Em. Shulmanroskes et al., THE PARTITIONING OF PHOSPHORAMIDE MUSTARD AND ITS AZIRIDINIUM IONS AMONG ALKYLATION AND P-N BOND HYDROLYSIS REACTIONS, Journal of medicinal chemistry, 41(4), 1998, pp. 515-529
NMR (H-1 and P-31) and HPLC techniques were used to study the partitio
ning of phosphoramide mustard (PM) and its aziridinium ions among alky
lation and P-N bond hydrolysis reactions as a function of the concentr
ation and strength of added nucleophiles at 37 degrees C and pH 7.4. W
ith water as the nucleophile, bisalkylation accounted for only 10-13%
of the product distribution given by PM. The remainder of the products
resulted from P-N bond hydrolysis reactions. With 50 mM thiosulfate o
r 55-110 mM glutathione (GSH), bisalkylation by a strong nucleophile i
ncreased to 55-76%. The rest of the PM was lost to either HOH alkylati
on or P-N bond hydrolysis reactions. Strong experimental and theoretic
al evidence was obtained to support the hypothesis that the P-N bond s
cission observed at neutral pH does not occur in the parent PM to prod
uce nornitrogen mustard; rather it is an aziridinium ion derived from
PM which undergoes P-N bond hydrolysis to give chloroethylaziridine. I
n every buffer studied (bis-Tris, lutidine, triethanolamine, and Tris)
, the decomposition of PM (with and without GSH) gave rise to P-31 NMR
signals which could not be attributed to products of HOH or GSH alkyl
ation or P-M bond hydrolysis. The intensities of these unidentified si
gnals were dependent on the concentration of buffer.