CHEMISTRY OF RIBOSE AND DEOXYRIBOSE 21 



methane-dimethyl-dihydrazone^°^ have been used for this purpose. Ribose 

 may also be characterized by preparing 2-{'n6o-tetrahydroxybutyl)ben- 

 zimidazole (ribobenzimidazole)^"- ^'^ ^"^^ ^"^ from ribonic acid and o-phenyl- 

 enediamine. This latter method of characterization is not entirely un- 

 equivocal since Dimler and Link^"^ have demonstrated that the conversion 

 of ribose to ribonic acid by oxidation with alkaline hypoiodite results in 

 slight (5 %) epimerization and so the product is contaminated with arabonic 

 acid. Epimerization at this stage may be avoided by using the improved 

 procedure for preparing aldonic acids described by Hudson and Isbell,!"* 

 but there is a further risk of epimerization during the condensation of the 

 aldonic acid with o-phenylenediamine, particularly if there is insufficient 

 acid present. ^^'^^ (For a review^ of substituted benzimidazoles derived from 

 sugar acids see Richtmyer.^"^) 



The j8-tetraacetate^^' ""^ and /3-tetrabenzoate^" and various mercap- 

 tals"^- "^ have frequently been used. Zinner"* recommends the di-n-propyl 

 and di-isobutyl mercaptals for the characterization of ribose. Chromato- 

 graphic methods have been used to identify ribose in mixtures of sugars 

 and to separate it from such mixtures. [Compare Chapters 6 and 7.] Various 

 reagents have been used to demonstrate the position of the sugar spots on 

 paper chromatograms : aniline hydrogen phthalate"*- "® in moist butanol 

 gives a bright red color with pentoses which may be differentiated from 

 aldohexoses, uronic acids and deoxysugars as these give various shades of 

 green and brown. It is possible with this reagent to detect 1 ng. of ribose. 

 Benzidine can be used as a developing agent"^ and pentoses are shown as 

 chocolate-browTi colored spots on a chromatogram. Jones et aZ."^ have 

 described experiences using various acidic spray reagents, as for example, 

 p-anisidine hydrochloride and aniline trichloroacetate and have reported 

 Rf values for ribose. Potassium permanganate with sodium carbonate has 



"« J. V. Braun, Ber. 46, 3949 (1913). 



»« N. K. Richtmyer and C. S. Hudson, J. Am. Chem. Soc. 64, 1612 (1942). 



«7 R. J. Dimler and K. P. Link, J. Biol. Chem. 150, 345 (1943). 



"8 C. S. Hudson and H. S. Isbell, /. Research Natl. Bur. Standards 3, 57 (1929). 



"* N. K. Richtmyer, Advances in Carbohydrate Chem. 6, 175 (1951). 



" P. A. Levene and R. S. Tipson, J. Biol. Chem. 92, 109 (1931). 



" R. Jeanloz, H. G. Fletcher, Jr., and C. S. Hudson, J. Am. Chem. Soc. 70, 4052 



(1948). 

 " E. Hardegger, E. Schreier, and Z. El Heweihi, Helv. Chim. Acta 33, 1159 (1950). 

 " H. Zinner, Chem. Ber. 86, 496 (1953). 



1* (a) H. Zinner, Chem. Ber. 83, 275 (1950); (b) see also Chem. Ber. 86, 495 (1953). 

 15 S. M. Partridge, Nature 164, 443 (1949). 



^' Judith Blass, M. Macheboeuf, and G. Nunez, Bull. soc. chim. biol. 32, 130 (1950). 

 " R. H. Horrocks, Nature 164, 444 (1949). 

 '8 L. Hough, J. K. N. Jones, and W. H. Wadman, J. Chem. Soc. 1950, 1702. 



