56 W. G. OVEREND AND M. STAGEY 



for methyl deoxyglycosides cannot be based only on optical rotation measurements 

 and application of Hudson's^"' system that the more dextrorotatory anomer of a 

 D-compound is termed a-D-, the other anomer being the /3-d form, since it is not cer- 

 tain that the contribution of the asymmetric center at carbon atom 1 will be of the 

 same sign in methyl 2-deoxyglycosides as in the related methyl glycosides. The 

 a,/3-relationship between methyl 2-deoxyglycosides was studied by Stacey and his 

 colleagues.^*' They showed that 1% methanolic hydrogen chloride separately con- 

 verts the a- and /3-isomers of methyl 2-deoxy-L-ribopyranoside into the a,|3-mixture 

 from which they were initially isolated. 



An outstanding property of the 0-glycosides of 2-deoxysugars is the lability of 

 the glycosidic substituent towards acid. Calculations from the experimental data of 

 the velocity constant (K) for the hydrolysis of the methyl glycosides of D-arabinose 

 and 2-deoxy-L-ribose (i.e., 2-deoxy-L-arabinose), with 0.01 N hydrochloric acid at 

 100°, gave the following results:'"'' 



(1) D-Arabinose: 



Methyl glycoside a-pyranoside /3-pyranoside a,/3-furanoside 



K 



1 , ^0 — ?■„ , . 

 = - log (t in minutes) 



t r — r 



0.00064 0.00064 0.0068 



(2) 2-Deoxy-h-ribose: 



Methyl glycoside a-pyranoside /3-pyranoside a,|3-furanoside 



K 0.18 0.22 1.4 



It was noted by Stacey and co-workers^*' that, on distillation of methyl 2-deoxy- 

 Qr,/3-L-ribofuranoside, polymeric material was formed whenever cautious superheat- 

 ing occurred. 



h. N -Glycosides 



A'^-Phenyl-2-deoxy-D-^ and -L-ribosylamine^" have been obtained in 

 crystalline form by the usual methods of synthesis, and are useful for the 

 isolation and characterization of this deoxypentose. It is thought that these 

 derivatives have a pyranose (l,5)-lactol ring structure; the stereochemical 

 configuration of the sugar-base linkage is unknown. A^-Glycosides of 2- 

 deoxysugars are unable to undergo the Amadori rearrangement, and it is 

 considered likely that the specificity of the reaction of deoxyribose with 

 secondary amines to yield colored products is a function of the inability of 

 2-deoxysugar derivatives to participate in this rearrangement. 



Although deoxyribonucleosides have been isolated from natural sources, 

 attempts to synthesize them have been less successful. The reaction inves- 

 tigated was the coupling of an acetyl(or benzoyl)-l-bromo-2-deoxysugar 

 with the silver salt of a base. Attempts to prepare 3,4-di-0-benzoyl-2- 

 deoxy-D-ribopyranosyl bromide by treating syrupy 1,3, 4-tri-0-benzoyl-2- 

 deoxy-D-ribose with hydrogen bromide in acetic acid resulted in extensive 

 decomposition. Treatment of syrupy 1 ,3,4-tri-O-acetyl-D-ribose with 

 ethereal hydrogen chloride also resulted in decomposition, although in this 



303 C. S. Hudson, J. Am. Chem. Soc. 31, 66 (1909). 



304 T. Reichstein, Angew. Chem. 63, 412 (1951). 



