T. Ishizu et al., COMPLEX-FORMATION OF CYCLO(L-PHE-L-PRO)(4) WITH NORADRENALINE HYDROCHLORIDE, Chemical and Pharmaceutical Bulletin, 42(5), 1994, pp. 1146-1148
The C-13-NMR spectrum of cyclo(L-Phe-L-Pro), (1) and Dt-noradrenaline
hydrochloride (DL-NA.HCl) in a mixture of CDCl3 and CD3OD suggested th
e formation of a complex, which was demonstrated to be 1:1 from examin
ation of the titration curves. The complex retained the C-2-symmetric
conformation of 1 containing two cis-peptide bonds, and was linked thr
ough hydrogen bonds between the carbonyl groups of the Phe(1) and Pro(
2) residues, and the ammonium moiety of NA.HCl.