5-氟胞苷和5''-脱氧-5-氟胞苷的合成

5-氟胞嘧啶经苯甲酰化保护后分别与供糖体四乙酰核糖和5-脱氧三乙酰核糖缩合,再经氨解,以45.7%和42.6%的收率分别制得5-氟胞苷和5'-脱氧-5-氟胞苷.     

5＇-脱氧-5-氟胞苷类衍生物的合成及其抗肿瘤活性

目的设计并合成具有抗肿瘤活性的5＇-脱氧-5-氟胞苷类衍生物。方法2＇,3＇-O-二乙酰-5＇-脱氧-5-氟胞苷在三氯氧磷存在下与1,2,4-三唑缩合得到1-（2＇,3＇-O-二乙酰-5＇-脱氧-β-D-呋喃核糖）-4-（1,2,4-三唑-1-基）-5-氟嘧啶-2-（1H）-酮（3）,后者用不同的亲核基团取代核苷C-4位上的三唑基团,制备一系列含有烷基胺、烷氧基和脒基的5＇-脱氧-5-氟胞苷类衍生物。结果合成了15个未见报道的新化合物,化合物的结构经1H-NMR、FAB-MS及元素分析确证。结论抗肿瘤活性测试表明,其中某些化合物的活性与对照药物卡培他滨相当,对肺癌、结肠癌、乳腺癌和肝癌细胞显示出较好的抑制活性。     

5''''-脱氧-5-氟胞苷类衍生物的合成及其抗肿瘤活性

目的 设计并合成具有抗肿瘤活性的5'-脱氧-5-氟胞苷类衍生物.方法 2',3'-O-二乙酰-5'-脱氧-5-氟胞苷在三氯氧磷存在下与1,2,4-三唑缩合得到1-(2',3'-O-二乙酰-5'-脱氧-β-D-呋喃核糖)-4-(1,2,4-三唑-1-基)-5-氟嘧啶-2-(1H)-酮(3),后者用不同的亲核基团取代核苷C-4位上的三唑基团,制备一系列含有烷基胺、烷氧基和脒基的5'-脱氧-5-氟胞苷类衍生物.结果 合成了15个未见报道的新化合物,化合物的结构经1H-NMR、FAB-MS及元素分析确证.结论 抗肿瘤活性测试表明,其中某些化合物的活性与对照药物卡培他滨相当,对肺癌、结肠癌、乳腺癌和肝癌细胞显示出较好的抑制活性.     

5′-脱氧-5-氟胞苷类衍生物的合成及其抗肿瘤活性

目的设计并合成具有抗肿瘤活性的5′-脱氧-5-氟胞苷类衍生物。方法2′,3′-O-二乙酰-5′-脱氧-5-氟胞苷在三氯氧磷存在下与1,2,4-三唑缩合得到1-(2′,3′-O-二乙酰-5′-脱氧-β-D-呋喃核糖)-4-(1,2,4-三唑-1-基)-5-氟嘧啶-2-(1H)-酮(3),后者用不同的亲核基团取代核苷C-4位上的三唑基团,制备一系列含有烷基胺、烷氧基和脒基的5′-脱氧-5-氟胞苷类衍生物。结果合成了15个未见报道的新化合物,化合物的结构经1H-NMR、FAB-MS及元素分析确证。结论抗肿瘤活性测试表明,其中某些化合物的活性与对照药物卡培他滨相当,对肺癌、结肠癌、乳腺癌和肝癌细胞显示出较好的抑制活性。     

2＇-脱氧-5-氟尿苷的合成工艺改进

目的：改进2＇-脱氧-5-氟尿苷的合成工艺。方法：参照文献方法,以氟尿嘧啶为起始原料,经硅醚化、缩合、溴化、氢化和皂化等工艺合成2＇-脱氧-5-氟尿苷,并对其关键步骤进行了改进。结果：该合成工艺对2＇-脱氧-5-氟尿苷有较高的收率,总收率为34.31%。结论：工艺更趋于合理,操作条件更为简单,三废易于处理,适合于工业化生产。     

2''''-脱氧-5-氟尿苷的合成工艺改进

目的:改进2'-脱氧-5-氟尿苷的合成工艺。方法:参照文献方法,以氟尿嘧啶为起始原料,经硅醚化、缩合、溴化、氢化和皂化等工艺合成2'-脱氧-5-氟尿苷,并对其关键步骤进行了改进。结果:该合成工艺对2'-脱氧-5-氟尿苷有较高的收率,总收率为34.31%。结论:工艺更趋于合理,操作条件更为简单,三废易于处理,适合于工业化生产。     

抗肿瘤药物2''''-脱氧-5-氟尿苷合成研究

目的合成抗肿瘤药物2'-脱氧-5-氟尿苷.方法以5-氟尿嘧啶核苷为原料,经丙酰澳酰化溴代得2'溴代-3',5'-O-二丙酰基-5-氟尿嘧啶核苷,然后氢化得产物2'-脱氧-3',5'-O-二丙酰基-5-氟尿嘧啶核苷,最后经皂化合成2'-脱氧-5-氟尿苷.结果以5-氟尿嘧啶核苷为起始原料经3步反应合成了2'-脱氧-5-氟尿苷.结论本合成方法工艺简便,原料易得,条件温和,总收率为72.0%,适于工业制备.     

抗肿瘤药物2′-脱氧-5-氟尿苷合成研究

目的:合成抗肿瘤药物2′-脱氧-5-氟尿苷。方法:以5-氟尿嘧啶核苷为原料,经丙酰溴酰化溴代得2′-溴代-3,′5′-O-二丙酰基-5-氟尿嘧啶核苷,然后氢化得产物2′-脱氧-3,′5′-O-二丙酰基-5-氟尿嘧啶核苷,最后经皂化合成2′-脱氧-5-氟尿苷。结果:以5-氟尿嘧啶核苷为起始原料经3步反应合成了2′-脱氧-5-氟尿苷。结论:本合成方法工艺简便,原料易得,条件温和,总收率为72.0%,适于工业制备。     

HPLC法同时测定人血浆中5-氟尿嘧啶及其活性代谢物5-氟-2＇-脱氧尿嘧啶核苷的浓度

目的：建立一种同时测定人体血浆中5-氟尿嘧啶及其活性代谢物5-氟-2＇-脱氧尿嘧啶核苷浓度的HPLC法。方法：以肌苷为内标，血浆样品用硝酸银（10％）沉淀蛋白质，采用C18柱，检测波长为266nm，流动相：0．01mol·L^-1磷酸盐（用2mol·L^-1氢氧化钠溶液调pH为7．0）-甲醇（96：4），流速1．0mL·min^-1，柱温为45℃。结果：5-氟尿嘧啶和5-氟-2＇-脱氧尿嘧啶核苷分别在0．1～20μg·mL^-1（r=0．9997）和0．2～40μg·mL^-1（r=0．9997）浓度范围内线性关系良好，最低检测浓度分别为5和10ng·mL^-1，方法回收率分别为98．2％～101．2％、99．5％～102．3％，日内、日间RSD均小于6％。结论：方法灵敏、快速、准确，适用于临床上测定5-氟尿嘧啶及其活性代谢物5-氟-2＇-脱氧尿嘧啶核苷的血药浓度及药动学的研究。     

5-氟胞嘧啶核苷的合成

5-氟胞嘧啶核苷(1)是曾作为抗肿瘤药研发的氟西他滨(flurocitabine)的合成中间体[1],1964年报道的合成路线[2]反应条件苛刻,操作繁琐,收率仅24%～27%.本研究参考相关文献[3～6],以六甲基二硅氮烷(HMDS)和三甲基氯硅烷(TMSCl)为硅烷化试剂,与5-氟胞嘧啶(2)反应制得2,4-二(三甲基硅烷基)-5-氟胞嘧啶(3),3与四乙酰核糖缩合得2',3',5'-三乙酰基-5-氟胞嘧啶核苷(4),最后氨解制得1(图1).操作简便,条件温和,总收率46%.     

5'-Deoxy-5'-methylthioadenosine: a nucleoside which differentiates between adenosine receptor types

The activities of an endogenous nucleoside, 5'-deoxy-5'-methylthioadenosine (MTA), on adenosine sensitive sites such as adenosine A1 and A2 receptors and the P-site, as well as on purine nucleoside transport, have been studied. This nucleoside competitively antagonized the A2 receptor-mediated stimulation of neuroblastoma adenylate cyclase, produced a GTP-dependent and 8-p-sulfophenyltheophylline-sensitive inhibition of adenylate cyclase activity in rat cerebellar membranes, and decreased the spontaneous contractile activity of isolated segments of rabbit jejunum. MTA was neither active at the P-site nor did it diminish the binding of [3H]nitrobenzylthioinosine, a nucleoside transport inhibitor. We conclude that (a) MTA is an agonist at the adenosine A1 receptor but an antagonist at the A2 receptor, and (b) the adenosine receptor which causes relaxation of rabbit jejunum is not a neuroblastoma-type A2 receptor which activates adenylate cyclase.     

Effects of 5-fluorocytidine on mammalian transfer RNA and transfer RNA methyltransferases.

Effects of 5-fluorocytidine on mouse liver tRNA and mouse liver tRNA methyltransferases were investigated. tRNA isolated from drug-treated tissue was shown to contain 5-fluorocytidine and 5 fluorouridine. The amounts of all 5-substituted pyrimidine nucleosides such as 5-methylcytidine, 5-methyluridine, pseudouridine and 5,6-dihydrouridine were substantially reduced. The decreased methylation of tRNA was shown to result from decreased tRNA cytosine-5-methyltransferase and tRNA uracil-5-methyltransferase activities and capacities. Incorporation of 5-fluorouridine into tRNA, as well as the effects of 5-fluorocytidine administration on the modified uridine derivatives in tRNA, suggested the in vivo conversion of 5-fluorocytosine derivatives to 5-fluorouracil derivatives, as administration of the latter had been shown previously to cause the same effects. The inhibition of tRNA cytosine-5-methyltransferase after administration of 5-fluorocytidine resembles the effect of another cytidine analog, 5-azacytidine, which is known to cause lack of 5-methylcytidine in mouse liver tRNA and the inhibition of this particular tRNA methyltransferase.     

5'-Deoxy-5'-methylthioadenosine phosphorylase--III. Role of the enzyme in the metabolism and action of 5'-halogenated adenosine analogs

5'-Deoxy-5'-halogenated adenosines are alternative substrates for 5'-deoxy-5'-methylthioadenosine phosphorylase (MTAPase), an enzyme responsible for the metabolism of 5'-deoxy-5'-methylthioadenosine (MTA), a by-product of polyamine biosynthesis. The relative reactivity of these nucleosides with MTAPase from HL-60 human promyelocytic leukemia cells is MTA greater than 5'-deoxy-5'-fluoroadenosine (5'-FlAdo) greater than 5'-chloro-5'-deoxyadenosine (5'-ClAdo) greter than 5'-bromo-5'-deoxyadenosine (5'-BrAdo) greater than 5'-deoxy-5'-iodoadenosine (5'-IAdo). In MTAPase-containing cells, the adenine released from the 5'-halogenated adenosine was incorporated into adenine nucleotide pools; cleavage by (MTAPase appeared to be the rate-limiting step in this process. 5'-BrAdo and 5'-IAdo were growth inhibitors (EC50 values less than 10 microM) of MTAPase-containing cell lines (HL-60 human promyelocytic leukemia and the L5178Y murine lymphoblastic leukemia) but were much less active (EC50 values greater than 65 microM) against MTAPase-deficient cell lines (the CCRF-CEM human T cell leukemia and the L1210 murine leukemia). The full cytotoxicity of these compounds, therefore, appeared to be related to their phosphorolysis by MTAPase. Indirect evidence suggests that 5-halogenated ribose-1-phosphate derivatives of 5'-BrAdo or 5'-IAdo produced by the MTAPase reaction were the active metabolites of these 5'-halogenated adenosines.     

Identification of the cytosolic carboxylesterase catalyzing the 5'-deoxy-5-fluorocytidine formation from capecitabine in human liver.

Capecitabine, a prodrug of 5-fluorouracil, is first metabolized to 5'-deoxy-5-fluorocytidine (5'-DFCR) by carboxylesterase (CES), which is mainly expressed in microsomes. Recently, we clarified that 5'-DFCR formation was catalyzed by the enzyme in cytosol as well as microsomes in human liver. In the present study, the cytosolic enzyme involved in 5'-DFCR formation from capecitabine was identified. This enzyme was purified in the cytosolic preparation by ammonium sulfate precipitation, Sephacryl S-300 gel filtration, Mono P chromatofocusing, and Superdex 200 gel filtration. The purified enzyme was identified by the amino acid sequence analysis to be CES1A1 or a CES1A1 precursor. Based on the result of the N-terminal amino acid sequence analysis, the purified enzyme has no putative signal peptide, indicating that it was CES1A1. The apparent Km and Vmax values of 5'-DFCR formation were 19.2 mM and 88.3 nmol/min/mg protein, respectively. The 5'-DFCR formation catalyzed by the purified enzyme was inhibited by both diisopropylfluorophosphate and bis(p-nitrophenyl)phosphate in a concentration-dependent manner. 7-Ethyl-10-hydroxycamptothecin (SN-38) formation from irinotecan also occurred in the purified enzyme, cytosol, and microsomes. In conclusion, the cytosolic enzyme involved in 5'-DFCR formation from capecitabine would be CES1A1. It is suggested that the cytosolic CES has significant hydrolysis activity and plays an important role as the microsomal CES in drug metabolism. It is worthy to investigate the metabolic enzyme in cytosol involved in the activation of ester-type prodrugs such as capecitabine.     

Bioactivation of capecitabine in human liver: involvement of the cytosolic enzyme on 5'-deoxy-5-fluorocytidine formation.

Capecitabine, an anticancer prodrug, is thought to be biotransformed into active 5-fluorouracil (5-FU) by three enzymes. After oral administration, capecitabine is first metabolized to 5'-deoxy-5-fluorocytidine (5'-DFCR) by carboxylesterase (CES), then 5'-DFCR is converted to 5'-deoxy-5-fluorouridine (5'-DFUR) by cytidine deaminase. 5'-DFUR is activated to 5-FU by thymidine phosphorylase. Although high activities of drug metabolizing enzymes are expressed in human liver, the involvement of the liver in capecitabine metabolism is not fully understood. In this study, the metabolism of capecitabine in human liver was investigated in vitro. 5'-DFCR, 5'-DFUR, and 5-FU formation from capecitabine were investigated in human liver S9, microsomes, and cytosol in the presence of the inhibitor of dihydropyrimidine dehydrogenase, 5-chloro-2,4-dihydroxypyridine. 5'-DFCR, 5'-DFUR, and 5-FU were formed from capecitabine in cytosol and in the combination of microsomes and cytosol. Only 5'-DFCR formation was detected in microsomes. The apparent K(m) and V(max) values of 5-FU formation catalyzed by cytosol alone and in combination with microsomes were 8.1 mM and 106.5 pmol/min/mg protein, and 4.0 mM and 64.0 pmol/min/mg protein, respectively. The interindividual variability in 5'-DFCR formation in microsomes and cytosol among 14 human liver samples was 8.3- and 12.3-fold, respectively. Capecitabine seems to be metabolized to 5-FU in human liver. 5'-DFCR formation was exhibited in cytosol with large interindividual variability, although CES is located in microsomes in human liver. In the present study, it has been clarified that the cytosolic enzyme would be important in 5'-DFCR formation, as is CES.     

2'-Deoxy-2'-spirocyclopropylcytidine revisited: a new and selective inhibitor of the hepatitis C virus NS5B polymerase

The current therapy for hepatitis C virus (HCV) infection has limited efficacy, in particular against the genotype 1 virus, and a range of side effects. In this context of high unmet medical need, more efficacious drugs targeting HCV nonstructural proteins are of interest. Here we describe 2'-deoxy-2'-spirocyclopropylcytidine (5) as a new inhibitor of the HCV NS5B RNA-dependent RNA polymerase, displaying an EC(50) of 7.3 μM measured in the Huh7-Rep cell line and no associated cytotoxicity (CC(50) > 98.4 μM). Computational results indicated high similarity between 5 and related HCV inhibiting nucleosides. A convenient synthesis was devised, facilitating synthesis of multigram quantities of 5. As the exposure measured after oral administration of 5 was found to be limited, the 3'-mono- and 3',5'-diisobutyryl ester prodrugs 20 and 23, respectively, were evaluated. The oral dosing of 23 led to substantially increased exposure to 5 in both rats and dogs.     

2'-Deoxy-2'-methylenecytidine and 2'-deoxy-2',2'-difluorocytidine 5'-diphosphates: potent mechanism-based inhibitors of ribonucleotide reductase

It has been found that 2'-deoxy-2'-methyleneuridine (MdUrd), 2'-deoxy-2'-methylenecytidine (MdCyd), and 2'-deoxy-2',2'-difluorocytidine (dFdCyd) 5'-diphosphates (MdUDP (1) MdCDP (2) and dFdCDP (3), respectively) function as irreversible inactivators of the Escherichia coli ribonucleoside diphosphate reductase (RDPR). 2 is a much more potent inhibitor than its uridine analogue 1. It is proposed that 2 undergoes abstraction of H3' to give an allylic radical that captures a hydrogen atom and decomposes to an active alkylating furanone species. RDPR also accepts 3 as an alternative substrate analogue and presumably executes an initial abstraction of H3' to initiate formation of a suicide species. Both 2 and 3 give inactivation results that differ from those of previously studied inhibitors. The potent anticancer activities of MdCyd and dFdCyd indicate a significant chemotherapeutic potential. The analogous RDPR of mammalian cells should be regarded as a likely target and/or activating enzyme for these novel mechanism-based inactivators.