Ribonucleoside H-Phosphonates. Pyridine vs Quinoline - Influence on Condensation Rate

Abstract

Abstract Condensation of 5′-O-monomethoxytrity1-2′-O-t-butyldimethylsilyl- uridine 3′-H-phosphonate (triethylammonium salt) (1) with 2′,3′-0- dibenzoyluridine (2) using pivaloyl chloride (PV-C1)1, 2-chloro-5,5- dimethyl-l,3,2-dioxaphosphorinane 2-oxide (NPCP)2 and bis(2-oxo-3- oxazolidiny1)phosphinic chloride (OXPI2 as condensing agents, has been investigated. Pyridine or quinoline3 was used as a base and nucleophilic catalyst in the following solvent systems: neat pyridine or quinoline, pyridine (or quinoline)/acetonitrile (4:1, v/v,), pyridine (or quinoline)/acetonitrile (1 :1, v/v,), and pyridine (or quinoline)/acetonitrile (1:4, v/v,). Stoicheiometric amounts of 1 and 2 (concentration 25 pM) and 3 equiv. of the appropriate condensing reagent were used in all reactions.