CHEMISTRY OF NUCLEOSIDES AND NUCLEOTIDES 



151 



which the trityl group may he removed by hydrogenolysis. The resulting 

 1 ,2,3-triacetyl-D-ribofuranose is converted on acetylation into 1,2,3,5- 

 tetraacetyl-D-ribofuranose and hence into acetobromoribofuranose." jS-Tet- 



CH.-OTn 



HO- 

 HO- 



CHa-OTri 



CH,-OH 



AcO- 

 AcO- 



CHOH 



■CH-OAc 



AcO- 

 AcO- 



- CH-OAc 



CH,-OAc 



CH,-OAc 



AcO- 

 AcO- 



CH-Br 



Acelobrorno-D-nbofuranose 



CH-OAc 



raacetyl-D-ribofuranose is also stated to be formed by acetylation of D-ri- 

 bose at elevated temperatures.*' 



Repetition of the nucleoside syntheses described above with 2,6-di- 

 chloroadenine and acetochloro-D-ribofuranose (prepared in an analogous 

 manner) gives adenosine*^ and guanosine.*^ Acetobromo-D-arabofuranose is 

 prepared similarly, but this gives a-glycosides with theophylline and aden- 

 ine.*^ Xylofuranosides may also be prepared by this route. This synthetic 

 method is not readily applicable to the silver salt of adenine itself since the 

 basicity of the purine is sufficient to effect dehydrohalogenation of the sugar 

 derivative. The difficulty may be overcome by acetylation or benzoylation 

 of the amino groups. From the chloromercury salt of 2 ,6-diacetamidopurine 

 and acetochlororibofuranose an acetylated 9-D-ribofuranoside is obtained. 

 Acetyl groups may be removed readil}^ from this compound giving 9-D-ribo- 

 furanosyl-2,6-diaminopurine. Partial removal of acetyl groups followed by 

 deamination with nitrous acid then complete deacetylation gives guanosine 

 in good yield.** Adenosine is prepared in an analogous manner and deamina- 

 tion of the diaminopurine riboside gives crotonoside (see p. 158).** 



«' H. Zinner, Ber. 83, 153 (1950). 



" J. Davoll, B. Lythgoe, and A. R. Todd, J. Chem. Soc. 1948, 967. 



" J. Davoll, B. Lythgoe, and A. R. Todd, /. Chem. Soc. 1948, 1685. 



" N. W. Bristow and B. Lythgoe, J. Chem. Soc. 1949, 2306; P. Chang and B. Lythgoe, 



ibid. 1950, 1992. 

 «5 J. Davoll and B. A. Lovvy, J. Am. Chem. Soc. 73, 1650 (1951). 

 6« J. Davoll, J. Am. Chem. Soc. 73, 3174 (1951). 



