SIMPLIFIED AND COST-EFFECTIVE SYNTHESES OF FULLY PROTECTED PHOSPHORAMIDITE MONOMERS SUITABLE FOR THE ASSEMBLY OF OLIGO(2'-O-ALLYLRIBONUCLEOTIDES)

Simplified, high yielding syntheses of suitably protected 2'-O-allylri bonucleoside-3'-O-phosphoramidites starting from standard ribonucleosi des have been elucidated. Specific 2'-O-allylation is readily achieved using amidine protection of the exocyclic amino groups of adenosine a nd cytidine and in the case of guanosine the allylation is carried out on an easily prepared intermediate bearing transient protection of th e lactam function.