174 J. BADDILEY 



groups are removed by catalytic hydrogenation and the isopropylidene 

 residue by acid hydrolysis as before. A good yield of adenosine-5'-phosphate 

 is obtained in this way.^'^ 



Phosphorylation of 2' ,3'-isopropylidene cytidine and 2' ,3'-isopropylidene 

 uridine with dibenzyl phosphorochloridate, followed by hydrogenation and 

 hydrolysis, gives cytidine-5'-phosphate and uridine-5'-phosphate.^^^ Uri- 

 dine-5'-phosphate has also been prepared by phosphorylation of 2',3'-iso- 

 propylidene uridine with phosphoryl chloride.^^ Guanosine-5'-phosphate 

 may be prepared from 2',3'-isopropylidene guanosine and phosphoryl 

 chloride but not from dibenzyl or diphenyl phosphorochloridate.'^^ 



b. The a and b Isomers 



Syntheses of the 3'-phosphates of adenosine, guanosine, cytidine, and 

 uridine have been reported. These syntheses, however, are either ambiguous 

 or based on erroneous assumptions concerning the structure of intermedi- 

 ates. The ready interconversion of the a and b series and the unsuspected 

 difficulty in characterizing the products at the time invalidates much of this 

 work. Direct phosphorylation under various conditions with phosphoryl 

 chloride of adenosine,^"'' guanosine, and uridine^"' gives products which 

 were claimed to be identical with the nucleotides obtained from ribonu- 

 cleic acid. Similarly, phosphorylation of 5'-trityluridine and 5'-tritylcyti- 

 dine,^^' ~^- followed by removal of protecting groups, was thought to give 

 the 3'-phosphates. These syntheses are ambiguous, and it has been shown in 

 the case of adenosine that phosphorylation of the 5'-trityl compound leads 

 to mixtures of a and b nucleotides. '^° 



Although unambiguous syntheses of the 2'- and 3 '-phosphates of purine 

 and pyrimidine nucleosides have been claimed, '^^' 203-205 j^ jg j^q^ known 

 that the compounds obtained were 5'-phosphates.'^'' 2"® These syntheses 

 were based on benzylidene nucleosides, which were believed to be 3',5'- 

 benzylidene compounds^^' ^"^ but which have since been shown to be 

 2',3'-compounds. 



c. The Cyclic Phosphates 



The four cyclic phosphates obtained by cautious alkaline hydrolysis of 

 ribonucleic acid are prepared from the appropriate a or 6 nucleotides by 



199 J. Baddiley and A. R. Todd, J. Chem. Soc. 1947, 648. 



^"0 G. R. Barker and J. M. Gulland, J. Chem. Soc. 1942, 231. 



2o> J. M. Gulland and G. I. Hobday, J. Chem. Soc. 1940, 746. 



202 H. Bredereck, Z. physiol. Chem. 224, 79 (1934). 



^"^ J. M. Gulland and H. Smith, J. Chem. Soc. 1947, 338. 



2»4 J. M. Gulland and H. Smith, /. Chem. Soc. 1948, 1527. 



2" J. M. Gulland and H. Smith, J. Chem. Soc. 1948, 1532. 



206 D. M. Brown, L. J. Haynes, and A. R. Todd, J. Chem. Soc. 1950, 408. 



^o-' J. M. Gulland and W. G. Overend, /. Chem. Soc. 1948, 1380. 



