Igor Goljer

Modulation of Wnt signaling through inhibition of secreted frizzled-related protein I (sFRP-1) with N-substituted piperidinyl diphenylsulfonyl sulfonamides.

The diphenylsulfonyl sulfonamide scaffold represented by 1 (WAY-316606) are small molecule inhibitors of the secreted protein sFRP-1, an endogenous antagonist of the secreted glycoprotein Wnt. Modulators of the Wnt pathway have been proposed as anabolic agents for the treatment of osteoporosis or other bone-related disorders. Details of the structure-activity relationships and biological activity from the first structural class of this scaffold will be discussed.

Identification of phenylsulfone-substituted quinoxaline (WYE-672) as a tissue selective liver X-receptor (LXR) agonist.

A series of phenyl sulfone substituted quinoxaline were prepared and the lead compound 13 (WYE-672) was shown to be a tissue selective LXR Agonist. Compound 13 demonstrated partial agonism for LXRbeta in kidney HEK-293 cells but did not activate Gal4 LXRbeta fusion proteins in huh-7 liver cells. Although 13 showed potent binding affinity to LXRbeta (IC(50) = 53 nM), it had little binding affinity for LXRalpha (IC(50) > 1.0 microM) and did not recruit any coactivator/corepressor peptides in the LXRalpha multiplex assay. However, compound 13 showed good agonism in THP-1 cells with respect to increasing ABCA1 gene expression and good potency on cholesterol efflux in THP-1 foam cells. In an eight-week lesion study in LDLR -/- mice, compound 13 showed reduction of aortic arch lesion progression and no plasma or hepatic triglyceride increase. These results suggest quinoxaline 13 may have an improved biological profile for potential use as a therapeutic agent.

Structure determination and analysis of local bending in an A-tract DNA duplex: comparison of results from crystallography, nuclear magnetic resonance, and molecular dynamics simulation on d(CGCAAAAATGCG).

We have presented a detailed analysis for structure determinations for the DNA duplex d(CGCAAAAATGCG) obtained from X-ray crystallography, nuclear magnetic resonance, and molecular dynamics simulation. Each of the structures for the duplex deviates from the structure of the canonical form of B-DNA in a number of observable characteristics. Specifically, the three determinations all contain DNA axis deflections at the junctions of the A-tract with the flanking sequences. The analysis provided shows that the general characteristics of the structures obtained for d(CGCAAAAATGCG) from X-ray, NMR, and MD methods turn out to be quite similar. The extent to which this result can be generalized remains to be established by consideration of similar cross-comparisons on diverse oligonucleotide structures.

In Vitro Glucuronidation of Thyroxine and Triiodothyronine by Liver Microsomes and Recombinant Human UDP-Glucuronosyltransferases

Glucuronidation, which may take place on the phenolic hydroxyl and carboxyl groups, is a major pathway of metabolism for thyroxine (T4) and triiodothyronine (T3). In this study, a liquid chromatography/mass spectrometry (LC/MS) method was developed to separate phenolic and acyl glucuronides of T4 and T3. The method was used to collect the phenolic glucuronide of T4 for definitive characterization by NMR and to determine effects of incubation pH, species differences, and human UDP-glucuronosyltransferases (UGTs) involved in the formation of the glucuronides. Formation of T4 phenolic glucuronide was favored at pH 7.4, whereas formation of T4 acyl glucuronide was favored at pH 6.8. All the UGTs examined catalyzed the formation of T4 phenolic glucuronide except UGT1A4; the highest activity was detected with UGT1A3, UGT1A8, and UGT1A10, followed by UGT1A1 and UGT2B4. Formation of T3 phenolic glucuronide was observed in the order of UGT1A8 > UGT1A10 > UGT1A3 > UGT1A1; trace activity was observed with UGT1A6 and UGT1A9. UGT1A3 was the major isoform catalyzing the formation of T4 and T3 acyl glucuronides. In liver microsomes, phenolic glucuronidation was the highest in mice for T4 and in rats for T3 and lowest in monkeys for both T4 and T3. Acyl glucuronidation was highest in humans and lowest in mice for T4 and T3. Phenolic glucuronidation was higher than acyl glucuronidation for T4 in humans; in contrast, the acyl glucuronidation was slightly higher than phenolic glucuronidation for T3. UGT activities were lower toward T3 than T4 in all the species. The LC/MS method was a useful tool in studying glucuronidation of T4 and T3.

Oxygen-bridged tetrahydropyridines, hexahydropyridines, and dihydropyridones via a Hantzsch-like synthesis with 4-(2-hydroxyphenyl)but-3-en-2-one

Substituted oxygen-bridged tetrahydro-2-pyridones and tetrahydropyridines (4) and (7) were synthesized by condensation of 4-(2-hydroxyphenyl)but-3-en-2-one (1) with Meldrums acid (2) and 3-aminocrotononitrile, respectively, in the presence of ammonium acetate. Analogous cyclo-condensations of (1) with methyl 3-amino-2,4-dicyanobut-2-enoate (8) and methyl 3-amino-2-cyanopentene-2-dioate (10) led to oxygen-bridged hexahydropyridines (9) and (11), respectively, of different stereochemistry in the piperidine rings. The dichotomy in the stereospecific routes to these oxygen-bridged heterocycles is discussed. Preparation of 4-aryl substituted dihydro-2-pyridones is also reported.

Evaluating Indole-Related Derivatives as Precursors in the Directed Biosynthesis of Diazepinomicin Analogues

The effectiveness of precursor-directed biosynthesis to generate diazepinomicin (1) analogues with varied ring-A substitutents was investigated by feeding commercially available, potential ring-A precursors such as fluorinated tryptophans, halogenated anthranilates, and various substituted indoles into growing actinomycete culture DPJ15 (genus Micromonospora). Two new monofluorinated diazepinomicin analogues (2 and 3) were identified and characterized by spectroscopic methods. Both derivatives showed modest antibacterial activity against the Gram-positive coccus Staphylococcus aureus with MIC values in the range 8-32 microg/mL.

Metabolism of Intravenous Methylnaltrexone in Mice, Rats, Dogs, and Humans

Methylnaltrexone (MNTX), a selective μ-opioid receptor antagonist, functions as a peripherally acting receptor antagonist in tissues of the gastrointestinal tract. This report describes the metabolic fate of [3H]MNTX or [14C]MNTX bromide in mice, rats, dogs, and humans after intravenous administration. Separation and identification of plasma and urinary MNTX metabolites was achieved by high-performance liquid chromatography-radioactivity detection and liquid chromatography/mass spectrometry. The structures of the most abundant human metabolites were confirmed by chemical synthesis and NMR spectroscopic analysis. Analysis of radioactivity in plasma and urine showed that MNTX underwent two major pathways of metabolism in humans: sulfation of the phenolic group to MNTX-3-sulfate (M2) and reduction of the carbonyl group to two epimeric alcohols, methyl-6α-naltrexol (M4) and methyl-6β-naltrexol (M5). Neither naltrexone nor its metabolite 6β-naltrexol were detected in human plasma after administration of MNTX, confirming an earlier observation that N-demethylation was not a metabolic pathway of MNTX in humans. The urinary metabolite profiles in humans were consistent with plasma profiles. In mice, the circulating and urinary metabolites included M5, MNTX-3-glucuronide (M9), 2-hydroxy-3-O-methyl MNTX (M6), and its glucuronide (M10). M2, M5, M6, and M9 were observed in rats. Dogs produced only one metabolite, M9. In conclusion, MNTX was not extensively metabolized in humans. Conversion to methyl-6-naltrexol isomers (M4 and M5) and M2 were the primary pathways of metabolism in humans. MNTX was metabolized to a higher extent in mice than in rats, dogs, and humans. Glucuronidation was a major metabolic pathway in mice, rats, and dogs, but not in humans. Overall, the data suggested species differences in the metabolism of MNTX.

Regio- and stereoselectivity in the 1,3-dipolar cycloaddition of C,N-diarylnitrones to 3,3-methylene-5,5-dimethyl-2-pyrrolidinone

SummaryRegio- and stereoselectivity of the nitrone cycloaddition with 3,3-methylene-5,5-dimethyl-2-pyrrolidinone ((1) is discussed. Nitrones react regioselectively with1 to give a mixture of diastereoisomeric spiro-cycloadducts3 and4, in which3 always dominates. Both3 and4 result from the approach which binds the carbon of the nitrone with the exocyclic carbon of1 and the oxygen to the spiro carbon. The structure and steric configuration of the adducts have been assigned on the basis of1H- and13C-NMR spectroscopy, mainly by nuclear Overhauser effect difference spectroscopy. AM1 calculations of the reactants were performed, the regio- and stereochemistry of the cycloaddition seems to be controlled by steric effects.ZusammenfassungEs wird die Regio- und Stereoselektivität der Cycloaddition von Nitronen an 3,3-Methylen-5,5-dimethyl-2-pyrolidinon (1) diskutiert. Nitrone reagieren mit1 regioselektiv zu einer Mischung von diastereomeren Spirocycloaddukten3 und4, wobei3 stets dominierend ist. Sowohl3 als auch4 resultieren aus der gleichen Reaktionsanordnung unter Bindung des Nitron-Kohlenstoffatoms an das exocyclische Kohlenstoffatom von1 und des Sauerstoffatoms an den Spiro-Kohlenstoff. Die Stereochemie der Addukte wurde auf Basis von1H- und13C-NMR-Spektroskopie, insbesondere aus Differenz-Nuclear-Overhauser-Messungen, abgeleitet. Es wurden auch AM1-Rechnungen durchgeführt. Die Regio- und Stereochemie der Cycloaddition scheint von sterischen Effekten bestimmt zu sein.

Efficient, Regioselective Palladium-Catalyzed Tandem Heck-Isomerization Reaction of Aryl Bromides and Non-Allylic Benzyl Alcohols

An efficient and mild method to couple aryl bromides and activated non-allylic alcohols in a Heck reaction with tandem isomerization to selectively afford high yields of 1,5-diarylalkan-1-ones has been developed. Mechanistic insight was gained through NMR studies of products derived from deuterium-labeled intermediates.

Preparation and stereoselectivity of 1,3-dipolar cycloaddition of C-glycosyl nitrones to N-arylmaleimides

SummaryThe cycloaddition of 3′-hydroxyglycosyl-N-methylnitrone (1) to N-arylmaleimides gave thesyn isoxazolidines6, whereas 3′-acetoxyglycosyl-N-methylnitrone (2) afforded theanti isoxazolidines8 and10. The formation of6 was rationalized by anexo attack, stereoelectronically preferred through the hydrogen bond between the pentose hydroxyl group and one of the carbonyl groups of N-arylmaleimide. The sterically preferredendo attack avoiding the repulsions between N-arylmaleimide and sugar moiety was proposed for addition of2. The structure and steric configuration of the products have been assigned on the basis of1H- and13C-NMR spectroscopy, mainly by nuclear Overhauser effect difference spectroscopy. AM1 calculations of the nitrones and MM2 calculations of the adducts were performed.ZusammenfassungDie Cycloaddition von 3′-Hydroxyglycosyl-N-methylnitron (1) an N-Arylmaleimide gab diesyn-Isoxazolidine6, mit 3′-Acetoxyglycosyl-N-methylnitron (2) wurden hingegen dieanti-Isoxazolidine8 und10 erhalten. Die Bildung von6 wurde mit einemexo-Angriff erklärt, der stereoelektronisch wegen einer Wasserstoffbrückenbindung zwischen der Hydroxylgruppe der Pentose und einer Carbonylgruppe des N-Arylmaleimides bevorzugt wird. Für die Addition von2 wurde ein sterisch bevorzugterendo-Angriff vorgeschlagen, da dabei ungünstige Wechselwirkungen zwischen der N-Arylmaleimid- und der Zuckereinheit vermieden werden. Die Struktur und Stereochemie der Produkte wurde mittels1H- und13C-NMR unter Verwendung von NOE-Differenzmessungen ermittelt. Es wurden auch AM1-Rechnungen für die Nitrone und MM2-Rechnungen für die Addukte durchgeführt.