Boranephosphonates. Unraveling chemistry of the P-BH₃ functional group

Abstract

Nucleoside boranephosphonates are an important class of nucleotide analogues in which one of the non-bridging oxygen atoms has been replaced by a borane moiety (-BH₃). In the presence of iodine nucleoside boranephosphonates react with 1° and 2° amines to afford the corresponding phosphoramidates, while with 3° and heteroaromatic amines, the borane group is modified forming new derivatives with the P-B-N bond system. We investigated mechanistic aspects of these reactions and showed that both of them followed the same initial steps that involved most likely formation of λ³-boranephosphonate as a key, electrophilic intermediate. It reacts further, eventually leading to either the corresponding phosphoramidate diester or the B-ammoniumboranephosphonate derivative, depending on the type of amine used.

Graphical Abstract

Keywords:

• Boranephosphonates
• phosphoramidates
• pyridiniumboranephosphonates
• oxidation with iodine
• mechanism
• nucleotide analogues

Acknowledgements

Financial support from the National Science Centre, Republic of Poland (the Preludium grant Nr 2018/31/N/STP/03589 to JG), is greatefully acknowledged.