The synthesis of 3-(triethylstannyl)propanoic acid (TESPA), an organom
etallic reporter group that enables the mass labeling of oligonucleoti
des with stable isotopes of tin, is described. Synthesized from commer
cially available isotopically-enriched SnO2 in a five step process, th
e NHS ester of TESPA is produced with an overall yield of 40 %. This s
implification of the standard synthetic scheme, with two less syntheti
c steps and a coincident 60 % yield increase, is accomplished through
the use of the reagent N-(acryloxy)succinimide and the free radical in
itiator AMPN. The conditions for the attachment of the reporter group
to priming oligonucleotides and the subsequent HPLC isolation of the l
abeled primers are also detailed.