In the present work, new synthetic approaches to the synthesis of nucleoside phosphorofluoridate and phosphorofluoridothioate diesters have been developed. These procedures involve either oxidative transformation of the corresponding H-phosphonate or H-phosphonothioate diesters in the presence of fluoride anion or iodine-promoted desulfurization of phosphorothioate or phosphorodithioate diesters in the presence of fluoride anion. Also, efficient protocols for the synthesis of nucleoside phosphorofluoridate, nucleoside phosphorofluoridothioate and nucleoside phosphorofluoridodithioate monoesters were developed.

Furthermore, the chemistry of a new class of P(III) compounds containing selenium, i. e. H-phosphonoselenoate monoesters was developed and synthetic procedures for the conversion of these compounds into the corresponding diesters were designed. In addition, the usefulness of H-phosphonoselenoate diesters for the preparation of various selenium-containing nucleotide analogues was demonstrated.

Finally, the possibility of employing triphenylphosphine selenide as a reagent for selenizing P(III) compounds was examined. Under mild conditions, this commercially available reagent was found to convert phosphite triesters and H-phosphonate diesters efficiently into the corresponding phosphoroselenoate derivatives.