Labeled oxazaphosphorines for applications in MS studies. Synthesis of deuterium labeled cyclophosphamides and ifosfamides

Design, Synthesis, and Biological Evaluation of Artemisinin-Piperazine-Phosphoramide Mustard Hybrids as Potential Anticancer Agents

A series of novel artemisinin-piperazine-phosphoramide mustard (PPM) hybrids were designed and synthesized by incorporating phosphoramide mustard (PM) into dihydroartemisinin (DHA) via an efficient, catalyst-free two-step sequential substitution. Artemisinin-PPM hybrids showed better cytotoxic potency against HepG2 cells than both the parent DHA and the reference, vincristine (VCR). Structure-activity relationship (SAR) studies showed that the cytotoxicity was significantly enhanced by the introduction of a thiazole moiety. Hybrid 7h, the most potent compound with the highest selectivity index IC50 (HEK-293T) / IC50 (HepG2) = 16, displayed 7.4-fold stronger potency than VCR against HepG2 cells. In addition, hybrid 7h was substantially more cytotoxic on all human cancer cells tested than on the corresponding non-cancerous cells. Flow cytometric analysis showed that 7h significantly blocked the cell cycle in the G0/G1 phase and induced apoptosis in a concentration-dependent manner.

Hydroxylation and N-dechloroethylation of Ifosfamide and deuterated Ifosfamide by the human cytochrome p450s and their commonly occurring polymorphisms

The hydroxylation and N-dechloroethylation of deuterated ifosfamide (d4IFO) and ifosfamide (IFO) by several human P450s have been determined and compared. d4IFO was synthesized with deuterium at the alpha and alpha' carbons to decrease the rate of N-dechloroethylation and thereby enhance hydroxylation of the drug at the 4' position. The purpose was to decrease the toxic and increase the efficacious metabolites of IFO. For all of the P450s tested, hydroxylation of d4IFO was improved and dechloroethylation was reduced as compared with nondeuterated IFO. Although the differences were not statistically significant, the trend favoring the 4'-hydroxylation pathway was noteworthy. CYP3A5 and CYP2C19 were the most efficient enzymes for catalyzing IFO hydroxylation. The importance of these enzymes in IFO metabolism has not been reported previously and warrants further investigation. The catalytic ability of the common polymorphisms of CYP2B6 and CYP2C9 for both reactions were tested with IFO and d4IFO. It was determined that the commonly expressed polymorphisms CYP2B6*4 and CYP2B6*6 had reduced catalytic ability for IFO compared with CYP2B6*1, whereas CYP2B6*7 and CYP2B6*9 had enhanced catalytic ability. As with the wild-type enzymes, d4IFO was more readily hydroxylated by the polymorphic variants than IFO, and d4IFO was not dechloroethylated by any of the polymorphic forms. We also assessed the use of specific inhibitors of P450 to favor hydroxylation in human liver microsomes. We were unable to separate the pathways with these experiments, suggesting that multiple P450s are responsible for catalyzing both metabolic pathways for IFO, which is not observed with the closely related drug cyclophosphamide.

Labeled oxazaphosphorines for applications in mass spectrometry studies. 2. Synthesis of deuterium-labeled 2-dechloroethylcyclophosphamides and 2- and 3-dechloroethylifosfamides

The prodrugs cyclophosphamide (CP) and ifosfamide (IF) each metabolize to an active alkylating agent through a cytochrome P450-mediated oxidation at the C-4 position. Competing with this activation pathway are enzymatic oxidations at the exocyclic α and α' carbons, which result in dechloroethylation of CP and IF. The incidence of oxidation at one position relative to another is believed to be at least one factor underlying the high degree of interpatient variability in both CP and IF pharmacokinetics. As standards for the mass spectrometry quantification of dechloroethylation, the following were synthesized: (1) [4,4,5,5-(2) H4 ]-2-dechloroethylcyclophosphamide (equivalent to [4,4,5,5-(2) H4 ]-3-dechloroethylifosfamide); (2) [α,α,4,4,5,5-(2) H6 ]-2-dechloroethylcyclophosphamide (equivalent to [α,α,4,4,5,5-(2) H6 ]-3-dechloroethylifosfamide); and (3) [α,α,4,4,5,5-(2) H6 ]-2-dechloroethylifosfamide. The common precursor to all of the target compounds was [2,2,3,3-(2) H4 ]-3-aminopropanol. A one-pot reaction of this compound with POCl3 and unlabeled or labeled 2-chloroethylamine hydrochloride gave the d4 and d6 labeled 2-dechloroethylcyclophosphamides. The construction of the 2-dechloroethylifosfamide from the aminopropanol required five discreet steps. Optimization of the synthetic pathways and stability studies are discussed.

Determination of dimethoxyphenethylamine derivatives in urine by deuterium labeled internal standards

The use of gas chromatography-mass spectrometry (GC-MS) in forensic analysis is increasing. To exploit fully the capabilities of MS, labeled standards, that can be used to improve the performance of the quantitative analysis, and to increase accuracy and precision, are required. A series of deuterated internal standards, corresponding to the 2C-series of phenethylamine derivatives, including 4-bromo-2,5-dimethoxyphenethylamine-d6 (2C-B), 4-chloro- 2,5-dimethoxyphenethylamine-d6 (2C-C), 4-iodo-2,5-dimethoxy-phenethylamine-d6 (2C-I), 4-ethylthio-2,5-dimethoxy-phenethylamine-d6 (2C-T-2) and 2,5-dimethoxy-4-n-propylthiophenethylamine-d6 (2C-T-7), were synthesized. These deuterated compounds were used to analyze for the corresponding unlabeled compounds in urine. The analysis was performed using GC-MS, with the selected ion monitoring (SIM) technique, whereby good results were achieved.