Opioid peptides. Structure-activity relationships of dermorphin endothiotetrapeptides. VII

We describe the synthesis and preliminary in vitro and in vivo pharmacological tests of five endothiotetrapeptide analogues of the opioid heptapeptide dermorphin H-Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser.-NH2. The modification obtained by substituting Phet for Phe3 or Glyt for Gly4 provided further analogues with significant opioid activity.     

Structure-activity relationships of antiarrhythmic 6-substituted decahydroisoquinolines.

A series of diastereoisomeric 6-benzoyloxy- and 6-benzamido-2-methyldecahydroisoquinolines has been prepared and screened for antiarrhythmic effectiveness. In a continuation of our interest in identifying significant physicochemical properties of antiarrhythmic decahydroisoquinolines, octanol-water partition coefficients and pKa values have been determined for each member of the series. In general, antiarrhythmic activities superior to that of quinidine were observed. From a general structure-activity viewpoint, substitutions possessing greater lipophilicities produced compounds with superior antiarrhythmic properties. However, there appears to be optimal lipophilic character beyond which increased lipophilicity results in a decrease in antiarrhythmic potency. No discernible correlations with pKa values were evident. As noted in our earlier studies the esters were more potent and more lipophilic than the corresponding amides. No obvious correlations with stereochemistry were found; however, in three pairs of diastereoisomers, the more lipophilic cis compounds were found to be the superior isomers. A surprisingly high potency was noted with a tetrahydroisoquinoline benzamide--a finding unexpected from our earlier work. The 3,4-dichlorobenzamido grouping appeared to be the substituting moiety for optimal antiarrhythmic effectiveness.     

Opioid peptides. Structure-activity relationships in [OGly4] dermorphin tetrapeptides. X

We describe the synthesis and preliminary in vitro and in vivo pharmacological tests of four [OGly4] tetrapeptide analogues of the opioid heptapeptide dermorphin H-Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2. The modification obtained by substituting aminoxy-acetic acid (OGly) for Gly4 provided analogues with substantial reduction of activity.     

Structure-activity relationships of the lissoclinamides: cytotoxic cyclic peptides from the ascidian Lissoclinum patella

Two new lissoclinamides (lissoclinamides 7 and 8) have been isolated from the aplousobranch ascidian Lissoclinum patella. These lissoclinamides are cyclic heptapeptides with the same structural features as lissoclinamides 4 and 5 reported earlier, containing an oxazoline ring, one proline, one valine, two phenylalanine residues, and thiazole and/or thiazoline rings. All four peptides have the same sequence of amino acids around the ring and differ from one another only in their stereochemistry or the number of thiazole and thiazoline rings. The cytotoxicities of the compounds were tested with human fibroblast and bladder carcinoma cell lines and normal lymphocytes. Slight changes in structure resulted in marked differences in the cytotoxicities of these compounds. The most potent is lissoclinamide 7, containing two thiazoline rings, which rivals didemnin B in cytotoxicity in vitro.     

Structure-activity relationships in nikethamide type analeptics. 3. Synthesis of 6-methylnikethamide]

Synthesis of 6-Methyl-nicethamide Analogues As potentially analeptically active substances with partially fixed functional groups, structural analogues of 6-methyl-nicethamide, in the form of amides, imides and lactams, are described.     

Structure-activity studies on bradykinin and related peptides: agonists.

1. Bradykinin, kallidin, T-kinin, [Hyp3]-bradykinin and several analogues were prepared by solid-phase synthesis and purified by high performance liquid chromatography. 2. The various peptides were tested for their abilities to relax the dog carotid and renal arteries, or to contract the rabbit jugular vein and aorta, in order to measure their activities on BK2 (the first three preparations) or BK1 (the rabbit aorta) receptors. The dog renal artery without endothelium was also used as a BK1 receptor system. 3. T-kinin was found to be less active than bradykinin, while the replacement of Pro3 with Hyp favoured BK2 receptor occupation. [Hyp3,Tyr(Me)8]-BK was found to be a selective BK2 receptor agonist. 4. Amidation or methylation of the C-terminal carboxyl decreased activity, while extension of the N-terminal with Sar or D-Arg increased affinity and selectivity for BK1 (Sar) and affinity for BK2 (D-Arg) receptors. Acetylation of N-terminal amide brought affinity down to 10% or less. 5. Replacement of the peptide bonds Phe8-Arg9 to protect from kininase I and II, decreased affinities slightly, but was incompatible with additional changes at the N-terminal or in the peptide bond Gly4-Phe5. 6. Substitution of C-terminal Phe in desArg9-BK (the BK1 receptor stimulant) with D-Phe increased potency and selectivity for BK1 receptors while protecting from carboxypeptidases. Sar[D-Phe8]desArg9-BK was found to be a potent and selective BK1 receptor agonist.     

Antinociceptive properties of chalcones. Structure-activity relationships.

Eleven chalcones were prepared and tested as antinociceptive agents using the writhing test in mice. Some compounds, given intraperitoneally, caused potent and dose-related antinociception, being several times more active than some reference drugs. The results evidenced that some physico-chemical parameters are involved in the pharmacological activity. 3,4-Dichlorochalcone (2) was the most effective compound, and was also studied in another model of pain in mice, the formalin test. Here it inhibited only the inflammatory pain (second phase), being equipotent to the reference drugs.     

Structure-activity relationships of bifunctional peptides based on overlapping pharmacophores at opioid and cholecystokinin receptors

Cholecystokinin (CCK) has been identified as a pronociceptive endogenous peptide which also possesses antiopioid actions. CCK may be upregulated in conditions of chronic pain or during sustained morphine administration resulting in attenuation of opioid-mediated pain relief. These complex interactions between opioids and endogenous CCK receptor systems have suggested the need for a new paradigm in drug design for some states of chronic pain. In these circumstances the rational design of potential drugs for the treatment of these conditions must be based on one ligand for multiple targets. We have designed a single peptide which can interact with delta and mu opioid receptors as agonists and with CCK receptors as antagonists. The ligands were designed based on a model of overlapping pharmacophores of opioid and CCK peptide ligands, which incorporates opioid pharmacophores at the N-terminal and CCK tetrapeptide pharmacophores at the C-terminal of the designed ligands. We measured binding and activities of our bifunctional peptides at opioid and CCK receptors. Compound 11 (Tyr-d-Ala-Gly-d-Trp-NMeNle-Asp-Phe-NH(2)) demonstrated opioid agonist properties at delta and mu receptors (IC(50) = 63 +/- 27 nM and 150 +/- 65 nM, respectively in MVD and GPI tissue assays) and high binding affinity at CCK-1 and CCK-2 receptors (K(i) = 320 and 1.5 nM, respectively). Compound 9 (Tyr-d-Nle-Gly-Trp-Nle-Asp-Phe-NH(2)) displayed potent agonist activity at delta and mu receptors (IC(50) = 23 +/-10 nM and 210 +/- 52 nM, respectively in MVD and GPI tissue assays), with a balanced binding affinity for CCK-1 and CCK-2 receptors (K(i) = 9.6 and 15 nM, respectively). These results provide evidence supporting the concept that opioid and CCK receptors have overlapping pharmacophores required for binding affinity and biological activity and that designing overlapping pharmacophores of two peptides into a single peptide is a valid drug design approach.     

Structure-activity relationships of beta-amino acid-containing integrin antagonists.

Interest in the development of specific antagonists of the beta3 family of integrins (platelet alphaIIbbeta3 and the vitronectin receptor alphavbeta3) has been principally driven by efforts to design more potent antithrombotic agents than either aspirin or the thienopyridine-type ADP receptor modulators. The platelet fibrinogen receptor (aIIbb3) and the vitronectin receptor (alphavbeta3) bind the RGD tripeptide sequence found within adhesive ligands. Because of this, many approaches to antagonists of beta3 receptors have utilized an RGD mimetic to identify antagonists. Integrin antagonists of many structurally diverse classes have been discovered. One of the larger beta3 integrin antagonist classes employs beta-amino acids to mimic the aspartate residue of the RGD mimetic. Structure-activity investigations have revealed the potent activity of agents which have substituents appended to both the alpha and beta position of the beta-amino acid units of these antagonists. Several clinical candidates targeting platelet aIIbb3 contain these beta-amino acid units and are currently being evaluated clinically.     

Third-generation and investigational cephalosporins: I. Structure-activity relationships and pharmacokinetic review

The structure-relationships and pharmacokinetic properties of the new second- and third-generation cephalosporins are reviewed. The new second-generation cephalosporins include ceforanide, cefotiam, and cefuroxime. The third-generation cephalosporins include cefmenoxime, cefoperazone, cefotaxime, cefsulodin, ceftazidime, ceftizoxime, ceftriaxone, and moxalactam. These new cephalosporins are semisynthetic analogs with different chemical substitutions on a 7-aminocephalosporanic nucleus. As a result of these chemical modifications, improvements in the antibacterial spectrum as well as pharmacokinetic properties have occurred. In general, the new cephalosporins have longer half-lives, higher and prolonged serum concentrations, and increased cerebrospinal fluid penetration. Selected cephalosporins also have increased biliary tract concentrations. A classification scheme for these new agents, based on generation and susceptibility to Pseudomonas aeruginosa, is presented.     

Synthesis and antitumor activity of tropolone derivatives. 6. Structure-activity relationships of antitumor-active tropolone and 8-hydroxyquinoline derivatives

The bis derivative 6 of 8-hydroxyquinoline, which, like tropolones, readily forms a chelate, was synthesized and found to have high potency (dose = 12.5 mg/kg, T/C % = 164) against leukemia P388 in mice approximately equivalent to that of the bistropolone 1b. 8-Hydroxyquinoline analogues with broad structural variation were synthesized and their structure-activity relationships followed the same pattern as in the tropolone series. In addition, the bistropolones 1a-e were tested for their ability to bind to tubulin and found to have no such property. The results of this study suggested that bistropolone and bis(8-hydroxyquinoline) derivatives must form a chelate with the metal necessary for the enzyme, such as ribonucleotide reductase, which catalyzes the DNA biosynthetic pathways.