Abstract:
The related tripeptides glycyl-l-prolyl-l-glutamic acid (GPE) and glycyl-l-2-methylprolyl-l-glutamic acid (G-2-MePE) were labelled with commercially available [1,2,3,4,5-13C5, 2-15N1]-l-glutamic acid in 3 steps in excellent overall yield with high isotope incorporation. A related cyclic dipeptide was labelled with [2,2-2H2, 2-15N1]glycine giving a mixture of compounds resulting from deuterium scrambling.