Mechanism of action of antitumor 3-(2-haloethyl) aryltriazenes on deoxyribonucleic acid

A series of novel 3-(2-haloethyl)aryltriazenes, many of which exhibit marked antileukemic activity in animal test neoplasms, react readily with DNA under physiological conditions. With regard to a single strand scission (SSS), in contrast to the related 2-haloethynitrosoureas which exhibit both Type I and Type II SSS (single strand scission) of DNA, the triazenes appear to react via Type II SSS of DNA by base alkylation followed by depurination or depyrimidination and subsequent hydrolysis of the apurinic site. The latter reaction was confirmed using apurinic site-specific endonuclease VI. A 3-(2-chloroethyl)aryltriazene readily degraded poly A by phosphate alkylation at a rate much faster than given by comparable nitrosoureas. Overall, the triazenes showed a preference for reaction at the more acidic phosphate sites in the DNA owing to their unique acid-promoted decomposition. This may, in part, account for the lack of detection of DNA interstrand cross-links and indicates a fundamentally different mechanism of action of the 3-(2-haloethyl)triazenes from the 2-haloethylnitrosoureas.     

Correlation of nitrosourea murine bone marrow toxicity with deoxyribonucleic acid alkylation and chromatin binding sites

All of the clinically available nitrosourea antitumor agents produce serious treatment-limiting bone marrow toxicity. A reduction in this toxicity can be achieved by attaching the chloroethylnitrosourea cytotoxic group to C2 (chlorozotocin) or C1 (1-(2-chloroethyl)-3-(β-d-glucopyranosyl)-1-nitrosourea, GANU) of glucose. Both glucose analogs are less myelotoxic in mice than 1-(2-chloroethyl)-3-cyclohepyl-1-nitrosourea (CCNU) or 1-(4-amino-2-methylpyrimidin-5-yl)methyl-3-(2-chloroethyl)-3-nitrosourea (ACNU), while retaining comparable antitumor activity against the murine L121o leukemia. To define the nuclear mechanisms for this reduced myelotoxicity, alkylation of L1210 and murine bone marrow DNA was quantitated. With the use of the endonucleases micrococcal nuclease and DNase I, the sites of alkylation within the chromatin substructure were determined. Experiments were performed on L1210 leukemia or bone marrow cells that had been incubated in vitro for 2 hr with 0.1 mM [¹⁴C]chloroethyl drug. The quantitative alkylation of DNA by GANU was 1.3-fold greater in L1210, as compared to bone marrow, cells. This ratio of DNA alkylation is comparable to the 1.3 ratio we previously reported for chlorozotocin [L. C. Panasci, D. Green and P. S. Schein, J. clin. Invest.64, 1103 (1979)]. In contrast, the ratio of alkylation (L1210: bone marrow DNA) for the myelotoxic ACNU was 0.66, similar to 0.59 for CCNU. Nuclease digestion experiments demonstrated that chlorozotocin and GANU preferentially alkylated internucleosomal linker regions of bone marrow chromatin, while nucleosome core particles were the preferred targets of CCNU and ACNU. The reduced myelotoxicity of chlorozotocin and GANU may be correlated with the advantageous ratio of L1210: bone marrow DNA alkylation and preferential alkylation of internucleosomal regions of bone marrow chromatin.     

Mechanism of action of 2-haloethylnitrosoureas on deoxyribonucleic acid. Nature of the intermediates from nitrosourea decomposition.

Direct current (DC) and differential pulse polarographic analyses were used to measure the rates of decomposition of a series of 2-haloethylnitrosoureas in aqueous solution. Measured by these methods, the rates of the first and rate-determining step which show a marked pH and solvent dependence agree with the overall rate of decomposition measured by gas evolution. In the 1,3-bis(haloethyl)-1-nitrosourea series, changing the nature of the halogen X has a small effect on the rate of decomposition. In the 3-cyclohexyl-1-(2-haloethyl)-1-nitrosourea series, changing X for OH or OCH₃ results in the rate of hydrolysis being reduced considerably. A free—NH₂ group in the nitrosourea structure as in CNU, MNU, ENU, CPNU, 4-CBNU and 5-CPNU accelerates considerably the rate of decomposition relative to the BCNU and CCNU series. Arrhenius parameters for the decomposition in aqueous pH 7.1 solution in the temperature range 28–47° were obtained for BFNU, BCNU and BBNU: log A, ?20.1± 1.4,?21.6± 0.7 and ?22.3±1.6; E_a, 24.4 ± 2.0, 26.5± 1.0 and 27.2 m 2.3 kcal/mole. The corresponding values for BINU were estimated as log A,?23.3± 3.0; E_a, 28.0± 3.0 kcal/mole. Examination of the decomposition products of 1,3-bis(2-chloropropyl)-1-nitrosourea (BCNU-β-Me) and 1,3-bisl 1-(chloromethyl)ethyl]-1-nitrosourea (BCNU-α-Me) favors decomposition pathway B via the diazohydroxide and cyclic chloronium ion for BCNU-β-Me and via the diazohydroxide and/or 2-chloro-1-methylethyl carbonium ion for BCNU-α-Me. While there is no evidence for the contribution of pathway A via a 2-imino-N-nitrosooxazolidinone for these compounds, consideration of product type and yields implicates a third decomposition pathway, via a 1,2,3-oxadiazoline intermediate. Additional evidence for an oxadiazoline intermediate is obtained by the isolation of 2-bromoethanol when BCNU is decomposed in the presence of a high concentration of sodium bromide.     

The effect of alkylating agents and other drugs on the accumulation of melphalan by murine L1210 leukaemia cells in vitro

The effect of cytotoxic and other drugs on the accumulation of melphalan by L1210 murine leukaemia cells was studied. We have confirmed that uptake is an active process competitively inhibited by l-leucine. In 36 experiments in amino acid-free medium the mean concentration of melphalan taken up was 225 pmoles/10⁶ cells. High pressure liquid Chromatographie analysis showed that the majority of the drug is present as free native melphalan. 1, 3-Bis(2-chloroethyl)-1-nitrosourea (BCNU) was the only drug that stimulated accumulation, but without significant effect on influx or efflux rates. Busulphan, chlorambucil, cyclophosphamide, interferon, methotrexate and prednisolone had no effect on accumulation after 30 min melphalan transport. Adriamycin, CCNU, methyl CCNU, mustine and vincristine all impaired melphalan accumulation as did the non-cytotoxic drugs aminophylline, chlorpromazine and ouabain. Adriamycin, aminophylline, chloropromazine, indomethacin and ouabain all reduced melphalan influx.     

Phase II trial of PCNU in advanced malignant melanoma: an Eastern Cooperative Oncology Group pilot study

Summary PCNU, a chloroethylnitrosourea with high alkylating activity, low carbamoylating activity, optimal octanol: water partition coefficient and broad activity in animal systems, was administered to 32 evaluable patients with measurable metastatic melanoma by brief intravenous infusions every six weeks. The initial dose was 75 or 100 mg/m², with escalation or reduction for toxicity, and a total of 58 evaluable courses were given. Half of the patient population had received no prior chemotherapy. One objective complete response (duration 585 days) and four objective partial responses (durations 55, 169, 405 and 102 days) occurred, the last recorded in a patient previously treated with DTIC. These responses included visceral, nodal and subcutaneous disease. The response rate was 16% with a 95% confidence interval of 5.5 to 33.7%. Thrombocytopenia was dose-limiting and leukopenia was relatively mild. Gastrointestinal toxicity was less severe than expected for a nitrosourea. PCNU has comparable clinical activity to that of other nitrosoureas in patients with advanced melanoma.     

A structure--activity study of seven new water soluble nitrosoureas.

The in vitro alkylating activity, carbamoylating activity, decomposition rates and octanol-water partition coefficients (Log P) of seven water soluble chloroethylnitrosourea antitumor agents and a reference lipid soluble analog were correlated with their biological activities in mice. The alkylating activity of each compound demonstrated a significant inverse linear correlation with both the decomposition rate in 0.1 M sodium phosphate buffer. pH7.4 (r = -0.92,P< 0.01), and the molar ld₁₀ dose (r = 0.87, P< 0.01). A direct relationship was found between the Log P values and both the alkylating activity (r = -0.86. P< 0.01) and the molar ld₁₀ dose (r = 0.77, P< 0.025). However, the addition of the variable. Log P, in multiple regression analysis did not contribute significantly to any of the direct correlations of chemical parameters with biological variables. In comparison, carbamoylating activity did not function as an independent variable for the relative myelotoxicity or lethality of each compound. All water soluble drugs except for chlorozotocin and 1-(2 chloroethyl)-3-(β-d-glucopyranosyl)-1-nitrosourea, the two analogs with glucose carriers, produced a significant reduction in circulating neutrophils at their respective ld₁₀ doses. There was no correlation between relative myelotoxicity and alkylating activity, carbamoylating activity or Log P. The glucose moiety appears to function as an independent variable for reducing nitrosourea cytotoxicity to bone marrow cells without significantly altering antitumor activity.     

In vitro pharmacokinetics and pharmacodynamics of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU)

The relationship between treatment efficacy and the pharmacokinetics (PK) and pharmacodynamics (PD) of anticancer drugs is poorly defined. 1,3-Bis(2-chloroethyl)-1-nitrosourea (BCNU) is an alkylating agent used in the treatment of brain and other forms of cancer. It is postulated that BCNU kills cells by forming DNA interstrand cross-links. The present study was undertaken to characterize the PK and PD of BCNU in mouse L1210 cells. L1210 cells were exposed to BCNU (0-160 microM) and analyzed for intracellular BCNU concentrations, DNA interstrand cross-links, cell cycle phase, and cytotoxicity. The half-life of BCNU in cells was approximately 40 min. The maximum reduction of mitochondrial enzyme activity (maximum cell death) achieved within 24 hr after exposure to BCNU was concentration-dependent and could be described by a Hill equation. At lower concentrations, the area under the DNA interstrand cross-link-time curve linearly correlated with the maximum cell death and the area under the BCNU concentration-time curve. BCNU induced cell accumulation in the G(2)/M phase of the cell cycle, which continued even after apparent completion of cross-link repair. Loss of membrane permeability was minimal (approximately 2%) during the first 24 hr. Thereafter, cells died exponentially over the next 9 days, primarily by necrosis. In conclusion, while cytotoxicity was concentration-dependent, an indirect relationship was found among the time-course of BCNU concentrations, DNA interstrand cross-links, and cell death. Because of the disparity between the time-scale of PK and PD, focusing only on the early events may provide limited information about the process of anticancer drug-induced cell death.     

Morphological transformation of hamster embryo cells by cancer chemotherapeutic agents

Studies were made on induction of morphological transformation of hamster embryo cells by various types of cancer chemotherapeutic agents, including alkylating agents, antimetabolites, antibiotics and natural products. Cyclophosphamide, actinomycin D, mitomycin C and adriamycin hydrochloride, which are widely used as cancer chemotherapeutic agents and are also known to be carcinogenic in animals, produced significant morphological transformation. Two other compounds that are known to be carcinogenic in vivo, thio-TEPA and daunomycin hydrochloride, did not induce transformation. The anti-metabolites 6-mercaptopurine, 5-fluorouracil, cytosine arabinoside and methotrexate also did not produce morphological transformation of hamster embryo cells.     

O~6-苄基鸟嘌呤增强 1,3-二 (2 -氯乙基)-亚硝基脲对人肝癌细胞及其移植瘤的抗肿瘤作用(英文)

应用噻唑蓝 (MTT)法检测 O6-苄基鸟嘌呤(O6- BG)与 1 ,3-二 (2 -氯乙基 ) -亚硝基脲 (BCNU)合用的细胞毒作用及透射电镜检测凋亡细胞的方法研究了 O6- BG对 O6-烷基鸟嘌呤 - DNA烷基转移酶(O6- AGT )阳性的人肝癌细胞 SMMC- 772 1对BCNU细胞毒作用敏感性的影响及其与 BCNU合用治疗移植瘤的协同效果 .结果显示 :1 .5- 6.0 mg· L-1的 O6- BG预先作用 2 h后 ,SMMC- 772 1细胞对 BCNU的敏感性明显增加 ;0 .75- 6.0 mg· L-1的 O6- BG可完全快速地抑制肿瘤细胞的 AGT活性并持续 1 2 h;ip 90 mg· kg-1的 O6- BG预处理 2 h后给予 2 5mg·kg-1的 BCNU治疗 ,可使动物 sc接种的人肝癌移植瘤生长延迟 38.6d,诱导肿瘤细胞凋亡 ,并且可明显抑制肿瘤组织的转移酶活性 .说明 O6- BG与 BCNU合用于 AGT阳性的肿瘤将具有明显的治疗效果     

Stereoselective monooxygenation of carcinostatic 1-(2-chloroethyl)-3-(cyclohexyl)-1-nitrosourea and 1-(2-chloroethyl)-3-(trans-4-methylcyclohexyl)-1-nitrosourea by purified cytochrome P-450 isozymes

Three highly purified forms of liver microsomal cytochrome P-450 (P-450a, P-450b and P-450c) from Aroclor 1254-treated rats catalyzed 1-(2-chloroethyl)-3-(cyclohexyl)-1-nitrosourea (CCNU) and 1-(2-chloroethyl)-3-(trans-4-methylcyclohexyl)-1-nitrosourea (MeCCNU) monooxygenation in the presence of purified NADPH-cytochrome P-450 reductase, NADPH, and lipid. Differences in the regioselectivity of CCNU and MeCCNU monohydroxylation reactions by the cytochrome P-450 isozymes were observed. Cytochrome P-450-dependent monooxygenation of CCNU gave only alicyclic hydroxylation products, but monooxygenation of MeCCNU gave alicyclic hydroxylation products, an αhydroxylation product on the 2-chloroethyl moiety, and a trans-4-hydroxymethyl product. A high degree of stereoselectivity for hydroxylation of CCNU and MeCCNU at the cis-4 position of the cyclohexyl ring was demonstrated. All three cytochrome P-450 isozymes were stereoselective in primarily forming the metabolite cis-4-hydroxy-trans-4-Methyl-CCNU from MeCCNU. The principal metabolite of CCNU which resulted from cytochromes P-450a and P-450b catalysis was cis-4-hydroxy CCNU, whereas the principal metabolites from cytochrome P-450c catalysis were the trans-3-hydroxy and the cis-4-hydroxy isomers. Total amounts of CCNU and MeCCNU hydroxylation with cytochrome P-450b were twice that with hepatic microsomes from Aroclor 1254-treated rats. Catalysis with cytochromes P-450a and P-450c was substantially less effective than that observed with either cytochrome P-450b or hepatic microsomes from Aroclor 1254-treated rats.     

Antitumour imidazotetrazines--IV. An investigation into the mechanism of antitumour activity of a novel and potent antitumour agent, mitozolomide (CCRG 81010, M & B 39565; NSC 353451)

8-Carbamoyl-3-(2-chloroethyl)imidazo[5,1-d]-1,2,3,5-tetrazin-4-(3H )-one- mitozolomide (CCRG 81010, M & B 39565, NSC 353451) is a potent inhibitor of the growth of a number of experimental tumours and can potentially decompose to give either an isocyanate or the monochloroethyltriazene (MCTIC). In vitro CCRG 81010 is not cross-resistant with the bifunctional alkylating agents against the Walker carcinoma. To investigate the mechanism of the antitumour activity of CCRG 81010 a comparison has been made with BCNU and MCTIC on precursor incorporation into macromolecules in TLX5 mouse lymphoma cells. Whereas BCNU produces a rapid and extensive inhibition of both (methyl 3H) thymidine and [5-3H]uridine incorporation into acid-insoluble material, neither CCRG 81010 or MCTIC have an early effect on precursor incorporation. Inhibition of precursor uptake is also not produced by concentrations of 2-chloroethylisocyanate that inhibit intracellular glutathione reductase activity. The potential carbamoylating activity of CCRG 81010 has also been assessed by comparing its effect with that of BCNU and 2-chloroethyl isocyanate on enzymes known to be inhibited by carbamoylation. Such enzymes, glutathione reductase, chymotrypsin and gamma-glutamyltranspepidase are not inhibited by CCRG 81010 under conditions where BCNU and 2-chloroethyl isocyanate show complete inhibition of enzyme activity, suggesting an absence of carbamoylating species. The results suggest that the most likely antitumour metabonate produced from CCRG 81010 is the triazene MCTIC.     

LC-MS/MS法研究1-[1-(6-甲氧基-2-萘基)乙基]-2-(4-硝基苄基)-6,7-二甲氧基-1,2,3,4-四氢异喹啉氢溴酸盐在大鼠体内的代谢产物

采用液相色谱-串联质谱法对大鼠灌胃1-［1-(6-甲氧基-2-萘基)乙基］-2-(4-硝基苄基)-6,7-二甲氧基-1,2,3,4-四氢异喹啉氢溴酸盐(编号P91024)后粪便、尿液、胆汁和血浆中的主要代谢产物进行研究。通过比较给药样品和空白样品的全扫描总离子流色谱和选择离子扫描色谱图差别寻找I相代谢产物；根据其一级和二级质谱图，确定I相代谢产物的分子结构。完全提取I相代谢产物后的样品溶液，再用葡糖醛酸酶酶解，得II相结合物的苷元部分，采用与I相代谢产物鉴定同样方法寻找和鉴定II相代谢产物苷元的结构，进而确证II相代谢产物的分子结构。从大鼠粪便中鉴定出P91024的2个I相代谢物，从胆汁中鉴定出1个I相和5个II相代谢产物，从尿液中鉴定出1个I相和3个II相代谢产物，从血浆中鉴定出4个I相和1个II相代谢产物；并分别分析推测出它们的结构。P91024在大鼠体内被代谢转化为多种产物，利用LC-MS/MS可以快速寻找和鉴定。     

血吸虫病化学治疗的研究 ⅩⅩⅩⅥ.4-苯基(或烯丙基)-5-(吡嗪-2)-1,2,4-三唑-3-硫酮衍生物的合成

本文报导28个4-苯基(或烯丙基)-5-(吡嗪-2)-1,2,4-三唑-3-硫酮衍生物的合成。这类化合物的合成是以吡嗪甲酸乙酯与水合肼反应得2-吡嗪甲酰肼,再与不同的异硫氰酸酯作用后,在2N氢氧化钠溶液中环合而得Ⅱ或Ⅲ,然后经烷化、酰化及Mannich反应,分别制得相应的化合物。其中Ⅲ₁和Ⅲ₂对感染日本血吸虫小白鼠有明显肝移作用。     

Brain uptake and CNS levels of 1-(2-chloroethyl)-1-nitroso-3-(2-hydroxyethyl)urea (HECNU)

The uptake of ¹⁴C-labeled 1-(2-chloroethyl)-1-nitroso-3-(2-hydroxyethyl) urea (HECNU) into the brain was investigated in the rat after intracarotid injection according to the method of OLDENDORF, as well as in cisternal cerebrospinal fluid obtained by suboccipital puncture after i.v. injection of the drug.The brain uptake index was 31.9 ± 2.9%. Cerebrospinal fluid/blood quotients after i.v. injection were 0.82 at 10 min and 1.10 at 60 min. The results of both methods clearly show that HECNU, in spite of its hydrophilic property, easily penetrates the blood-brain barrier.     

Effect of caloric restriction on hepatic nuclear DNA damage in male Fischer 344 rats treated with aflatoxin B1.

Caloric restriction is known to reduce chemically-induced tumor incidence in laboratory animals. The effect is believed to be mediated in part by modification of hepatic drug metabolism, including both phase I and phase II enzymes. Using aflatoxin B1 (AFB1) as a model carcinogen, we studied the effect of caloric restriction on the modification of rat liver nuclear DNA by AFB1 and DNA damage due to the formation of apurinic sites from the AFB1-DNA adduct removal process. Caloric restriction reduced the metabolic activation of AFB1 which resulted in a decrease of AFB1-DNA binding by more than 50%. The results of the study of the effect of caloric restriction on the AFB1-induced DNA strand breakage assayed by the alkaline unwinding technique showed that caloric restriction protected the formation of apurinic sites from the AFB1-DNA adducts and reduced the double strand DNA breakages by 1.3-2.5-fold. Thus, the lower initial AFB1-DNA binding and less DNA damage, presumably by the less apurinic sites formed during the depurination process of AFB1-DNA adducts, contributed to the protective effect of caloric restriction.     

Application of lipid microspheres for the treatment of cancer

Lipid microspheres can act as a carrier for antitumor agents. We incorporated a lipophilic antitumor agent, l,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) into microspheres by homogenizing a soybean oil solution of BCNU with egg yolk lecithin. Lipid microsphere-encapsulated BCNU showed a significantly enhanced antitumor activity with reduced toxicity in mice with L1210 leukemia when compared to the corresponding dose of free BCNU. Lipid nanospheres, smaller particles containing BCNU with an average size of 50 nm, also showed a similar level of in vivo antitumor activity. An in vitro study showed that [¹⁴C]triolein uptake by tumor cells was increased by incorporation into microspheres. The in vitro uptake of small microspheres was lower than that of standard microspheres. However, the in vivo half-life of small microspheres was longer, they avoided capture by the reticuloendothelial system and showed higher accumulation at tumor sites. Thus, lipid microspheres may be useful for delivering various lipophilic chemotherapy agents.     

Reductive activation of the prodrug 1,2-bis(methylsulfonyl)-1-(2-chloroethyl)-2-[[1-(4-nitrophenyl)ethoxy]carbonyl]hydrazine (KS119) selectively occurs in oxygen-deficient cells and overcomes O-alkylguanine-DNA alkyltransferase mediated KS119 tumor cell resistance

1,2-Bis(methylsulfonyl)-1-(2-chloroethyl)-2-[[1-(4-nitrophenyl)ethoxy]carbonyl]hydrazine (KS119) is a prodrug of the 1,2-bis(sulfonyl)hydrazine class of antineoplastic agents designed to exploit the oxygen-deficient regions of cancerous tissue. Thus, under reductive conditions in hypoxic cells this agent decomposes to produce the reactive intermediate 1,2-bis(methylsulfonyl)-1-(2-chloroethyl)hydrazine (90CE), which in turn generates products that alkylate the O⁶-position of guanine in DNA. Comparison of the cytotoxicity of KS119 in cultured cells lacking O⁶-alkylguanine-DNA alkyltransferase (AGT) to an agent such as Onrigin™, which through base catalyzed activation produces the same critical DNA G-C cross-link lesions by the generation of 90CE, indicates that KS119 is substantially more potent than Onrigin™ under conditions of oxygen deficiency, despite being incompletely activated. In cell lines expressing relatively large amounts of AGT, the design of the prodrug KS119, which requires intracellular activation by reductase enzymes to produce a cytotoxic effect, results in an ability to overcome resistance derived from the expression of AGT. This appears to derive from the ability of a small portion of the chloroethylating species produced by the activation of KS119 to slip through the cellular protection afforded by AGT to generate the few DNA G-C cross-links that are required for tumor cell lethality. The findings also demonstrate that activation of KS119 under oxygen-deficient conditions is ubiquitous, occurring in all of the cell lines tested thus far, suggesting that the enzymes required for reductive activation of this agent are widely distributed in many different tumor types.     

KS900: A hypoxia-directed, reductively activated methylating antitumor prodrug that selectively ablates O-alkylguanine-DNA alkyltransferase in neoplastic cells

To most effectively treat cancer it may be necessary to preferentially destroy tumor tissue while sparing normal tissues. One strategy to accomplish this is to selectively cripple the involved tumor resistance mechanisms, thereby allowing the affected anticancer drugs to gain therapeutic efficacy. Such an approach is exemplified by our design and synthesis of the intracellular hypoxic cell activated methylating agent, 1,2-bis(methylsulfonyl)-1-methyl-2-[[1-(4-nitrophenyl)ethoxy]carbonyl]hydrazine (KS900) that targets the O-6 position of guanine in DNA. KS900 is markedly more cytotoxic in clonogenic experiments under conditions of oxygen deficiency than the non-intracellularly activated agents KS90, and 90M, when tested in O⁶-alkylguanine-DNA alkyltransferase (AGT) non-expressing cells (EMT6 mouse mammary carcinoma, CHO/AA8 hamster ovary, and U251 human glioma), and than temozolomide when tested in AGT expressing cells (DU145 human prostate carcinoma). Furthermore, KS900 more efficiently ablates AGT in HL-60 human leukemia and DU145 cells than the spontaneous globally activated methylating agent KS90, with an IC₅₀ value over 9-fold lower than KS90. Finally, KS900 under oxygen-deficient conditions selectively sensitizes DU145 cells to the chloroethylating agent, onrigin, through the ablation of the resistance protein AGT. Thus, under hypoxia, KS900 is more cytotoxic at substantially lower concentrations than methylating agents such as temozolomide that are not preferentially activated in neoplastic cells by intracellular reductase catalysts. The necessity for intracellular activation of KS900 permits substantially greater cytotoxic activity against cells containing the resistance protein O⁶-alkylguanine-DNA alkyltransferase (AGT) than agents such as temozolomide. Furthermore, the hypoxia-directed intracellular activation of KS900 allows it to preferentially ablate AGT pools under the oxygen-deficient conditions that are present in malignant tissue.     

3-(S)-(-)-(1-氨甲酰基-1,1-二苯甲基)吡咯烷酒石酸盐的制备

以L-苹果酸(2)为原料,经与苄胺缩合、还原、氢解脱苄、磺酰化、烷基化、脱保护基、水解后成盐制得氢溴酸达非那新关键中间体3-(S)-(-)-(1-氨甲酰基-1,1-二苯甲基)吡咯烷酒石酸盐,总收率约22%(以2计).     

Decomposition reactions of (hydroxyalkyl) nitrosoureas and related compounds: possible relationship to carcinogenicity

(Hydroxyalkyl)nitrosoureas and the related cyclic carbamates N-nitrosooxazolidones are potent carcinogens. The decompositions of four such compounds, 1-nitroso-1-(2-hydroxyethyl)urea (I), 3-nitrosooxazolid-2-one (II), 1-nitroso-1-(2-hydroxypropyl)urea (III), and 5-methyl-3-nitrosooxazolid-2-one (IV), in aqueous buffers at physiological pH were studied to determine if any obvious differences in decomposition pathways could account for the variety of tumors obtained from these four compounds. The products predicted by the literature mechanisms for nitrosourea and nitrosooxazolidone decompositions (which were derived from experiments at pH 10-12) were indeed the products formed, including glycols, active carbonyl compounds, epoxides, and, from the oxazolidones, cyclic carbonates. Furthermore, it was shown that in pH 6.4-7.4 buffer epoxides were stable reaction products. However, in the presence of hepatocytes, most of the epoxide was converted to glycol. The analytical methods developed were then applied to the analysis of the decomposition products of some related dialkylnitrosoureas, and similar results were obtained. The formation of chemically reactive secondary products and the possible relevance of these results to carcinogenesis studies are discussed.