribose-3-phosphate by acidic hy- 

 drolysis of a pure adenosine triphosphate isolated from the autotrophic 

 bacterium Thiohacillus thio-oxydans. 



(3) Ribose-5-phosphate. Ribose-5-phosphate was first obtained by Levene 

 and Jacobs'' by subjecting the barium salt of inosinic acid to acidic hy- 

 drolysis. The pentose phosphate was isolated as the crystalline hydrated 

 barium salt. Shortly afterwards the same workers'^ showed that oxidation 

 of the pentose phosphate with either bromine or nitric acid yields a phos- 

 phoribonic acid. If position C-5 had been unsubstituted, nitric acid oxida- 

 tion would have been expected to produce a trihydroxyglutaric acid, and 

 so the phosphate residue was considered to be located at C-5 of the ribose 

 molecule. Much later^'^ further evidence was forwarded which substan- 

 tiated this conclusion, since lactonization of the D-ribonic acid phosphate 

 proceeded very slowly, equilibrium being reached only after 150 hours. 

 This is the behavior expected of a pentonic acid substituted at C-5 and 

 unable to form other than a 7(1 ,4)-lactone.-'^' ^'^ Furthermore, reduction 



212 P. A. Levene and A. Dmochovvski, J. Biol. Chcm. 93, 563 (1931). 



213 p. A. Levene and S. A. Harris, J. Biol. Chem. 98, 9 (1932). 



2>4 P. A. Levene and S. A. Harris, J. Biol. Chcm. 101, 419 (1933). 

 2'5 G. A. LePage and W. W. Umbreit, J. Biol. Chem. 148, 255 (1943). 

 2>« P. A. Levene and T. Mori, J. Biol. Chem. 81, 215 (1929). 

 217 p. A. Levene and H. S. Simms, /. Biol. Chem. 65, 31 (1925). 



