Chemo-enzymatic synthesis of the exocyclic olefin isomer of thymidine monophosphate

Abstract

Exocyclic olefin variants of thymidylate (dTMP) recently have been proposed as reaction intermediates for the thymidyl biosynthesis enzymes found in many pathogenic organisms, yet synthetic reports on these materials are lacking. Here we report two strategies to prepare the exocyclic olefin isomer of dTMP, which is a putative reaction intermediate in pathogenic thymidylate biosynthesis and a novel nucleotide analog. Our most effective strategy involves preserving the existing glyosidic bond of thymidine and manipulating the base to generate the exocyclic methylene moiety. We also report a successful enzymatic deoxyribosylation of a non-aromatic nucleobase isomer of thymine, which provides an additional strategy to access nucleotide analogs with disrupted ring conjugation or with reduced heterocyclic bases. The strategies reported here are straightforward and extendable towards the synthesis of various pyrimidine nucleotide analogs, which could lead to compounds of value in studies of enzyme reaction mechanisms or serve as templates for rational drug design.

Keywords: Metabolism; Nucleotide analogue; Synthesis; Thymidylate.

Figure 1

Thymidylic acid and some olefin analogues of biological significance.

Figure 2

Nucleophilic addition to the α,β-unsaturated system 2.

Scheme 1

Synthesis of the new thymidylate analogue 2.

Scheme 2

Preparation of thymidine analogue 16 and its conversion to thymidylate analogue 2.