Study of the role of Schiff base formation in the aromatization of 3-[18O]testosterone and 3,17-di-[18O]androstenedione by human placental aromatase

Synthesis, anti-inflammatory and anti-ulcer evaluations of thiazole, thiophene, pyridine and pyran derivatives derived from androstenedione

The reaction of androstenedione with bromine gave the 16-bromo derivative 2. The latter reacted with either cyanothioacetamide or thiourea to give the 2-cyanomethylthiazole derivative 4 and the 2-aminothiazole derivative 13. Compound 4 and 13 were used underwent some condensation, coupling and heterocyclization reactions to give thiophene, pyridine and pyran derivatives. The anti-inflammatory and anti-ulcer evaluations of the newly synthesized products were evaluated and the results showed that 23f showed the maximum antiulcer activity. In addition, toxicity of the most active compounds was studied against shrimp larvae and showed that compounds 2, 23c and 23f showed non-toxicity against the tested organisms.

Mechanism of human placental aromatase: a new active site model

Based on Akhtar's ferric peroxide mechanism and on recent studies in our own laboratory, we present a detailed proposal for aromatase action. This picture can account for the known stereochemical consequences at C-19 observed by others using isotopes of hydrogen and oxygen. The postulated process involves anchoring of the 19-hydroxymethyl and 19-oxo groups at the active site by a glutamate residue, which also serves to activate the 19-oxo group for attack by ferric peroxy species in the third oxidative step.

Metabolism of 19-methyl substituted steroids and a proposal for the third aromatase monooxygenation

The article summarizes the results of recent studies on the metabolism of 10-ethylestr-4-ene-3,17-dione, 10-[(1R)-1-hydroxyethyl]-, and 10-[(1S)-1-hydroxyethyl]estr-4-ene-3,17-dione, in placenta. These compounds are the 19-methyl analogs of androstenedione, 19-hydroxyandrostenedione, and 19-oxoandrostenedione, respectively. No conversion of 10-ethylestr-4-ene-3,17-dione to either estrogens or oxygenated metabolites was detected. Both 10-[(1R)-1-hydroxyethyl]- and 10-[(1S)-1-hydroxyethyl]estr-4-ene-3,17-dione were oxygenated to 10-(1,1-dihydroxyethyl)estr-4-ene-3,17-dione and isolated following in situ dehydration as 10-acetylestr-4-ene-3,17-dione. Evidence for the involvement of aromatase in these conversions is discussed. No conversion of 10-acetylestr-4-ene-3,17-dione to either estrogens or other oxygenated products was detected. These results lead us to propose a new mechanism for the third aromatase monooxygenation. We propose that the third oxygenation is initiated by 1 beta-hydrogen abstraction at C1 of 19,19-dihydroxyandrostenedione, followed by homolytic cleavage of the C10-C19 bond with concurrent formation of a delta 1(10),4-3-ketosteroid and a C19 carbon radical, and terminated by oxygen rebound at C19.