39800-16-3Relevant academic research and scientific papers
Activation Mechanisms of Mafosfamide and the Role of Thiols in Cyclophosphamide Metabolism
Kwon, Chul-Hoon,Borch, Richard F.,Engel, Jurgen,Niemeyer, Ulf
, p. 395 - 399 (2007/10/02)
cis-Mafosfamide (cis-5) (ASTA Z7557), a stable analogue of cis-4-hydroxycyclophosphamide (cis-2), undergoes rapid decomposition in aqueous phosphate buffer or plasma at pH 7.4 and 37 deg C.The reaction kinetics of cis-5 are complex, and trans-mafosfamide (trans-5) and cis-2 are produced and subsequently disappear over the course of the reaction.The rates of decomposition of cis-5 as well as cis-2 were much faster in plasma than in buffer.The cis-trans isomerization of cis-5 occured by a specific-base-catalyzed process via iminocyclophosphamide (8) as a transient intermediate.In contrast, formation of cis- and trans-mafosfamide (5) from cis-2 and MESNA (sodium 2-mercaptoethanesulfonate) proceeded by an acid-catalyzed process via the hemithioacetal intermediate (6).The significance of these findings with respect to cyclophosphamide metabolism is discussed.
The Mechanism of Activation of 4-Hydroxycyclophosphamide
Borch, Richard F.,Millard, Jo Ann
, p. 427 - 431 (2007/10/02)
4-Hydroxycyclophosphamide (2/3) of unknown stereochemistry is the initial metabolite formed after administration of cyclophosphamide (1).Ultimate conversion to the cytotoxic metabolite phosphoramide mustard (6) is initiated by ring opennig of 4-hydroxycyclophosphamide to produce aldophosphamide (4).The ring-opennig reaction and subsequent equilibration of 2-4 are subject to general-acid catalysis, and the equilibrium composition is independent of buffer structure and pH.In contrast, formation of 6 from 4 proceeds by general-base-catalyzed β-elimination. trans-4-Hydroxycyclophosphamide undergoes ring opening ca. 4 times faster than the cis isomer, and cyclization of 4 favors the trans isomer by a factor of ca. 3 over the cis isomer.The rapid equilibration of 2-5 and the absence of elimination to give 6 at pH ca. 5 provides a convenient method to prepare a stable equilibrium mixture of activated cyclophosphamide metabolites suitable for in vitro use.
Base-catalyzed hydrolysis of 4-hydroperoxycyclophosphamide: Evidence for iminocyclophosphamide as an intermediate
Borch,Getman
, p. 485 - 490 (2007/10/02)
cis-4-Hydroperoxycyclophosphamide (5) undergoes facile reaction with acqueous phosphate or Tris buffers at pH 7-8 and 30 °C. The kinetics of 5 are complex,and the trans-4-hydroperoxy isomer 6 is produced and subsequently disappears over the course of the reaction. Addition of hydrogen peroxide to the reaction mixture retards the disappearance rate of 5 and increases the amount of 6 generated. Rate constants for the reversible disappearance of 5 and appearance of 6 and 4-hydrocyclophosphamide (2) have been determined by nonlinear least-squares methods. The reaction is catalyzed by hydroxide ion, Tris free base, and HPO42-, with catalytic constants of 0.032 min-1 (pH 8.0), 0.052, and 0.115 M-1, respectively. The major product in the presence of Tris is the oxazolidine arising from the addition of Tris to aldophosphamide, not 2 as assumed previously. These results are consistent with a mechanism involving general-base-catalyzed elimination to produce iminocyclophosphamide as a transient intermediate; the imine can react with the hydrogen peroxide evolved in the reaction to give 5 and 6, with water to give 2, or, in general, by addition of a nucleophile to C-4. The significance of these findings with respect to other 4-substituted cyclophosphamides is discussed.
NMR Spectroscopic Studies of Intermediary Metabolites of Cyclophosphamide. A Comprehensive Kinetic Analysis of the Interconversion of cis- and trans-4-Hydroxycyclophosphamide with Aldophosphamide and the Concomitant Partitioning of Aldophosphamide between Irreversible Fragmentation ...
Zon, Gerald,Ludeman, Susan Marie,Brandt, Joan A.,Boyd, Victoria L.,Oezkan, Gunay,et al.
, p. 466 - 485 (2007/10/02)
Multinuclear (31P, 13C, 2H, and 1H) Fourier-transform NMR spectroscopy, with and without isotopically enriched materials, was used to identify and quantify, as a function of time, the following intermediary (short-lived) metabolites of the anticancer prodrug cyclophosphamide (1, Scheme I): cis-4-hydroxycyclophosphamide (cis-2), its trans isomer (trans-2), aldophosphamide (3), and its aldehyde-hydrate (5).Under a standard set of reaction conditions (1 M 2,6-dimethylpyridine buffer, pH 7.4, 37 deg C), the stereospecific deoxygenation of synthetic cis-4-hydroperoxycyclophosphamide (cis-12, 20 mM) with 4 equiv of sodium thiosulfate (Na2S2O3) afforded, after ca.20 min, a "pseudoequilibrium" distribution of cis-2, 3, 5, and trans-2, i.e., the relative proportions of these reactants (57:4:9:30, respectively) remained constant during their continual disappearance.NMR absorption signals indicative of "iminophosphamide" (8) and enol 6 were not detected ( "3" trans-2, as well as the rate constant (k3) for the irreversible fragmentation of 3.The values of k3 at pH 6.3, 7.4, and 7.8 were equal to 0.030 +/- 0.004, 0.090 +/- 0.008, and 0.169 +/- 0.006 min-1, respectively.Replacement of the HC(O)CH2 moiety in 3 with HC(O)CD2 led to a primary kinetic isotope effect (kH/kD = 5.6 +/- 0.4) for k3.The apparent half-lives (τ*1/2) for cis-2, "3", and trans-2 under the standard reaction conditions, at "pseudoequilibrium" (constant ratio of cis-2/"3"/trans-2), were each equal to ca.38 min, which is considerably shorter than the widely cited colorimetrically derived half-lives reported by earlier investigators.The values of τ*1/2 for cis-2, "3", and trans-2 were affected by pH in the same manner as that found for k3 but were relatively insensitive to the presence of either K(+), Na(+), Ca(2+), or Mg(2+).The presence of certain primary amines led to marked decreases in τ*1/2 and, in some cases, the formation of acyclic adducts of aldehyde 3.The relatively stable adduct formed from 3 and tris(hydroxymethyl)aminomethane (Tris) at pH 7.4 and 37 deg C gave rise to a 31P NMR signal that other investigators have mistakenly ascribed to 2. 31P NMR spectroscopy was also used to examine, in considerable detail, the manifold effects of N-acetyl-L-cysteine upon the chemistry of 2, "3", and 4, which featured the formation of a mixture of diastereomeric, acyclic ...
Mass spectrometric characterization of activated N-(2-chloroethyl)amino oxazaphosphorine derivative.
Przybylski,Ringsdorf,Lenssen,Peter,Voelcker,Wagner,Hohorst
, p. 209 - 215 (2007/10/08)
The hydroperoxy and several alkylthio derivatives of the antitumor agents cyclophosphamide (2-bis(2-chloroethyl)amino tetrahydro-2H-1,3,2-oxazaphosphorine 2-oxide), ifosfamide (3-(2-chloroethyl)-2-(2-chloroethylamino)tetrahydro-2H-1,3,1-oxazaphosphorine 2-oxide) and trofosfamide (3-(2-chloroethyl)-2-(bis(2-chloroethyl)amino)tetrahydro-2H-1,3,2-oxazaphosphorine 2-oxide) were characterized by electron impact and field desorption mass spectrometry. The compounds, which are stabilized derivatives of the activated hydroxylated intermediates of cyclophosphamide (ifosfamide, trofosfamide), could be identified as 4-hydroperoxy and 4-alkylthio oxazaphosphorines. The existence of diastereomers of these products was demonstrated by thin-layer chromatography and f.d. mass spectra. Derivatization with benzylmercaptan was found to be an appropriate method for the quantitative isolation and mass spectral identification of the activated metabolic intermediates of cyclophosphamide from biological material. Using this reaction, 4-hydroxycyclophosphamide and its acyclic tautomer, aldophosphamide, which are too unstable for direct identification, were detected in urine and serum of patients treated with 3H-cyclophosphamide.
