New Boron Analogues of Pyrophosphates and Deoxynucleoside Boranophosphates

Tetraethyldicyanoborane pyrophosphate (2) and 3'-(diethylphosphite-cyanoborano)-5'-dimethoxytrityl.N(4)-benzoyl-deoxycytidine (3) have been synthesized in 70% and 76% yields, respectively. The compatibility of the substituted boranophosphates with common protecting groups is hereby demonstrated. Boron containing biologically active compounds, such as nucleosides and nucleotides (1-6) and amino acids (7-9) are important due to their potential therapeutic activity, research and diagnostic applications. Many boron containing compounds have shown promising activity as anticancer, (10.) (11.) (12) antiinflammatory,(13) and antiosteoporotic (13)agents. Oligonucleotdes in which a non-bridging oxygen atom is replaced by a borane(BH(3)) group are a very important class of modified nucleic acids. (1.) (3.) (14-16) The BH(3) group is isoelectronic with oxygen in natural oligonucleotides and isoelectronic and isostructural with the oligonucleotide methyl phosphonates, which are nuclease resistant. On the other hand, the α-borano triphosphates are good substrates for DNA polymerases and incorporation of boranophosphates into DNA causes an increase in the resistance to exo- and endonucleases (2.) (17a) as compared to non-modified DNA. There are also notable applications of the α-borano triphosphates in PCR sequencing (17a) and nucleic acid detection (17b).