Diribonucleoside 2 ,3 -cyclic phosphates

Proceeding from 5 -0-acetylazauridine (80), a mixture of 2 - and 3 -monophosphates (81, 82) was prepared by phosphorylation with polyphosphoric acid, and these were converted into the 2, 3 -cyclic phosphate (83). From the 2, 3 -0-isopropylidene derivative of 3-methyl-6-azauridine the 5 -phosphate was prepared by treatment with cyanoethylphosphate and the corresponding diphosphate from its morpholidate through the action of phosphoric acid. ° Furthermore, a diribonucleoside phosphate (85) with a natural 3 -5 internucleotide linkage was prepared from 6-azauridine, The starting material for the preparation of such derivatives was 5 -0-acetyl-2 -0 -tetrahydro-pyranyluridine-3 -phosphate (84) which was condensed with di-G-acetylazauridine (86) or with 2b3 -0-isopropylidene-6-azauridine (76) with the aid of dicyclohexylcarbodiimide. ... 

Field desorption spectra of unprotected diribonucleoside phosphates afforded (79) both the 5 - and 3 -mononucleotide as fragment ions. Further cyclizations gave 3, 5 -cyclic phosphates from the 5 -nucleotides and both 3, 5 - and 2, 3 -cyclic phosphates from the 3 -nucleotides (Scheme 1). 

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