154 



J. BADDILEY 



j^ CH.OCH.Ph 



MeSf ^NH, I ^MeS(r^N = CH-(CHOAc),-CHo-OCHsPh 



V I + (CH0Ac)3 »• XT 



NHj CHO NH, 



-N. 



-o- 



OH OH 

 I I 

 ^MeSff^'^NH-CH-CH-CH-CH-CH.OCHjPh 



NH, 



-N: 



-0- 



AcO OAc 



(f^'^NH-CH-CH-CH-CH-CHj-OCHjPh 

 N^NH-CHS 

 NH, 



-0- 



OH OH 

 I I 

 l-CH-CH-CH-CH, 



•OCHoPh 



MeSf^ 



N 



N.^N 



J' 



(1) AcjO 



NH, 



(2) Ni/H 



(3) NaOMe 



N 



-0 



OH OH 

 I I 

 LCH-CH-CH-CH-CH,-OH 



I 



N. 



NH, 



5'-Benzyl-2-methylthioadenosine 



Adenosine 



are obtained.*' • *■ However, acetyl groups may be used for protection, if at 

 all stages deacetylation is avoided. In this way 9-D-galactofuranosyl-2- 

 methylthioadenine has been prepared from 2,3,5,6-tetraacetyl-D-galacto- 

 furanose.*^ 



Purine nucleosides may also be synthesized from iminazoles. This method 

 is more or less restricted to the xanthine glycosides,*'* • ** but with that 

 limitation is quite useful and has been applied to the synthesis of xanthosine 

 itself.*^ Starting from an acetohalogeno-sugar and the silver derivative of 

 4,5-dicarbomethoxyiminazole a glycoside is obtained. This is converted to 

 a diamide with simultaneous deacetylation by the action of ammonia, and 

 cyclization to the purine is effected by potassium hypobromite in a modi- 

 fied Hofmann reaction. 



«i G. W. Kenner, B. Lythgoe, and A. R. Todd, /. Chem. Soc. 1948, 957. 

 "2 G. W. Kenner, H. J. Rodda, and A. R. Todd, J. Chem. Soc. 1949, 1613. 

 " K. J. M. Andrews, G. W. Kenner, and A. R. Todd, /. Chem. Soc. 1949, 2302. 

 8^ R. A. Baxter and F. S. Spring, /. Chem. Soc. 1947, 378. 

 " R. A. Baxter, A. C. McLean, and F. S. Spring, J. Chem. Soc. 1948, 523. 

 «6 G. A. Howard, A. C. McLean, G. T. Newbold, F. S. Spring, and A. R. Todd, /. 

 Chem. Soc. 1949, 232. 



