ABSTRACT
The irreversible aromatase inhibitor exemestane (6) reacts with nitromethane and sodium ethanolate to yield the Michael adduct 9. The aldehyde 10 is obtained by Nef reaction of the nitro compound 9 and affords the 1,4-dihydropyridine (DHP) 11 by Hantzsch reaction using methyl beta-aminocrotonate in acetic acid. The new compounds showed a reduced inhibitory potency towards aromatase (IC50 values: 9, 0.91 microM; 10, 2.5 microM; 11, 10 microM) compared to 6 (IC50 = 0.23 microM). The 1,4-DHP 11 was dehydrogenated with CAN or electrochemically (E1/2 =1.18 V) to yield the corresponding pyridine 12.
Subject(s)
Androstadienes/chemical synthesis , Androstadienes/pharmacology , Aromatase Inhibitors/chemical synthesis , Aromatase Inhibitors/pharmacology , Crystallography, X-Ray , Humans , Indicators and Reagents , Magnetic Resonance Spectroscopy , Microsomes/drug effects , Microsomes/enzymology , Models, Molecular , Molecular Conformation , Oxidation-Reduction , Spectrophotometry, Infrared , Spectrophotometry, Ultraviolet , Spectroscopy, Fourier Transform InfraredABSTRACT
Aromatase (P450arom) is a target of pharmacological interest for the treatment of breast cancer. In this paper, we report the design, synthesis, and in vitro biological evaluation of a series of new (di)benzopyranone-based inhibitors of this enzyme. The design of the new compounds was guided by a CoMFA model previously developed for a series of nonsteroidal aromatase inhibitors. Both the chromone and the xanthone nuclei were taken as molecular skeletons, and the functions supposed to be critical for binding to the aromatase active site - a heterocyclic ring (imidazole or 1,3,4-triazole) linked to the aromatic moiety by a methylene unit and an H-bond accepting function (CN, NO(2), Br) located on the aromatic ring at a suitable distance from the heterocyclic nitrogen carrying the lone pair--were attached to them. The chromone, xanthone, and flavone derivatives were prepared by conventional synthetic methods from the appropriate methyl analogues. Aromatase inhibitory activities were determined by the method of Thompson and Siiteri, using human placental microsomes and [1 beta,2 beta-(3)H]testosterone as the labeled substrate. All the compounds were also tested on 17 alpha-hydroxylase/C17,20-lyase (P450 17), an enzyme of therapeutic interest for the treatment of prostatic diseases. The goal to find new potent inhibitors of aromatase was reached with the xanthone derivatives 22d,e (IC(50) values 43 and 40 nM, respectively), which exceeded the potency of the known reference drug fadrozole and also showed high selectivity with respect to P450 17. Moreover, compounds 22g-i based on the same xanthonic nucleus showed fairly high potency as P450 17 inhibitors (IC(50) values 220, 130, and 42 nM, respectively). Thus, they might be new leads for the development of drug candidates for androgen-dependent diseases.
Subject(s)
Aromatase Inhibitors , Chromones/chemical synthesis , Enzyme Inhibitors/chemical synthesis , Steroid 17-alpha-Hydroxylase/antagonists & inhibitors , Xanthenes/chemical synthesis , Xanthones , Chromones/chemistry , Chromones/pharmacology , Drug Design , Enzyme Inhibitors/chemistry , Enzyme Inhibitors/pharmacology , Humans , In Vitro Techniques , Male , Microsomes/drug effects , Microsomes/enzymology , Models, Molecular , Placenta/ultrastructure , Structure-Activity Relationship , Testis/ultrastructure , Xanthenes/chemistry , Xanthenes/pharmacologyABSTRACT
A Negishi-type coupling reaction between 6-bromo-2-methoxyquinoline (1a) and various 4-bromo-N,N-dialkyl-benzamides gave access to 6-substituted 2-methoxy-quinolines 1-3 and 1H-quinolin-2-ones 4-12. Most of these compound proved to be inhibitors of steroid 5alpha reductases with activity and selectivity both being strongly dependent on the features of the heterocycle and the size of the N,N-dialkylamide substituent. The most active inhibitor for the human type 2 isozyme was 6-[4-(N,N-diisopropylcarbamoyl)phenyl]-1H-quinolin-2-one 4 (Ki 800 +/- 85 nM), showing mostly competitive inhibitory patterns. A type 1 selective inhibitor could be identified with 6-[4-(N,N-diisopropylcarbamoyl)phenyl]-N-methyl-quinolin-2-one (5, IC50 510 nM).
Subject(s)
5-alpha Reductase Inhibitors , Enzyme Inhibitors/chemical synthesis , Enzyme Inhibitors/pharmacology , Isoenzymes/antagonists & inhibitors , Quinolines/chemical synthesis , Quinolines/pharmacology , Animals , Drug Evaluation, Preclinical , Enzyme Inhibitors/chemistry , Humans , Magnetic Resonance Spectroscopy , Molecular Structure , Quinolines/chemistry , Rats , Tumor Cells, CulturedABSTRACT
In the search for potent inhibitors of P450 17, the key enzyme in androgen biosynthesis, a series of steroidal inhibitors were synthesized and tested toward rat and human P450 17. Small aliphatic heterocycles (aziridine, oxirane, thiirane, diaziridine, diazirine, azetidine) were introduced into the 17beta-position of anstrost-5-en-3beta-ol. After identifying that aziridine is the most suitable functional group to coordinate with the heme iron, modifications of the steroidal skeleton were performed for further optimization. A wide range of inhibitory potencies toward P450 17 were found for the 21 test compounds. The most potent inhibitors toward the human and rat enzyme were aziridine compounds 3 (IC(50) rat: 0.21 microM, K(i) = 3 nM; IC(50) human: 0.54 microM, K(i) = 8 nM), 5 (IC(50) rat: 0.43 microM, K(i) = 7 nM; IC(50) human: 0.29 microM, K(i) = 4 nM), and 8 (21R:21S = 1:1; IC(50) rat: 0.53 microM, K(i) = 9 nM; IC(50) human: 0.40 microM, K(i) = 6 nM) which were more potent than the reference ketoconazole (IC(50) rat: 67 microM; IC(50) human: 0.74 microM). The inhibitory potency depends markedly on the stereochemistry at C20 of the inhibitors. This effect is more pronounced for the rat enzyme. Tested for selectivity, the highly potent inhibitors show poor inhibitory activity toward P450 arom, P450 scc, P450 TxA(2), and 5alpha-reductase. Tested for in vivo activity, 3 and 8 (0.019 mmol/kg) decreased the plasma testosterone concentration in rats by 81% and 84% after 2 h.