Synthesis of 16α-3H androgen and estrogen substrates for 16α-hydroxylase

The synthesis of 16α-³H androgens and estrogens is described. 1-(³H)-Acetic acid in the presence of zinc dust reacts with 16α-bromo-17-ketosteroids to produce 16α-³H-17-ketosteroids. This chemical reaction was used to prepare 16α-³H-dehydroepiandrosterone (I) and 16α-³H-estrone acetate (XI) from 16α-bromo-dehydroepiandrosterone (X) and from 16α-bromo-estrone acetate (XII), respectively. Using appropriate microbiological techniques, it was possible to convert these radiolabelled substrates into 16α-³H-androstenedione (II) and 16α-³H-estradiol-17β (VII). 16α-³H-Estrone (VI) was obtained by the chemical hydrolysis of 16α-³H-estrone acetate. The label distribution as determined by microbiological 16α-hydroxylations indicated a specific labelling of 77% for androgens and 65% for estrogens in the 16α position. These substrates can be used for measuring the 16α hydroxylase activity, an important step in the biosynthesis of estriol (VIII) and estetrol (IX).     

16α-hydroxylation of progesterone by a strain ofactinomyces globosus

В систематическое исследование трансформации свойств Actinomycetes было было установлено, что 17 из 76 видов тестировани е преобразованы прогестерон по 16 га-гидрокси -п рогестерона. Оптимальные условия для этой трансформац ии были изучены этой трансформации б ыли изучены следующие результат ы:

1. (1)
   Оптимальное рН для данного типа трансформации была 6–7. На нижней hydroxylation ценностей была меш ает.     
   
   

Species and Tissue Distribution of Proteins Binding 16α,17α-Cycloalkanoprogesterone Derivatives

The binding of [³H]progesterone and [³H]16,17-cycloalkanoprogesterones to proteins from rat, rabbit, and human uteri and other organs was studied. We found that 16,17-cycloalkanoprogesterone derivatives display affinities for the uterine progesterone receptors comparable with that of the natural hormone and no substantial species differences in the affinity. Rabbit uterus was found to have no proteins distinct from the progesterone receptor that specifically bind [³H]16,17-cycloalkanoprogesterones. At the same time, in the human uterus, we found another protein that binds some of these progesterone derivatives; it turned out to be similar to the protein from rat uterus. A similar protein with the same selectivity and affinity for steroids was also found in rat and human kidneys. Blood serum, liver, lung, and a number of other tissues were found to contain a protein of the third type that binds the same 16,17-cycloalkanoprogesterones and exhibits submicromolar K _d values for these steroids and a very low affinity for progesterone. We speculated that the introduction of a bulky substituent adjacently to the 17-side chain of progesterone could result in a change in the general biodynamics of the derivative including its transport, uptake, and accumulation in tissues, which may determine the selectivity of its effect.     

Unusual oxidative transformations of a steroidal 16α,17α,22-triol

A number of unexpected reactions were observed during attempts to invert configuration at C16 in 16α,17α,22-triol 3a. The PDC oxidation of 3a produced the D-seco-aldehyde 4a. Analogous compound 4b was obtained by Swern oxidation of the 16α,17α-dihydroxy-22-O-TES-ether 3b in addition to the desired 16-ketone 7. The unprotected triol 3a yielded pentacyclic products 5 and 6 under similar conditions. The Mitsunobu reaction of the triol 3a afforded 16-ketone 8 with inverted configuration of the side chain. During heating of a solution of 3a in THF with NaH at reflux autoxidation to the 16-ketone cyclic hemiketal 5, identical to one of the Swern oxidation products, took place.     

Transformation of 16-dehydroprogesterone and 17α-hydroxyprogesterone by Mucor piriformis

Mucor piriformis was used to study the mode of transformation of 16-dehydroprogesterone (I, pregna-4, 16-diene-3, 20-dione) and 17-hydroxyprogesterone (II, 17-hydroxypregn-4-ene-3, 20-dione). Biotransformation products formed from I were 14-hydroxypregna-4, 16-diene-3, 20-dione (Ia), 7, 14-dihydroxypregna-4, 16-diene-3, 20-dione (Ib), 3, 7, 14-trihydroxy-5-pregn-16-en-20-one (Ic), and 3, 7, 14-trihydroxy-5-pregn-16-en-20-one (Id). Metabolites Ic and Id appear to be hitherto unknown. Time-course studies suggested that the transformation is initiated by hydroxylation at the 14-position (Ia) followed by hydroxylation at the 7-position (Ib). Microsomes (105,000 g sediment) prepared from 16-dehydroprogesterone-induced cells hydroxylate I to its 14-hydroxy derivative (Ia) in the presence of NADPH. Incubation of Ia with the organism resulted in the formation of Ib, Ic and Id. Biotransformation products formed from compound II were 17, 20-dihydroxypregn-4-en-3-one (IIa), 7, 17-dihydroxypregn-4-ene-3, 20-dione (IIb), 6, 17, 20-trihydroxypregn-4-en-3-one (IIc) and 11, 17, 20-trihydroxypregn-4-en-3-one (IId). Time-course studies indicated that IIa is the initial product formed, which is further hydroxylated either at the 6 or 11 position. Incubation of IIa with the organism resulted in the formation of IIc and IId. Reduction of the 4-en-3-one system and 20-keto group has not been observed before in organisms of the order Mucorales. In addition, M. piriformis has been shown to carry out hydroxylation at the C-6, C-7, C-11 and C-14 positions in the steroid molecules tested.     

Molecular docking and 3D-QSAR of 16α,17α-cycloalkanoprogesterone derivatives as ligands of the progesterone receptor

A series of 42 (pregna-D′-pentarane) steroid ligands was used to generate models predicting ligand affinity to the progesterone receptor. The best result (Q ² = 0.91) was obtained using a combination of molecular docking, molecular dynamics simulation and artificial neural networks. Good predictive power of the model was validated using a group of 8 pentaranes synthesized separately and tested in vitro (R _test ² = 0.77). This model can be used for determination of ligand-receptor binding affinity and accurate ranking of binding capacity of compounds tested.     

16α,17α-Cycloalkane Derivatives of Progesterone Intensively Bind to a Rat Serum Protein

The interaction of 6-methyl-[1,2-³H]16,17-cyclohexanoprogesterone with rat serum proteins has been studied. Specific binding of this ligand characterized by K _d = 0.36 ± 0.10 M and concentration of binding sites (B_max) of about 1 M (27.8 ± 12.5 pmol/mg total protein) was found. According to competitive analysis, the affinity of the studied progestins to a protein that differs from transcortin was to some extent correlated with their hydrophobicity. The dissociation kinetics of ³H-ligand–protein complexes were biphasic, the binding sites forming stable and labile complexes with ³H-ligand being eluted in the same region during ion-exchange chromatography. In overall properties, the serum protein differs from the progesterone receptor and the pregna-D"-pentarane-specific protein from rat uterus. It is suggested that the revealed protein may provide high progestagenic activity of 6-methyl-16,17-cyclohexanoprogesterone by prolonging its retention in the bloodstream.     

Immunological determination of hydroxylated 6α-fluor-16α-methyl deoxycorticosterone derivatives in fungal steroid transformation

Summary Antisera and monoclonal antibodies were raised against the 9 and 11 hydroxylated derivatives of 6-fluor-16-methyl deoxycorticosterone via 3-0-carboxy-methyloxim-bovine serum albumin immunogenic conjugates. The properties of the antibodies and several immunoassay systems were evaluated including an enzyme immunoassay with nitrocellulose as the solid phase and an insoluble, colored reaction product allowing visual evaluation of assays. The performance of the techniques was evaluated for the industrial important fungus, Curvularia lunata.Abbreviations AP alkaline phosphatase - BCIP 5-bromo-4-chloro-3-indolyl phosphate - BSA bovine serum albumin - DMF dimethyl formamide - EDC 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide - ELISA enzyme linked immunosorbent assay - FMDOC 6-fluor-16-methyl deoxycorticosterone - MAB monoclonal antibodies - NC nitrocellulose - RIA radioimmunoassay - TBS TRIS buffered saline - TLC thin layer chromatography Dedicated to Professor Dr. H. J. Rehm on the occasion of his 60th birthday     

Partial purification and kinetics of oestriol 16α-glucuronyltransferase from the cytosol fraction of human liver

An enzyme that conjugates the 16α-hydroxyl group of oestriol with glucuronic acid was found in the cytosol fraction of human liver. The enzymic activity could not be sedimented when the cytosol fraction was centrifuged at 158000g_av. for 120min. The oestriol 16α-glucuronyltransferase was purified 100-fold by 0–30% saturation of the cytosol fraction with ammonium sulphate followed by filtration of the precipitate through Sephadex G-200. The activity was eluted at the void volume. The product of the reaction, oestriol 16α-monoglucuronide, was identified by paper chromatography and by crystallization of radioactive product to constant specific radioactivity. The optimum temperature was 37°C, and the activation energy was calculated to be 11.1kcal/mol. The apparent Michaelis–Menten constants for oestriol and UDP-glucuronic acid were 13.3 and 100μm respectively. Cu²⁺, Zn²⁺ and Hg²⁺ inhibited, whereas Mg²⁺, Mn²⁺ and Fe²⁺ stimulated the enzyme. Substrate-specificity studies indicated that the amount of oestradiol-17β, oestradiol-17α and oestrone conjugated was not more than about 5% of that found for oestriol. Oestriol 16α-monoglucuronide, a product of the reaction, did not inhibit the 16α-oestriol glucuronyltransferase; in contrast, UDP, another product of the reaction, inhibited the enzyme competitively with respect to UDP-glucuronic acid as the substrate, and non-competitively with respect to oestriol as the substrate. ATP and UDP-N-acetylglucosamine did not affect the oestriol 16α-glucuronyltransferase. 17-Epioestriol acted as a competitive inhibitor and 16-epioestriol as a non-competitive inhibitor of the glucuronidation of oestriol. 5α-Pregnane-3α,20α-diol also inhibited the enzyme non-competitively. It is most likely that the oestriol 16α-glucuronyltransferase described here is bound to the membranes of the endoplasmic reticulum.     

Spectrophotometric Methods for Monitoring the Microbial Transformation of Steroids: I. Determination of 9α-Fluorohydrocortisone and 9α-Fluoro-16α-Hydroxyhydrocortisone in Fermentation Broths

A method has been devised for the determination of 9alpha-fluorohydrocortisone and 9alpha-fluoro-16alpha-hydroxyhydrocortisone in fermentation broths. The method involves extraction of the two steroids from the broth with ethyl acetate, separation through the formation of the water-soluble borate complex of the vicinally hydroxylated steroid, and estimation of each steroid spectrophotometrically.     

Synthesis of 5α-Androstane-3α,16α,17β-triol from 3β-hydroxy-5-androsten-17-one

5α-Androstane-3α, 16α 17β-triol was synthesized from 3β-hy-droxy-5-androsten-17-one. The procedure Involved catalytic hydrogenation of 3β-hydroxy-5-androsten-17-one to 3β-hydroxy-5α-androstan-17-one. This was followed by conversion of the 3β-hydroxy group to 3α-benzoyloxy group by the Mitsunobu reaction. Further treatment with isopropenyl acetate yielded 5α-androsten-16-ene-3α, 17-diol 3-benzoate 17-acetate. This was then converted to 3α, 17-dihydroxy-5α-androstan-16-one 3-benzoate 17-acetate via the unstable epoxide intermediate after treatment with $\text{m}$-cloroperoxybenzoic acid. LiAlH₄ reduction of this compound formed 5α-androstane-3α, 16α, 17β-trlol. ¹H and ¹³C NMR of various steroids are presented to confirm the structure of this compound.     

The Synthesis of O-Substituted 6-Oximes of 16α,17α-Cyclohexanopregn-4-ene-3,6,20-trione Labeled by Tritium in Position 1,2

6-O-(3-Methoxycarbonylpropyl)- and 6-O-(3-carboxypropyl)oximes of 16,17-cyclohexanopregn-4-ene-3,6,20-trione labeled by tritium in position 1,2 were synthesized. When using homogenous catalysts, the molar radioactivity of the resulting preparations was 1.5–1.7 PBq/mol.     

11α-Hydroxylation of 16α,17-epoxyprogesterone by Rhizopus nigricans in a biphasic ionic liquid aqueous system

11α-Hydroxylation of 16α,17-epoxyprogesterone (EP) by Rhizopus nigricans is an essential step in the synthesis of many steroidal drugs, while low conversion of the biohydroxylation is a tough problem to be solved urgently in industry. Two ionic liquids (ILs) of [BMIm][PF(6)] and [BMIm][NTf(2)] were used in the biotransformation of EP by R. nigricans. The results indicated that the conversion carried out in [BMIm][PF(6)]-aqueous biphasic system was greatly increased to above 90% at 18 g/L feeding concentration. A simplified mechanism was proposed to explain the improvement of the bioconversion in a biphasic ionic liquid aqueous system. Besides, successive three batches of bioconversion were carried out in the biphasic system with a total conversion of 87% at phase ratio 10 and 75% at phase ratio 5, respectively. Since recycling of the [BMIm][PF(6)] is quite easy, there is a great potential for the application of ILs in fungi biotransformation to implement green production.     

Letter to the editor Synthesis of 16-fluoromethylene-prostaglandin F2α

Prostaglandin (PG) E₂, thromboxane (TX) B₂ and the stable breakdown product of prostacyclin, 6-oxo-PGF_1α are present in carrageenin-induced inflammatory exudates. Carrageenin-impregnated polyester sponges were implanted subcutaneously in rats and inflammatory exudates were collected 4–192 h after implantation. The concentrations of cyclo-oxygenase products in sponge fluids was measured by radioimmunoassay after extraction and purification. All three products were detectable after 4 h and reached a peak at 12–24 h. Mean TXB₂ concentrations reached 74 ng/ml at 12 h but decreased to less than 10 ng/ml after 24 h. PGE₂ concentrations were 65 ng/ml at 24 h, after which there was no significant increase and then dropped to about 20 ng/ml between 96 and 192 h. 6-oxo-PGF_1α reached a concentration of 33 ng/ml at 24 h which did not change significantly until levels fell to less than 10 ng/ml between 96 and 192 h. The presence of PGE₂, TXB₂ and 6-oxo-PGF_1α was confirmed by gas-liquid chromatography and mass spectrometry. Total leukocyte numbers increased steadily and were at their highest (116.0 × 10⁶ cells/ml) at 192 h. These results suggest that thromboxanes and prostacyclin, as well as PGE₂, contribute to the acute inflammatory response.     

The suppressive effect of the catatoxic steroid,pregnenolone-16α-carbonitrile,on liver microsomal cholesterol-7α-hydroxylase

The effect of the catatoxic steroid, 3β-hydroxy-20-oxo-5-pregnene-16α-carbonitrile [pregnenolone-16α-carbonitrile (PCN)] on hepatic microsomal cholesterol-7α-hydroxylase, the probable rate-limiting enzyme of bile acid biosynthesis, has been studied. Short term administration (3 days) of PCN in the diet of rats resulted in a significant decrease in the liver microsomal cholesterol-7α-hydroxylase activity, in contrast to a marked stimulation of microsomal cytochrome P-450 and ethylmorphine demethylase activity. PCN significantly depressed the cholesterol-7α-hydroxylase activity in the livers of rats with elevated levels of the enzyme produced by cholestyramine feeding. The results indicate the presence of separate control mechanisms in the regulation of bile acid synthesis and drug metabolism.     

Synthesis of 7,8α-dihydro-14α-deoxyecdysteroids

A Pd-C-catalyzed hydrogenation in methanol and in the presence of sodium methylate is a simple, convenient and high yielding reduction method to convert the 7,14-dien-6-one ecdysteroids to their corresponding 7,8α-dihydro-14α-deoxyecdysteroids.     

Synthesis ofα-triazolylα-amino acid derivatives

Summary We report the synthesis of-triazolyl-amino esters by 1,3 dipolar cycloaddition of acetylenic compounds and-azido-amino esters.     

α-Isopropylmalate synthase from Alcaligenes eutrophus H 16

The purified isopropylmalate synthase of Alcaligenes eutrophus H 16 reacted with the following -keto acids and acyl-coenzyme A derivatives (in the sequence of decreasing affinities): -ketoisovalerate, -keto-n-valerate, -ketobutyrate and pyruvate; acetyl-CoA, propionyl-CoA, butyryl-CoA. malonyl-CoA, valeryl-CoA, and crotonyl-CoA. -Ketoisocaproate, however, is a strong inhibitor of the enzyme. All reactions catalyzed by isopropylmalate synthase were inhibited to the same extent by the endproduct l-leucine. the substrate saturation curves of -ketoisovalerate or other -keto acids and of acetyl-coenzyme A or other acyl-CoA derivatives had intermediary plateau regions; the Hill coefficient alternated between n _H -values higher and lower than 1.0, indicating changes from positive to negative and from negative to positive cooperativity for the substrates. The products, isopropylmalate and free coenzyme A, showed competitive inhibition patterns against both substrates (-ketoisovalerate and acetyl-CoA). Free coenzyme A (1 M) inactivated the enzyme irreversibly. The 3-phosphate of coenzyme A and the free carboxyl group of -ketoisovalerate were involved in optimal binding of these substrates, but 3-dephospho-acetyl-coenzyme A and the methylester of -ketoisovalerate were also converted by this enzyme. A CH₃–CH₂-grouping of the -keto acids seemed to be necessary for binding this substrate.Abbreviations Used CoA Coenzyme A - Tris Tris(hydroxymethyl)aminomethane hydrochloride - DTNB 5,5-dithiobis-(2-nitrobenzoic acid) - IPM -Isopropylmalate - KIV -Ketoisovalerate Prepared from doctoral thesis of the University of Göttingen 1973     

α-Isopropylmalate synthase from Alcaligenes eutrophus H 16

-Isopropylmalate (IPM) synthase, the first enzyme in the biosynthesis of l-leucine, was purified to a specific activity of 12 mole/min x mg protein from the valine-isoleucine double auxotrophic mutant A-81 of the hydrogen bacterium Alcaligenes eutrophus H 16. The activity in crude extracts of derepressed cells was 0.106 moles of isopropylmalate formed per min and per mg protein. Gel electrophoresis and regel electrophoresis of the isolated main band resulted in several distinct bands, which were not altered by the additions of substrate -ketoisovalerate, feedback inhibitor leucine or other effectors.The isoelectric points of the enzyme protein was between 3.9 and 4.0. The molecular weight was 114500 daltons and 100000 respectively in the absence and presence of the feedback inhibitor leucine. The enzyme activity depended strongly on the pH, the optimum is at pH 8.2. The enzyme was could labile and exhibits temperature anomalies.Abbreviations Used CoA Coenzyme A - Tris Tris(hydroxymethyl)aminomethane hydrochloride - DTNB 5,5-dithiobis-(2-nitrobenzoic acid) - IPM -Isopropylmalate - KIV -Ketoisovalerate Prepared from doctoral thesis of the University of Göttingen 1973     

α-Isopropylmalate synthase from Alcaligenes eutrophus H 16

The -isopropylmalate synthase (EC 4.1.3.12) from Alcaligenes eutrophus H 16 was inhibited by l-leucine and -ketoisocaproate. The extent of inhibition was influenced by substrate- and inhibitor concentrations as well as by the pH. Intermediary plateaus, which always appeared in the inhibition curves, suggested cooperative effects. The maximal Hill coefficient was found to be two. At low concentrations of leucine the inhibition mechanism was of the competitive type with respect to substrate acetyl coenzyme A and of the noncompetitive type with respect to substrate -ketoisovalerate. The inhibition was specifically relieved by the addition of valine or isoleucine. The anomalous effect of temperature on enzyme activity was diminished by leucine. The Arrhenius energy of the reaction increased from about 11 kcal/mole in the absence of leucine to about 18 kcal/mole in the presence of leucine. The further addition of valine reversed this effect. The physiological relevance of the -ketoisocaproate-mediated inhibition is discussed.Abbreviations IPM -isopropylmalate - KIC -ketoisocaproate - KIV -ketoisovalerate - DTNB 5:5 Dithiobis-(2-nitrobenzoe acid)