Synthesis of 4′‐C‐Acylated Thymidines

Abstract Two synthetic pathways towards 4′‐C‐acylthymidines are presented. These modified mononucleosides are precursors of the 2′‐deoxyribonucleotide 4′‐C‐radical. They were converted into their corresponding 3′‐O‐[(2‐cyanoethyl) N,N‐diisopropylphosphoramidites] 3a–c and incorporated in oligonucleotides by solid‐phase synthesis. The structure of some modified nucleosides was revealed by X‐ray crystal‐structure analysis.