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1.  Sulfur-Containing 1,3-Dialkylxanthine Derivatives as Selective Antagonists at A1-Adenosine Receptors 
Journal of medicinal chemistry  1989;32(8):1873-1879.
Sulfur-containing analogues of 8-substituted xanthines were prepared in an effort to increase selectivity or potency as antagonists at adenosine receptors. Either cyclopentyl or various aryl substituents were utilized at the 8-position, because of the association of these groups with high potency at A1-adenosine receptors. Sulfur was incorporated on the purine ring at positions 2 and/or 6, in the 8-position substituent in the form of 2- or 3-thienyl groups, or via thienyl groups separated from an 8-aryl substituent through an amide-containing chain. The feasibility of using the thienyl group as a prosthetic group for selective iodination via its Hg2+ derivative was explored. Receptor selectivity was determined in binding assays using membrane homogenates from rat cortex [[3H]-N6-(phenylisopropyl) adenosine as radioligand] or striatum [[3H]-5′-(N-ethylcarbamoyl)adenosine as radioligand] for A1- and A2-adenosine receptors, respectively. Generally, 2-thio-8-cycloalkylxanthines were at least as A1 selective as the corresponding oxygen analogue. 2-Thio-8-aryl derivatives tended to be more potent at A2 receptors than the oxygen analogue. 8-[4-[(Carboxymethyl)oxy]phenyl]-1,3-dipropyl-2-thioxanthine ethyl ester was >740-fold A1 selective.
PMCID: PMC3479653  PMID: 2754711
2.  Functionalized Congener Approach to Muscarinic Antagonists: Analogues of Pirenzepine 
Journal of medicinal chemistry  1991;34(7):2133-2145.
The M1-selective muscarinic receptor antagonist pirenzepine (5,11-dihydro-11-[(4-methyl-1-piperazinyl)acetyl]-6H-pyrido[2,3-b] [1,4]benzodiazepin-6-one) was derivatized to explore points of attachment of functionalized side chains for the synthesis of receptor probes and ligands for affinity chromatography. The analogues prepared were evaluated in competitive binding assays versus [3H]-N-methylscopolamine at four muscarinic receptor subtypes (m1AChR-m4AChR) in membranes from rat heart tissue and transfected A9L cells. 9-(Hydroxymethyl)pirenzepine, 8-(methylthio)pirenzepine, and a series of 8-aminosulfonyl derivatives were synthesized. Several 5-substituted analogues of pirenzepine also were prepared. An alternate series of analogues substituted on the 4-position of the piperazine ring was prepared by reaction of 4-desmethylpirenzepine with various electrophiles. An N-chloroethyl analogue of pirenzepine was shown to form a reactive aziridine species in aqueous buffer yet failed to affinity label muscarinic receptors. Within a series of aminoalkyl analogues, the affinity increased as the length of the alkyl chain increased. Shorter chain analogues were generally much less potent than pirenzepine, and longer analogues (7–10 carbons) were roughly as potent as pirenzepine at m1 receptors, but were nonselective. Depending on the methylene chain length, acylation or alkyl substitution of the terminal amine also influenced the affinity at muscarinic receptors.
PMCID: PMC3469255  PMID: 2066986
3.  In Vitro and In Vivo Profiles of ACH-702, an Isothiazoloquinolone, against Bacterial Pathogens▿ 
ACH-702, a novel isothiazoloquinolone (ITQ), was assessed for antibacterial activity against a panel of Gram-positive and Gram-negative clinical isolates and found to possess broad-spectrum activity, especially against antibiotic-resistant Gram-positive strains, including methicillin-resistant Staphylococcus aureus (MRSA). For Gram-negative bacteria, ACH-702 showed exceptional potency against Haemophilus influenzae, Moraxella catarrhalis, and a Neisseria sp. but was less active against members of the Enterobacteriaceae. Good antibacterial activity was also evident against several anaerobes as well as Legionella pneumophila and Mycoplasma pneumoniae. Excellent bactericidal activity was observed for ACH-702 against several bacterial pathogens in time-kill assays, and postantibiotic effects (PAEs) of >1 h were evident with both laboratory and clinical strains of staphylococci at 10× MIC and similar in most cases to those observed for moxifloxacin at the same MIC multiple. In vivo efficacy was demonstrated against S. aureus with murine sepsis and thigh infection models, with decreases in the number of CFU/thigh equal to or greater than those observed after vancomycin treatment. Macromolecular synthesis assays showed specific dose-dependent inhibition of DNA replication in staphylococci, and biochemical analyses indicated potent dual inhibition of two essential DNA replication enzymes: DNA gyrase and topoisomerase IV. Additional biological data in support of an effective dual targeting mechanism of action include the following: low MIC values (≤0.25 μg/ml) against staphylococcal strains with single mutations in both gyrA and grlA (parC), retention of good antibacterial activity (MICs of ≤0.5 μg/ml) against staphylococcal strains with two mutations in both gyrA and grlA, and low frequencies for the selection of higher-level resistance (<10−10). These promising initial data support further study of isothiazoloquinolones as potential clinical candidates.
doi:10.1128/AAC.01666-10
PMCID: PMC3101440  PMID: 21464250
4.  Dual Targeting of DNA Gyrase and Topoisomerase IV: Target Interactions of Heteroaryl Isothiazolones in Staphylococcus aureus▿  
Heteroaryl isothiazolones (HITZs) are antibacterial agents that display excellent in vitro activity against Staphylococcus aureus. We recently identified a series of these compounds that show potent bactericidal activities against methicillin-resistant Staphylococcus aureus (MRSA). We report here the results of in vitro resistance studies that reveal potential underlying mechanisms of action. HITZs selected gyrA mutations exclusively in first-step mutants of wild-type S. aureus, indicating that in contrast to the case with most quinolones, DNA gyrase is the primary target. The compounds displayed low mutation frequencies (10−9 to 10−10) at concentrations close to the MICs and maintained low MICs (≤0.016 μg/ml) against mutants with single mutations in either gyrA or grlA (parC). These data suggested that HITZs possess significant inhibitory activities against target enzymes, DNA gyrase and topoisomerase IV. This dual-target inhibition was supported by low 50% inhibitory concentrations against topoisomerase IV as measured in a decatenation activity assay and against DNA gyrase as measured in a supercoiling activity assay. Good antibacterial activities (≤1 μg/ml) against staphylococcal gyrA grlA double mutants, as well as low frequencies (10−9 to 10−10) of selection of still higher-level mutants, also suggested that HITZs remained active against mutant enzymes. We further demonstrated that HITZs exhibit good inhibition of both S. aureus mutant enzymes and thus continue to possess a novel dual-targeting mode of action against these mutant strains. In stepwise acquisition of mutations, HITZs selected quinolone resistance determining region mutations gyrA(Ser84Leu), grlA(Ser80Phe), grlA(Ala116Val), and gyrA(Glu88Lys) sequentially, suggesting that the corresponding amino acids are key amino acids involved in the binding of HITZs to topoisomerases. The overall profile of these compounds suggests the potential utility of HITZs in combating infections caused by S. aureus, including multidrug-resistant MRSA.
doi:10.1128/AAC.00158-07
PMCID: PMC1913236  PMID: 17502409
5.  In Vitro and In Vivo Antibacterial Activities of Heteroaryl Isothiazolones against Resistant Gram-Positive Pathogens▿  
The activities of several tricyclic heteroaryl isothiazolones (HITZs) against an assortment of gram-positive and gram-negative clinical isolates were assessed. These compounds target bacterial DNA replication and were found to possess broad-spectrum activities especially against gram-positive strains, including antibiotic-resistant staphylococci and streptococci. These included methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-nonsusceptible staphylococci, and quinolone-resistant strains. The HITZs were more active than the comparator antimicrobials in most cases. For gram-negative bacteria, the tested compounds were less active against members of the family Enterobacteriaceae but showed exceptional potencies against Haemophilus influenzae, Moraxella catarrhalis, and Neisseria spp. Good activity against several anaerobes, as well as Legionella pneumophila and Mycoplasma pneumoniae, was also observed. Excellent bactericidal activity against staphylococci was observed in time-kill assays, with an approximately 3-log drop in the numbers of CFU/ml occurring after 4 h of exposure to compound. Postantibiotic effects (PAEs) of 2.0 and 1.7 h for methicillin-susceptible S. aureus and MRSA strains, respectively, were observed, and these were similar to those seen with moxifloxacin at 10× MIC. In vivo efficacy was demonstrated in murine infections by using sepsis and thigh infection models. The 50% protective doses were ≤1 mg/kg of body weight against S. aureus in the sepsis model, while decreases in the numbers of CFU per thigh equal to or greater than those detected in animals treated with a standard dose of vancomycin were seen in the animals with thigh infections. Pharmacokinetic analyses of treated mice indicated exposures similar to those to ciprofloxacin at equivalent dose levels. These promising initial data suggest further study on the use of the HITZs as antibacterial agents.
doi:10.1128/AAC.01315-06
PMCID: PMC1855488  PMID: 17242152

Results 1-5 (5)