B. Koksch et al., SYNTHESIS, STRUCTURE AND BIOLOGICAL-ACTIVITY OF ALPHA-TRIFLUOROMETHYL-SUBSTITUTED THYREOTROPIN RELEASING HORMONE, Journal of fluorine chemistry, 80(1), 1996, pp. 53-57
The incorporation of alpha-trifluoromethyl pyroglutamic acid into thyr
eotropin releasing hormone TRH, results in the complete stability of t
he pGlu-His bond against proteolytic degradation by pyroglutamyl amino
peptidase II. The influence of the trifluoromethyl group on structure
and receptor affinity has been studied.