Effects of anti-ecdysteroid quaternary derivatives of azole analogues of metyrapone on the post-embryonic development of the red cotton bug (Dysdercus cingulatus F).

In order to improve the larvicidal activity of the azole analogues of metyrapone, previously found to have a strong inhibitory activity on ecdysone 20-monooxygenase (E-20-M) from the fleshfly Neobellieria bullata Parker, soft-alkylated compounds (3-(1,1-dimethyl-2-oxo-2-phenylethyl)-1-dodecanoyloxymethyl-1H-imidazolium chloride, sPIM) and (1-(1,1-dimethyl-2-oxo-2-phenylethyl)-4-dodecanoyloxymethyl-1H-1,2,4-triazolium chloride, sPTM), derivatives of phenyl-imidazolyl-metyrapone (PIM) and phenyl-1,2,4-triazolyl-metyrapone (PTM), respectively, were synthesized. Both sPIM and sPTM, designed as propesticides, inhibited E-20-M in vitro at 10(-4) M concentration, which was unexpected since they had been expected to be inactive in vitro and to gain activity only within the organism. sPTM significantly delayed the pupariation of N. bullata larvae and this effect could be reversed by the simultaneous application of 20-hydroxyecdysone (20E), supporting the hypothesis that sPTM can act by interfering with the moulting hormone system. Due to this in vitro activity, sPTM and sPIM cannot be considered to be simple drug precursors, and their structure should contain structural elements (pharmacophores) responsible for the observed biological effects. In order to examine this hypothesis, derivatives of sPTM and sPIM were synthesised in which the hydrolytically labile N(+)-CH2O(CO)- moiety was changed to the more stable N(+)-CH2CH2(CO)-group. In three new stable derivatives, a dodecylamino or a phenyl group, respectively, is attached to the carbonyl group to obtain PTM and PIM derivatives quaternised with a 2-dodecylcarbamoylethyl or a 3-oxo-3-phenylpropyl group. In one derivative, the 2-oxo-2-phenylethyl quaternising group has one fewer carbon atom. In addition to their moderate activity (LC50 = 10(-6)-10(-5) M) against the red cotton bug Dysdercus cingulatus F, they delayed development and caused developmental abnormalities, including mortality in the pharate phase, mortality during moulting and wing deformations. These symptoms and the delay in development are characteristic of known compounds inhibiting the synthesis of 20E or interfering in the moulting processes. The facts that the frequent appearance of insects with developmental abnormalities and the delay in development could be reversed by co-application of 20E indicate that the moulting system might be the site of action. We presume that the quaternary azole derivatives of PIM and PTM can themselves also interact with the moulting system.

Comparison of non-isotopic exchange methods for n.c.a. labelling of 2-iodophenyl-metyrapone.

The Cu(I)-assisted aromatic halogen exchange proved useful for preparation of macroscopic amounts of 2-iodophenyl-metyrapone as well as for the n.c.a. radioiodinated analogue. Semi-preparative HPLC-isolation provided the compound with high purity for use as chromatographic standard and for the determination of the inhibition constant of the 2-iodo-analogue. The non-isotopic exchange led to a high specific activity (> 5000 GBq/mumol) of 2-[123I]iodophenyl-metyrapone. A reaction in acetic acid at elevated temperatures proved superior to an exchange in aqueous solution with in-situ reduction of Cu2+. Even without Cu+ high radiochemical yields of > 80% were obtained, while addition of Cu+ provided the radiotracer with 95% radiochemical yield within 5 minutes in acetic acid.

Synthesis of 2-[131I]iodophenyl-metyrapone using Cu(I)-assisted nucleophilic exchange labelling: study of the reaction conditions.

2-Bromophenyl-metyrapone has been synthesized as a precursor for Cu(I)-assisted labelling with radioiodine. A labelling yield of > 95% was obtained and the specific activity of the purified product was 120 GBq/mumol. The iodo for bromo exchange requires an excess of reducing agents to maintain the Cu(I) redox potential. The effects of the amount of reactants, temperature and time were studied. The labelling yield showed a direct dependence on the amount of precursor and Cu(+)-catalyst used for the reaction, and an increase with reaction time (optimal at 60 min) and temperature (optimal at 100 degrees C). Studies of the stability, lipophilicity and binding of 2-[131I]iodophenyl-metyrapone to serum protein indicated high in vitro stability, high lipophilicity (log P = 2.19) and a loose association with serum proteins.

Synthesis of N-oxide derivatives of metyrapone and their detection as in vitro metabolites.

A variety of possible N-oxidation products of 2-methyl-1, 2-bis(3-pyridyl)propan-1-one (metyrapone) have been synthesized by peracid oxidation, and characterized using various spectroscopic techniques. Specific and sensitive chromatographic techniques have been developed for the separation and identification of its in vitro metabolites. Incubation of metyrapone with rat or mouse hepatic microsomes, in the presence of a NADPH-regenerating system, leads to the formation of metyrapol (keto-reduction), and two mono-N-oxides.

New inhibitors of steroid 11beta-hydroxylase. Structure--activity relationship studies of metyrapone-like compounds.

A series of metyrapone analogues was synthesized for study as inhibitors of steroid 11beta-hydroxylase. Racemic mixtures of the new compounds were evaluated in vitro. Preliminary results revealed several analogues to be effective inhibitors of deoxycorticosterone hydroxylation. 2-(3-pyridyl)propiophenone (13) and alpha,beta-diphenyl-3-pyridineethanol (16) were the most active new compounds. Each was 65% as potent as metyrapone; 3-Pyridyl alpha-3-pyridylbenzyl ketone (3), 2-phenyl-2-(3-pyridyl)acetophenone (4), alpha-(diphenylmethyl)-3-pyridinemethanol (17), and 1,2-di-3-pyridyl-1-propanol (26) were 52, 32, 25, and 41% as inhibitory as metyrapone, respectively. Diphenylmethyl 3-pyridyl ketone (5), benzyl 3-pyridyl ketone (10), 2-(3-pyridyl)acetophenone (12), 2-phenyl-1-(3-pyridyl)-1-propanone (11), alpha,beta-di-3-pyridylphenethyl alcohol (15), and 1,2-di-3-pyridylethanol (27) had less than 25% the activity of metyrapone. All compounds displaying a metyrapone-like inhibition contained appropriately substituted alcoholic or ketonic functions. A phenyl or methyl group alpha to the carbon bearing the oxygen was necessary for appreciable activity. A 3-phridyl group alpha to the carbonyl carbon could be replaced by a phenyl group. For optimal activity, however, the other 3-pyridyl group of metyrapone could not be exchanged for a phenyl group.