CHEMISTRY OF RIBOSE AND DEOXYRIBOSE 15 



2'-deoxyribosicles of guanine, hypoxanthine, cytosine and thymine, afforded 

 proof of the presence of a furanose sugar in each compound. 



Besides 2-deoxy-D-ribose, other derivatives of D-ribose occur naturally. 3-Amino- 

 D-ribose has been shown to be one of the products of hydrolysis of Puromycin,^^' *" 

 and 5-thiomethyl-D-ribose occurs in the adenylthiomethylpentose^' which has been 

 isolated from yeast, crude vitamin Bi or crude cozymase. [Cf. Baddiley, Chapter 4.] 

 Reduction products of D-ribose are also found in Nature. For example ribitol (adoni- 

 tol) is isolable from Adonis vernalis L."' ^^ and the reduced ribityl residue forms part 

 of the riboflavin (vitamin B2 , 6,7-dimethyl-9-(D-ribityl)isoalloxazine) molecule 

 and of the coenzyme D-riboflavin-5'-phosphate (flavin mononucleotide). Despite the 

 absence of the ring structure of the sugar in these derivatives of ribitol, the stereo- 

 chemistry of the sugar residue is of great biological importance.*'' Synthesis of analo- 

 gous flavins containing other sugar residues gives rise to substances of quite different 

 biological activity. Flavin adenine dinucleotide, a mi.xed diphosphate ester of ribo- 

 flavin and adenosine, contains both ribofuranose and ribityl residues in its molecule. 

 This substance, which is the coenzyme chiefly involved in transporting electrons from 

 the reduced pyridine nucleotides to cytochrome, has been demonstrated in blood 

 cells,** liver, heart,** brain, kidnej^ intestine*' and muscle.*' It is probably a matter 

 of some significance that, in naturally occurring derivatives of ribose, the sugar is 

 present in the furanose form. 



III. Chemistry of Ribose 



1. Preparation 



The first synthesis of ribose was achieved by Fischer and Piloty''' in 

 1891 by epimerization of L-arabonic acid to L-ribonic acid and subsequent 

 reduction of its lactone to syrupy L-ribose. Since that time many attempts 

 have been made to convert derivatives of glucose and arabinose into ribose. 

 Blanksma and Alberda van Ekenstein^^ repeated the work of Fischer and 

 Piloty and obtained a syrupy product which was contaminated with 

 ribitol. Subsequently, the crude ribose was purified through its p-bromo- 

 phenylhydrazone and crystalhne L-ribose was obtained for the first time.'^ 

 The same workers repeated the synthesis in the D-series and by pyridine 

 treatment succeeded in converting D-arabonic acid (IV) into D-ribonic 



" C. W. Waller, P. W. Fryth, B. L. Hutchings, and J. H. Williams, J. Am. Chem. 



Soc. 75, 2025 (1953). 

 *» B. R. Baker and R. E. Schaub, J. Am. Chem. Soc. 75, 3864 (1953). 

 *' J. A. Mandel and E. K. Dunham, J. Biol. Chem. 11, 85 (1912). 

 *2 W. V. Podwissotzky, Arch, pharm. 227, 141 (1889); quoted by R. W. Jeanloz and 



H. G. Fletcher, Jr., Advances in Carbohydrate Chem. 6, 145 (1951). 

 *3 E. Merck, Arch, pharm. 231, 129 (1893). 

 «^ E. L. Hirst, J. Chem. Soc. 1949, 522. 



*5 J. R. Klein and H. I. Kohn, /. Biol. Chem. 136, 177 (1940). 

 ** S. Ochoa and R. J. Rossiter, Biochem. J. 33, 2008 (1939). 

 «' A. V. Trufanov, Biokhimiya 6, 301 (1941). 

 68 A. V. Trufanov, Biokhimiya 7, 188 (1942). 

 *' J. J. Blanksma and W. Alberda van Ekenstein, Chem. Weekblad 5, 777 (1908). 



