A. Bak et al., N-terminal 4-imidazolidinone prodrugs of Leu-enkephalin: synthesis, chemical and enzymatic stability studies, EUR J PH SC, 7(4), 1999, pp. 317-323
Four N-terminal 4-imidazolidinone prodrugs of Leu-enkephalin are prepared a
nd characterized. Their enzymatic and chemical stability are assessed using
high-performance liquid chromatography. The prodrug derivatives are shown
to degrade stoichiometrically to Leu-enkephalin in phosphate buffer [t(1/2)
(0.05 M phosphate buffer without KCl): acetone prodrug (II) 930 min; cyclo
pentanone prodrug (LII): 216 min; cyclohexanone prodrug (IV): 432 min; 4-me
thylcyclohexanone prodrug (V): 792 min]. Furthermore, the prodrugs are show
n to afford global stabilization of the Leu-enkephalin molecule towards the
enzymes, aminopeptidase N and angiotensin converting enzyme, primarily res
ponsible for degradation of Leu-enkephalin at the blood-brain barrier and i
n plasma. Therefore, the 4-imidazolidinones, being metabolic stable and bio
reversible, may be suitable prodrug candidates for delivery of Leu-enkephal
in to important target areas such as the brain, if given intravenously. (C)
1999 Elsevier Science B.V. All rights reserved.