The incorporation of alpha-trifluoromethyl pyroglutamic acid into thyreotropin releasing hormone TRH, results in the complete stability of the pGlu-His bond against proteolytic degradation by pyroglutamyl aminopeptidase II. The influence of the trifluoromethyl group on structure and receptor affinity has been studied.
BURGER, KLAUS;GAA, KARL, CHEM.-ZTG., 114,(1990) N, C. 101-104