Synthesis and biological activity of the penem antibiotic MEN 10700 and its orally absorbed ester MEN 11505.

The synthesis and biological properties of the new penem antibiotic MEN 10700 (6) and of its selected oral prodrug MEN 11505 (8f) are described. MEN 10700 showed a broad spectrum of activity, with high potency both on Gram-positive and Gram-negative strains. It also exhibited good antibacterial activity toward anaerobes and on strains selected for their resistance to other antibacterial agents (cefotaxime- or ceftazidime-resistant Gram-negative strains, ciprofloxacin-resistant E. coli, extended spectrum beta-lactamase producing and cephalosporinase inducible enterobacteria). MEN 10700 showed a very high stability to enzymatic degradation by renal dehydropeptidase DHP-I. After oral administration in rats of the pivaloyloxymethyl ester prodrug MEN 11505, the relative bioavailability of MEN 10700 was calculated as F=43%.

Design and synthesis of nonpeptide angiotensin II receptor antagonists featuring acyclic imidazole-mimicking structural units.

Extensive molecular modelling studies, including conformational analysis and the comparison of molecular electrostatic potential distributions, wee used to evaluate structural parameters of new antagonists containing acyclic replacements of the N = C-N imidazole region. The synthesis and the biological screening of a series of acyl biphenyltetrazole derivatives were planned and realized to gain an insight into the structure-activity relationships of this unusual class of Angiotensin II antagonists.

A 3D QSAR CoMFA study of non-peptide angiotensin II receptor antagonists.

A series of non-peptide angiotensin II receptor antagonists was investigated with the aim of developing a 3D QSAR model using comparative molecular field analysis descriptors and approaches. The main goals of the study were dictated by an interest in methodologies and an understanding of the binding requirements to the AT1 receptor. Consistency with the previously derived activity models was always checked to contemporarily test the validity of the various hypotheses. The specific conformations chosen for the study, the procedures invoked to superimpose all structures, the conditions employed to generate steric and electrostatic field values and the various PCA/PLS runs are discussed in detail. The effect of experimental design techniques to select objects (molecules) and variables (descriptors) with respect to the predictive power of the QSAR models derived was especially analysed.

Synthesis and renin inhibitory activity of novel angiotensinogen transition state analogues modified at the P(2)-histidine position.

With the aim of finding new renin inhibitors with improved bioavailability properties, two angiotensinogen transition state analogues 1a and 1b, containing a novel unnatural amino acid at the P(2) position, namely the (2R,3S)- and (2S,3S)-2-amino-3-(1,3-dithiolan-2-yl)-3-hydroxypropanoic acid (ADHPA), have been synthesized and tested for human renin inhibitory activity and for chemical and enzymatic stability. Only compound 1a (the S-isomer) possessed a significant activity, which was lower than that of the corresponding histidyl derivative KRI-1314, and combined with a low stability to the gut enzyme chymotrypsin.

N-3-substituted pyrimidinones as potent, orally active, AT1 selective angiotensin II receptor antagonists.

A novel series of nonpeptide angiotensin II (A II) antagonists containing a pyrimidinone ring which carries a C-linked biphenyltetrazole moiety and a carboxyheteroaryl group on the 3-position have been prepared. Their affinity for the AT1 receptor was determined in a binding assay on rat adrenal cortical membranes. The in vivo antihypertensive properties were tested by evaluating the inhibition of the pressor response to A II followed by iv and id administration. Extensive molecular modeling studies, including comparison of molecular electrostatic potential distributions, conformational analysis, and overlays on a computational pharmacophore model of A II, were used to evaluate structural parameters of the new compounds, in comparison to other known A II antagonists (e.g., DUP-753 and SK&F 108566). According to the modeling studies, the introduction of a (carboxyheteroaryl)methyl moiety at the 3-position of the pyrimidinone ring led to derivatives with increased potency. Methyl 2-[[4-butyl-2-methyl-6-oxo-5-[[2'-(1H-tetrazol-5-yl)[1,1'-biphenyl ]- 4-yl]methyl]-1-(6H)-pyrimidinyl]methyl]-3-thiophenecarboxylate (3k, LR-B/081), one of the most potent compounds in the series (Ki = 1.4 nM), exhibited a marked antihypertensive activity on oral administration to conscious renal hypertensive rats, with long duration of action. It was selected for clinical evaluation in the treatment of hypertension in man.

Molecular pharmacology of LR-B/081, a new non-peptide angiotensin AT1 receptor antagonist.

This report describes the molecular pharmacological properties of LR-B/081 (methyl 2-[[4-butyl-2-methyl-6-oxo-5-[[2'-(1H-tetrazol-5- yl) [1,1'-biphenyl]-4-yl]methyl]-1 (6H)-pyrimidinyl]methyl]- 3-thiophenecarboxilate), a novel non-peptide angiotensin II receptor antagonist. This compound potently displaced [3H]angiotensin II from angiotensin AT1 (Ki = 1.4 nM, rat adrenal cortex), but not from angiotensin AT2 (Ki > 1 microM, bovine cerebellar cortex) receptors and did not show affinity for other receptor systems (Ki > 10 microM). In saturation studies, LR-B/081 both increased KD and decreased Bmax values in a dose-dependent fashion. The rate of dissociation of [3H]angiotenin II from angiotensin AT1 receptors was not affected by the presence of 1 microM LR-B/081 and the association rate of [3H]angiotensin II was not decreased by the presence of 1 or 30 nM LR-B/081, indicating that the Bmax reduction was not due to an allosteric interaction or to a delay in reaching the steady-state conditions. These data underline the complexity of the antagonistic nature of LR-B/081, presenting features of both competitive and noncompetitive antagonism.

Pharmacology of LR-B/057, a novel orally active AT1 receptor antagonist.

We studied the pharmacologic properties of LR-B/057, a novel nonpeptide angiotensin II (AII) receptor antagonist. The compound potently displaced [3H]AII from AT1 but not from AT2 receptors in rat adrenal cortex (Ki 3 nM), but did not modify the dissociation rate of the radioligand from the receptors. Both its affinity and the nature of its interaction with AT1 receptors (saturation studies) were markedly affected by the presence of bovine serum albumin (BSA) in the binding assay. In rabbit aorta, LR-B/057 caused nonparallel shifts to the right of the dose-response curve to AII and decreased the maximal response (pKB 9.6). Oral (p.o.) administration of LR-B/057 to conscious rats dose-dependently antagonized the pressor response to AII. LR-B/057 administered either intravenously (i.v.) or p.o. to conscious renal hypertensive rats produced a powerful dose-dependent antihypertensive effect. These results show that LR-B/057 is a potent and selective antagonist at AT1 receptors and has p.o. bioavailability.

Pharmacology of LR-B/081, a new highly potent, selective and orally active, nonpeptide angiotensin II AT1 receptor antagonist.

1. The pharmacological profile of LR-B/081, (methyl 2-[[4-butyl-2-methyl- 6-oxo-5-[[2'-(1H-tetrazol-5-yl)[1,1'-biphenyl]-4-yl]methyl]-1(6H)- pyrimidinyl]methyl]-3-thiophenecarboxylate), a novel antagonist at the angiotensin II (AII) AT1-receptor, was studied in vitro and in vivo. 2. In rabbit aortic strips incubated with LR-B/081 (1-1,000 nM), the concentration-response curve to AII was displaced to the right in a nonparallel fashion and the maximal contraction was progressively reduced, indicating that the compound is an insurmountable antagonist in this preparation (apparent pKB = 9.50 +/- 0.23). However, the interaction of LR-B/081 with AII receptors was found to be reversible, since the maximal response to AII was restored by coincubation with losartan, a surmountable AII AT1-antagonist. Contractions elicited by KCl or phenylephrine were not affected by 10 microM LR-B/081. 3. In rat isolated perfused kidney, LR-B/081 and losartan antagonized the AII-induced vasoconstriction [IC50 (95% confidence limits) = 17(13-24) and 39(32-54) nM, respectively]. The LR-B/081 antagonism was incompletely reversed by excess AII, while losartan was fully displaced. The IC50 values of LR-B/081 and losartan obtained against vasoconstriction induced by endothelin-1 and noradrenaline were two orders of magnitude higher. 4. In pithed rats, the intravenous administration of LR-B/081 (0.2-2 mumol kg-1) dose-dependently shifted to the right in a nonparallel fashion the dose-pressor response curve to AII. The maximal pressor response to AII was reduced by LR-B/081 in a dose-dependent fashion. The coadministration of losartan induced a progressive recovery of the maximal pressor response to All, indicating that in vivo the interaction of LR-B/081 with All receptors is reversible. LR-B/081 at 6 micromol kg-1, i.v. also did not affect the vasopressor response induced by noradrenaline in the pithed rat.5. In conscious normotensive rats, single oral administration of LR-B/081 at 6 micromol kg-1 markedly inhibited the All-induced pressor response; the inhibition lasted more than 24 h.6. In conscious renal hypertensive rats, intravenous LR-B/081 appeared as potent as losartan (ED40mmHg(95% confidence limits) = 0.50(0.36-0.70) and 0.86(0.57-1.3) micromol kg-1, respectively). A single intravenous(2 micromol kg-1) or oral (6 micromol kg-1) administration of LR-B/081 induced a marked fall in blood pressure which lasted for at least 12 h.7. In conscious spontaneously hypertensive rats, LR-B/081 at 20 micromol kg-1 , p.o., induced a marked and sustained fall in blood pressure. The duration of the antihypertensive effect was longer than 12 h.Heart rate was not modified by LR-B/081 treatment. Repeated oral administration of 17 micromol kg-1LR-B/081 for 16 days did not result in the development of tolerance.8 These results demonstrate that LR-B/081 is a potent, selective and orally active antagonist of All at the AT1-receptor subtype, which markedly lowers the blood-pressure in conscious renal and spontaneously hypertensive rats.

Nonpeptide angiotensin II receptor antagonists. Synthesis, in vitro activity, and molecular modeling studies of N-[(heterobiaryl)methyl] imidazoles.

With the aim of explaining the influence of the structural changes on the biphenylic moiety on the activity, a series of N-[(heterobiaryl)methyl]imidazoles (I), constructed on the model of DuPont compounds by replacing either the central or terminal phenyl ring with a heteroaromatic one, such as furan, thiophene, thiazole, and pyridine, was synthesized. Compared to the reference DuPont compound (EXP-7711), all the heterobiaryl derivatives showed a reduced potency both in receptor binding (rat adrenal capsular membranes) and in the functional assay (angiotensin II-induced contraction of rabbit aorta strips). The lower activity was justified by the extensive molecular modeling studies, which took into consideration the conformational and electrostatic features of several heterobiaryl derivatives. On the basis of the results obtained, it was hypothesized that the central aromatic ring of the biarylic portion works as a spacer, orienting in the right way the terminal phenyl ring, whose electronic distribution is, instead, crucial to its fitting well with a lipophilic pocket at the receptor site.

A 3D QSAR approach to the search for geometrical similarity in a series of nonpeptide angiotensin II receptor antagonists.

A 3D QSAR methodology based on the combined use of conformational analysis and chemometrics was applied to perform a comparative analysis of the 3D conformational features of 13 nonpeptide angiotensin II receptor antagonists showing different levels of binding affinity. Conformational analysis by using a molecular mechanics MM2 method was carried out for each of these structures to obtain conformational minima. These minima were described by ten interatomic distances which define the relative spatial disposition of five significant atoms belonging to relevant functional groups present in all the 13 molecules. The structure-activity relationship between the interatomic distances and the biological activity was then assessed by using chemometric methods (cluster analysis, principal component analysis, classification methods). With our indirect approach based on the search for geometrical similarity it was possible, even though structural information on the receptor active site was lacking, to identify the 3D geometrical requirements for the binding affinity of nonpeptide angiotensin II receptor inhibitors.

Pharmacokinetics of diltiazem and a new analogue, LR-A/113, in the conscious rat.

Pharmacokinetics and metabolism of diltiazem and a new analogue, LR-A/113, have been studied in the rat. Conscious rats, with the jugular vein cannulated, received the compounds by intravenous (3 mg/kg body weight) or oral (50 mg/kg body weight) route. Parent compounds and their N-demethyl and N-deacetyl metabolites were assayed at serial times in blood. Half-life of elimination of diltiazem was significantly shorter than that of LR-A/113, both after oral (37 +/- 9 vs 59 +/- 26 min) and intravenous (29 +/- 12 vs 57 +/- 16 min) administration. N-deacetyl-diltiazem concentrations after oral administration were higher than the parent compound and N-demethyldiltiazem; LR-A/113 blood concentrations were higher than those of its two metabolites. Metabolites were measurable only in traces after intravenous administration. Oral bioavailability was very low, 3.5% for diltiazem and 4.2% for LR-A/113. In conclusion, the substitution of a methyl by an isopropyl group appears to slow in vivo elimination of the analogue of diltiazem, LR-A/113.

Structure-activity relationship of Ca2+ channel blockers: a study using conformational analysis and chemometric methods.

A structure-activity relationship study has been done on 8 compounds with the activity known as 'Ca2+ channel blockers'. Conformational analysis was carried out using a molecular mechanics method. The 3D-QSAR approach was used and the most polar functional groups present in all the molecules were considered. Eight interatomic distances are necessary to define the relative spatial disposition of these relevant molecular fragments. The structure-activity relationship between interatomic distances and biological activity was performed using statistic and chemometric methods. In particular, with Principal Component Analysis, it was possible to reduce the number of interatomic distances: only six of the eight distances are sufficient to describe the system in a useful way. A classification method was iteratively used to select the most probable conformations linked to the biological activity and to build a model able to classify conformations according to their biological behaviour. Cluster analysis on the active selected conformations subsequently allowed the identification of two different geometrical patterns for the active compounds. Finally the validity of the model was verified by correctly predicting the activity of other molecules not used in the construction of the model but possessing known activity.

Synthesis and antiarrhythmic activity of new 3-[2-(omega-aminoalkoxy)phenoxy]-4-phenyl-3-buten-2-ones and related compounds.

A number of the title compounds (1) and a few related hydroquinone derivatives (2) have been synthesized and tested for antiarrhythmic activity in vivo (protection against CaCl2-induced ventricular fibrillation in anesthetized rat) and in vitro (ability to reduce the maximum driven frequency of an electrical stimulus in isolated rabbit atria). The effects induced by modification of the enol ether moiety in the parent compound 1a were also examined. Many of the compounds exhibited antiarrhythmic properties stronger than quinidine and procainamide, associated with a more favorable LD50/ED50 ratio. Compounds 1a (LR-18,460, 3-[2-[2-(diethylamino)ethoxy]phenoxy]-4-phenyl-3-buten-2-one) and 1h (LR-18,795, 3-[2-[3-(dimethylamino)propoxy]phenoxy]-4-phenyl-3-buten-2-one) were submitted to further antiarrhythmic testing, which confirmed their effectiveness and superiority to quinidine in all the experiments. After safety evaluation studies, both were selected for clinical investigation.

Drug latentiation of isoxsuprine: synthesis and preliminary pharmacological activities of four monoesters.

Four new esters (1 b-e) involving the phenolic group of isoxsuprine have been prepared. Preliminary pharmacological evaluation showed that the pivaloyl ester (1 e) (LR693) lowers blood pressure values more gradually than isoxsuprine with a longer-lasting effect. This compound was selected for further assessment as a long-acting peripheral vasodilator.

Synthesis and pharmacological activity of some 2,3-dihydro-1,4-benzodioxin and 1,3-benzodioxol derivatives, as cyclic analogs of isoxsuprine.

A few analogs of the isoxsuprine drug with the phenoxyethyl group incorporated into the heterocyclic 2,3-dihydro-1,4-benzodioxin or 1,3-benzodioxol ring have been synthesized. Among these compounds, the benzodioxol derivative (I e) has been found to possess hypotensive activity in rats in the same range as isoxsuprine, with no alpha-adrenolytic and central sedative properties. Cardiovascular studies in dogs have shown that (I e) is less potent than isoxsuprine, although its activity is longer-lasting at an equally hypotensive dose.

Synthesis and pharmacological evaluation of some 2,3-dihydro-3-phenyl-1,4-benzodioxin derivatives.

The synthesis and some pharmacological properties of five 2,3-dihydro-3-phenyl-1,4-behzodioxin derivatives (II d-h) are reported. The new compounds generally result more active as local anaesthetics, but less effective as anti-arrhythmic agents than the corresponding 1,3-benzodioxole derivatives.

[New esters of N-arylanthranilic acids]. / Nuovi esteri di acidi N-arilantranilici

A series of acyloxy- and alkyloxymethyl esters of meclofenamic, flufenamic and mefenamic acids has been synthesized and its antiinflammatory, analgesic and antipyretic activities have been compared with those of the corresponding acids and the methyl, beta,gamma-isopropylidene-dioxypropyl, N,N-diethylaminoethyl esters. The acyloxy- and alkyloxymethyl esters are the most interesting compounds, because they possess pharmacological activity of the same order as that of the corresponding acids and a lower toxicity. The ethoxymethyl ester of the N-(2,6-dichloro-m-tolyl)anthranilic acid is presently under clinical investigation.