Studies of Phosphorylation. II. Reaction of 2′, 3′-<i>O</i>-Isopropylideneinosine and -guanosine with Phosphoryl Chloride1

Abstract

Abstract Several reactions accompanied by the phosphorylation of 2′, 3′-O-isopropylidene nucleosides with phosphoryl chloride in the absence of an organic solvent were investigated. When the reaction temperature exceeded 30°C, 2′, 3′-O-isopropylideneinosine gave 5′-chloro-5′-deoxy 2′, 3′-O-isopropylideneinosine and 5′-deoxy-2′, 3′-O-isopropylidene-3, 5′-cycloinosine. This cycloinosine, was then further subjected to rapid cleavage in a pyrimidine ring to give 5-amino-4-carbamoyl-N5, 5′-cyclo-1-β-d-(5′-deoxy-2′, 3′-O- isopropylideneribofuranosyl)-imidazole, 5-amino-4-cyano-N5, 5′-cyclo-1-β-d-(5′-deoxy-2′, 3′-O-isopropylideneribofuranosyl)-imidazole, and the N5-formyl derivative of the latter. Similar sequences of the chlorination at the 5′-position and the cyclization between 3 and 5′-positions were observed in the case of 2′, 3′-O-isopropylideneguanosine, but the resulting 5′-deoxy-2′, 3′-O-isopropylidene-3, 5′-cycloguanosine was not susceptible to ring cleavage under the conditions used. The factors affecting these reactions were described, and possible mechanisms were proposed.