Cytotoxic activity and fragmentation of aziridines in microsomes

Decarboxylative ring-opening of 2-oxazolidinones: a facile and modular synthesis of β-chalcogen amines

We report herein the synthesis of primary and secondary β-chalcogen amines through the regioselective ring-opening reaction of non-activated 2-oxazolidinones promoted by in situ generated chalcogenolate anions. The developed one-step protocol enabled the preparation of β-selenoamines, β-telluroamines and β-thioamines with appreciable structural diversity and in yields of up to 95%.

Synthesis of novel IP agonists via N-aminoethyl cyclic amines prepared by decarboxylative ring-opening reactions

An efficient synthesis of a highly potent and selective IP (PGI₂ receptor) agonist that is not structurally analogous to PGI₂ is described. This synthesis is accomplished through the following key steps: Nucleophilic ring-opening of 3-(4-chlorophenyl)-oxazolidin-2-one prepared by a one-pot procedure with 4-piperidinol and selective O-alkylation of 1-(2-(4-chlorophenylamino)ethyl)piperidin-4-ol. The obtained compound is a potent and selective IP agonist displaying a long duration of action.

Aziridine biotransformation by microsomes and lethality to hepatocytes isolated from rat

To clarify the relationship of aziridine biotransformation to their cytotoxic activities, the metabolism of optical isomers of typical cytotoxic and non-cytotoxic aziridines was studied in isolated hepatocytes, rat liver microsomes, mitochondria and L-1210 mouse leukemia cells. Cytotoxic 1-methyl-2-beta-naphthylaziridine (NAZ) gave nitrosomethane as one of the bioactivation products in isolated hepatocytes and simultaneously induced a marked decrease in cellular ATP followed by cell lethality. NAZ itself did not directly affect the respiratory function of mitochondria in isolated hepatocytes or in buffer solution, however, it inhibited the mitochondrial activity in the presence of microsomes in the buffer solution. Nitroso-t-butane or nitrosomethane dimer, used as a substitute for extremely labile nitrosomethane, strongly inhibited the respiration of mitochondria. On the other hand, optical isomers of 2-aziridinecarboxylic acid (AZC) which did not give nitrosomethane in isolated hepatocytes or microsomes also did not show cytotoxicity. Thus, the cytotoxicity of NAZ seems to be induced by bioactivation via cellular oxidases with the nitrosomethane generated being a major toxic component. This may occur with most of the cytotoxic aziridine derivatives.

Enzyme-induced aziridine formation by rat liver microsomes

The metabolic reaction of 2-chloroethylaminobenzoquinone derivatives with rat liver microsomes was studied. In buffer solution containing cellular macromolecules such as DNA or protein, 2-chloroethylaminobenzoquinones were usually stable and could be recovered quantitatively after an appropriate period of incubation. However, in microsomal solution, they were gradually converted into aziridinobenzoquinones via elimination of hydrogen chloride by NADPH-dependent enzyme action. Based on the study of the enzymatic cyclization reaction of 4-chlorobutylaminonaphthoquinone, we concluded that the hydroquinone derivative is an important intermediate for aziridine formation.