Synthesis of [3H,33P]‐phosphoramide and ‐isophosphoramide mustards and metabolites [3H]‐chloroethylaziridine and ‐aziridine for studies of DNA alkylation

Abstract Reduction of diethyliminodiacetate with [3H]‐LiAlH4 and then reaction with SOCl2 gave bis(2‐chloro‐2‐[3H]‐ethyl)amine hydrochloride. This compound, together with [33P]‐phosphorus oxychloride, provided for the synthesis of [3H,33P]‐phosphoramide mustard (as its cyclohexylammonium salt) in three steps over 2 days. Similarly, 2‐[3H]‐ethanolamine was reacted with SOCl2 to give 2‐chloro‐2‐[3H]‐ethylamine hydrochloride which, along with [33P]‐POCl3, was used to synthesize [3H,33P]‐isophosphoramide mustard in two steps over 1 day. 1H NMR studies were carried out to determine optimal times for in situ formation and storage of chloroethylaziridine and aziridine. A solution of 10 mM bis(2‐chloroethyl)amine hydrochloride in 0.1 M phosphate/D2O, pD 7.9 at 37°C for 3 h gave chloroethylaziridine without contamination by starting material or hydrolysis products. For aziridine, the disappearance of 0.2 M 2‐chloroethylamine hydrochloride in 2 M NaOD/D2O at pD 14, 37°C, gave k = 0.00455 min−1 (R2 = 1.000) and τ1/2 = 2.55 h; no hydrolysis product was observed over the course of the NMR experiment (4 h). It was concluded that ∼13 h (5 half‐lives) of reaction time would yield a solution of aziridine which was relatively free of contaminants. Using these reaction conditions, 3H‐labeled chloroethylamines were used to synthesize 1‐(2‐chloro‐2‐[3H]‐ethyl)‐2‐[3H]‐aziridine and 2‐[3H]‐aziridine in situ. Copyright © 2007 John Wiley & Sons, Ltd.