The synthesis of oligoribonucleotides. Part XI. Preparation of ribonucleoside 2′-acetal 3′-esters by selective deacylation

Abstract

The rates of deacylation of 5′-O-acetyl-, -methoxyacetyl-, -phenoxyacetyl-, -formyl-, and -chloroacetyl-uridines (10a–e, respectively) in aqueous and methanolic ammonia have been measured. From these data, a procedure has been developed for the general preparation of 2′-O-(methoxytetrahydropyranyl)-3′-O-acyl ribonucleosides (9) by selective deacylation of suitably designed 2′-O-(methoxytetrahydropyranyl)-3′,5′-di-O-acyl derivatives (8). Two series of 2′-acetal 3′-esters (9), designed as building blocks for oligoribonucleotide synthesis, have been prepared from each of the four main ribonucleosides: one series (derived from uridine, 4-N-benzoylcytidine, adenosine, and 2-N-benzoylguanosine) consists of 3′-acetates or -benzoates and the other series (derived from uridine, 4-N-p-anisoylcytidine, 6-N-p-anisoyladenosine, and 2-N-benzoylguanosine) consists of 3′-methoxy-acetates. All these 2′-O-(methoxytetrahydropyranyl)-3′-O-acyl ribonucleosides (9) have been obtained in satisfactory yields and all except one have been isolated as pure crystalline solids.