Regioselective synthesis of ¹³C₁-labeled 2-deoxyribonolactones

Syntheses of the five regioselectively ¹³C₁-labeled 5-O-benzyl-2-deoxyribonolactones are described. ¹³C₁-Labeled deoxyribonolactones were prepared by addition of KCN to epoxides 7 and subsequent lactonization of the resulting nitriles. Integration of the independent schemes leading to the five isotopomers of 9 results in an efficient and cost effective preparation of labeled mixtures of ¹³C mono-labeled deoxyribonolactones. These mixtures are the pivotal intermediates in the preparation of 'population labeled' ¹³C-labeled nucleoside phosphoramidites for solid-phase oligonucleotide synthesis.