7-DEAZAGUANOSINE - PHOSPHORAMIDITE AND PHOSPHONATE BUILDING-BLOCKS FOR SOLID-PHASE OLIGORIBONUCLEOTIDE SYNTHESIS

Abstract

The synthesis of oligoribonucleotide building blocks (phosphonates and phosphoramidites) of 7-deazaguanosine (2-amino-7-(beta-D-ribofuranosyl)-7H-pyrrolo[2,3-d]pyrimidin-4(3H)-one , 1) is described. Silylation of the 2'-hydroxy group of 7-deaza-N2-isobutyryl-5'-0-(4-monomethoxytrityl)guanosine (5) was studied with regard to the 2'-selectivity. Best results were obtained with triisopropylsilyl chloride/AgNO3. The 2'-0-protected intermediates (6a and 6b) were converted into the phosphonates (3a, b) or methylphosphoramidites (4a, b), which were successfully used for solid-phase oligoribonucleotide synthesis of (c7G-C)3 (9).