A potent nonpeptide cholecystokinin antagonist selective for peripheral tissues isolated from Aspergillus alliaceus.

A new, competitive, nonpeptide cholecystokinin (CCK) antagonist, asperlicin, was isolated from the fungus Aspergillus alliaceus. The compound has 300 to 400 times the affinity for pancreatic, ileal, and gallbladder CCK receptors than proglumide, a standard agent of this class. Moreover, asperlicin is highly selective for peripheral CCK receptors relative to brain CCK and gastrin receptors. Since asperlicin also exhibits long-lasting CCK antagonist activity in vivo, it should provide a valuable tool for investigating the physiological and pharmacological actions of CCK.

A structurally unique, potent, and selective oxytocin antagonist derived from Streptomyces silvensis.

The in vitro and in vivo oxytocin/arginine vasopressin (OT/AVP) antagonist properties of two cyclic hexapeptides derived from a newly discovered natural product (L-156,373) of Streptomyces silvensis are described. In radioligand binding assays, L-156,373 [cyclo(L-Pro-D-Phe-N-OH-L-Ile-D-piperazyl-L-piperazyl-N-Me-D -Phe)] exhibited moderate affinity for rat uterine OT receptors (Ki, 150 nM), with some selectivity (approximately 20-fold) vs. liver AVP-V1 and kidney AVP-V2 receptors. Dehydroxylation of N-hydroxyisoleucine and oxidation of the piperazic acid residues of L-156-373 produced an interesting derivative, L-365,209. These structural modifications increased OT receptor affinity and selectivity by 20- and 2.5-5-fold, respectively. In the isolated rat uterus, L-365,209 was a potent (apparent dissociation constant, 1.7 nM) and competitive OT antagonist. L-365,209 also blocked the effects of AVP at both AVP-V1 (phosphatidylinositol turnover in rat hepatocytes) and AVP-V2 (adenylate cyclase in rat kidney medulla) receptors, but only at low micromolar concentrations. L-365,209, given iv to anesthetized rats, antagonized the action of exogenous OT on the uterus (ID50, 460 micrograms/kg) with a relatively long duration of action. L-365,209 represents a unique class of compounds that provides an entirely new approach for the design of antagonists for these neurohypophyseal hormones.

Urinary metabolites of timolol from humans and laboratory animals. Syntheses and beta-adrenergic blocking activities.

Syntheses are reported for three metabolites (2-4) of timolol (1) formed by oxidative metabolism of the morpholine ring. GLC-MS comparisons are presented which establish that the two metabolites whose structures were previously in question are identical with their synthetic counterparts 2 and 3. In 2, metabolic oxidation of the 4-morpholinyl group of 1 had occurred at the carbon next to oxygen to give the 2-hydroxy-4-morpholinyl moiety, whereas in 3, the morpholine of 1 has been oxidized one step further and then ring opened to produce the N-(2-hydroxyethyl)glycine substituent. Biological testing of synthetic samples of the three major metabolites from human urine (3, 4, and 6) indicated that only 4, in which the morpholine moiety has been degraded to a 2-hydroxyethylamino group, had significant beta-adrenergic blocking activity (one-seventh that of timolol in anesthetized dogs).

8-O-acetylharpagide is a nonsteroidal ecdysteroid agonist.

We have identified a novel nonsteroidal ecdysteroid agonist. This compound was isolated from a methanol extract of Ajuga reptans L. (Lamiaceae) and the structure was identified by spectroscopic methods as 8-O-acetylharpagide. We have characterised this compound as an ecdysteroid agonist in a transactivation assay using beta-galactosidase as the reporter gene regulated by ecdysteroid response elements. In this assay, 8-O-acetylharpagide has an EC50 of 22 microM. The compound also competes with tritiated-ponasterone A for binding to the Drosophila ecdysteroid receptor. Finally, it induces differentiation of Drosophila Kc cells as would be expected of an ecdysteroid agonist. This iridoid glycoside is common to several plant species and may play a role in the natural defense mechanisms of plants.

Mechanism of activation of the antitumor antibiotic neocarzinostatin by mercaptan and sodium borohydride.

The structures of mercaptan and sodium borohydride reaction products of neocarzinostatin chromophore A (NCS Chrom A) are compared. Implications on the mechanism of activation of NCS are discussed.

13C NMR study of thiostrepton and thiopeptin components.

A detailed 13C NMR study of thiostrepton and two series of thiopeptin components is consistent with their proposed structures and allows many unequivocal assignments to be made.

Total structure of the highly modified peptide antibiotic components of thiopeptin.

On the basis of 1H and 13C NMR evidence, the structures of two series of the highly modified sulfur-containing peptide antibiotic thiopeptin were elucidated.

Structure elucidation of angiotensin converting enzyme inhibitor L-681,176 from Streptomyces sp. MA 5143a.

L-681,176 (1, C12H23N5O7) is an inhibitor of angiotensin converting enzyme produced by Streptomyces sp. MA 5143a. The structure of L-681,176 has been determined by NMR and mass spectral analysis.

The solution conformation of the peptide antibiotic thiostrepton: a 1H NMR study.

The majority of the 84 protons in the 1H NMR spectrum of thiostrepton at 300 MHz were unambiguously assigned on the basis of double resonance experiments under different conditions of solvent, temperature and 2H-exchange by comparison with the known crystal structure determined by Anderson et al.1) Evidence is presented to suggest that the side chain, the nature of which remained undefined on X-ray analysis, is comprised of two dehydroalanine residues which supports the conclusions reached by Tori et al.2) on the basis of 13C NMR spectroscopy. These two residues are missing in thiostrepton A2, a minor artifact. All available 1H NMR evidence suggests thiostrepton to have a similar conformation in deuterochloroform solution to that found in the crystal form.

The structure of heneicomycin.

The antibiotic heneicomycin (1), C44H62N2O11, was isolated from cultures of Streptomyces filipinensis as an amorphous yellow powder. Mass spectral and NMR analysis showed the compound to be a deoxy modification of aurodox (2), a member of the elfamycin antibiotic family. A marked change in mass spectral fragmentation compared to aurodox and 1H NMR couplings indicated the absence of the hydroxyl at position 30 of aurodox (position 3 of the tetrahydropyran).

Cochinmicins, novel and potent cyclodepsipeptide endothelin antagonists from a Microbispora sp. II. Structure determination.

Cochinmicins I, II, and III are competitive endothelin antagonists produced by Microbispora sp. ATCC 55140. The cochinmicins are cyclic depsipeptides containing six alpha-amino acids and a pyrrolecarboxylic acid. Based upon MS, 1D and 2D NMR, and LC data, the structures and absolute stereochemistries of the cochinmicins have been assigned. All three components have the same basic sequence and contain one equivalent each of D-allo-threonine, D-alanine, L-phenylalanine, D-phenylalanine, 5-chloropyrrole-2-carboxylic acid (or pyrrole-2-carboxylic acid in cochinmicin I), plus two equivalents of 3,5-dihydroxyphenylglycine (DHPG). The phenylalanine residues were differentiated via a methanolysis product which contained only one of the phenylalanine residues. Both DHPG residues have the D configuration in the more active cochinmicins I and III. Cochinmicin II contains both D- and L-DHPG and these residues have been differentiated in the sequence based upon 1H NMR data.

Novel cholecystokinin antagonists from Aspergillus alliaceus. II. Structure determination of asperlicins B, C, D, and E.

Asperlicins B (1, C31H29N5O5), C (2, C25H18N4O2), D (3, C25H18N4O2), and E (4, C25H18N4O3) are novel cholecystokinin antagonists produced by Aspergillus alliaceus. The structures of these compounds have been determined by 1H NMR and MS analysis.

On the biosynthesis of asperlicin and the directed biosynthesis of analogs in Aspergillus alliaceus.

Feeding of 14C-labeled amino acids to resting cells of Aspergillus alliaceus strongly supported the intuitive hypothesis that asperlicin is biosynthesized from tryptophan, anthranilate and leucine. The resting cell system was used also to prepare 25 asperlicin analogs via directed biosynthesis in presence of analogs of tryptophan and leucine.

Asperlicin, a novel non-peptidal cholecystokinin antagonist from Aspergillus alliaceus. Structure elucidation.

Asperlicin (1, C31H29N5O4) is a novel cholecystokinin antagonist produced by Aspergillus alliaceus. The structure of asperlicin has been determined by NMR and mass spectral analysis, and X-ray crystallography.

Pneumocandin D0, a new antifungal agent and potent inhibitor of Pneumocystis carinii.

Pneumocandin D0 (9), a new member of the echinocandin class of antifungal agents, has been isolated as a minor constituent from fermentation broths of the filamentous fungi Zalerion arboricola (ATCC 20957). The structure of 9 has been determined mainly on the basis of spectroscopic analysis and by comparison with published data for similar compounds. To date, pneumocandin D0 has been found to be the most potent inhibitor of Pneumocystis carinii development in vivo within the natural-occurring echinocandin family of antifungal agents.

L-681,217, a new and novel member of the efrotomycin family of antibiotics.

L-681,217 is a new broad spectrum antibiotic isolated from fermentation broth. The compound is a structurally unique member of the efrotomycin family of growth permittant antibiotics.

Analogs of cyclosporin A modified at the D-Ala8 position.

The conversion of [2-deutero-3-fluoro-D-Ala8]cyclosporin A (1) to a dehydroalanine analog [delta-Ala8]cyclosporin A (2) was achieved with lithium diisopropylamide in THF at low temperature. This dehydro compound is a useful intermediate for the preparation of position 8 analogs of cyclosporin A formed from it by the conjugate addition of thiol compounds. NMR conformational studies have provided evidence for the restoration of D-stereochemistry in the modified Ala8 residues. The preparation of several of these cyclosporin analogs and their bioactivities are described.

L-696,474, a novel cytochalasin as an inhibitor of HIV-1 protease. II. Isolation and structure.

A novel HIV-1 protease inhibitor, L-696,474 (C30H39NO4, 477), was isolated from the fermentations of the fungus Hypoxylon fragiforme (ATCC 20995, MF5511) and purified by silica gel chromatography followed by crystallization. Spectroscopic studies have shown the competitive inhibitor L-696,474 to be a novel cytochalasin. Two related novel cytochalasins were also isolated and had no effect on the enzyme.

Pneumocandins from Zalerion arboricola. III. Structure elucidation.

Pneumocandin B0 (6) and six related lipopeptides are antifungal and anti-Pneumocystis carinii agents from mutants of Zalerion arboricola, whose structures were determined mainly on the basis of spectroscopic analysis. They belong, along with pneumocandin A0 (L-671,329) previously isolated from these laboratories, to the echinocandin class of antifungal agents. The product from base-catalyzed ring opening involving the hemiaminal position of the dihydroxyornithine residue of B0, has been clearly defined as 6b. Modifications were limited to the 3-hydroxy-4-methylproline, 3,4-dihydroxyhomotyrosine and 4,5-dihydroxyornithine residues of pneumocandin A0.

Difficidin and oxydifficidin: novel broad spectrum antibacterial antibiotics produced by Bacillus subtilis. II. Isolation and physico-chemical characterization.

The isolation of difficidin (1) and oxydifficidin (2) from fermentation broth of Bacillus subtilis ATCC 39320 and the physico-chemical characterization of these labile antibiotics are described. The structures of the compounds represent a new class of antibiotics, characterized as highly unsaturated 22-membered macrolide phosphates. Difficidin and oxydifficidin undergo reversible thermal isomerization to 3 and 4 respectively. Biological evaluation of the isomers is presented.