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1.
J Org Chem ; 65(7): 1919-23, 2000 Apr 07.
Article in English | MEDLINE | ID: mdl-10774010

ABSTRACT

Efforts to improve the synthesis of 24(S),25-epoxycholesterol (1) from stigmasterol (3) have included identification of 6 alpha-hydroxy-i-steroid 11 as a byproduct from the ozonolysis of 9 and an attempt to effect conversion of sulfone 14 to diol 18 via Payne rearrangement and nucleophilic trapping of epoxide 25, which led instead to 27 and 28 (97% yield). A more efficient synthesis of 1 was achieved via coupling of cuprate 21 with allylic acetate 31 to give 73% of 16, in the most efficient conversion yet of a C22 intermediate to desmosterol (5) or its acetate 6.


Subject(s)
Cholesterol/analogs & derivatives , Desmosterol/chemical synthesis , Catalysis , Cholesterol/chemical synthesis , Magnetic Resonance Spectroscopy
2.
Mol Endocrinol ; 14(1): 27-39, 2000 Jan.
Article in English | MEDLINE | ID: mdl-10628745

ABSTRACT

Transcription of genes encoding cytochrome P450 3A (CYP3A) monooxygenases is induced by a variety of xenobiotics and natural steroids. There are marked differences in the compounds that induce CYP3A gene expression between species. Recently, the mouse and human pregnane X receptor (PXR) were shown to be activated by compounds that induce CYP3A expression. However, most studies of CYP3A regulation have been performed using rabbit and rat hepatocytes. Here, we report the cloning and characterization of PXR from these two species. PXR is remarkably divergent between species, with the rabbit, rat, and human receptors sharing only approximately 80% amino acid identity in their ligand-binding domains. This sequence divergence is reflected by marked pharmacological differences in PXR activation profiles. For example, the macrolide antibiotic rifampicin, the antidiabetic drug troglitazone, and the hypocholesterolemic drug SR12813 are efficacious activators of the human and rabbit PXR but have little activity on the rat and mouse PXR. Conversely, pregnane 16alpha-carbonitrile is a more potent activator of the rat and mouse PXR than the human and rabbit receptor. The activities of xenobiotics in PXR activation assays correlate well with their ability to induce CYP3A expression in primary hepatocytes. Through the use of a novel scintillation proximity binding assay, we demonstrate that many of the compounds that induce CYP3A expression bind directly to human PXR. These data establish PXR as a promiscuous xenobiotic receptor that has diverged during evolution.


Subject(s)
Aryl Hydrocarbon Hydroxylases , Receptors, Cytoplasmic and Nuclear/chemistry , Receptors, Steroid/chemistry , Xenobiotics/metabolism , Amino Acid Sequence , Animals , Anticholesteremic Agents/pharmacology , Blotting, Northern , Cloning, Molecular , Cytochrome P-450 CYP3A , Cytochrome P-450 Enzyme System/metabolism , Diphosphonates/pharmacology , Dose-Response Relationship, Drug , Evolution, Molecular , Humans , Ligands , Liver/metabolism , Mice , Molecular Sequence Data , Oxidoreductases, N-Demethylating/metabolism , Pregnane X Receptor , Protein Binding , Rabbits , Rats , Receptors, Cytoplasmic and Nuclear/genetics , Receptors, Cytoplasmic and Nuclear/metabolism , Receptors, Steroid/genetics , Receptors, Steroid/metabolism , Recombinant Proteins/metabolism , Sequence Homology, Amino Acid , Transfection
3.
Bioorg Med Chem Lett ; 8(24): 3657-8, 1998 Dec 15.
Article in English | MEDLINE | ID: mdl-9934490

ABSTRACT

Analysis of the enantiomers of rosiglitazone in a PPAR gamma binding assay suggests that the (S)-(-)-isomer is responsible for the antidiabetic activity.


Subject(s)
Hypoglycemic Agents/pharmacology , Receptors, Cytoplasmic and Nuclear/drug effects , Thiazoles/pharmacology , Thiazolidinediones , Transcription Factors/drug effects , Hypoglycemic Agents/chemistry , Rosiglitazone , Stereoisomerism , Thiazoles/chemistry
4.
Chem Biol ; 4(12): 909-18, 1997 Dec.
Article in English | MEDLINE | ID: mdl-9427656

ABSTRACT

BACKGROUND: The peroxisome proliferator-activated receptors (PPARs) were cloned as orphan members of the nuclear receptor superfamily of transcription factors. The identification of subtype-selective ligands for PPARalpha and PPARgamma has led to the discovery of their roles in the regulation of lipid metabolism and glucose homeostasis. No subtype-selective PPARdelta ligands are available and the function of this subtype is currently unknown. RESULTS: A three-component library was designed in which one of the monomers was biased towards the PPARs and the other two monomers were chosen to add chemical diversity. Synthesis and screening of the library resulted in the identification of pools with activity on each of the PPAR subtypes. Deconvolution of the pools with the highest activity on PPARdelta led to the identification of GW 2433 as the first high-affinity PPARdelta ligand. [3H]GW 2433 is an effective radioligand for use in PPARdelta competition-binding assays. CONCLUSIONS: The synthesis of biased chemical libraries is an efficient approach to the identification of lead molecules for members of sequence-related receptor families. This approach is well suited to the discovery of small-molecule ligands for orphan receptors.


Subject(s)
Butyrates/chemical synthesis , Nuclear Proteins/metabolism , Phenylurea Compounds/chemical synthesis , Receptors, Cytoplasmic and Nuclear/metabolism , Transcription Factors/metabolism , Binding, Competitive/drug effects , Cloning, Molecular , Humans , Ligands , Nuclear Proteins/genetics , Radiopharmaceuticals/chemical synthesis , Receptors, Cytoplasmic and Nuclear/genetics , Transcription Factors/genetics
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