Much current attention focuses on the renin-angiotensin system in relation to mechanisms controlling blood pressure and renal function. Recent demonstrations (ref. 1, ref. 2 and refs therein) that angiotensin-converting enzyme inhibitors show promising clinical antihypertensive properties have been of particular interest. We now report on the design of a novel series of substituted N-carboxymethyl-dipeptides which are active in inhibiting angiotensin-converting enzyme at nanomolar levels. We suggest that these compounds are transition-state inhibitors and that extensions of this design to other metalloendopeptidases merit further study.

A series of inhibitors of angiotensin converting enzyme (ACE, dipeptidyl carboxypeptidase, EC 3.4.15.1) is described which addresses certain conformational aspects of the enzyme-inhibitor interaction. In this study the alanylproline portion of the potent ACE inhibitor enalaprilat (2) is replaced by a series of monocyclic lactams containing the required recognition and binding elements. In order to more fully assess the lactam ring conformations and the key backbone angle psi as defined in 3 with respect to possible enzyme-bound conformations, a series of model lactams was investigated with use of molecular mechanics. The results point to a correlation between inhibitor potency (IC50) and the computed psi angle for the lowest energy conformation of the model compounds. Thus the psi angle as defined in 3 is an important determinant in the binding of inhibitors to ACE. The inhibition data in conjunction with the computational data have served to define a window of psi angles from 130 degrees to 170 degrees which seems to be acceptable to the ACE active site.

No abstract

Several phosphonamides, phosphoramides, and phosphates having the general structure R-Y-P(OXOH-X-CH(CHl)-CO-Pro have been synthesized and tested for inhibition of angiotensin-converting enzyme (dipeptidyl carboxypeptidase; peptidyldipeptide hydrolase, EC 3.4.15.1). Inhibition was found to depend on the nature of R, Y, and X such that the maximal effect was observed when X = NH, Y = CH2, and R = 4CH2 (50% inhibition at 7 nM). Substitution of CH2 or 0 at X and 0 at Y produced significantly less potent inhibitors. Groups shorter or longer than R = 4CH2 led to less active inhibitors, presumably due to nonoptimal interaction of the side chain with the SI subsite.Angiotensin-converting enzyme (dipeptidyl carboxypeptidase; peptidyldipeptide hydrolase, EC 3.4.15.1) cleaves angiotensin I to the potent vasopressor angiotensin II. It also inactivates the vasodepressor substance bradykinin. The possibility that inhibitors of the enzyme might have clinical importance in the treatment of hypertension has been demonstrated with teprotide (1-3) and more recently by extensive clinical studies using the orally active angiotensin-converting enzyme inhibitor captopril (4). Accordingly, there is much current interest in the synthesis of inhibitors of the enzyme (5, 6).Like thermolysin and carboxypeptidases A and B, angiotensin-converting enzyme contains a zinc atom in its active site (7) that, by analogy, is intimately involved in the cleavage of the scissile carboxamide bond of its substrates. Phosphoramidon (ref. 12 and references cited therein) has shown that the inhibition of metalloproteases by phosphorus compounds may be quite general. Indeed, Holmquist and Vallee (13) recently reported inhibition of angiotensin-converting enzyme by several phosphoramidates, including monophenylphospho-L-phenylalanyl-L-phenylalanine, which exhibited Ki = 1.0 uM. Galardy (14) has reported that phospho-L-alanyl-L-proline is a potent inhibitor of the enzyme and exhibited a Ki of 1.4 nM at pH 7.5.The compounds we shall describe are derivatives of the general structure I. In analogy with the binding ofphosphoramidon to thermolysin, substructure lB is proposed to position itself at the zinc site of the enzyme and to approximate the geometry of a hydrated amide transition state. Substructure UI should then be able to bind in the S, subsite of angiotensin-converting enzyme and corresponds to the R1 substitution so important in the recently described (15) N-carboxymethyldipeptide inhibitors of the enzyme. Substructure IC was chosen because 2-substituted propanoylproline derivatives had been shown to afford very potent inhibitors of angiotensin-converting enzyme (15, 16).MATERIALS AND METHODS A description of our assay procedure has been published (15).2-Methyl-3-phosphonylpropionyl-L-proline (1). d,l-2-Methyl-3-phosphonylpropionic acid (6 g) was stirred with SOC12 (100 ml) overnight at room temperature. Concentration afforded the carboxyl chloride, which was coupled to benzyl L-prolinate hydrochloride (8.4 g) in aqueous dioxane under Sch...

No abstract