WALDO E. COHN 



RNA, doubly esterified phosphate, the evidence indicated that 

 these, upon alkahne hydrolysis, gave rise to this same cyclic 

 phosphate intermediate which subsequently was hydrolyzed 

 to yield both glycerophosphate isomers (4,5). 



(a) 



■^\ 



CHg-O-R-OH 



CH 



CH, 



OH 

 OH 



OH 



a-GLYCEROPHOSPHATE 



CH,-OH 



CH -0 -P-OH 



\. 



CHgOH 



OH 



)9 -GLYCEROPHOSPHATE 



CHg-O 



CH -0 



I 



CHg- OH 





P-OH 



(b) 



CHg-O-P-OR 



I OH 



CH -OH 



I 



CHg-OH 



CHg-OH 



,<^. 



CH -0 — P, -OH 

 I ^OH 



CHg-OH 



^Q_ OH' 



OH" 



CHg-O-^ ^O 



CHg-OH 



+ R-OH 



o^\ 



CH-0-P.-OR 

 I OH 



CH2- OH 



/ 



P — OR 



OH- CHg-O-P^OH 



CH -0 

 1 

 CHg-OH 



CH -OH 



I 



CH2-OH 



OH 



Fig. 2. Phosphomigration in the glycerophosphates, showing inter- 

 mediate cycUzation (4,5): {a) acid catalyzed phosphomigration in glycero- 

 phosphoric acids; intermediate demonstrated (15); (6) acid- or alkaH- 

 catalyzed hydrolysis of esterified glycerophosphates with production of both 

 glycerophosphoric acids; intermediate postulated. 



Here, then, was a complete parallel to the situation newly 

 uncovered with respect to RNA, regarded as a series of phospho- 

 diesters containing, as in glycerophosphate esters, a free alcoholic 

 hydroxy! cis to the phosphorylated hydroxyl. It was proposed, 

 then (10), that RNA of a 3 ',5' (or 2 ',5') linkage could hydrolyze 

 by intermediate cyclization of the phosphate to the 2' (or 3') 



464 



