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We describe a new sensitive and specific method for the quantification of serum malonate (malonic acid, MA), which could be a new biomarker for de novo lipogenesis (fatty acid synthesis). This method is based upon a stable isotope-dilution technique using LC-MS/MS. MA from 50 microl of serum was derivatized into di-(1-methyl-3-piperidinyl)malonate (DMP-MA) and quantified by LC-MS/MS using the positive electrospray ionization mode. The detection limit of the DMP-MA was approximately 4.8 fmol (500 fg) (signal-to-noise ratio = 10), which was more than 100 times more sensitive compared with that of MA by LC-MS/MS using the negative electrospray ionization mode. The relative standard deviations between sample preparations and measurements made using the present method were 4.4% and 3.2%, respectively, by one-way ANOVA. Recovery experiments were performed using 50 microl aliquots of normal human serum spiked with 9.6 pmol (1 ng) to 28.8 pmol (3 ng) of MA and were validated by orthogonal regression analysis. The results showed that the estimated amount within a 95% confidence limit was 14.1 +/- 1.1 pmol, which was in complete agreement with the observed X(0) = 15.0 +/- 0.6 pmol, with a mean recovery of 96.0%. This method provides reliable and reproducible results for the quantification of MA in human serum.

We describe a highly sensitive and specific method for the quantification of key regulatory oxysterols in biological samples. This method is based upon a stable isotope dilution technique by liquid chromatography-tandem mass spectrometry (LC-MS/MS). After alkaline hydrolysis of human serum (5 microl) or rat liver microsomes (1 mg protein), oxysterols were extracted, derivatized into picolinyl esters, and analyzed by LC-MS/MS using the electrospray ionization mode. The detection limits of the picolinyl esters of 4beta-hydroxycholesterol, 7alpha-hydroxycholesterol, 22R-hydroxycholesterol, 24S-hydroxycholesterol, 25-hydroxycholesterol, 27-hydroxycholesterol, and 24S,25-epoxycholesterol were 2-10 fg (5-25 amol) on-column (signal-to-noise ratio = 3). Reproducibilities and recoveries of these oxysterols were validated according to one-way layout and polynomial equation, respectively. The variances between sample preparations and between measurements by this method were calculated to be 1.8% to 12.7% and 2.9% to 11.9%, respectively. The recovery experiments were performed using rat liver microsomes spiked with 0.05 ng to 12 ng of oxysterols, and recoveries of the oxysterols ranged from 86.7% to 107.3%, with a mean recovery of 100.6%. This method provides reproducible and reliable results for the quantification of oxysterols in small amounts of biological samples.

A simultaneous method for quantification of four catechol estrogens, namely, 2-hydroxyestrone, 2-hydroxyestradiol, 4-hydroxyestrone, and 4-hydroxyestradiol by liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) was developed in a positive mode for analyzing a simple picolinyl derivatization. Reaction of these estrogens with picolinyl derivatization reagent resulted in the formation of di- or tri-picolinyl derivatives, and the derivatives exhibited single charged protonated molecules as base peaks in a positive mode in electrospray ionization/mass spectrometry (ESI-MS). Picolinyl derivatives of these catechol estrogens provided approximately 10 times greater ESI responses in LC-ESI-MS/MS (selected reaction monitoring) compared with those of underivatized molecules in a negative mode. The use of picolinyl derivatizatives, solid-phase extraction, and a 13C-labeled internal standard helped us in determining these catechol estrogens whose quantification limit was 20 pg for every sample. The present method was applied for quantifying these catechol estrogens in a biological sample.

We have developed a highly sensitive and specific method for the analysis of serum sterol profiles. Sterols in 1 mul of dried serum were derivatized into picolinyl esters (3beta-picolinate) and analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) using the electrospray ionization (ESI) mode. In addition to cholesterol, 19 cholesterol precursors, cholestanol, campesterol, sitosterol, and sitostanol were identified simultaneously. Quantitative analyses for the picolinyl esters of 11 available sterols were performed, and detection limits were found to be less than 1 pg on-column. Reproducibilities and recoveries of 8 noncholesterol sterols were validated according to one-way layout and polynomial equation, respectively. The variances between sample preparations and between measurements by this method were calculated to be 1.6% to 8.2% and 2.5% to 16.5%, respectively. The recovery experiments were performed using 1 mul aliquots of normal human serum spiked with 1 ng to 6 ng of sterols, and recoveries of the sterols ranged from 88.1% to 102.5% with a mean recovery of 98.1%. The present method provides reliable and reproducible results for the identification and quantification of neutral sterols, especially in small volumes of blood samples, which is useful for serological diagnosis of inherited disorders in cholesterol metabolism and for noninvasive evaluation of cholesterol biosynthesis and absorption in humans.

Treatment of aldosterone with 35% HCl in EtOH or in MeOH followed by the picolinyl derivatization gave the picolinyl derivative of aldosterone-ethyl ether, 8, or methyl ether, 9, as a single and well-shaped liquid chromatographic peak. Picolinyl derivatization of aldosterone produced 21-picolinyl derivative of 18,20-anhydro-hemiacetal derivatives, 6, with poor chromatographic peak with wide half-width. Further conversion of 6 to 8 required long reaction time (>4 h). Structure of each picolinyl or alkyl ether-picolinyl derivative, was carefully elucidated by nuclear magnetic resonance spectroscopy, electron ionization mass spectrometry and liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). Enhancement of sensitivity (approximately 10-fold) in positive-LC-ESI-MS/MS of aldosterone was confirmed by the use of the alkyl ether-picolinyl derivatization when compared to the underivatized molecule.

Aromatase, which is responsible for the conversion of androgens to estrogens, is a potential therapeutic target for the selective lowering estrogen level in patients with estrogen-dependent breast cancer. We prepared and tested series of the pyridine- and other heterocyclic ring-containing derivatives of 2- and 4-aminoestrones, estrone, and estradiol, compounds 5, 10, 12 and 15. The isonicotinyl derivatives of 2- and 4-aminoestrone, compounds 5c and 10c, were fairly potent competitive inhibitors of aromatase (K(i), 2.1+/-0.14 and 1.53+/-0.08 microM for 5c and 10c, respectively) and other compounds did not show, to a significant extent, the aromatase inhibitory activity. This result suggests that the isonicotinyl-substituted derivatives 5c and 10c would be accessible to the active site of aromatase.

We describe a highly sensitive and specific method for the quantification of serum 7alpha-hydroxy-4-cholesten-3-one (C4), which has been used as a biomarker for bile acid biosynthesis. This method is based upon a stable isotope dilution technique by liquid chromatography-tandem mass spectrometry (LC-MS/MS). C4 was extracted from human serum (2-50 mul) by a salting-out procedure, derivatized into the picolinoyl ester (C4-7alpha-picolinate), and then purified using a disposable C(18) cartridge. The resulting picolinoyl ester derivative of C4 was quantified by LC-MS/MS using the electrospray ionization mode. The detection limit of the C4 picolinoyl ester was found to be 100 fg (signal-to-noise ratio = 10), which was approximately 1,000 times more sensitive than the detection limit of C4 with a conventional HPLC-ultraviolet method. The relative standard deviations between sample preparations and between measurements by our method were calculated to be 5.7% and 3.9%, respectively, by one-way layout analysis. The recovery experiments were performed using serum spiked with 20.0-60.0 ng/ml C4 and were validated by a polynomial equation. The results showed that the estimated concentration with 95% confidence limit was 23.1 +/- 2.8 ng/ml, which coincided completely with the observed X(0) +/- SD = 23.3 +/- 1.0 ng/ml with a mean recovery of 93.4%. This method provides highly reliable and reproducible results for the quantification of C4, especially in small volumes of blood samples.

To study the stereochemical aspects of the aromatase reaction of androst-4-en-17-one (1) and its 5-ene isomer 4, competitive inhibitors of aromatase, the [19S-(3)H]- and [19R-(3)H]-labeled 19-hydroxy derivatives 2 and 5, were synthesized through NaB(3)H(4) reduction of the corresponding 19-aldehydes 3 and 6 as a key reaction. The hitherto unknown stereochemistry of the NaB(3)H(4) reduction was established based on the deuterium-labeling experiments with NaB(2)H(4). A comparison of (1)H-NMR spectra of the NaB(2)H(4) reduction products of 19-als 3 and 6 with those of the respective authentic steroids revealed that the ratios of 19S-(2)H to 19R-(2)H were 90 : 10 for the 4-ene steroid 2 and 70 : 30 for the 5-ene isomer 5, respectively. Jones oxidation of the [19S-(2)H]19-ols, followed by the non-labeled NaBH(4) reduction, gave the corresponding [19R-(2)H]19-ols 2 and 5 (R-(2)H : S-(2)H=90 : 10 for steroid 2 and 70 : 30 for steroid 5). The stereoselectively (3)H-labeled compounds 2 and 5 were similarly obtained in these sequences.

To gain insight into the mechanism for irreversible inactivation of aromatase by 6beta-bromoandrostenedione (1), one of the earliest discovered suicide substrates, in relation to the catalytic function of the enzyme, the 2,2-dimethyl derivative of compound 1, steroid 4, and its 6alpha-isomer 5, as well as 2-methyl-1,4-diene steroid 8 and its 6alpha-bromide 10, were synthesized. All of the steroids inhibited aromatase activity in human placental microsomes with apparent K(i)'s ranging between 10 and 81 nM. The 2,2-dimethyl-6beta- and 6alpha-bromo steroids 4 and 5 were extremely powerful inhibitors (K(i): 14 and 10 nM, respectively), but these two did not cause a time-dependent inactivation of aromatase in the presence of NADPH; in contrast, the 2-methyl-1,4-diene steroids 8 and 10 caused time-dependent inactivation with apparent k(inact) of 0.035 and 0.071 min(-1), respectively, in a suicide manner. These results indicate that the 2,2-dimethyl function of the 6beta-bromide 4 would prevent the inactivation of aromatase caused by inhibitor 1 in a suicide manner, probably through steric activity, whereas the 2-methyl group of steroid 8 did not significantly affect the suicidal inactivation by the parent 1,4-diene steroid, a typical suicide substrate.

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.

To gain insight into the binding aspects of 6alpha- and 6beta-methylandrostenediones (1 and 2), potent competitive inhibitors and effective substrates of aromatase, at the active site of the enzyme, we synthesized their 19-hydroxy and 19-oxo derivatives to determine their inhibition of aromatase activity as well as their aromatization rates in human placental microsomes. The 6beta- and 6alpha-methyl-19-ols 12 and 13 were produced from 19-(tert-butyldimethylsiloxy)androstenedione (6) in 6 steps in which the Grignard reaction of 5alpha,6alpha-epoxy steroid 8 with CH3MgBr was employed as a key reaction. Oxidation of the 19-ols 12 and 13 yielded the corresponding 19-als 14 and 15. The 6alpha-methyl steroids 13 and 15 were good competitive inhibitors of aromatase (Ki< or =100 nM), and their aromatization rates obtained by gas chromatography-mass spectrometric analysis were 110 and 205 pmol/min/mg protein, respectively. In contrast, the 6beta-methyl isomers 12 and 14 were non-competitive inhibitors, with Ki values of more than 500 nM, and they were aromatized at rates of 16 and 20 pmol/min/mg protein, respectively. These results reveal that there is a marked difference in binding to the active site between the 19-oxygenated 6alpha-methyl and 6beta-methyl inhibitors where the binding manner of the 6alpha-steroids, rather than the 6beta-isomers, is suitable as a substrate for aromatase.

4Beta,5beta-epoxy derivatives of 16alpha-hydroxyandrostenedione (2), one of the natural substrates for aromatase, and its 19-oxygenated compounds 4 and 5 were synthesized as mechanistic and catalytic probes for the enzyme reaction. Treatment of 16alpha-bromoandrostenedione (13) or its 19-hydroxy analog 19 which was prepared from 3beta-hydroxy-19-(tert-butyldimethylsiloxy)androst-5-en-17-one (16) in three steps, with H2O2 and NaOH followed by controlled alkaline hydrolysis with NaOH in aqueous pyridine stereospecifically yielded 4beta,5beta-epoxy-16alpha-ol 15 or 4beta,5beta-epoxy-16alpha,19-diol 22, respectively. Oxidation of 16beta-bromo-4beta,5beta-epoxy-19-ol 21 with pyridinium dichromate followed by controlled alkaline hydrolysis produced 4beta,5beta-epoxy-16alpha-hydroxy-19-al 24.

16Alpha-hydroxy-17-keto steroids, 1, 3, and 8, and their 17beta-hydroxy-16-keto isomers, 4, 5, and 9, were transformed into the corresponding 17beta-alkoxy-16-keto derivatives on treatment with trimethylsilyl iodide (TMSI) in the presence of alkyl alcohol in CHCl3 in poor to high yields.

Deoxygenation reaction of steroidal 16,17-ketols 1, 2 and 6 as well as their silyl ethers 3 and 7 and 16- and 17-iodoketone analogs 11, 12, and 14 with trimethylsilyl iodide (TMSI) or HI under various conditions was examined. The results indicate that the deoxygenation producing 16- and 17-ketones 9 and 8 proceeds through multiple reaction pathways; a direct iodination of a siloxy group of the ketol silyl ethers by iodide ion to give the iodoketones (path b), addition of TMSI to a carbonyl group of the ketol silyl ethers to yield diiodo derivatives 22 and 23 through iodo-bis-TMS compounds 20 and 21 (path a), and cleavage of ether bond of dimers 15-18 initially produced are, at least, involved. In these sequences, rearrangement of the 16-ketols 1 and 2 to the 17β-ketol 6 also plays a significant role. The yields of the ketones 9 and 8 and their relative amounts would be dependent on the relative importance of each pathway in the reaction.

[3β, 7, 7, 17α-2H4]Androst-5-ene-17β, 19-diol (6) and [3, 3, 7, 7, -2H4]androst-4-ene-17β, 19-diol (15-d4) were synthesized as internal standards for gas chromatographic-mass spectrometric analysis of the 19-hydroxylation of androst-5-en-17-one (1) and its 4-ene isomer 2, inhibitors of estrogen biosynthesis, using human placental aromatase. Treatment of [7, 7-2H2]3β-tosylate 3 with Zn-NaI-D2O, followed by reduction with NaBD4, gave compound 6 (d4, 79.8 atom%). Compound 15-d4 was synthesized via 3β, 17β-dihydroxy-5-en-7-one 10 as a key intermediate. Deoxygenation of the 5-en-7-one 10 and [7, 7-2H2]17β-hydroxy-4-en-3-one 13-d2, produced from compound 10 in two steps, with AlCl2D2 was used for the deuterium labeling reaction, producing compound 15-d4 (d4, 93.5 atom%). The 19-oxygenation products of aromatase inhibitors 1 and 2 could be analyzed, after NaBH4 reduction, as the corresponding 17β, 19-diol bis-trimethylsilyl ethers using the internal standards 6 and 15-d4.

Reaction of various steroidal 16, 17-ketols, 16α-hydroxy-17-ketones 1-3, and 15, 16β-hydroxy-17-ketone 4, and 17β-hydroxy-16-ketones 5-7, and 17, along with methyl ethers of 16α- and 17β-ketols, 1 and 5, with an excess of trimethylsilyl iodide (TMSI) or with HI in CHCl3, produced the deoxygenated products, a mixture of the corresponding 17-and 16-ketones, in low to quantitative yields, in which the 17-ketone was the major product in each case. When the 16β-deuterated 16α-ketol 3 and the 17α-deuterated 17β-ketol 7 were reached with TMSI for a brief period (15 min), the deuterium content at C-16β and C-17α of the recovered steroids 3 and 7 was reduced by 17 and 35%, respectively. The present results indicate that the deoxygenation proceeds not only through a direct iodination pathway producing α-iodoketone but also through other reaction pathways.

A series of 6α- and 6β-alkylestradiols (5 and 6) (alkyl : methyl, ethyl, n-propyl, n-pentyl, and n-heptyl) were synthesized as possible aromatase reaction products of 6-alkylandrost-4-ene-3, 17-diones and their Δ1-derivatives, potent competitive and mechanism-based inhibitors of aromatase. Treatment of 6-oxoestradiol with Grignard reagents followed by acid-catalyzed dehydration and subsequent catalytic hydrogenation over Pd-C gave the 6-alkylestradiols (5 and 6). GC-MS (electron impact mode) of trimethylsilyl derivatives of bis-trimethylsilyl derivatives of compounds 5 and 6 revealed that the 6α-alkyl compounds, 5, emerged with a longer retention time compared to the corresponding 6β-alkyl isomers, 6, where the retention time was in proportion to the length of the 6-alkyl chain in each series. In the MS, a molecular ion (M+) peak was the base peak for all the 6-alkylestrogens, with strong and characteristic fragment ion peaks corresponding to M+-131 and at m/z 325. A selected ion monitoring method using a molecular ion will be sensitive enough for analysis of the aromatization reaction of the 6-alkylandrogens.

To gain insight into the catalytic function of aromatase and its substrate specificity, we studied reversible inhibition of 16alpha-hydroxyandrostenedione (16alpha-OHAD) aromatization in human placental microsomes by several suicide substrates of androstenedione (AD) aromatization, including 4-hydroxyAD (1), 6-oxoAD (2) and its 19-hydroxy analogue 3, androst-5-ene-4,7,17-trione (4), and 10beta-acetoxyandrost-5-en-7,17-dione (5) that, in contrast, do not cause a suicide inactivation of 16alpha-OHAD aromatization. All inhibitors examined blocked 16alpha-OHAD aromatization in a competitive manner with apparent K(i) values ranging from 0.50 to 980 nM. The relative K(i) values between inhibitors 1-5 obtained in the 16alpha-OHAD aromatization experiments were markedly different from those obtained in the AD aromatization experiments. The results predict that all inhibitors examined bind to the 16alpha-OHAD binding site in a manner that does not cause suicide inactivation of 16alpha-OHAD aromatization. These findings would be useful for understanding the active (binding) site structure as well as the catalytic function of aromatase.

Aromatization of 16alpha-hydroxyandrostenedione (16alpha-OH AD) with aromatase in human placental microsomes was studied by gas chromatography-mass spectrometry (GC-MS) using 12,4,6,6,9alpha,16beta,17alpha-2H7]estriol as an internal standard. 16alpha-OH AD was incubated with the microsomes in the presence of NADPH in air. The metabolite was extracted with ethyl acetate and treated with NaBH4. The reduced product, estriol, was isolated by Sep-Pak C18 cartridge and then analyzed as the tris(trimethylsilyl)ether by a GC-MS (EI mode). The production of estriol was dependent upon protein concentration and incubation time. Apparent Km and Vmax values of the microsomal aromatase for 16alpha-OH AD were 568 nM and 25.5 pmol/min/mg protein, respectively. In this assay, aromatase activity, estriol formation, could be determined at a level as low as 1 pmol/min/mg protein. Aromatase inhibitors, 4-hydroxy- and 6-oxo-androstenediones, prevented the estriol formation in a competitive manner with 25 and 30 nM of apparent Ki values, respectively.

[2 beta,7,7,16 beta-2H4]16 alpha,19-Dihydroxyandrost-4-ene-3,17-dione (14) and [7,7,16 beta-2H3]3 beta,16 alpha,19-trihydroxyandrost-5-en-17-one (16), with high isotopic purity, respectively, were synthesized from unlabeled 3 beta-(tert-butyldimethylsiloxy)-androst-5-ene-17 beta-yl acetate (1). The deuterium introduction at C-7 was carried out by reductive deoxygenation of the 7-keto compound 3 with dichloroaluminum deuteride and that at C-2 beta and/or C-16 beta by controlled alkaline hydrolysis of 16-bromo-17-ketone 11 or 12 with NaOD in D2O and pyridine. [7,7-2H2]3 beta-Hydroxyandrost-5-en-17-one (6), obtained from compound 1 by a five-step sequence, was converted to compound 14 or 16 by an eight-step or seven-step sequence, respectively. The labeled steroids 14 and 16 are useful as internal standards for gas chromatography-mass spectrometry analysis of the endogenous levels.

Report an efficient deoxygenation of the 21-alkoxy group and the conversion of the 17α-hydroxy 20-ketone to a D-homosteroid upon treatment with TMSI in the presence of MeOH

To gain insight into the binding manner of androst-4-ene-6,17-dione (4) and its 5-en-4-one analog 9, good competitive inhibitors of aromatase, in the active site of the enzyme, their 19-oxygenated derivatives were evaluated as inhibitors of human placental aromatase. The 19-hydroxy steroids 6, 7, and 10 and the 19-oxo analogs 8 and 12 were much poorer competitive inhibitors than their corresponding parent 19-methyl steroids. Conversion of the 17-keto inhibitors 4, 6, and 10 to the 17beta-ols 5, 7, and 11, respectively, markedly decreased their affinity to the enzyme. The results suggest that steroids 4 and 9 would bind to the active site in a similar manner to that involved in the binding of the substrate androstenedione (1).

Androst-4-ene-3,6-dione derivatives 2-4 and 3 alpha-methoxy-4-en-6-one steroid 7 were prepared and tested for their ability to inhibit aromatase in human placental microsomes. The 16 alpha-bromide 2, the 16 alpha-alcohol 3, and the 3 alpha-methoxide 7 of this series were effective competitive inhibitors of aromatase with apparent Ki's of 150 nM, 1.18 microM, and 700 nM. Compound 2 caused a time-dependent, biphasic loss of aromatase activity in the presence of reduced nicotinamide adenine dinucleotide phosphate (NADPH) while compound 7 caused a time-dependent, pseudo-first order inactivation of the activity, with kinact's of 0.417 and 0.036 min-1 for compounds 2 and 7. NADPH and oxygen were required for the time-dependent inactivation and the substrate, androst-4-ene-3,17-dione, prevented it in each case.

To gain insight into the catalytic function of aromatase, we studied 19-oxygenation of 19-methyl-substituted derivative of the natural substrate androstenedione (AD), compound 1, with human placental aromatase by use of gas chromatography-mass spectrometry (GC-MS). Incubation of the 19-methyl derivative 1 with human placental microsomes in the presence of NADPH under an aerobic condition did not yield a detectable amount of [19S]19-hydroxy product 2 or its [19R]-isomer 3 when the product was analyzed as the bis-methoxime-trimethylsilyl (TMS) derivative by GC-MS; moreover, the production of estrogen was not detected as the bis-TMS derivative of estradiol (detection limit: about 3 ng and 10 pg per injection for the 19-ol and estradiol, respectively). The results reveal that the 19-methyl steroid 1 does not serve as a substrate of aromatase, although it does serve as a powerful inhibitor of the enzyme.

Reduction of a double bond at C-1 of 1,4-dien-3-one steroids 7 and 8 with LiAl2H4 in THF or NaB2H4 in MeOH and H2O gave stereospecifically [1alpha-2H]-labeled 4-en-3-one steroids 9 and 10, respectively. When the deuterated solvents, MeO2H and 2H2O, were used for the reaction of steroid 8 with NaB2H4, [1alpha,2xi-2H2]-labeled compound 10 was produced. This indicates that the reaction proceeds through the initial hydride attack at the C-1alpha position, followed by ketonization of the 2-en-3-ol intermediate.

C(10)-C(19) bond cleavage reaction of 19-hydroxy- and 19-oxoandrost-4-ene-3,6,17-triones (5, 6) was explored under various conditions. Treatment of steroids 5 and 6 with KOH in MeOH gave the A-ring aromatized product 6-oxoestrone (11) in a fair yield, respectively, in contrast, the treatment with a weak base yielded 4-methyl steroid 17 (20%) in the case of 19-alcohol 5 or 19-nor-Delta(5(10))-steroid 9 (12-67%) along with compound 11 (6-27%) in the case of 19-aldehyde 6. Reaction of compound 6 with HCl in MeOH produced 3-methyl ethers of 6-oxoestrone and Delta(6)-estrone, compounds 12 and 14 (ca. 20% each). Thus, 6-oxosteroids 5 and 6 showed unique C(10)-C(19) bond cleavage reactions with a base or acid.

Conformational analysis of potent competitive inhibitors of aromatase, androst-4-enes 5, as well as 2, 4-diene steroids 3, 4, and 6 was carried out, using theoretical calculations, to determine the stereochemistry of their aromatase-catalyzed oxygenation. In the steroids examined, both the 19-alcohols and the 19-aldehydes favor the above-A ring conformation among the possible three in each. The results suggest that the 3-deoxy steroid 5a as well as the 2, 4-diene steroids 4a and 6a would be oxygenated at C-19 by aromatase through the same stereomechanism as that involved in the androstenedione aromatization.

Estrogen, if it is produced in the gastrointestinal tract, may overflow into the systemic circulation in the case of increased portal-systemic shunting. This idea is in accord with a significant step-up in serum estradiol (E2) concentration in the portal vein of rats, compared with that in the artery. Gene expression of aromatase, estrogen synthetase, was demonstrated by RT-PCR in the gastric mucosa of male and female adult rats, equivalent to that in the ovary. Aromatase activity and production of E2 in the gastric mucosa were demonstrated by 3H2O assay and gas chromatography-mass spectrometry, and they were inhibited by aromatase inhibitor, 4-hydroxyandrostenedione. Conversion of 14C-androstenedione to 14C-E2 through 14C-testosterone in cultured gastric mucosa was also demonstrated. Parietal cells exhibited strong signals for aromatase mRNA and immunoreactive protein by in situ hybridization histochemistry and immunohistochemistry. Estrogen receptor α mRNA and immunoreactive protein were demonstrated in hepatocytes by RT-PCR, in situ hybridization histochemistry, and immunohistochemistry. Total gastrectomy reduced portal venous E2 concentration, without changing systemic E2 concentration, together with down-regulation of estrogen receptor α mRNA level in the liver. These findings indicate that gastric parietal cells play a potent endocrine role in secreting estrogen that may function as a regulator of the gastro-hepatic axis.

The time-dependent inactivation of aromatase by epoxy analogs of the good aromatase inhibitors, androst-4-ene-6,17-dione (3) and androst-5-ene-4,17-dione (7), 4beta,5beta-epoxy and 5beta,6beta-epoxy compounds 10 and 13 and their 19-oxo derivatives 11 and 14, was examined in either the presence or absence of NADPH. The 4beta,5beta-epoxy-19-oxo steroid 11 along with the 19-methyl-5beta,6beta-epoxide 13 inactivated human placental aromatase in a mechanism-based manner, in the presence of NADPH, with rate constants for inactivation (k(inact)) of 0.133 min(-1) for steroid 11 and 0.100 min(-1) for steroid 13, whereas the two other steroids, 10 and 14, did not. On the other hand, none of four epoxides studied caused time-dependent inactivation of aromatase in an affinity-labeling manner in the absence of NADPH. These results are the first report showing that inhibitors 11 and 13 are suicide substrates having an epoxyketone structural feature.

To gain insight into the aromatization sequence of androst-4-ene-3,6,17-trione (1), a suicide substrate of aromatase, the aromatization of its 19-hydroxy and 19-oxo analogs 2 and 3 with human placental microsomes, was studied using GC-MS. Steroids 2 and 3 were separately incubated with the microsomes in the presence of NADPH in air. The GC-MS analysis of the trimethylsilyl derivative of the aromatization product indicated that both the 19-oxygenated steroids 2 and 3 were aromatized to yield 6-oxoestrogens, 6-oxoestrone (4) and 6-oxoestradiol (5), in each experiment. The aromatization rates of substrates 2 and 3 were 605+/-48 and 1794+/-75 pmol/mg protein/10 min, respectively. These relatively higher rates, compared to that of the parent steroid 1 (73.2+/-6.6 pmol/mg protein/10 min), indicates that the suicide substrate 1 is aromatized through the 19-oxygenated intermediates 2 and 3.

To gain insight into the relationships between the aromatase inhibitory activity of 6-alkyl-substituted androgens, potent competitive inhibitors, and their ability to serve as a substrate of aromatase, we studied the aromatization of a series of 6alpha- and 6beta-alkyl (methyl, ethyl, n-propyl, n-pentyl and n-heptyl)-substituted androst-4-ene-3,17-diones (ADs) and their androsta-1,4-diene-3,17-dione (ADD) derivatives with human placental aromatase, by gas chromatography-mass spectrometry. Among the inhibitors examined, ADD and its 6alpha-alkyl derivatives with alkyl functions less than three carbons long, together with 6beta-methyl ADD, are suicide substrates of aromatase. All of the steroids, except for 6beta-n-pentyl ADD and its n-heptyl analogue as well as 6beta-n-heptyl AD, were found to be converted into the corresponding 6-alkyl oestrogens. The 6-methyl steroids were aromatized most efficiently in each series, and the aromatization rate essentially decreased in proportion to the length of the 6-alkyl chains in each series, where the 6alpha-alkyl androgens were more efficient substrates than the corresponding 6beta isomers. The Vmax of 6alpha-methyl ADD was approx. 2.5-fold that of the natural substrate AD and approx. 3-fold that of the parent ADD. On the basis of this, along with the facts that the rates of a mechanism-based inactivation of aromatase by ADD and its 6alpha-methyl derivative are similar, it is implied that alignment of 6alpha-methyl ADD in the active site could favour the pathway leading to oestrogen over the inactivation pathway, compared with that of ADD. The relative apparent Km values for the androgens obtained in this study are different from the relative Ki values obtained previously, indicating that there is a difference between the ability to serve as an inhibitor and the ability to serve as a substrate in the 6-alkyl androgen series.

19-Nor (2) and 5 alpha-reduced (3) derivatives of androst-4-ene-3,6,17-trione (1) as well as 5 alpha-androstan-17-ones 4-6 were tested for their abilities to inhibit aromatase in human placental microsomes. All the steroids except 5 alpha-6-one 4 were fair to good competitive inhibitors of the enzyme, with apparent Ki's ranging from 50 to 820 nM in which 5 alpha-3-one 5 was the most potent among them. The inhibitory activities of the 19-nor and 5 alpha-reduced derivatives (2 and 3) were less potent than that of the parent compound 1. Inhibitor 2 caused a time-dependent, pseudo-first-order inactivation of aromatase activity with a rate constant for inactivation of 0.148 min-1 in the presence of NADPH in air. The substrate androstenedione prevented the inactivation and L-cysteine did not protect aromatase from the inactivation.

[1 beta-3H]16 alpha-Hydroxyandrostenedione (16 alpha-OHA) (715 mCi/mmol) was prepared from commercially available [1 beta-3H]androstenedione (A) by the microbiological method with Streptomyces roseochromogenes and its structure and purity were determined by chromatographic and reverse isotope dilution methods. When [1 beta-3H]16 alpha-OHA was incubated with human placental microsomes and reduced nicotinamide adenine dinucleotide phosphate (NADPH), 3H2O-release into the medium was dependent upon protein concentration and incubation time. An apparent Km and Vmax of the microsomal aromatase for the [1 beta-3H]substrate were 650 nM and 34 pmol/min/mg protein, respectively. In this assay, aromatase activity could be determined as low as 0.1 nmol estrogen formation/min/mg protein. 3-Deoxyandrostenedione, a potent competitive inhibitor of the A aromatization, also blocked the 16 alpha-OHA aromatization in a competitive manner with Ki of 15 nM.

16 alpha-Hydroxyandrost-4-ene-3,17,19-trione (10) was synthesized from the 16 alpha-hydroxy-6 beta,19-epoxy-17-one 3 via protection of the 16 alpha-hydroxy function as its tert-butyldimethylsilyl ether or acetate. Reductive cleavage of the epoxy ring of the silyl ether 4 or the acetate 5 with zinc dust gave the 19-alcohol 6 or 7, which was treated with pyridinium dichromate or Jones reagent, respectively, and then hydrolyzed with diluted sulfuric acid, yielding the desired steroid 10. 3 beta,16 alpha-Dihydroxyandrost-5-ene-17,19-dione (14) was also synthesized from 5 alpha-bromo-3 beta,16 alpha-diacetoxy-6 beta, 19-epoxyandrostan-17-one (11) through the intermediates 12 and 13 with the 3 beta- and 16 alpha-hydroxy functions protected as their acetates in a reaction sequence similar to that above.

Reaction of the 3-oxo-4-androsten-derivative 1 or 4 with 1.2eq of o-iodosylbenzoic acid in methanolic KOH gave the methoxy products, the 4-methoxide 2 or 5 and the 6β-methoxide 3 or 6, along with the dehydrated compound, the 4, 6-dienone 7 or 8, respectively. Treatment of the 6-methoxide 3 or 6 with trimethylsilyl iodide yielded the 5α-androstane-3, 6-dioxo derivative 11 or 12 in high yield. The same hypervalent oxidation of the 17-oxo steroid 15, 18, 21 or 24 using excess iodine and a longer reaction time produced the corresponding 16α-hydroxy-17, 17-dimethylacetal 16, 19, 22 or 25, which was converted into the 16α-hydroxy-17-one 17, 20, 23 or 26 by treatment with diluted HCl in every case.

Synthesis of 1, 3, 5 (10)-estratriene-3, 16α, 17β-triol-d6 and -d7 (4), 3, 16α-dihydroxy-1, 3, 5 (10)-estratrien-17-one-d5 (5) and sodium 3, 17β-dihydroxy-1, 3, 5 (10)-estratrien-16α-yl-β-D-glucopyranosuronate-d6 (8) is described. Treatment of 2, 4, 16α-tribromo-3-hydroxy-1, 3, 5 (10)-estratrien-17-one (1) with sodium hydroxide-OD in deuterium oxide-pyridine under controlled conditions gave the [16β-2H] 16α-hydroxy-17-one (2). The ketol 2 was converted into the triol-d6 (4) via sodium borodeuteride reduction in the presence of palladium chloride. Similar treatment of the 17-ethyleneacetal of 2 followed by acid hydrolysis gave compound 5-d5. Reaction of 2 with methyl 1-bromo-1-deoxy-2, 3, 4-tri-O-acetyl-α-D-glucopyranosuronate using silver carbonate as a catalyst yielded the 16-monoglucuronide acetate methyl ester (6). The reductive removal of the bromines of 6 and subsequent alkaline hydrolysis gave the glucuronide-d6 (8). Mass spectrometric analysis showed compounds 4, 5, and 8 to have good isotopic purity.

The reaction of 21-bromo-3β-hydroxy-17α-methoxypregn-5-en-20-one (5) with NaOCH3 in MeOH under reflux gave the 21-aldehyde 9 in modest yield along with the 21-hydroxy derivative 6. The 21-acetates 8 and 13 were obtained in good yields by prolonged reaction of the 21-bromides 5 and 11 with CH3COO-.

Reaction of the corticoids 1-6 with iodotrimethylsilane in MeCN produced the regiospecifically deoxygenated products, 21-hydroxy-20-ketones 7-11, in moderate to high yields. On the other hand, employment of CHCl3 as a solvent resulted in lower yields of the 21-ketols 7 and 8, accompanied by increased production of the 20-ketones 12 and 13. The 21-ketol 7 was efficiently converted into the 20-ketone 12, while the 17α-hydroxy isomer 14 was recovered unchanged. Rapid and quantitative conversion of the 21-iodo-20-ketone 17 into the 20-ketone 12 by this iodosilane treatment suggests that the conversion of the ketol 7 into the ketone 12 probably occurs via the iodide 17.

Preparation de 3 derives de l'hydroxy-21 pregnene-4dione-3,20 a partir de l'hydroxy-3β pregnene-5one-20, par bromation puis oxydation par CrO 3 , suivie d'une hydrolyse par le systeme K 2 CO 3 −H 2 O/acetone

A method for separatory determination of d- and l-pentazocine in blood plasma by radioimmunoassay has been developed. In order to obtain antiserum optically specific to l-pentazocine a hapten-carrier conjugate was prepared from l-pentazocine 2'-carboxymethyl ether by coupling with bovine serum albumin (BSA) using the mixed anhydride method. The antiserum elicited in the rabbit by immunization with this antigen proved to be highly specific to l-pentazocine by cross-reaction studies with the d-form and principal metabolites. The anti-dl-pentazocine antiserum was similarly produced in the rabbit immunized with the dl-pentazocine 2'-caboxymethyl ether-BSA conjugate. The plasma level of d-pentazocine could be estimated indirectly by subtracting the observed value of the l-enantiomer from that of total pentazocine. The plasma concentration of d- and l-pentazocine in man after administration of an officinal dose of the racemate was determined by the established method.

Oxygenation of 2,4-dibromoestrogens with nitric acid in acetic acid gave the corresponding 2,4-dibromo-10β-hydroxy-1,4-dien-3-one derivatives in excellent yields. These 10β-hydroxy-dienones were subjected to catalytic hydrogenation over palladium-on-charcoal to afford the saturated 5ξ-3-oxo derivatives, in very high yields. The saturated products were then converted into the corresponding 19-nor steroids by treatment with acid, perchloric acid, p-toluenesulfonic acid or Nafion-H

16α-Hydroxy-4-androstene-3, 17-dione-d5 (4) and 3β, 16α-dihydroxy-5-androsten-17-one-d6 (10) were synthesized. Treatment of 16α-bromo-5-androstene-3, 17-dione (2) with deuterium oxide and methanol-OD gave the 4-en-3-oxo derivative-d 3. The bromide 3 was converted into the 16α-hydroxide-d5 4 via controlled alkaline hydrolysis using sodium hydroxide-OD in deuterium oxide-pyridine. 3β-Hydroxy-5-androsten-17-one-d5 (8), which was obtained from 17, 17-ethylenedioxy-5-androsten-3-one (5) via treatment with potassium tert-butoxide in tert-butanol-OD, followed by lithium aluminum tri-tert-butoxydeuteride reduction and then acid hydrolysis, was derivatized to the 16α-bromide 9 by treatment with cupric bromide. The bromide 9 was similarly hydrolyzed to yield the 16α-hydroxide-d6 10.

Synthesis of 16..cap alpha..-hydroxy-17-oxo steroids and 3..beta..,16..cap alpha..-dihydroxy-5-17-oxoandrosten-3-yl sulfate from 16..cap alpha..-bromo-17-oxo steroids and the reaction mechanism of the controlled alkaline hydrolysis are described. Treatment of the bromo ketones with NaOH in aqueous DMF gave the 16..cap alpha..-hydroxy 17-ketones stereoselectively in 95% yield without formation of other ketols. The sodium salt of 3-sulfate was also obtained in one step in 85% yield from the corresponding bromo ketone. Isotope-labeling experiments and time-course studies showed that equilibration between the 15-bromo epimers occurs by the reaction mechanism described in this report. The 16..beta..-morpholino derivaive obtained by reaction with morpholine was shown to be an isomerized product of the 16..cap alpha.. isomer which is produced also by S/sub N/2 displacement of the 16..beta..-bromine. The mechanism of ketol rearrangement to the 17..beta..-hydroxy-16-oxo compound was found to involve a hydration to the carbonyl function. The new hydration dehydration mechanism is proposed for the ketol rearrangement.