Synthesis of 3-(triethylstannyl)propanoic acid: an organotin mass label for DNA

The synthesis of 3-(triethylstannyl)propanoic acid (TESPA), an organometallic reporter group that enables the mass labeling of oligonucleotides with stable isotopes of tin, is described. Synthesized from commercially available isotopically-enriched SnO2 in a five step process, the NHS ester of TESPA is produced with an overall yield of 40%. This simplification of the standard synthetic scheme, with two less synthetic steps and a coincident 60% yield increase, is accomplished through the use of the reagent N-(acryloxy)succinimide and the free radical initiator AMPN. The conditions for the attachment of the reporter group to priming oligonucleotides and the subsequent HPLC isolation of the labeled primers are also detailed.