Synthesis, biological activity, and DNA-damage profile of platinum-threading intercalator conjugates designed to target adenine

PT-ACRAMTU {[PtCl(en)(ACRAMTU)](NO3)2, 2; ACRAMTU = 1-[2-(acridin-9-ylamino)ethyl]-1,3-dimethylthiourea, 1, en = ethane-1,2-diamine} is the prototype of a series of DNA-targeted adenine-affinic dual intercalating/platinating agents. Several novel 4,9-disubstituted acridines and the corresponding platinum-acridine conjugates were synthesized. The newly introduced 4-carboxamide side chains contain H-bond donor/acceptor functions designed to promote groove- and sequence-specific platinum binding. In HL-60 (leukemia) and H460 (lung) cancer cells, IC50 values in the micromolar to millimolar range were observed. Several of the intercalators show enhanced cytotoxicity compared to prototype 1, but conjugate 2 appears to be the most potent hybrid agent. Enzymatic digestion assays in conjunction with liquid chromatography-electrospray mass spectrometry analysis indicate that the new conjugates produce PT-ACRAMTU-type DNA damage. Platinum-modified 2'-deoxyguanosine, dG, and several dinucleotide fragments, d(NpN)*, were detected. One of the conjugates showed significantly higher levels of binding to A-containing sites than conjugate 2 (35 +/- 3% vs 24 +/- 3%). Possible structure-activity relationships are discussed.     

Adenine-N3 in the DNA minor groove - an emerging target for platinum containing anticancer pharmacophores

The minor-groove is an important receptor for enzymes and proteins involved in the processing and expression of genomic DNA. Small molecules capable of interfering with these processes by virtue of their ability to form adducts within the recognition sequences targeted by these enzymes/proteins have potential applications as cytotoxic and gene-regulating agents. Until recently, the targeting of the minor groove by platinum-based agents has been a widely unexplored opportunity. As part of this focused review on irreversible minor-groove modifying agents acting on adenine-N3, we summarize work performed in our laboratory and by our collaborators on a novel platinum-acridine conjugate, PT-ACRAMTU ([PtCl(en)(ACRAMTU)](NO(3))(2), en = ethane-1,2-diamine, ACRAMTU = 1-[2-(acridin-9-ylamino)ethyl]-1,3-dimethylthiourea, acridinium cation). The design of this agent as a non-cisplatin type pharmacophore has led to a groundbreaking discovery, the unprecedented intercalator-driven formation of platinum-adenine-N3 adducts in the minor groove of DNA. The minor-groove reactivity of PT-ACRAMTU represents a new paradigm in platinum-DNA interactions, which opens new avenues in the design of platinum-based therapeutics acting by a mechanism different from that of agents currently in clinical use.     

Reactions of 2,6-dimethyl-1,3-dioxane-4-ol (aldoxane) with deoxyguanosine and DNA

In a recent study, we identified several new DNA adducts of the carcinogen acetaldehyde, including N(2)-(2,6-dimethyl-1,3-dioxan-4-yl)deoxyguanosine (N(2)-aldoxane-dG, 2). Our goal in this study was to investigate further the formation of 2 by allowing 2,6-dimethyl-1,3-dioxane-4-ol (aldoxane, 5) to react with dG and DNA. Aldoxane is readily formed by trimerization of acetaldehyde. The reaction of aldoxane with dG and DNA produced diastereomers of N(2)-aldoxane-dG (2) as observed in the reactions of acetaldehyde with dG and DNA, supporting the intermediacy of aldoxane in their formation. Unexpectedly, however, an array of other adducts was formed in these reactions, including 3-(2-deoxyribos-1-yl)-5,6,7,8-tetrahydro-8-hydroxy-6-methylpyrimido[1,2-a]purine-10(3H)one (3), 2-amino-7,8-dihydro-8-hydroxy-6-methyl-3H-pyrrolo[2,1-f]purine-4(6H)one (13), N(2)-(3-hydroxybutylidene)dG (9), N(2)-[(2-hydroxypropyl)-6-methyl-1,3-dioxane-4-yl]dG (14), and N(2)-ethylidene-dG (1). Adduct 1 was the major product and was found to be quite stable in DNA. The adducts result from a cascade of aldehydes, e.g., 2-butenal (crotonaldehyde, 12), 3-hydroxybutanal (7) and its dimer (2-hydroxypropyl)-6-methyl-1,3-dioxane-4-ol (paraldol, 6), and acetaldehyde, produced from aldoxane under the reaction conditions. The reactions of aldoxane with dG and DNA were compared with those of paraldol. The paraldol reactions gave products resulting from reactions of dG and DNA with paraldol, 3-hydroxybutanal, and crotonaldehyde (adducts 3, 13, and 9) but the products of the aldoxane and acetaldehyde reactions (adducts 1 and 2) were not observed, indicating that paraldol is more stable under the reaction conditions than is aldoxane. The results of this study provide new insights about the formation of DNA adducts from aldehydes via condensation products of the latter.     

Detection and quantitation of acrolein-derived 1,N2-propanodeoxyguanosine adducts in human lung by liquid chromatography-electrospray ionization-tandem mass spectrometry

Acrolein, a widely distributed environmental pollutant, reacts with dGuo in DNA to form two pairs of 1,N2-propano-dGuo adducts: (6R/S)-3-(2'-deoxyribos-1'-yl)-5,6,7,8-tetrahydro-6-hydroxypyrimido[1,2-a]purine-10(3H)one (alpha-OH-Acr-dGuo) and (8R/S)-3-(2'-deoxyribos-1'-yl)-5,6,7,8-tetrahydro-8-hydroxypyrimido[1,2-a]purine-10(3H)one (gamma-OH-Acr-dGuo). alpha-OH-Acr-dGuo is more mutagenic and mainly induces G --> T transversions. A recent study demonstrated that acrolein-DNA adducts are preferentially formed in p53 mutational hotspots in human lung cancer, but there are no reports on the presence of these adducts in the human lung. To directly investigate this question, we have developed a sensitive and specific liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) method for the quantitative analysis of Acr-dGuo adducts in DNA. Our method is based on the enzymatic hydrolysis of DNA isolated from the human lung in the presence of [13C10,15N5]Acr-dGuo as internal standards. Acr-dGuo adducts are enriched from the hydrolysates by solid-phase extraction and analyzed by LC-ESI-MS/MS using selected reaction monitoring. The method is accurate and precise, and the identity of the adducts was confirmed by monitoring different transitions from the same parent ion and by carrying out reactions with NaOH and NaBH4, which produced N2-(3-hydroxypropyl)-dGuo or 1,N2-(1,3-propano)-dGuo from gamma-OH-Acr-dGuo and alpha-OH-Acr-dGuo, respectively. Thirty DNA samples from lung tissue were analyzed, and Acr-dGuo adducts were detected in all samples. Both alpha-OH- and gamma-OH-Acr-dGuo were observed in most of the samples; total adduct concentrations ranged from 16-209 adducts/109 nucleotides. These results demonstrate for the first time that both types of Acr-dGuo adducts are present in human lung DNA. There was no difference in adduct levels between current and ex-smokers. Collectively, the results support a plausible role for acrolein as one cause of p53 mutations in the human lung.     

Research on substances with antiviral activity. III. Structure of the monosubstituted derivatives of 1 H-benzo-[e] indene-1,3(2H)-dione]

The N.M.R. spectra of 1H-benz[e]indene-1,3(2H)-dione (I), 1H-benz[e]indene-2,3-dihydro-1-one (II), 7-methyl-3H-benz[e]indene-1,2-dihydro-3-one (III) and of their oximes, phenylhydrazones and 4-methylthiosemicarbazones show the preferential substitution at 3 position for monoderivatives of (I). This is very interesting in correlation with the structure-activity relationship of derivatives of (I) and (II), some of which have shown in vitro antiviral action in previous research.     

Inhibition of DNA Synthesis by a Platinum-Acridine Hybrid Agent Leads to Potent Cell Kill in Non-Small Cell Lung Cancer

The platinum-acridine anti-cancer agent [PtCl(en)(LH)](NO(3))(2) (1) (en = ethane-1,2-diamine, LH = N-(2-(acridin-9-ylamino)ethyl)-N-methylpropionimidamide, acridinium cation) and the clinical drug cisplatin were studied in chemoresistant non-small cell lung cancer (NSCLC) cell lines for their cytotoxic potency and cell-kill mechanisms. In the three cell lines tested (NCI-H460, NCI-H522, and NCI-H1435) compound 1 shows a pronounced cytotoxic enhancement of 40-200-fold compared to cisplatin at inhibitory concentrations reaching the low-nanomolar range. Based on changes in cell adhesion and cell morphology, monitored in real time by impedance measurements, compound 1 kills NCI-H460 cells significantly more efficiently than cisplatin at equitoxic concentrations. Flow cytometry analysis of NCI-H460 cells reveals a robust S-phase arrest of cells treated with compound 1, whereas cells treated with cisplatin progress to G2/M of the cell cycle. A pronounced inhibition of DNA replication in 75% of viable cells is observed in NCI-H460 cells treated with compound 1 at an IC(90) molar concentration for 48 h, based on the reduced incorporation of the fluorophore-clickable nucleoside analogue 5-ethynyl-2′-deoxyuridine (EdU) into newly synthesized DNA. The distinct cell-cycle perturbations and cell-kill potential of compound 1 are discussed in the light of the DNA interactions of this agent and its potential to overcome cisplatin resistance in NSCLC.     

Identification of paraldol-deoxyguanosine adducts in DNA reacted with crotonaldehyde

Crotonaldehyde (1) is a mutagen and carcinogen, but its reactions with DNA have been only partially characterized. In a previous study, we found that substantial amounts of 2-(2-hydroxypropyl)-4-hydroxy-6-methyl-1,3-dioxane (paraldol, 7), the dimer of 3-hydroxybutanal (8), were released upon enzymatic or neutral thermal hydrolysis of DNA that had been allowed to react with crotonaldehyde. We have now characterized two paraldol-deoxyguanosine adducts in this DNA: N(2)-[2-(2-hydroxypropyl)-6-methyl-1,3-dioxan-4-yl]deoxyguanosine (N(2)-paraldol-dG, 13) and N(2)-[2-(2-hydroxypropyl)-6-methyl-1, 3-dioxan-4-yl]deoxyguanylyl-(5'-3')-thymidine [N(2)-paraldol-dG-(5'-3')-thymidine, 14]. Four diastereomers of N(2)-paraldol-dG (13) were observed. Their overall structures were determined by (1)H NMR, by MS, and by reaction of paraldol with deoxyguanosine and DNA. (1)H NMR data showed that two diastereomers had all equatorial substituents in the dioxane ring, while two others had an axial 6-methyl group. Preparation of paraldol with the (R)- or (S)-configuration at the 6-position of the dioxane ring and the carbinol carbon of the 2-(2-hydroxypropyl) group allowed partial assignment of the absolute configurations of N(2)-paraldol-dG (13). Four diastereomers of N(2)-paraldol-dG-(5'-3')-thymidine (14) were observed. Their overall structure was determined by (1)H NMR, MS, and hydrolysis with snake venom or spleen phosphodiesterase. Reactions of nucleosides and nucleotides with paraldol demonstrated that adducts were formed only from deoxyguanosine and its monophosphates. Experiments with DNA that had been reacted with crotonaldehyde indicated that N(2)-paraldol-dG-containing adducts in DNA are relatively resistant to enzymatic hydrolysis. The results of this study demonstrate that the reaction of crotonaldehyde with DNA is more complex than previously recognized and that stable N(2)-paraldol-dG adducts are among those that should be considered in assessing mechanisms of crotonaldehyde mutagenicity and carcinogenicity.     

Synthesis, characterization, and in vitro antitumor activity of osteotropic diam(m)ineplatinum(II) complexes bearing a N,N-bis(phosphonomethyl)glycine ligand

A series of osteotropic (bone-seeking) [(bis(phosphonomethyl)amino-kappaN)acetato-kappaO(2-)]platinum(II) complexes attached to diammine, ethane-1,2-diamine, cis-R,S-cyclohexane-1,2-diamine, trans-S,S-cyclohexane-1,2-diamine, or trans-R,R-cyclohexane-1,2-diamine has been synthesized in accord with the concept of drug targeting and characterized by elemental analysis, (1)H, (13)C, and (31)P NMR spectroscopy. The in vitro antitumor activity in ovarian cancer cells (CH1) has been determined by means of the MTT assay. In this cisplatin-sensitive cell line the complexes containing cyclohexane-1,2-diamine (chxn) displayed a high activity in comparison to the diammine and ethane-1,2-diamine counterparts. In agreement with structure-activity relationships of other chxn-containing platinum(II) complexes both [(bis(phosphonomethyl)amino-kappaN)acetato-kappaO(2-)](trans-cyclohexane-1,2-diamine)platinum(II) complexes show superior potency than the corresponding cis-congener whereas the trans-R,R isomer displays the highest activity. Within the series of complexes under investigation, potency decreases depending on the coordinated amine ligand in the following order: trans-R,R-chxn > trans-S,S-chxn > NH(3) > or = cis-R,S-chxn > en.     

Identification of DNA adducts of acetaldehyde

Acetaldehyde is a mutagen and carcinogen which occurs widely in the human environment, sometimes in considerable amounts, but little is known about its reactions with DNA. In this study, we identified three new types of stable acetaldehyde DNA adducts, including an interstrand cross-link. These were formed in addition to the previously characterized N(2)-ethylidenedeoxyguanosine. Acetaldehyde was allowed to react with calf thymus DNA or deoxyguanosine. The DNA was isolated and hydrolyzed enzymatically; in some cases, the DNA was first treated with NaBH(3)CN. Reaction mixtures were analyzed by HPLC, and adducts were isolated and characterized by UV, (1)H NMR, and MS. The major adduct was N(2)-ethylidenedeoxyguanosine (1), which was identified as N(2)-ethyldeoxyguanosine (7) after treatment of the DNA with NaBH(3)CN. The new acetaldehyde adducts were 3-(2-deoxyribos-1-yl)-5,6,7, 8-tetrahydro-8-hydroxy-6-methylpyrimido[1,2-a]purine-10(3H)one (9), 3-(2-deoxyribos-1-yl)-5,6,7,8-tetrahydro-8-(N(2)-deoxyguanosyl+ ++)- 6-methylpyrimido[1,2-a]purine-10(3H)one (12), and N(2)-(2, 6-dimethyl-1,3-dioxan-4-yl)deoxyguanosine (11). Adduct 9 has been previously identified in reactions of crotonaldehyde with DNA. However, the distribution of diastereomers was different in the acetaldehyde and crotonaldehyde reactions, indicating that the formation of 9 from acetaldehyde does not proceed through crotonaldehyde. Adduct 12 is an interstrand cross-link. Although previous evidence indicates the formation of cross-links in DNA reacted with acetaldehyde, this is the first reported structural characterization of such an adduct. This adduct is also found in crotonaldehyde-deoxyguanosine reactions, but in a diastereomeric ratio different than that observed here. A common intermediate, N(2)-(4-oxobut-2-yl)deoxyguanosine (6), is proposed to be involved in formation of adducts 9 and 12. Adduct 11 is produced ultimately from 3-hydroxybutanal, the major aldol condensation product of acetaldehyde. Levels of adducts 9, 11, and 12 were less than 10% of those of N(2)-ethylidenedeoxyguanosine (1) in reactions of acetaldehyde with DNA. As nucleosides, adducts 9, 11, and 12 were stable, whereas N(2)-ethylidenedeoxyguanosine (1) had a half-life of 5 min. These new stable adducts of acetaldehyde may be involved in determination of its mutagenic and carcinogenic properties.     

Regioisomeric synthesis and characteristics of the alpha-hydroxy-1,N(2)-propanodeoxyguanosine

Acrolein, a known mutagen, undergoes reaction in vitro under physiological conditions with both 2'-deoxyguanosine and native DNA to give rise to exocyclic adducts of the 5,6,7,8-tetrahydropyrimido[1,2-a]purine-10(3H)-one class having a hydroxyl group at either the 6 or the 8 position (these positions are respectively designated alpha and gamma when referring to the 1,N(2)-(propano-bridge). Previously, we have shown that the 8-hydroxy derivative has very low mutagenicity probably because, in double-stranded DNA, this residue exists in the open-chain aldehydic form [N(2)-(3-oxopropyl)-2'-deoxyguanosine] (5). To continue our investigation in this area, we needed ample supplies of the 6-hydroxy isomers. This current paper describes high-yield simple methods for the synthesis in bulk of the 6-hydroxy and the 6-methoxy exocyclic adducts 1 and 3 and a new efficient synthesis of 1,N(2)()-(prop-1,3-diyl)-2'-deoxyguanosine (4), previously used as a chemically stable model in studying the physico-biological implications of 1,N(2) exocyclic adduction to dG.     

Unusual Reactivity of a Potent Platinum-Acridine Hybrid Antitumor Agent

The formation of unusual seven-membered, sterically overloaded chelates [Pt(en)(L/L′)](NO(3))(2) (4a/4b) from the corresponding potent hybrid antitumor agents [PtCl(en)(LH/L′H)](NO(3))(2) (3a/3b) is described, where en is ethane-1,2-diamine and L(H) and L′(H) are (protonated) N-(2-(acridin-9-ylamino)ethyl)-N-methylpropionimidamide and N-(2-(acridin-9-ylamino)ethyl)-N-methylacetimidamide, respectively. Compounds 3a and 3b inhibit H460 lung cancer cell proliferation with IC(50) values of 12 ± 2 nM and 2.8 ± 0.3 nM, respectively. The new derivative 3b proves to be not only the most cytotoxic platinum-acridine hybrid of this kind, but also one of the most potent platinum-based anticancer agents described to date. The chelates 4a and 4b do not undergo ligand substitution reactions with nucleobase nitrogen and cysteine sulfur and do not intercalate into DNA. Despite their inertness, the two chelates appear to maintain micromolar activity in H460 cells. The results are discussed in the context of potential DNA-mediated and DNA-independent cell kill mechanisms and the potential use of the chelates as prodrugs.     

Mono- and polynuclear [alkylamine]platinum(II) complexes of [1,2-bis(4-fluorophenyl)ethylenediamine]platinum(II): synthesis and investigations on cytotoxicity, cellular distribution, and DNA and protein binding

A series of mononuclear and dinuclear alkylamine derivatives of [meso-1,2-bis(4-fluorophenyl)ethylenediamine]platinum(II) (m-4F-PtL-R1 and (m-4F-PtL)2-R2; R(1) = alkylamine, R(2) = alkyldiamine, L = DMSO or Cl) as well as the DAB(PA)(4) polyimine dendrimer complex ((m-4F-PtDMSO)4DAB(PA)4; DAB(PA)4 = N,N,N',N'-tetrakis(3-aminopropyl)butane-1,4-diamine) were synthesized and tested for cytotoxicity, intracellular distribution, and DNA and protein binding. All compounds strongly bound to human serum albumin by hydrophobic and electrostatic interactions. These inactivation reactions hindered the uptake into tumor cells and prevented strong cytotoxic effects. If serum-free medium was used, a high accumulation grade in MCF-7 breast cancer cells and a high DNA binding was observed. As most efficient compound (m-4F-PtDMSO)4DAB(PA)4 was identified. It showed a 20-fold higher cellular uptake and an approximately 700-fold higher DNA binding than cisplatin.     

Nitrosative guanine deamination: ab initio study of deglycation of N-protonated 5-cyanoimino-4-oxomethylene-4,5-dihydroimidazoles

5-Cyanoimino-4-oxomethylene-4,5-dihydroimidazoles (1) (R at N1) have been discussed as possible intermediates in nitrosative guanine deamination, which are formed by dediazoniation and deprotonation of guaninediazonium ion. The parent system 1 (R = H) and its N1 derivatives 2 (R = Me) and 3 (R = MOM) are considered here. Protonation of 1-3, respectively, may occur either at the cyano-N to form cations 4 (R = H), 6 (R = Me), and 8 (R = MOM) or at the imino-N to form cations 5 (R = H), 7 (R = Me), and 9 (R = MOM), respectively. This protonation is the first step in the acid-catalyzed water addition to form 5-cyanoimino-imidazole-4-carboxylic acid, which then leads to oxanosine. There also exists the option of a substitution reaction by water at the R group of 6-9, and this dealkylation forms N-[4-(oxomethylene)-imidazol-5-yl]carbodiimide (10) and N-[4-(oxomethylene)-imidazol-5-yl]cyanamide (11). In the case of DNA, the R group is a deoxyribose sugar, and attack by water leads to deglycation. To explore this reaction option, the S(N)1 and S(N)2 reactions of 6-9 with water were studied at the MP2/6-31G*//RHF/6-31G* and CCSD/6-31G*//RHF/6-31G* levels, with the inclusion of implicit solvation at the IPCM(MP2/6-31G*)//RHF/6-31G* level, and the electron density distributions of tautomers 1, 10, and 11 were analyzed. The low barriers determined for the MOM transfer show that the deglycation could occur at room temperature but that the process cannot compete with water addition.     

Characterization of the reaction products of 2'-deoxyguanosine and 1,2,3,4-diepoxybutane after acid hydrolysis: formation of novel guanine and pyrimidine adducts

1,2,3,4-diepoxybutane (DEB), an important in vivo metabolite of 1,3-butadiene (BD), is a potent mutagen and a known carcinogen. Recently, DEB has been shown to react with 2'-deoxyguanosine (dG) at 37 degrees C and pH 7.4 to yield a series of nucleoside adducts, resulting from alkylation at the 7-, 1-, and N(2)-positions of dG. In addition, adducts with fused ring systems are formed. In the present study, new adducts are characterized after DEB was allowed to react with dG at pH 7.4 and the reaction mixture was then subjected to acid hydrolysis. These adducts are 7-hydroxy-6-hydroxymethyl-5,6,7,8-tetrahydropyrimido[1,2-a]purin-10(1H)one (H2), 2-amino-1-(4-chloro-2,3-dihydroxybutyl)-1,7-dihydro-6H-purin-6-one (H4), 2-amino-1-(2,3,4-trihydroxybutyl)-1,7-dihydro-6H-purin-6-one (H1'/H5'), 7,8-dihydroxy-1,5,6,7,8,9-hexahydro-1,3-diazepino[1,2-a]purin-11(11H)one (H2'), and 5-(3,4-dihydroxy-1-pyrrolidinyl)-2,6-diamino-4(3H)pyrimidinone (H3'). The previously characterized guanine adducts, 2-amino-7-(3-chloro-2,4-dihydroxybutyl)-1,7-dihydro-6H-purin-6-one (H3) and 2-amino-7-(2,3,4-trihydroxybutyl)-1,7-dihydro-6H-purin-6-one (H4'), were also detected. Acid hydrolysis of purified dG-DEB adducts confirmed that H2, H3/H4', H2', and H4/H1'/H5' are the hydrolysis products of N-(2-hydroxy-1-oxiranylethyl)-2'-deoxyguanosine (P4-1 and P4-2), 6-oxo-2-amino-9-(2-deoxy-beta-d-erythro-pentofuranosyl)-7-(2-hydroxy-2-oxiranylethyl)-6,9-dihydro-1H-purinium ion (P5 and P5'), 7,8-dihydroxy-3-(2-deoxy-beta-d-erythro-pentofuranosyl)-3,5,6,7,8,9-hexahydro-1,3-diazepino[1,2-a]purin-11(11H)one (P6), and 1-(2-hydroxy-2-oxiranylethyl)-2'-deoxyguanosine (P8 and P9), respectively. On the other hand, the novel pyrimidine adduct H3' is formed by the decomposition of P5 and P5' during the incubation and hydrolysis. These results may facilitate the development of useful biomarkers of exposure to DEB and its precursor BD.     

Synthesis and biological activity of carbocyclic lexitropsins with a bioreductive fragment

Carbocyclic oligopeptides containing of two, three or four aromatic rings with N,N-dimethylpropyl-1,3-diamine group as C-terminus fragment of compounds and 5-[bis(2-chloroethyl)amino]-2,4-dinitrobenzamide as N-terminal were synthesized. These lexitropsins present antitumour activity on the neoplastic cells hepatoblastoma HEP G2. These experiments were evaluated in hypoxic and oxygen conditions. Significant differences of activity in oxygen and hypoxic conditions were shown only in compound, N-(3-dimethylaminopropyl)-N'-([3-[5-bis(2-chlorethyl)amino]-2,4-dinitrobenzamide])-phenyl]urea dihydrochloride 1 (IC50 = 8545 nM in oxygen vs. IC50 = 710 nM in hypoxia). The rest of compounds (2-6) do not indicate differences of activity in oxygen and hypoxia.     

Bisguanidine, bis(2-aminoimidazoline), and polyamine derivatives as potent and selective chemotherapeutic agents against Trypanosoma brucei rhodesiense. Synthesis and in vitro evaluation

The in vitro screening for trypanocidal activity against Trypanosoma brucei rhodesiense of an in-house library of 62 compounds [i.e. alkane, diphenyl, and azaalkane bisguanidines and bis(2-aminoimidazolines)], which were chosen for their structural similarity to the trypanocidal agents synthalin (1,10-decanediguanidine) and 4,4'-diguanidinodiphenylmethane and the polyamine N(1)-(3-amino-propyl)propane-1,3-diamine, respectively, is reported. The original synthetic procedure for the preparation of 21 of these compounds is also reported. Most compounds displayed low micromolar antitrypanosomal activity, with five of them presenting a nanomolar inhibitory action on the parasite: 1,9-nonanediguanidine (1c), 1,12-dodecanediguanidine (1d), 4,4'-bis[1,3-bis(tert-butoxycarbonyl)-2-imidazolidinylimino]diphenylamine (28a), 4,4'-bis(4,5-dihydro-1H-2-imidazolylamino)diphenylamine (28b), and 4,4'-diguanidinodiphenylamine (32b). Those molecules that showed an excellent in vitro activity as well as high selectivity for the parasite [e.g. 1c (IC(50) = 49 nM; SI > 5294), 28b (IC(50) = 69 nM; SI = 3072), 32b (IC(50) = 22 nM; SI = 29.5), 41b (IC(50) = 118 nM; SI = 881)] represent new antitrypanosomal lead compounds.     

A new family of water-soluble, third generation antitumor platinum complexes

[1,1-Cyclobutanedicarboxylato(2)-O,O'](1,3-dioxane-5,5-dimethan amine- N,N')platinum(II), 3a, a third generation, very water-soluble platinum complex, has been synthesized along with several of its analogues. All members of the new family contain a 1,3-dioxane or 1,3-dioxolane-1,3-diamine as their basic ligand, a moiety which contributes to their increased water solubility, and a bidentate acid ligand, which is responsible for their good stability. They were all easily crystallized and characterized by 1H NMR and elemental analysis, and the parent complex 3a was further characterized by 13C NMR. Their very desirable physical properties combined with their broad spectrum of antitumor activity and reduced toxicity make them good candidates of further development.     

Reactions of formaldehyde plus acetaldehyde with deoxyguanosine and DNA: formation of cyclic deoxyguanosine adducts and formaldehyde cross-links

We investigated the reactions of formaldehyde plus acetaldehyde with dGuo and DNA in order to determine whether certain 1,N(2)-propano-dGuo adducts could be formed. These adducts-3-(2'-deoxyribosyl)-5,6,7,8-tetrahydro-8-hydroxypyrimido[1,2-a]purine-(3H)-one (1) and 3-(2'-deoxyribosyl)-5,6,7,8-tetrahydro-6-hydroxypyrimido[1,2-a]purine-(3H)-one (3a,b)-have been previously characterized as products of the reaction of acrolein with dGuo and DNA. Adduct 1 predominates in certain model lipid peroxidation systems [Pan, J., and Chung, F. L. (2002) Chem. Res. Toxicol. 15, 367-372]. We hypothesized that this could be due to stepwise reactions of formaldehyde and acetaldehyde with dGuo, rather than by reaction of acrolein with dGuo. The results demonstrated that adducts 1 and 3a,b were relatively minor products of the reaction of formaldehyde and acetaldehyde with dGuo and that there was no selectivity in their formation. These findings did not support our hypothesis. However, substantial amounts of previously unknown cyclic dGuo adducts were identified in this reaction. The new adducts were characterized by their MS, UV, and NMR spectra as diastereomers of 3-(2'-deoxyribosyl)-6-methyl-1,3,5-diazinan[4,5-a]purin-10(3H)-one (10a,b). Adducts 10a,b were apparently formed by addition of formaldehyde to N1 of N(2)-ethylidene-dGuo, followed by cyclization. An analogous set of four diastereomers of 3-(2'-deoxyribosyl)-6,8-dimethyl-1,3,5-diazinan[4,5-a]purin-10(3H)-one (12a-d) were formed in the reactions of acetaldehyde with dGuo. These products are the first examples of exocyclic dGuo adducts of the pyrimido[1,2-a]purine type in which an oxygen atom is incorporated into the exocyclic ring. Formaldehyde-derived adducts were the other major products of the reactions of formaldehyde plus acetaldehyde with dGuo. Prominent among these were N(2)-hydroxymethyl-dGuo (9) and the cross-link di-(N(2)-deoxyguaonosyl)methane (13). We did not detect adducts 1, 3a,b, or 10a,b in enzymatic hydrolysates of DNA that had been allowed to react with formaldehyde plus acetaldehyde. However, we did detect substantial amounts of the formaldehyde cross-links di-(N(6)-deoxyadenosyl)methane (17), with lesser quantities of (N(6)-deoxyadenosyl-N(2)-deoxyguanosyl)methane (18), di-(N(2)-deoxyguanosyl)methane (13), and N(6)-hydroxymethyl-dAdo (19). Schiff base adducts of formaldehyde and acetaldehyde were also detected in these reactions. These results demonstrate that the reactions of formaldehyde plus acetaldehyde with dGuo are dominated by newly identified cyclic adducts and formaldehyde-derived products whereas the reactions with DNA result in the formation of formaldehyde cross-link adducts. The carcinogens formaldehdye and acetaldehyde occur in considerable quantities in the human body and in the environment. Therefore, further research is required to determine whether the adducts described here are formed in animals or humans exposed to these agents.     

d-生物素的不对称全合成研究

目的:探索工业生产可行的d-生物素的全合成方法。方法和结果:以(1S,2 S)-( + )-苏式-1-( 对硝基苯基)-2-氨基-1,3-丙二醇与顺-1 ,3-二苄基-四氢-4H-呋喃并[3,4-d] 咪唑-2,4,6-三酮(2) 缩合而成的顺-1,3-二苄基-5-[(1S,2S)-(+ )-苏式-1-羟甲基-2-( 对硝基苯基)-2-羟乙基]-四氢-4H-吡咯并[3 ,4-d] 咪唑-2,4,6-三酮(3) 经高立体选择性还原、水解内酯化成(3aS,6aR)-1 ,3-二苄基-四氢-4H-呋喃并[3 ,4-d] 咪唑-2,4(1H)-三酮(6),再经硫代、格氏反应、还原制成(3aS,6aR)-1 ,3-二苄基-4-羟基-4-(3-乙氧基丙基)-四氢-4H-噻吩[3,4-d] 咪唑-2(3H)-酮(9) ,后者经脱水、还原、裂解环合、脱苄4 步反应合成(3a R,8aS,8bS)-2-氧代-十氢咪唑并[4,5-c] 噻吩并[1 ,2-a] 锍鎓溴化物(12) ,继而缩合开环、水解即得d-生物素,以2 计算,总收率25-7 % 。结论:此法原料易得、操作简便、成本较低,适合工业化生产。