Synthesis of 3′‐BODIPY‐Labeled Active Esters of Nucleotides and a Chemical Primer Extension Assay on Beads

A solution‐phase synthesis of active esters of 3′‐fluorophore‐labeled deoxynucleoside 5′‐monophosphates was developed for thymine and cytosine as nucleobases by using two different BODIPY dyes. Starting from the respective 2′‐amino‐2′,3′‐dideoxynucleoside‐5′‐monophosphate, the fluorescent oxyazabenzotriazolides can be prepared in one‐pot procedures involving labeling and activation. Screening of a range of supports led to a chemical primer extension assay on beads with in situ detection of nucleobases in target DNA through optical read‐out.