New steroidal diazo ketones as potential photoaffinity labeling reagents for the mineralocorticoid receptor: synthesis and biological activities

Structure and Photochemistry of 18-Diazo-1,4,7,10,13,16-hexaoxacyclononadeca-17,19-dione and Its Sodium and Potassium Complexes. Control of the Ground-State Conformation of 2-Diazo-1,3-dicarbonyl Fragment via Host−Guest Complexation

[reaction: see text] The macrocyclic 18-diazo-1,4,7,10,13,16-hexaoxacyclononadeca-17,19-dione (3-diazo-2,4-dioxo-19-crown-6, 1) readily forms complexes with potassium (2, stability constant in methanol is K(K+) = 229 +/- 25 M(-1)) and sodium ions (3, K(Na+) = 84.2 +/- 7.9 M(-1) in methanol). According to B3LYP/6-31G+(d,p) calculations and temperature-dependent 1H NMR spectroscopy, the predominant conformation of 1 has a Z,Z arrangement of the diazo and carbonyl groups. The X-ray crystal structure analysis showed that the potassium complex (2) has the same Z,Z arrangement, while the sodium analogue (2) exists in conformation with Z,E geometry of the diazodicarbonyl moiety. Direct 254 nm photolysis of diazo compounds 1-3 in methanol results in the formation of 3-methoxy-2,4-dioxo-19-crown-6 (5), the product of the insertion of corresponding alpha,alpha'-dicarbonylcarbene into the O-H bond of the solvent. The triplet-sensitized photolysis of diazomalonates 1-3 produces 2,4-dioxo-19-crown-6 (6), which is apparently formed via the triplet state of the intervening carbene.

Experimental and Theoretical Investigation of Reversible Interconversion, Thermal Reactions, and Wavelength-Dependent Photochemistry of Diazo Meldrum's Acid and Its Diazirine Isomer, 6,6-Dimethyl-5,7-dioxa-1,2-diaza-spiro[2,5]oct-1-ene-4,8-dione1

The photochemical or thermal decomposition of diazo Meldrum's acid (1) in methanolic solutions yields ketoester 3a, the product of the Wolff rearrangement, while products produced from the singlet carbene were not detected. This observation, combined with the analysis of activation parameters for the thermal decomposition of 1, as well as with the results of DFT B3PW91/6-311+G(3df,2p) and MP2/aug-cc-pVTZ//B3PW91/6-311+G(3df,2p) calculations, allows us to conclude that the Wolff rearrangement of 1 is a concerted process. The outcome of the photolysis of diazo Meldrum's acid depends on the wavelength of irradiation. Irradiation with 254 nm light results in an efficient (Phi(254) = 0.34) photo-Wolff reaction, while at 355 nm, the formation of diazirine 2 becomes the predominant process (Phi(350) = 0.024). This unusual wavelength selectivity indicates that Wolff rearrangement and isomerization originate from different electronically excited states of 1. The UV irradiation of diazirine 2 leads to the loss of nitrogen and the Wolff rearrangement, apparently via a carbene intermediate. This process is accompanied by a reverse isomerization to diazo Meldrum's acid. Triplet-sensitized photolysis of both isomers results in the formation of Meldrum's acid, the product of a formal reduction of 1 and 2. Mild heating of diazirine 2 produces quantitative yields of diazo Meldrum's acid. The activation parameters for thermal reactions of diazo 1 and diazirino 2 isomers were determined in aqueous and dioxane solutions.

Photoaffinity labelling of the human mineralocorticoid receptor with steroids having a reactive group at position 3, 18 or 21

The ability of a glucocorticoid (triamcinolone acetonide: TA) and three progesterone derivatives with photoreactive groups at different positions (promegestone: R5020; 18-oxo-18-vinylprogesterone: 18OVP; 21-diazoprogesterone: 21DP) to bind covalently to the human mineralocorticoid receptor (hMR) expressed in Sf9 insect cells was assessed. Sedimentation gradient analysis and exchange assays with aldosterone showed that [3H]TA, a partial mineralocorticoid agonist, and [3H]R5020, a pure antimineralocorticoid, were covalently bound to hMR after UV irradiation, with a labelling efficiency of approx. 3-5%. UV irradiation did not alter the heterooligomeric structure of the hMR, since the irradiated [3H]TA- and [3H]R5020-hMR complexes sedimented at approx. 9-10 S, as did the non-irradiated complexes. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis revealed a band labelled by [3H]TA or [3H]R5020, having a molecular mass of 120 kDa. This band was not detected in the presence of an excess of the corresponding unlabelled steroid or when the cytosol was recovered from non-infected Sf9 cells. Electrophoresis of a truncated hMR (hMRDelta(1-351)) photolabelled with [3H]TA revealed a 80 kDa band, compatible with the molecular mass of the truncated hMR. Limited chymotrypsin proteolysis of the [3H]TA photolabelled hMR generated a 30 kDa fragment covalently associated with [3H]TA. As the 30 kDa fragment generated by chymotrypsin has been shown to encompass the entire ligand-binding domain of the hMR (B. Couette, J. Fagart, S. Jalaguier, M. Lombès, A. Souque, M.E. Rafestin-Oblin, Biochem. J. 315 (1996) 421-427), the present experiments provide evidence that [3H]TA is covalently bound to the ligand binding domain of the hMR. Exchange assays with [3H]A also revealed that unlabelled 18OVP and 21DP, two mineralocorticoid agonists bearing photoreactive groups at skeleton positions crucial for the ligand-MR interaction, are covalently bound to hMR with an approx. 30-35% labelling efficiency.

18-Vinyldeoxycorticosterone: a potent inhibitor of the bovine cytochrome P-450(11) beta

18-Vinylprogesterone (18-VP) and 18-ethynylprogesterone (18-EP) have proved to be potent suicide inhibitors of P-450(11) beta, the last enzyme of aldosterone biosynthesis (Delorme, C.; Piffeteau, A.; Viger, A.; Marquet, A. Eur. J. Biochem. 1995, 232, 247; Delorme, C.; Piffeteau, A.; Sobrio, F.; Marquet, A. Eur. J. Biochem. 1997, 248, 252). This paper describes the synthesis of 18-vinyldeoxycorticosterone (18-VDOC), an analogue of deoxycorticosterone (DOC), the physiological substrate of the enzyme, and the evaluation of its reversible inhibiting properties for deoxycorticosterone and corticosterone oxidation by the bovine enzyme. 18-VDOC has been obtained by hydroxylation at C-21 of a 18-VP precursor. Its reversible Ki values are, respectively, 0.3 microM for the 11 beta-hydroxylation and 0.8 microM for the 18-hydroxylation. Hence, 18-VDOC is the strongest competitive inhibitor of bovine P-450(11) beta described so far, but in contrast with 18-VP, it does not inhibit more efficiently the 18-hydroxylation than the 11-hydroxylation.