Abstract
An efficient method for the selective isotopic labeling of carboxylic acids is reported. By reacting an amino acid with excess carbodiimide and 18O-H2O, a kinetically enhanced multiple turnover reaction provides the 18O-labeled product in high yield and excellent isotopic enrichment. This reaction is fully compatible with standard Fmoc, Boc, Trt, and OtBu protecting groups and provides a means to selectively label the α-carboxylic acids of functionalized amino acids with stable oxygen isotopes.
Seyfried, M S