39800-29-8Relevant academic research and scientific papers
Synthesis, Activation, and Cytotoxicity of Aldophosphamide Analogues
Borch, Richard F.,Valente, Ronald R.
, p. 3052 - 3058 (2007/10/02)
A series of perhydrooxazine analogues of aldophosphamide has been prepared, and their 31P NMR kinetics and in vitro cytotoxicity have been evaluated.These compounds were developed on the basis of the idea that ring opening and tautomerization to an enamine intermediate might provide a mechanistic alternative to the β-elimination reaction for release of phosphoramide mustard.The 4,4,6-trimethyltetrahydro-1,3-oxazine moiety was selected on the basis of its rapid rate of iminium ion generation and relatively slow rate of hydrolysis.These analogues underwent phosphorodiamidate release by three distinct mechanisms: hydrolysis to aldophosphamide and subsequent β-elimination; cyclization to produce the 4-hydroxycyclophosphamides, which release phosphorodiamidate by ring opening and elimination; and tautomerization to the enamine with rapid expulsion of phosphorodiamidate.Kinetic studies demonstrated that hydrolysis to the aldehyde contributed minimally to the overall activation process and that the enamine pathway represented the major route of activation.For those analogues that could undergo cyclization this pathway competed effectively with enamine release, and these analogues were essentially equivalent to their 4-hydroxycyclophosphamide counterparts in cytotoxicity.A series of tetra-N-substituted phosphorodiamidates that cannot undergo cyclization was prepared to explore the effects of cyclization on the cytotoxicity of these analogues.The tetrakis(chloroethyl)phosphorodiamidates were highly potent in vitro against both cyclophosphamide-sensitive and -resistant L1210 and P388 cell lines, and one of these analogues had significant antitumor activity against L1210 leukemia in vivo.These results demonstrate that the enamine mechanism provides a viable pathway for delivery of phosphorodiamidates and that this approach can be used to deliver phosphorodiamidates that are non-cross-resistant in cyclophosphamide-resistant cell lines.
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 ...
In situ preparation and fate of cis-4-hydroxycyclophosphamide and aldophosphamide: 1H and 31P NMR evidence for equilibration of cis- and trans-4-hydroxycyclophosphamide with aldophosphamide and its hydrate in aqueous solution
Borch,Hoye,Swanson
, p. 490 - 494 (2007/10/02)
cis-4-Hydroxycyclophosphamide (2) and aldophosphamide (4) were generated in aqueous phosphate or cacodylate buffer by dimethyl sulfide reduction of cis-4-hydroperoxycyclophosphamide and by sodium periodate cleavage of 3,4-dihydroxybutyl N,N-bis(2-chloroethyl)phosphorodiamate, respectively; the reactions of 2 and 4 were examined by 1H and 31P NMR. Within 30-60 min (pH or pD 7.0, 25 °C) the same pseudoequilibrium mixture was established in both reactions, with cis- and trans-4-hydroxycyclophosphamide (2 and 3), aldophosphamide (4), and its hydrate (5) present in the approximate ratio of 4:2:0.3:1. Structures of the intermediates were assigned unambiguously based upon analysis of the chemical shifts and coupling constants in the proton spectra determined in D2O buffers, and the 31P assignments followed by correlation of component ratios at equilibrium. Free energy differences of 0.4, 0.4, and 0.7 kcal/mol at 25 °C were estimated between 2, 3, 5, and 4, respectively, with 2 being the most stable. The aldehyde 4 reacted most rapidly with water to give hydrate 5; cyclization of 4 to 3 occurred faster than to 2. Compound 5 is formed much faster than 3 from the diol cleavage, but 5 and 3 are produced at comparable rates from 2, suggesting that conversion of 2 to 3 can proceed by a mechanism other than ring opening. The rate of equilibration appears to be independent of buffer structure, indicating that bifunctional catalysis is not important in the ring-opening reaction. β-Elimination from 4 is rate limiting for the production of acrolein, and the rate for phosphate is 2- to 3-fold faster than for cacodylate under identical conditions. These results provide the first definitive evidence for the stability of the elusive aldehyde 4 in aqueous solution and for the existence of a preequilibrium among 2-5 prior to rate-limiting expulsion of phosphoramide mustard from 4.
