Carbon-carbon-linked (pyrazolylphenyl)oxazolidinones with antibacterial activity against multiple drug resistant gram-positive and fastidious gram-negative bacteria

In an effort to expand the spectrum of activity of the oxazolidinone class of antibacterial agents to include Gram-negative bacteria, a series of new carbon-carbon linked pyrazolylphenyl analogues has been prepared. The alpha-N-substituted methyl pyrazole (10alpha) in the C3-linked series exhibited very good Gram-positive activity with MICs <or=0.5-1 microg/mL and moderate Gram-negative activity with MICs=2-8 microg/mL against Haemophilus influenzae and Moraxella catarrhalis. This analogue was also found to have potent in vivo activity with an ED(50)=1.9 mg/kg. Beta-substitution at the C3-linked pyrazole generally results in a loss of activity. The C4-linked pyrazoles are slightly more potent than their counterparts in the C3-linked series. Most of the analogues in the C4-linked series exhibited similar levels of activity in vitro, but lower levels of activity in vivo than 10alpha. In addition, incorporation of a thioamide moiety in selected C4-linked pyrazole analogues results in an enhancement of in vitro activity leading to compounds several times more potent than eperezolid, linezolid and vancomycin. The thioamide of the N-cyanomethyl pyrazole analogue (34) exhibited an exceptional in vitro activity with MICs of <or= 0.06-0.25 microg/mL against Gram-positive pathogens and with MICs of 1 microg/mL against fastidious Gram-negative pathogens.

Identification of novel potent hydroxamic acid inhibitors of peptidyl deformylase and the importance of the hydroxamic acid functionality on inhibition

Peptidyl deformylase (PDF) is a metallo protease that catalyzes the removal of a formyl group from the N-termini of prokaryotic prepared polypeptides, an essential step in bacterial protein synthesis. Screening of our compound collection using Staphylococcus aureus PDF afforded a very potent inhibitor with an IC(50) in the low nanomolar range. Unfortunately, the compound that contains a hydroxamic acid did not exhibit antibacterial activity (MIC). In order to address the lack of activity in the MIC assay and to determine what portion of the molecule was responsible for binding to PDF, we prepared several analogues. This paper describes our findings that the hydroxamic acid functionality found in 1 is mainly responsible for the high affinity to PDF. In addition, we identified an alternative class of PDF inhibitors, the N-hydroxy urea 18, which has both PDF and antibacterial activity.

Tipranavir (PNU-140690): a potent, orally bioavailable nonpeptidic HIV protease inhibitor of the 5,6-dihydro-4-hydroxy-2-pyrone sulfonamide class

A broad screening program previously identified phenprocoumon (1) as a small molecule template for inhibition of HIV protease. Subsequent modification of this lead through iterative cycles of structure-based design led to the activity enhancements of pyrone and dihydropyrone ring systems (II and V) and amide-based substitution (III). Incorporation of sulfonamide substitution within the dihydropyrone template provided a series of highly potent HIV protease inhibitors, with structure-activity relationships described in this paper. Crystallographic studies provided further information on important binding interactions responsible for high enzymatic binding. These studies culminated in compound VI, which inhibits HIV protease with a Ki value of 8 pM and shows an IC90 value of 100 nM in antiviral cell culture. Clinical trials of this compound (PNU-140690, Tipranavir) for treatment of HIV infection are currently underway.

Structure-based design of nonpeptidic HIV protease inhibitors: the sulfonamide-substituted cyclooctylpyramones

Recently, cyclooctylpyranone derivatives with m-carboxamide substituents (e.g. 2c) were identified as potent, nonpeptidic HIV protease inhibitors, but these compounds lacked significant antiviral activity in cell culture. Substitution of a sulfonamide group at the meta position, however, produces compounds with excellent HIV protease binding affinity and antiviral activity. Guided by an iterative structure-based drug design process, we have prepared and evaluated a number of these derivatives, which are readily available via a seven-step synthesis. A few of the most potent compounds were further evaluated for such characteristics as pharmacokinetics and toxicity in rats and dogs. From this work, the p-cyanophenyl sulfonamide derivative 35k emerged as a promising inhibitor, was selected for further development, and entered phase I clinical trials.

Synthesis and biological activities of (R)-5,6-dihydro-N,N-dimethyl-4H-imidazo[4,5,1-ij]quinolin-5-amine and its metabolites

The imidazoquinoline (R)-5,6-Dihydro-N,N-dimethyl-4H-imidazo[4,5,1-ij]quinolin-5-amine [(R)-3] is a potent dopamine agonist when tested in animals but surprisingly shows very low affinity in in vitro binding assays. When incubated with mouse or monkey liver S9 microsomes, (R)-3 is metabolized by N-demethylation and oxidation to (R)-5,6-dihydro-5-(methylamino)-4H-imidazo[4,5,1-ij]quinolin-2(1H) -one [(R)-6], intermediate metabolites, where N-demethylation to the imidazoquinoline (R)-4 and where oxidation to the imidazoquinolinone (R)-5 has taken place, are also observed in these incubates. A cross-species study on the metabolism of (R)-3 in vitro has shown large variations in the extent of metabolism from species to species. Imidazoquinolinones (R)-5 and (R)-6 have comparable activity to (R)-3 in animals and also show good dopaminergic (D2) and serotonergic (5HT1A) activities in binding assays. It is probable that these metabolites account at least in part for the in vivo activity found for (R)-3. Efficient syntheses for compounds 3-6 as single enantiomers from quinoline are presented together with information on the biological activities and metabolic stabilities of these compounds.

Structure-based design of novel HIV protease inhibitors: sulfonamide-containing 4-hydroxycoumarins and 4-hydroxy-2-pyrones as potent non-peptidic inhibitors

The low oral bioavailability and rapid biliary excretion of peptide-derived HIV protease inhibitors have limited their utility as potential therapeutic agents. Our broad screening program to discover non-peptidic HIV protease inhibitors previously identified compound I (phenprocoumon, Ki = 1 microM) as a lead template. Structure-based design of potent non-peptidic inhibitors, utilizing crystal structures of HIV protease/inhibitor complexes, provided a rational basis for the previously reported carboxamide-containing 4-hydroxycoumarins and 4-hydroxy-2-pyrones. The amino acid containing compound V (Ki = 4 nM) provided an example of a promising new series of HIV protease inhibitors with significantly improved enzymatic binding affinity. In this report, further structure-activity relationship studies, in which the carboxamide is replaced by a sulfonamide functionality, led to the identification of another series of nonamino acid containing promising inhibitors with significantly enhanced enzyme binding affinity and in vitro antiviral activity. The most active diastereomer of the sulfonamide-containing pyrone XVIII (Ki = 0.5 nM) shows improved antiviral activity (IC50 = 0.6 nM) and represents an example of a new design direction for the discovery of more potent non-peptidic HIV protease inhibitors as potential therapeutic agents for the treatment of HIV infection.

The amphiphilic properties of novenamines determine their activity as inhibitors of HIV-1 RNase H

Few inhibitors of the RNase H function associated with the HIV-1 reverse transcriptase have been discovered to date. We observed that three novenamines, U-34445, U-35122, and U-35401, are specific inhibitors of the HIV-1 RT RNase H function. All three compounds are strong amphiphiles and contain one ionizable group. Hence, a priori, in aqueous solutions the inhibitors might exist in at least four different physical states, namely protonated monomers, ionized monomers, protonated micelles, and ionized micelles. The three inhibitors all yielded anomalous dose-response curves, indicating that the four molecular species have different inhibitory potentials. In order to identify the inhibitory species, the amphiphilic properties of these compounds were studied. It was established that in alkaline solutions, around pH 8, all compounds are ionized and form micelles at concentrations above their CMC. Both the protonated and the ionized forms of these molecules form stable insoluble monomolecular layers at the air/water interface. The anomalies of the dose-response curves can be resolved by taking into account the fact that, in solution, the relative proportion of these molecules in each physical state depends on the pH and on their analytical concentration. Thus interpreted, the results indicate that RNase H is inhibited only by the ionized micellar form of these compounds and not by their monomeric form. Around their pKa (approximately pH 5), the three compounds reproducibly form uniformly sized, self-emulsified colloidal particles that may be used as an efficient drug delivery system.

Structure-based design of novel HIV protease inhibitors: carboxamide-containing 4-hydroxycoumarins and 4-hydroxy-2-pyrones as potent nonpeptidic inhibitors

The low oral bioavailability and rapid biliary excretion of peptide-derived HIV protease inhibitors have limited their utility as potential therapeutic agents. Our broad screening program to discover nonpeptidic HIV protease inhibitors had previously identified compound II (phenprocoumon, K(i) = 1 muM) as a lead template. Crystal structures of HIV protease complexes containing the peptide-derived inhibitor I (1-(naphthoxyacetyl)-L-histidyl-5(S)-amino-6-cyclohexyl-3 (R),4(R)-dihydroxy-2(R)-isopropylhexanoyl-L-isoleucine N-(2-pyridylmethyl)amide) and nonpeptidic inhibitors, such as phenprocoumon (compound II), provided a rational basis for the structure-based design of more active analogues. This investigation reports on the important finding of a carboxamide functionally appropriately added to the 4-hydroxycoumarin and the 4-hydroxy-2-pyrone templates which resulted in a new promising series of nonpeptidic HIV protease inhibitors with improved enzyme-binding affinity. The most active diastereomer of the carboxamide-containing compound XXIV inhibited HIV-1 protease with a K(i) value of 0.0014 muM. This research provides a new design direction for the discovery of more potent HIV protease inhibitors as potential therapeutic agents for the treatment of HIV infection.

Enzymatic phosphorylation of macrolide antibiotics

Five macrolide antibiotics (erythromycin A, 1; oleandomycin, 3a; tylosin, 4a; spiramycins, 5a; leucomycin A3, 6a) have been phosphorylated enzymatically using cell-free extracts derived from Streptomyces coelicolor UC 5240. The necessary cofactors and the rates of the conversion have been determined.

Novenamine is the active moiety in novobiocin

Novobiocin inhibits semiconservative DNA replication in procaryotes and more specifically DNA gyrase, an enzyme essential for DNA replication. Chemically, novobiocin consists of three distinct entities: the sugar noviose, a coumarin residue and a benzoic acid derivative. The subentity consisting of noviose plus the coumarin residue is referred to as novenamine; the subentity consisting of the coumarin plus the benzoic acid derivative is referred to as novobiocic acid. These subentities as well as noviose and the benzoic acid residue are essentially devoid of inhibitory activity against whole bacterial cells. These fragments were tested for their ability to inhibit DNA replication in a permeabilized Escherichia coli cell system and as potential inhibitors of DNA gyrase. Of all the fragments tested, only novenamine was found to inhibit DNA replication and DNA gyrase. The potency of novenamine essentially equaled that of novobiocin. This subunit thus represents the minimal structural entity necessary to interact with DNA gyrase.

Isolation and structure of antibiotic U-68,204, a new thiolactone

A new thiolactone-containing antibiotic U-68,204 was found to be produced by a soil actinomycete identified as Streptomyces thiolactonus UC 8478 (NRRL 15,439). The production, isolation, structure determination as well as the physical, spectroscopic and antibacterial properties of this C13H17NO3S compound are here reported. On the basis of these data, the antibiotic was identified as the 10-carboxamide of thiotetromycin.

Abnormalities of splenic enzyme networks in nude mice

The activities of various hydrolytic enzymes in splenic tissues of nude mice were compared with those of their controls of the same age. Since all of the enzymatic activities varied with age in both nude mice and in the controls, the difference between the two groups were difficult to define clearly. Principal component analysis enabled us to clearly categorize the enzymatic variations of both groups into two main components. One was related to the maturation process of the animals and the other to the pathological processes in the nude mice. The enzymes related especially to the latter component were formyl-methionine aminopeptidase (fMet-AP), mannosidase, and beta-N-acetyl-D-glucosaminidase (GlcNAc-ase). These enzymes may represent the abnormality of the surface of lymphocytes in the nude mice.

New antibiotic U-64846: fermentation, isolation and characterization

Antibiotic U-64846 is a new entity with the molecular formula C18H35C1N4O9 (MW 486). It is a very water soluble, reddish solid which decomposes above 300 degrees C and which is air-sensitive. The antibiotic is produced by Streptomyces braegensis and it inhibits a variety of Gram-positive bacteria. Acidic hydrolysis gave 3,7-diaminoheptanoic acid. The antibiotic gives 1H NMR, 13C NMR, IR and UV spectra which indicate it is not closely related to known antibiotic families.

Microbial hydroxylation of novobiocin and related compounds

A new soil actinomycete (UC 5762, NRRL 11111) was found to transform novobiocin to 11-hydroxynovobiocin. The product was isolated by solvent extraction and column chromatography, and identified by IR, UV, 1H NMR and 13C NMR spectroscopy. Related structures (8,9-dihydronovobiocin, novobiocic acid and chlorobiocin) were similarly transformed to their corresponding C-11 hydroxylated analogues. The microbial process is superior to chemical (selenium dioxide) oxidation which yielded a mixture of 11-hydroxy- and 11-oxonovobiocin.

Fermentation, isolation, characterization and structure of nitrosofungin

The new antifungal agent nitrosofungin was isolated in high yields from a mixed culture of two organisms consisting of a bacterium of the genus Alcaligenes (UC 9152) and Streptomyces plicatus UC 8272. The bacterium produces the agent, the streptomycete enhances the production by providing a precursor or an inducer. Nitrosofungin in high concentrations inhibits a broad variety of pathogenic fungi in vitro. The agent is relatively non-toxic in small laboratory animals and high blood levels are obtained after either oral or systemic administration. Nitrosofungin is only the second N-nitrosohydroxylamine isolated from microbial sources to date. It has been identified as 2-N-nitrosohydroxylamino-1-propanol, an acidic and highly water-soluble compound.

Desertomycin: purification and physical-chemical properties

Desertomycin was isolated from Streptomyces macronensis Dietz sp. nov. UC 8271. Extensive spectroscopic work led us to place desertomycin in the macrocyclic lactone family which contains monazomycin, scopafungin, primycin, azalomycin F4a and niphithricins A and B. The apparent molecular formula was determined by fast atom bombardment mass spectroscopy to be C57H109NO24 (MW = 1,191). Mild acid hydrolysis yielded mannose but contrary to published reports, glutamic acid is not a constituent of desertomycin.

3-Trehalosamine, a new disaccharide antibiotic

3-Amino-3-deoxy-alpha-D-glucopyranosyl-alpha-D-glucopyranoside (alpha, alpha--3-trehalosamine) was isolated from a culture of Nocardiopsis trehalosei sp. nov. (NRRL 12026). The structure was determined using a combination of spectroscopic techniques on derivatives of the component sugars, especially gas chromatography-mass spectrometry. The compound exhibited antibiotic activity against Gram-positive organisms at levels similar to what was found for the 2- and 4-trehalosamines.