Oligoribonucleotide Synthesis III. Synthesis of Trinucleotides Using a Stepwise Phosphotriester Method

A convenient general synthesis for protected di- and triribonucleotides of predetermined sequence is described. Starting with a 5′-p-methoxytrityl-2′-O-tetrahydropyranyl-ribonucleoside, the nucleoside unit destined to become the 5′-terminal of the oligomer, 2′-O-tetrahydropyranyl-nucleosides are coupled together by β,β,β-trichloroethyl 3′–5′-phosphotriester linkages. A two-step process is used for each coupling, (a) the terminal 3′-hydroxyl …