Chemo-Enzymatic Synthesis of Thymidine13C-Labelled in the 2′-Deoxyribose Moiety

A synthesis of [3′,4′-13C2]thymidine (1) is described in which [13C2]acetic acid (2) is converted into the nucleoside in twelve steps with 9% overall yield. D-2-Deoxyribose-5-phosphate aldolase (DERA, EC 4.1.2.4) and triosephosphate isomerase (TPI, EC 5.3.1.1) are used for the stereocontrolled formation of D-[3,4-13C2]-2-deoxyribose-5-phosphate (8) from [2,3-13C2]dihydroxyacetone monophosphate (DHAP, 7) and acetaldehyde in 80% yield. The route permits the introduction of isotopically enriched carbon atoms at any position or combination of positions in the furanose ring and the product can be coupled with any of the four naturally occurring base moieties.