Regio- and stereoselective introduction of 15β-hydroxy group and side chains to steroids by the palladium-catalyzed reaction of 1,3-diene monoepoxide

The Pd-catalyzed reaction of 1,3-diene monoepoxides with carbonucleophiles is applied to the regio- and stereoselective introduction of 15β-hydroxy group and side chains to steroid nuclei. 3β-Hydroxyandrost-5-en-17-one (15) was converted to 15,16β-epoxy-Δ¹⁷⁽²⁰⁾ isoheptylidene steroid 20 and ethylidene steroid 21. The former was subjected to the Pd-catalyzed reaction with dimethyl malonate and then converted to 15β-hydroxycholesterol (29). Similarly, 15β-hydroxyisocholesterol (32) was obtained from the ethylidene steroid 21 using the Pd-catalyzed reaction of methyl 3-oxo-5-methylhexanoate (24) as a key reaction.     

Studies on asterosaponins—V : A novel steroid conjugate, 5α-pregn-9(11)-ene-3β,6α-diol-20-one-3-sulfate,from a starfish saponin,asterosaponin A

A new crystalline steroid conjugate was obtained by partial acid hydrolysis of asterosaponin A, a steroidal saponin from the starfish, Asterias amurensis. The structure of the conjugate was established as 5α-pregn-9(11)-ene-3β,6α-diol-20-one-3-sulfate (2) on the basis of elemental analysis, IR and PMR spectra measurement and chemical reaction. Solvolysis of compound 2 yielded 5α-pregn-9(11)-ene-3β,6α-diol-20-one. Oxidation with chromium trioxide-pyridine complex followed by solvolysis afforded a new steroid, 5α-pregn-9(11)-ene-3β-ol-6,20-dione, whose structure was deduced by the measurement of ORD curve and PMR spectra. Thus, the location of carbohydrate moiety in asterosaponin A has been assigned to 6α-hydroxy group of the steroid conjugate.     

Chemoenzymatic synthesis of cryptophycin anticancer agents by an ester bond-forming non-ribosomal peptide synthetase module

Cryptophycins (Crp) are a group of cyanobacterial depsipeptides with activity against drug-resistant tumors. Although they have been shown to be promising, further efforts are required to return these highly potent compounds to the clinic through a new generation of analogues with improved medicinal properties. Herein, we report a chemosynthetic route relying on the multifunctional enzyme CrpD-M2 that incorporates a 2-hydroxy acid moiety (unit D) into Crp analogues. CrpD-M2 is a unique non-ribosomal peptide synthetase (NRPS) module comprised of condensation-adenylation-ketoreduction-thiolation (C-A-KR-T) domains. We interrogated A-domain 2-keto and 2-hydroxy acid activation and loading, and KR domain activity in the presence of NADPH and NADH. The resulting 2-hydroxy acid was elongated with three synthetic Crp chain elongation intermediate analogues through ester bond formation catalyzed by CrpD-M2 C domain. Finally, the enzyme-bound seco-Crp products were macrolactonized by the Crp thioesterase. Analysis of these sequential steps was enabled through LC-FTICR-MS of enzyme-bound intermediates and products. This novel chemoenzymatic synthesis of Crp involves four sequential catalytic steps leading to the incorporation of a 2-hydroxy acid moiety in the final chain elongation intermediate. The presented work constitutes the first example where a NRPS-embedded KR domain is employed for assembly of a fully elaborated natural product, and serves as a proof-of-principle for chemoenzymatic synthesis of new Crp analogues.     

Development and validation of a liquid-chromatography high-resolution tandem mass spectrometry approach for quantification of nine cytochrome P450 (CYP) model substrate metabolites in an in vitro CYP inhibition cocktail

Knowledge about the cytochrome P450 (CYP) inhibition potential of new drug candidates is important for drug development because of its risk of interactions. For novel psychoactive substances (NPS), corresponding data are not available. For developing a general drug inhibition cocktail assay, a liquid-chromatography high-resolution tandem mass spectrometry multi-analyte approach was developed and validated for quantifying low concentrations of O-diethyl phenacetin for CYP 1A2, 7-hydroxy coumarin for CYP 2A6, 4-hydroxy bupropion for CYP 2B6, N-diethyl amodiaquine for CYP 2C8, 4-hydroxy diclofenac for CYP 2C9, 5-hydroxy omeprazole for CYP 2C19, O-dimethyl dextromethorphan for CYP 2D6, 6-hydroxy chlorzoxazone for CYP 2E1, and 6-beta-hydroxy testosterone for CYP 3A in the incubation mixture in the presence of substrates and inhibitors. The tested matrix effects ranged from 63 to 141 % and the recoveries from 95 to 110 %. Time-saving one-point calibration allowed sufficient quantification, although some of the validation results for 7-hydroxy coumarin, 4-hydroxy bupropion, 4-hydroxy diclofenac, and 6-beta-hydroxy testosterone were outside the acceptance criteria (AC) but without influence of the IC₅₀ calculation. Validation showed also that the approach was sensitive and selective using mass spectral multiplexing. In conclusion, the presented assay was suitable for the quantification of the model substrate metabolites and could be used for the development of a CYP inhibition assay for testing most CYPs and a wide range of drugs of abuse.     

Studies on Wittig rearrangement of furfuryl ethers in steroidal side chain synthesis

Wittig rearrangement of 17(20)-ethylidene-16-furfuryloxy steroids 5-8 was examined. Reaction of 17E(20)-ethylidene-16α-furfuryloxy steroid 5 with t-BuLi in THF afforded (20S,22S)- and (20S,22R)-22-hydroxy steroids 9, 10 and 17Z(20)-ethylidene-16α-(2-furyl)hydroxymethyl steroid 11 in 61, 28, and 9% yields, respectively. Base treatment of 17E(20)-ethylidene-16β-furfuryloxy steroid 7 gave (20R,22R)-22-hydroxy steroid 13 and 17Z(20)-ethylidene-16β-(2-furyl) hydroxymethyl steroid 14 in 60 and 17% yields. In contrast, 17Z(20)-ethylidene-16-furfuryloxy steroids 6, 8 led to the corresponding 2,3-rearranged products in low yields (25% for (20R,22S)-22-hydroxy steroid 12; 31% for (20S,22R)-22-hydroxy steroid 10). Both (20S,22S)- and (20S,22R)-22-hydroxy steroids 9, 10 were converted by catalytic hydrogenation into known compounds 16, 17, key intermediates for the synthesis of biologically active steroids.     

Reaction of 5β,6β-epoxy-16α,17α-cyclohexapregnane with methylmagnesium iodide

On treatment with methylmagnesium iodide, 3β-acetoxy-5β,6β-epoxy-16α,17α-cyclo-hexapregnan-20-one undergoes 3-O-deacetylation along with the opening of the 5β,6β-epoxide ring to form 5α-methyl-6β-hydroxy steroid and the 6α-methyl-6β-hydroxy isomer, the 20-keto group remaining intact.     

A new synthesis of potent antitumor saponin OSW-1 via Wittig rearrangement

OSW-1 and its analogues in which thiophene ring was introduced at the side chain were synthesized employing Wittig rearrangement of 17E(20)-ethylidene-16α-(4′-methyl-2′-thienyl)methyloxy steroid. The synthesis required nine steps from the known 17E(20)-ethylidene-16α-hydroxy steroid in 15.6% overall yield.     

New 19-oxygenated steroid from the South China Sea gorgonian Dichotella gemmacea

A new 19-oxygenated steroid, 25-acetate-nebrosteroid K (1), and five known steroids (2–6), along with one known 19-hydroxy steroidal glycoside (7) were obtained from the gorgonian Dichotella gemmacea collected from the South China Sea. The structure and relative configuration of 1 were elucidated by using comprehensive spectroscopic data including NOESY spectra. Compound 1 represents the first example of 19-oxygenated steroid with a 19-oic acid methyl ester group isolated from gorgonians. All of the isolated compounds were evaluated for lethal activity to brine shrimp Artemia salina and cytotoxicity against A549 and HL-60 cell lines. Among them, 1 showed strong lethality towards A. salina.     

Efficient modification of steroid 20S-hydroxy functionality for industrial preparation of 1α,25-dihydroxy-22-oxavitamin D3, Maxacalcitol

A one-pot modification method of steroid 20S-hydroxy functionality involving sequential alkylation and reductive cleavage of epoxy bond has been established for the industrial preparation of a medicinally important 1α,25-dihydroxy-22-oxa-vitamin D₃2 (22-oxa-calcitriol), Maxacalcitol.     

Shapiro 1,2-酮基移位反应的研究

本文利用Shapiro反应的1,2-酮基移位反应, 经过五步使甾族化合物的6α-羟基移位到7α-羟基. 总产率是13 ％.     

Stereochemistry of NaBH4 reduction of a 19-carbonyl group of 3-deoxy androgens. Synthesis of [19S-3H]- and [19R-3H]-labeled aromatase inhibitors having a 19-hydroxy group

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.     

Triterpene glycosides from the sea cucumber Eupentacta fraudatrix. Structure and cytotoxic action of cucumariosides A2, A7, A9, A10, an, A13 and A14, seven new minor non-sulfated tetraosides and an aglycone with an uncommon 18-hydroxy group

Seven new minor triterpene glycosides, cucumariosides A2 (1), A7 (2), A9 (3), A10 (4), A11 (5), A13 (6) and A14 (7) have been isolated from the Far Eastern sea cucumber Eupentacta fraudatrix. Structures of the glycosides were elucidated by 2D NMR spectroscopy and MS. Glycosides 1-7 belong to the group of cucumariosides A, having linear tetrasaccharide carbohydrate moieties without any sulfate group and possessing 3-O-methyl-D-xylose as a terminal monosaccharide unit. Glycosides 1, 2, 5-7 differ from each other in side chain structures in aglycone moieties, while cucumarioside A10 (4) has a 23,24,25,26,27-pentanorlanostane aglycone with 18(16)-lactone. Cucumarioside A9 (3), having an uncommon 18-hydroxy group, is the second representative of the unique metabolically active glycosides that are regarded as intermediates of glycoside biosynthesis in sea cucumbers. Cytotoxic activities of glycosides 1-7 and cucumarioside A8 (8) against mouse spleen lymphocytes and the cells of the ascite form of mouse Ehrlich carcinoma, along with hemolytic activity against mouse erythrocytes and antifungal activity were studied. Cucumariosides A2 (1), A8 (8) and A13 (6) demonstrated high hemolytic activities. Glycosides 1, 4 and 6 showed moderate cytotoxic activity. Only cucumarioside A8 (8), having an 18-oxymethylene group and a 24(25)-double bond, was very active in all the tests.     

Characterization of prednisone, prednisolone and their metabolites by gas chromatography-mass spectrometry

Human urinary metabolites of the synthetic corticosteroids prednisone and prednisolone were detected in the course of gas chromatographic steroid profiling as methoxime-trimethylsilyl derivatives. Metabolites were provisionaly identified by combined gas chromatography-mass spectrometry. The major metabolites were 11-keto/11-hydroxy conversion products, 20-hydroxy and 4,5-dihydro analogues of the parent drugs. Cortisone, 6-hydroxy and fully saturated A-ring compounds were minor metabolites. Retention indices and mass spectral data are presented.     

Spectroscopic investigation of flavonoids. Detection of free phenolic hydroxyl groups in various positions

Summary 1. Sodium acetate ionizes the 7-hydroxy group in flavones, flavonols, and flavanones, and the 4-hydroxy group in chalcones, causing a considerable bathochromic displacement of the absorption maximum of the long-wave band. In isoflavones containing a free 7-hydroxy group a bathochromic displacement of the absorption maximum of the medium-wave part of the spectrum is found.2. A spectroscopic method using zirconyl nitrate and citric acid for detecting free hydroxy groups in positions 3 and 5 in flavonoids when they are present together and separately has been developed.Khimiya Prirodnykh Soedinenii, Vol. 1, No. 6, pp. 420–424, 1965     

Reaktionen mit phosphororganischen Verbindungen. XLII. Nucleophile Substitutionen an Hydroxysteroiden mit Hilfe von Triphenylphosphan/Azodicarbonsäureester

Nucleophilic Substitution Reactions of Hydroxysteroids using Triphenylphosphane/diethylazodicarboxylate Nucleophilic substitution reactions by means of the title reagent on various more or less hindered steroid alcohols with suitable nucleophils in benzene is described. It was not possible to run this substitution process in the hitherto used solvent THF. Cholestan-3α-ol ( 1 ) was transformed to the 3β-substituted products 3β-benzoyloxy-cholestane ( 1a ) and 3β-azido-cholestane ( 1b ). Testosterone ( 2 ) affords with the corresponding nucleophils after short heating in benzene the inverted 17α-substituted products 3a, 3b and 3c . Analogously the 17α-azido-derivative 5a arises from 17β-hydroxy-androst-3-on ( 4 ). In the presence of a ketogroup in the substrate a competitive reaction can occur as it is shown in the case of cholestan-3-on ( 6 ): the products are the en-hydrazo-dicarboxylate-steroids 7a and 7b . The sterically very hindered 11α-position in 11α-hydroxy-4-pregnen-3,20-dion ( 8 ) can be transformed also to the 11β-azide 9a . The substitution of a 6 β-hydroxy group in androstane-3β, 6β, 17β-triol-3,17-diacetate ( 10 ) to the 6α-azide 11a affords the elimination product 12 as main component. Trans-diaxial vicinal diols such as cholestane-2β,3α-diol ( 13 ) give a mixture of the α- and β-oxiranes 14a and 14b .     

Mass spectra of trimethylsilyl ethers of some Δ5-3β-hydroxy C 19 steroids

The mass spectra (20 eV electron energy) of a wide range of %Δ⁵-3β-hydroxy C₁₉ steroid TMS ethers have been examined with the aid of high-resolution mass measurements, together with deuterium and oxygen-18 labelling data. The validity of many previously proposed fragmentation modes has been confirmed. A number of ions regarded as diagnostic have been shown to be less specific than had been formerly supposed. Several novel fragmentations have been observed and investigated.     

Tetranitromethane as an efficient reagent for the conversion of epoxides into β-hydroxy nitrates

A convenient regioselective method for the preparation of β-hydroxy nitrates based on the ring opening reaction of epoxides by tetranitromethane in the presence of triethylamine is described. A series of substituted β-hydroxy nitrates were obtained in high yields under mild conditions.     

Synthesis of novel 5-hydroxy-3-alkoxy- and 5-hydroxy-3-alkylthioindole-2-carboxamides

The preparation of several novel 5-hydroxyindole-2-carboxamides is described. A 5-benzyloxyindole ester was elaborated to the 3-bromo, 3-hydroxy, and 3-alkoxy ester intermediates followed by conversion to the amide and debenzylation. A related 5-acetyloxy indole ester was converted to 3-sulfinyl and 3-alkylthio intermediates before simultaneous amidation and removal of the 5-hydroxy protecting group.     

Complexation and Sensing Behavior of Dansyl-appended Cyclodextrins and Cyclodextrin Dimers with Bile Salts

The dansyl-modified cyclodextrin derivatives 2 and 3 form complexes with the steroidal bile salts. The selectivity of the monomeric derivative 3 is similar to that of native g -cyclodextrin. All binding constants with 3 are lowered compared to g -cyclodextrin because of the competition for the cavity between the steroids and the dansyl moiety. Cholate ( 4a ) and deoxycholate ( 4b ) form weak complexes, the other bile salts ( 4c - e ) are complexed far more strongly. The difference is attributed to the absence of a 12-hydroxy group in the latter steroids. Data for dimer 2 reveal strongly enhanced binding of 4a and 4b and only slightly stronger complexes with the other steroids. Due to the low binding affinity of 3 for 4a and 4b , this receptor could not be used for their detection by fluorescence spectroscopy. Steroids 4c - e showed a decrease in fluorescence intensity. The detection of all steroids 4a - e was possible using 2 . The fluorescence intensity of the dimer increased or decreased, depending on which steroid was added.     

Eine Neue Einfache Synthese von L-Vinelose

Reduction of methyl 6-deoxy-2,3-0-isopropylidene-3-C-methyl-α-L-lyxo-hexopyranosid-4-ulose (2) with sodium tetrahydroborate or L-selectride produces exclusively the L-talo-configurated 4-hydroxy compound (3), which is transformed to methyl 6-deoxy-3,4-O-isopropylidene-3-C-methyl-α-L-talopyranoside (4). Methylation of the 2-hydroxy group and hydrolysis yields L-vinelose (6) .