The design and synthesis of high-affinity FKBP 12 ligands is described. These compounds potently inhibit the m-rrans-peptidylprolyl isomerase (rotamase) activity catalyzed by FKBP 12 with inhibition constants (Ki,app) as low as 1 nM, yet they possess remarkable structural simplicity relative to FK506 and rapamycin, from which they are conceptually derived. The atomic structures of three FKBP12-ligand complexes and of one unbound ligand were determined by X-ray crystallography and are compared to the FKBP12-FK506 and FKBP12-rapamycin complexes.
A series of unsaturated steroids bearing a 3-carboxy substituent has been prepared and assayed in vitro as inhibitors of human and rat prostatic steroid 5 alpha-reductase (EC 1.3.1.30). It is proposed that the observed tight binding of the 3-androstene-3-carboxylic acids is due to mimicry of a putative, high-energy, enzyme-bound enolate intermediate formed during the NADPH-dependent conjugate reduction of testosterone by steroid 5 alpha-reductase. These compounds were prepared through palladium(0)-catalyzed carbomethoxylations of enol (trifluoromethyl)sulfonates derived from 3-keto precursors. Modification of A and B ring unsaturation and substitution at C-3, -4, -6, and -11 was explored. Mono- and dialkylcarboxamides were employed as 17 beta side chains to enhance inhibitory activity with the human enzyme.
A series of 17 beta-carbamoyl-1,3,5(10)-estratriene-3-carboxylic acids has been prepared and evaluated in vitro as inhibitors of human and rat prostatic steroid 5 alpha-reductase (EC 1.3.1.30). Potent inhibition of the human enzyme, in particular, was observed and preliminary studies using rat enzyme suggest that the inhibition results from the formation of an enzyme-NADP(+)-inhibitor complex. The compounds were synthesized from estrone, generally employing a differentiated bis-triflate carbonylation strategy.
To probe the suggestion that D-1 (DA1) dopamine receptors might possess an accessory pi-binding site in a location complementary to a suitably oriented aromatic ring (i.e., in an axial orientation approximately orthogonal to the catechol nucleus) in agonists such as 2,3,4,5-tetrahydro-1-phenyl-1H-3-benzazepine-7,8-diol (1) and 3',4'-dihydroxynomifensine (2) that are selective for this subtype, cis- and trans-2,3,4,8,9,9a-hexahydro-4-phenyl-1H-indeno[1,7-cd]azepine-6,7-diol were prepared. These compounds are 5,6-ethano-bridged derivatives of the D-1 selective dopamine receptor agonist 1. Introduction of the bridge reduces the conformational mobility of the parent molecule. Comprehensive conformational analyses by molecular mechanical methods indicated that both the cis and trans isomers could attain a conformation that places the phenyl substituent in an axial orientation. X-ray analysis of the trans isomer showed an axial disposition of the phenyl ring; however, NMR studies suggest that this conformation is fixed in the trans isomer, but not in the cis. The dopamine receptor binding affinity and intrinsic activity of the cis isomer were considerably greater than those of its trans counterpart; the cis isomer also demonstrated a high degree of selectivity for the D-1 subtypes. One possible explanation of these results, suggested by the molecular modeling studies, is that both the axial orientation of the phenyl postulated to be required for binding to the receptor and a putatively requisite location of the nitrogen in approximately the plane of the catechol ring can be attained only by the cis isomer in which the tetrahydroazepine ring is in a twist conformation. Conversely, these results might simply suggest a preference of the D-1 receptors for benzazepine agonists having the phenyl group in an equatorial orientation. Still another possibility is that the D-1 receptor binding site is in a sterically hindered area accessible only to compounds that are relatively planar. However, it requires an axial 1-phenylbenzazepine for strong binding. Thus, a conformationally flexible cis isomer could more readily achieve the different conformations required to both gain access to and bind with the D-1 site.
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