Cytidine-3 -benzyl phosphate

A group of interesting reactions catalyzed by ribonuclease have been investigated. Cytidine 3 -methyl phosphate has been formed from cytidine 2, 3 -phosphate and methanol [Eq. (46)], or from cytidine 3 -benzyl phosphate and methanol [Eq. (47)]. The reactions may be explained on the basis of the known mechanism of action of ribonuclease. 

The possibility that, during the alkaline hydrolysis of ribonucleic acid, tri-esters (18) - could be intermediates was ruled out on mechanistic groxmds."f > Furthermore, it was shown that the tri-ester, uridine 2 3 -(methyl phosphate) (18, R = CH3), synthesized by methylation of uridine 2 3 -cychc phosphate with diazomethane, is resistant to ribo-nuclease. f However, it has been observed that, when the benzyl ester of cytidylic acid 6 is partially hydrolyzed in acid, a significant proportion of the o isomer of this phosphoric diester is formed." ) In addition, the dinucleoside phosphates, such as adenylyl-(3 —>5 )-cytidine (14a), are also isomerized to the corresponding (2 - 5 )-dinucleoside phosphates by treatment with acid. " These studies suggest that cyclic triesters (or derivatives thereof) may be intermediates in isomerization of these phospho-diesters in acidic mediiun. 

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