Polymer-assisted structural modification on nucleosides and nucleotides

A Multi-enzyme Cascade for the Biosynthesis of AICA Ribonucleoside Di- and Triphosphate

AICA (5'-aminoimidazole-4-carboxamide) ribonucleotides with different phosphorylation levels are the pharmaceutically active metabolites of AICA nucleoside-based drugs. The chemical synthesis of AICA ribonucleotides with defined phosphorylation is challenging and expensive. In this study, we describe two enzymatic cascades to synthesize AICA derivatives with defined phosphorylation levels from the corresponding nucleobase and the co-substrate phosphoribosyl pyrophosphate. The cascades are composed of an adenine phosphoribosyltransferase from Escherichia coli (EcAPT) and different polyphosphate kinases: polyphosphate kinase from Acinetobacter johnsonii (AjPPK), and polyphosphate kinase from Meiothermus ruber (MrPPK). The role of the EcAPT is to bind the nucleobase to the sugar moiety, while the kinases are responsible for further phosphorylation of the nucleotide to produce the desired phosphorylated AICA ribonucleotide. The selected enzymes were characterized, and conditions were established for two enzymatic cascades. The diphosphorylated AICA ribonucleotide derivative ZDP, synthesized from the cascade EcAPT/AjPPK, was produced with a conversion up to 91 %. The EcAPT/MrPPK cascade yielded ZTP with conversion up to 65 % with ZDP as a side product.

Synthesis and antibacterial activity of 5'-tetrachlorophthalimido and 5'-azido 5'-deoxyribonucleosides

Reported is an efficient synthesis of adenyl and uridyl 5'-tetrachlorophthalimido-5'-deoxyribonucleosides, and guanylyl 5'-azido-5'-deoxyribonucleosides, which are useful in solid-phase synthesis of phosphoramidate and ribonucleic guanidine oligonucleotides. Replacement of 5'-hydroxyl with tetrachlorophthalimido group was performed via Mitsunobu reaction for adenosine and uridine. An alternative method was applied for guanosine which replaced the 5'-hydroxyl with an azido group. The resulting compounds were converted to 5'-amino-5'-deoxyribonucleosides for oligonucleotide synthesis. Synthetic intermediates were tested as antimicrobials against six bacterial strains. All analogs containing the 2',3'-O-isopropylidine protecting group demonstrated antibacterial activity against Neisseria meningitidis, and among those analogs with 5'-tetrachlorophthalimido and 5'-azido demonstrated increased antibacterial effect.