Boron-containing nucleic acids. Synthesis of cyanoborane adducts of 2'-deoxynucleosides

Cyanoborane adducts of 2'-deoxynucleosides, specifically 2'-deoxyguanosine-N7-cyanoborane, 2'-deoxyadenosine-N1-cyanoborane, 2'-deoxyinosine-N7-cyanoborane, and 2'-deoxycytidine-N3-cyanoborane, were prepared by an exchange reaction of triphenylphosphine-cyanoborane (Ph 3 PBH 2 CH) with 3',5'-O-protected nucleosides