ABSTRACT
The mechanistic aspects of the alkali-catalyzed rearrangement of 16alpha-hydroxy-17-keto steroid 1 to 17beta-hydroxy-16-keto steroid 2 are elucidated by use of (18)O- and deuterium-labeling experiments. The (18)O-labeling experiments refute the gem-hydration-quasi-diaxial dehydration mechanism for the rearrangement previously proposed and support the conventional enolization mechanism. Moreover, equilibrium by gem-hydration-dehydration occurs at the C-17 carbonyl more efficiently than at the C-16 carbonyl. Enolization rate of a carbonyl group at C-16 of 17beta-ketol 2 toward the C-17 position (k(16,17)) was about 8-10 times higher than those of 16alpha-ketol 1 toward the C-16 position (k(17,16)) and ketol 2 toward the C-15 position (k(16,15)). The marked deuterium-isotope effect on each enolization was observed with k(H)/k(D) ranging between 5.4 and 8.8. The present findings reveal that the initial hydration-dehydration equilibration at the C-17 carbonyl of ketol 1 followed by enolization of the carbonyl gives the ene-diol intermediate that isomerizes quantitatively to the 16-keto isomer of which the 16-carbonyl moiety enolizes preferentially toward the C-17 position rather than the C-15 position, yielding the ene-diol. Computational calculations of ground state energies of ketols 1-M and 2-M, trans-cyclohexane/cyclopentane structures, and their activation energies in the rearrangement support the dynamic aspects of the rearrangement as well as the kinetics data of the enolization.
Subject(s)
Steroids/chemistry , Acetylation , Isomerism , Magnetic Resonance Spectroscopy , Mass SpectrometryABSTRACT
Diels-Alder reactions between N-phenylmaleimide, acting as the dienophile, and 2(1H)-pyridones having a methoxy or a chloro substituent, were carried out, under atmospheric and high pressure conditions, to give the corresponding isoquinuclidine derivatives. Stereoselectivity of the Diels-Alder reactions was studied using molecular orbital calculations.
Subject(s)
Maleimides/chemistry , Pyridines/chemistry , Magnetic Resonance Spectroscopy , Models, Molecular , Quinuclidines/chemistry , Spectrophotometry, Infrared , StereoisomerismABSTRACT
To explore a stereochemistry of hydrogen removal at C-1 of the powerful aromatase inhibitor 2-methyleneandrostenedione (1), of which the A-ring conformation is markedly different from that of the natural substrate androstenedione (AD), in the course of the aromatase-catalyzed A-ring aromatization producing 2-methylestrone (2), we synthesized [1alpha-2H]labeled steroid 1 and its [1beta-2H]stereoisomer, and the metabolic fate of the C-1 deuterium in aromatization was analyzed by gas chromatography-mass spectrometry (GC-MS) in each. Parallel experiments with the natural substrates [1alpha-2H] and [1beta-2H]ADs were also carried out. The GC-MS analysis indicated that 2-methyl estrogen 2 produced from [1alpha-2H]labeled substrate 1 retained completely the 1alpha-deuterium (1beta-H elimination), while product 2 obtained from [1beta-2H]isomer 1 lost completely the 1beta-deuterium. Stereospecific 1beta-hydrogen elimination was also observed in the parallel experiments with the labeled ADs as established previously. The results indicate that biochemical aromatization of the 2-methylene steroid 1 proceeds through the 1beta-hydrogen removal concomitant with cleavage of the C(10)-C(19) bond, yielding 1(10),4-dienone 9, in a similar manner to that involved in AD aromatization. This would give additional evidence for the stereomechanisms for the last step of aromatization of AD, requiring the stereospecific 1beta-hydrogen abstraction and cleavage of the C(10)-C(19) bond, and for the enolization of a carbonyl group at C-3 in the A-ring aromatization.
Subject(s)
Androstenedione/analogs & derivatives , Aromatase Inhibitors/metabolism , Hydrogen/chemistry , Androstenedione/metabolism , Deuterium/chemistry , Isomerism , Molecular Conformation , Molecular StructureABSTRACT
Diels-Alder reactions of 3-nitro-2(1H)-quinolones with 1,3-butadiene derivatives were carried out to give the phenanthridone derivatives under both atmospheric and high pressure conditions. Furthermore, the reactivity of 3-substituted 2(1H)-quinolones acting as a dienophile with 2,3-dimethyl-1,3-butadiene was examined using molecular orbital (MO) calculation.
Subject(s)
Nitro Compounds/chemical synthesis , Phenanthridines/chemical synthesis , Quinolones/chemical synthesis , Butadienes , Chromatography, Thin Layer , Indicators and Reagents , Magnetic Resonance Spectroscopy , Methylation , Spectrophotometry, InfraredABSTRACT
A novel Diels-Alder (DA) reaction with 4-nitro-1(2H)-isoquinolones acting as the dienophile afforded 5(6H)-phenanthridone derivatives. The DA reaction of 4-nitro-1(2H)-isoquinolone with 1-methoxy-1,3-butadiene gave biologically active 5(6H)-phenanthridone possessing in a high yield. Regioselectivity of 4-nitro-1(2H)-isoquinolones with 1-methoxy-3-silyloxy-1,3-butadiene was calculated using molecular orbital (MO) calculations.
Subject(s)
Isoquinolines/chemical synthesis , Nitro Compounds/chemical synthesis , Butadienes/chemistry , Chemical Phenomena , Chemistry, Physical , Chromatography, Thin Layer , Indicators and Reagents , Magnetic Resonance Spectroscopy , Models, Molecular , Molecular Conformation , Spectroscopy, Fourier Transform InfraredABSTRACT
The reactions of benzo[h]quinoline N-oxide with methylsulfinyl carbanion and deuterated methylsulfinyl carbanion, respectively, were studied theoretically. Differences in yield between these reactions were explained using ab initio molecular orbital methods by considering the zero-point energy correction and the barrier penetration effect. In these reactions, two transition states affected the total reaction rate. The hydrogen- or deuterium-transfer step played a significant role, accounting for the difference in reaction rates.
Subject(s)
Cyclic N-Oxides/analysis , Cyclic N-Oxides/metabolism , Models, Chemical , Quinolines/analysis , Quinolines/metabolism , Benzoquinones/analysis , Benzoquinones/chemistry , Benzoquinones/metabolism , Cyclic N-Oxides/chemistry , Isotopes , Quinolines/chemistry , Sulfuric Acid Esters/analysis , Sulfuric Acid Esters/chemistry , Sulfuric Acid Esters/metabolismABSTRACT
Cycloadditions of 1,3-butadiene derivatives having an electron-rich group at the 1-position with 4- or 3-substituted 2(1H)-quinolones were carried out to give the richly functionalized phenanthridines under both atmospheric and high pressure conditions. Furthermore, the reactivity of 4- or 3-substituted 2(1H)-quinolones acting as a dienophile with 1-substituted dienes was examined using MO calculation.
Subject(s)
Butadienes/chemistry , Quinolones/chemistry , Butadienes/metabolism , Cyclization , Molecular Conformation , Quinolones/metabolismABSTRACT
To gain insight into the nature of the substrate binding site and the catalytic function of aromatase, we studied the inhibition of androstenedione aromatization by 4beta,5beta-epoxy-16alpha-hydroxyandrostenedione (4) and its 19-hydroxy and 19-oxo derivatives, 5 and 6, as well as the biochemical aromatization of these steroids in human placental microsomes. The 19-methyl and 19-oxo compounds, 4 and 6, were weak competitive inhibitors of aromatase, with apparent K(i) values of 246 microM and 270 microM, respectively, whereas the 19-hydroxy compound 5 inhibited aromatase in a non-competitive manner with the K(i) of 135 microM. The 19-methyl compound 4 inactivated aromatase in a time-dependent manner with k(inact) of 0.213 min(-1) in the presence of NADPH in air, but the other two did not cause it. The conversion of the three epoxides into estrogen, as well as 19-oxygenation of 19-methyl steroid 4 with human placental microsomes in the presence of NADPH in air, were not detected by gas chromatography-mass spectrometry. The present results are consistent with the two binding sites theory in the active site of aromatase.
Subject(s)
Androstenedione/analogs & derivatives , Androstenedione/pharmacology , Aromatase Inhibitors , Epoxy Compounds/pharmacology , Estriol/biosynthesis , Placenta/enzymology , Androstenedione/chemistry , Aromatase/metabolism , Enzyme Inhibitors/pharmacology , Epoxy Compounds/chemistry , Fetus/drug effects , Fetus/enzymology , Humans , Placenta/drug effectsABSTRACT
Cycloaddition of 1-methyl-2(1H)-quinolones with electron-withdrawing groups such as methoxycarbonyl, cyano, and acetyl groups, at the 3 or 4-position with 2,3-dimethoxy- and 2-(trimethylsilyloxy)-1,3-butadienes afforded stereoselectively phenanthridone derivatives under atmospheric and high pressures. Furthermore, regioselectivities of the cycloaddition of 3- or 4-substituted 2 (1H)-quinolones with 2-(trimethylsilyloxy)-1,3-butadiene were examined using MO calculation.