Syntheses and Structure−Activity Relationships of Nonnatural β-C-Nucleoside 5‘-Triphosphates Bearing an Aromatic Nucleobase with Phenolic Hydroxy Groups:  Inhibitory Activities against DNA Polymerases

Five nonnatural β-C-nucleoside 5‘-triphosphates bearing a 3,4-dihydroxyphenyl (1TP), a 2-hydroxyphenyl (2TP), a 3-hydroxyphenyl (3TP), a 4-hydroxyphenyl (4TP), or a phenyl (5TP) group were synthesized, and their structure−activity relationships were examined for a series of DNA polymerase reactions in vitro under typical polymerase chain reaction conditions. We found that the 5‘-triphosphates (1TP−5TP) are not incorporated into DNA strands but inhibit the DNA polymerase reactions in the presence of natural nucleoside 5‘-triphosphates (dNTPs). 1TP having two phenolic hydroxy groups at the nucleobase moiety showed the most potent inhibitory effect against DNA synthesis by Ex Taq polymerase (IC50 = 30 μM). The competition assay indicated that 1TP and dNTPs are most likely to affect DNA polymerase reactions competitively. This finding may raise the appealing possibility that artificial nucleoside 5‘-triphosphates having phenolic hydroxy groups could exhibit potent inhibitory activity against DNA-directed enzymatic reactions.