1H NMR Spectroscopic Studies on the Reactions of Haloalkylamines with Bicarbonate Ions: Formation of N-Carbamates and 2-Oxazolidones in Cell Culture Media and Blood Plasma

Abstract

1H NMR spectroscopic methods have been applied to compare the in vitro reactivity of the renal papillary nephrotoxin 2-bromoethanamine (BEA) with those of selected halide-substituted nephrotoxic analogues, 2-chloroethanamine (CEA), 2-fluoroethanamine (FEA), and 1-phenyl-2-iodoethanamine (PIEA). The primary 1H NMR-detectable transformation during a 24 h incubation of confluent Madin Darby canine kidney (MDCK) cells with BEA, CEA, and FEA (at concentrations up to the IC50 determined by neutral red uptake) was the appearance in cell culture media of 2-oxazolidone (OX). Additional novel signals assigned as FEA carbamate (N-carbamoyl-2-fluoroethanamine) were observed in media collected following incubation of cells with FEA. We propose that N-carbamate intermediates are formed from the spontaneous reaction of these haloalkylamines with HCO(3-)-buffered growth media and that OX is formed from the carbamate via elimination of the hydrogen halide. Further 1H NMR experiments, conducted for up to 8 h at 25 degrees C on 5 mM solutions of BEA, CEA, and FEA in 2H2O containing a 20-fold excess of HCO3- at pH 7.6, demonstrated a time-dependent decrease in the concentration of the free haloalkylamines accompanied by the production of N-carbamate intermediates and OX. Under these pseudo-first-order reaction conditions, the formation of OX from BEA was complete within approximately 6 h. In similar reaction conditions OX formation from CEA (24 h after initiation) had reached 54% of its final equilibrium concentration. Equivalent experiments demonstrated that PIEA was almost completely converted to 4-phenyl-2-oxazolidinone (PHOX) within 2 h. These observations reveal the strong disposition of this series of haloalkylamines toward reaction with HCO3- and indicate that the compounds in this family may exist only transiently as free amines in vivo, where there will virtually always be excess HCO3-. The physiological relevance of the in vitro findings is further indicated by the NMR-detectable conversion of BEA to OX and also an alkylating aziridine (AZ) moiety in rat plasma containing BEA. The ability to form carbamoylated species and OX (or PHOX) may mediate the toxicity of this series of haloalkylamines and hence is potentially of considerable significance.

Reaction of Primary and Secondary Amines to Form Carbamic Acid Glucuronides

“…The excitotoxic potency of L-cysteine in a chick retina model in vitro was found to be dramatically enhanced in the presence of bicarbonate. The reaction of carbon dioxide with a series of haloethylamines, such as bromoethylamine, to form carbamic acids has also been suggested to be involved with the toxicity associated with these compounds [65]. In contrast, carbamic acid formation was shown to be able to inhibit N-nitrosation of a model 2° amine, morpholine, providing a protective effect [15].…”

High‐resolution 1H NMR and magic angle spinning NMR spectroscopic investigation of the biochemical effects of 2‐bromoethanamine in intact renal and hepatic tissue

“…High‐resolution 1 H NMR spectroscopic studies on biofluid samples have been used to investigate the metabolic effects of BEA administered i.p. to rats (3, 18, 19). Alterations in the 1 H NMR‐generated urinary profile following a single dose of BEA (150 mg/kg) included a depletion in the urinary concentrations of tricarboxylic acid cycle intermediates, urinary excretion of glutaric acid (1,5‐pentanedioic acid), and perturbations in the concentrations of renal osmolytes such as trimethylamine‐ N ‐oxide and dimethylglycine.…”

Carbon dioxide capture under ambient conditions using 2-chloroethylamine

“…(Anthony et al 1995) Inspired by this result, we speculated that CO 2 could be captured by 2-haloethylamine under ambient conditions. Indeed, while a mixture of CO 2 and air (in a ratio of about 1:1) was bubbled through an aqueous solution of 2-chloroethylamine hydrochloride and a base 2-oxazolidinone was produced rapidly.…”