Reverse C-glycosidase reaction provides C-nucleotide building blocks of xenobiotic nucleic acids

Abstract

AbstractC-Analogues of the canonicalN-nucleosides have considerable importance in medicinal chemistry and are promising building blocks of xenobiotic nucleic acids (XNA) in synthetic biology. Although well established for synthesis ofN-nucleosides, biocatalytic methods are lacking inC-nucleoside synthetic chemistry. Here, we identify pseudouridine monophosphateC-glycosidase for selective 5-β-C-glycosylation of uracil and derivatives thereof from pentose 5-phosphate (d-ribose, 2-deoxy-d-ribose,d-arabinose,d-xylose) substrates. Substrate requirements of the enzymatic reaction are consistent with a Mannich-like addition between the pyrimidine nucleobase and the iminium intermediate of enzyme (Lys166) and open-chain pentose 5-phosphate. β-Elimination of the lysine and stereoselective ring closure give the product. We demonstrate phosphorylation-glycosylation cascade reactions for efficient, one-pot synthesis ofC-nucleoside phosphates (yield: 33 – 94%) from unprotected sugar and nucleobase. We show incorporation of the enzymatically synthesizedC-nucleotide triphosphates into nucleic acids by RNA polymerase. Collectively, these findings implement biocatalytic methodology forC-nucleotide synthesis which can facilitate XNA engineering for synthetic biology applications.