Alkylation of dihydrofullerenes

The fulleride dianions C(60)(2-) and C(70)(2-) were generated by deprotonation of the corresponding hydrogenated fullerenes, 1,2-C(60)H(2) and 1,2-C(70)H(2). These anions were prepared in the presence of a variety of alkylating agents, and mono- or dialkylated products were obtained. Alkylation was not successful with sulfonate ester alkylating agents. Deprotonation of monoalkylated compounds, followed by second alkylation with a different alkylating agent, produced heterodialkylated compounds. The monoalkyated material was invariably the 1,2-isomers, while the dialkylated materials were generally 1,4-isomers, although some 1,2-isomer was observed in the C(70) context. The major product from alkylation of C(70)(2-) was the 7,23-isomer 13a, a structure where the alkylation took place near the equator of the fullerene cage, rather than at the more strained carbons near the poles.     

C-H to N substitution dramatically alters the sequence-specific DNA alkylation, cytotoxicity, and expression of human cancer cell lines

We designed and synthesized sequence-specific alkylating conjugates 1 and 2, which selectively alkylate matched sequences at nanomolar concentrations. Conjugates 1 and 2 differ only in that the C-H is substituted by an N in the second ring, which precisely recognizes and effectively alkylates DNA according to the recognition rule of Py-Im polyamides. We investigated sequence-specific DNA alkylation, cytotoxicity in 39 human cancer cell lines, and the effect on expression levels in cancer cell lines by Py-Im conjugates 1 and 2. The COMPARE analysis of the mean graphs showed that conjugates 1 and 2 did not correlate well with each other (r = 0.65) despite having a common DNA alkylating mechanism (purine N3 alkylation). Array-based gene expression analysis demonstrated that there are several oppositely regulated genes. The results suggest the intriguing possibility that DNA alkylating agents recognizing longer base-pair sequences may provide a promising approach for developing new types of antigene agents.     

Selective intercalation of charge neutral intercalators into GG and CG steps: implication of HOMO-LUMO interaction for sequence-selective drug intercalation into DNA

We have synthesized naphthopyranone epoxide 4 from D-isoascorbic acid together with its three diastereoisomers. DNA alkylation of ODNs containing 5'XGT3' and 5'TGY3' by 4 (11R, 13R), where X and Y are any nucleotide bases, occurred at all G residues except at G of the 5'TGC3' sequence. In contrast, the three other diastereoisomers of 4 showed only weak G alkylation activity. Differential (1)H NMR NOE of the 4-G adduct confirmed the G-N7 alkylation at the epoxide carbon of 4 with concomitant S(N)2 ring opening of the epoxide. Quantitative HPLC analysis of G alkylation efficiency for 4 showed the order of G alkylation susceptibility as TGGT approximately CGT > TGA > AGT > TGT > TGC. The order was fully consistent with those reported for aflatoxin B(1) oxide and kapurimycin A(3), suggesting that the sequence selectivity observed for these DNA alkylating agents is not structure dependent but most likely due to the intrinsic property of DNA sequences. We found that the order of G alkylation susceptibility obtained for 4 completely matched the calculated HOMO energy level of G-containing sequences. These results underscore that 4 is a unique molecular probe for ranking the HOMO level of G-containing sequences by well-known G alkylation chemistry and suggests that the intercalation of charge neutral intercalators is a HOMO-controlled process.     

Metal cation complexation and activation of reversed CPyI analogues of CC-1065 and duocarmycin SA: partitioning the effects of binding and catalysis

The synthesis and examination of a novel class of reversed CPyI analogues of CC-1065 and the duocarmycins are described. Capable of a unique metal cation activation of DNA alkylation, these agents allowed the effects of the DNA binding domain (10(4)-fold increase in DNA alkylation rate and efficiency) to be partitioned into two components: that derived from enhanced DNA binding affinity and selectivity (10-80-fold) and that derived from a contribution to catalysis (250-5000-fold). In addition, the reversed enantiomeric selectivity of these sequence selective DNA alkylating agents provides further strong support for a previously disclosed model where it is the noncovalent binding selectivity of the compounds, and not the alkylation subunit or the source of catalysis, that controls the DNA alkylation selectivity.     

Synthesis,Antiproliferative, and c‐Src Kinase Inhibitory Activities of 4‐Oxo‐4H‐1‐benzopyran Derivatives

A new class of 4‐oxo‐4H‐1‐benzopyran derivatives were synthesized and their antiproliferative activity examined against a panel of three human cancer cell lines, that is, breast carcinoma (MDA‐MB‐468), ovarian adenocarcinoma (SK‐OV‐3), and colorectal adenocarcinoma (HT‐29). Two compounds, that is, 3‐hexyl‐7,8‐dihydroxy‐4‐oxo‐4H‐1‐benzopyran and (E)‐ethyl 3‐(7‐methoxy‐4‐oxo‐4H‐1‐benzopyran‐3‐yl)acrylate were found to be potent against all three cancer cell lines studied at 50 μM concentration. Also, the inhibitory potency of the compounds was evaluated against active Src kinase. A few of these compounds exhibited modest Src kinase inhibitory activity (IC₅₀ = 52–57 μM). Structure‐activity relationship studies with respect to the nature and position of substituents on the lead compounds could be further exploited for the design and development of more potent antiproliferative agents and/or Src kinase inhibitors.     

Alteration in the choice of DNA repair pathway with increasing sequence selective DNA alkylation in the minor groove

BACKGROUND: Many conventional DNA alkylating anticancer drugs form adducts in the major groove of DNA. These are known to be chiefly repaired by both nucleotide (NER) and base (BER) excision repair in eukaryotic cells. Much less is known about the repair pathways acting on sequence specific minor groove purine adducts, which result from a promising new class of anti-tumour agents. RESULTS: Benzoic acid mustards (BAMs) tethering 1-3 pyrrole units (compounds 1, 2 and 3) show increasing DNA sequence selectivity for alkylation from BAM and 1, alkylating primarily at guanine-N7 in the major groove, to 3 which is selective for alkylation in the minor groove at purine-N3 in the sequence 5'-TTTTGPu (Pu=guanine or adenine). This increasing sequence selectivity is reflected in increased toxicity in human cells. In the yeast Saccharomyces cerevisiae, the repair of untargeted DNA adducts produced by BAM, 1 and 2 depends upon both the NER and BER pathways. In contrast, the repair of the sequence specific minor groove adducts of 3 does not involve known BER or NER activities. In addition, neither recombination nor mismatch repair are involved. Two disruptants from the RAD6 mutagenesis defective epistasis group (rad6 and rad18), however, showed increased sensitivity to 3. In particular, the rad18 mutant was over three orders of magnitude more sensitive to 3 compared to its isogenic parent, and 3 was highly mutagenic in the absence of RAD18. Elimination of the sequence specific DNA adducts formed by 3 was observed in the wild type strain, but these lesions persisted in the rad18 mutant. CONCLUSIONS: We have demonstrated that the repair of DNA adducts produced by the highly sequence specific minor groove alkylating agent 3 involves an error free adduct elimination pathway dependent on the Rad18 protein. This represents the first systematic analysis of the cellular pathways which modulate sensitivity to this new class of DNA sequence specific drugs, and indicates that the enhanced cytotoxicity of certain sequence specific minor groove adducts in DNA is the result of evasion of the common excision repair pathways.     

INACTIVATION OF NUCLEOTIDE EXCISION REPAIR IN CHINESE HAMSTER OVARY CELLS BY EXPOSURE TO AN ALKYLATING AGENT

Abstract— Unscheduled DNA synthesis and excision of pyrimidine dimers in Chinese hamster ovary cells irradiated with UV light were inhibited by prior exposure to the alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)(1–10 μ M ) Although the pathways for excision of pyrimidine dimers and alkylation damage are known to differ, alkylations from MNNG exposure appear to have a direct effect on the nucleotide excision repair system. These results indicate that the method of exposing cells to two DNA-damaging agents to determine whether they are repaired by common or different pathways can be quite unreliable because of other effects on the repair systems themselves.     

Catalytic Reductive N‐Alkylations Using CO2 and Carboxylic Acid Derivatives: Recent Progress and Developments

N‐Alkylamines are key intermediates in the synthesis of fine chemicals, dyes, and natural products, and hence are highly valuable building blocks in organic chemistry. Consequently, the development of greener and more efficient procedures for their production continues to attract the interest of both academic and industrial chemists. Reductive procedures such as reductive amination or N‐alkylation through hydrogen autotransfer by employing carbonyl compounds or alcohols as alkylating agents have prevailed for the synthesis of amines. In the last few years, carboxylic/carbonic acid derivatives and CO₂ have been introduced as alternative and convenient alkylating sources. The safety, easy accessibility, and high stability of these reagents makes the development of new reductive transformations with them as N‐alkylating agents a useful alternative to existing procedures. In this Review, we summarize reported examples of one‐pot reductive N‐alkylation methods that use carboxylic/carbonic acid derivatives or CO₂ as alkylating agents.     

Pseudoesters and Derivatives XXXV. Reactions of 4-Substituted-5-(Ethylthio)Furan-2(5H)-Ones Anions with Alkylating Agents

Alkylation of anions derived from 5-ethylthio-4-substituted furanones (1–3) is described. The regioselectivity depends on the alkylating agent but mainly on the nature of the substituent. The alkylation of 4-methoxyfuranone 3 proceeds regioselectively to afford the 5-alkylated derivative as sole product.     

Molecular design of a pyrrole-imidazole hairpin polyamides for effective DNA alkylation

New hairpin polyamide-CPI (CPI = cyclopropylpyrroloindole) conjugates, compounds 12-14, were synthesized and their DNA-alkylating activities compared with the previously prepared hairpin polyamide, compound 1, by high-resolution denaturing gel electrophoresis with 450 base pair (bp) DNA fragments and by HPLC product analysis of the synthetic decanucleotide. In accord with our previous results, alkylation by compound 1 occurred predominantly at the G moiety of the sequence 5'-AGTCAG-3' (site 3). However, compound 12, in which the structure of the alkylating moiety of compound 1 is replaced with segment A of duocarmycin A DU-86 (CPI), did not show any DNA alkylating activity. In clear contrast, the hairpin CPI conjugate 13, which differs from compound 1 in that it lacks one Py unit and possesses a vinyl linker, alkylated the A of 5'-AGTCAG-3' (site 3) efficiently at nanomolar concentrations. Alkylation by compound 14, which has a vinyl linker, occurred at the A of 5'-AGTCCA-3' (site 6) and at several minor alkylation sites, including mismatch alkylation at A of 5'-TCACAA-3' (site 2). The significantly different reactivity of the alkylating hairpin polyamides 1, 12, 13, and 14 was further confirmed by HPLC product analysis by using a synthetic decanucleotide. The results suggest that hairpin polyamide--CPI conjugate 13 alkylates effectively according to Dervan's pairing rule, and with a new mode of recognition in which the Im-vinyl linker (L) pair targets G-C base pairs. These results demonstrate that incorporation of the vinyl-linker pairing with Im dramatically improves the reactivity of hairpin polyamide--CPI conjugates.     

有机紫外吸收剂插层锌铝水滑石的制备及表征

采用离子交换法，以去离子水或乙二醇为分散介质，制备了层间为磺基水杨酸、4-羟基-3-甲氧基肉桂酸和2-羟基-4-甲氧基二苯甲酮-5-磺酸等紫外吸收剂阴离子插层的锌铝水滑石。利用XRD、IR、TG-DTA等技术对样品结构进行表征，采用UV-Vis吸收光谱研究产物的光化学特性，并用Gaussian-98软件包中ab initio分子轨道法(HF/6-31G)计算了3种有机紫外吸收剂的分子结构和电荷分布，提出了合理的客体分子在主体层间的排列方式，分析了其结构与光化学行为的关系。研究表明，由于有机紫外吸收剂进入层间，不仅客体与主体层板存在静电力和氢键相互作用，而且在限域空间中有利于客体之间的相互作用，从而使插层产物的紫外吸收范围和能力显著增强，是一类具有潜在应用价值的无机-有机超分子复合结构的紫外吸收材料。     

Alkylation of aromatic compounds with multi-component Lewis acid catalysts of ZnCl2 and ionic liquids with different organic cations

Alkylation of aromatic compounds with various alkylating agents such as benzyl chloride, benzyl alcohol and isopropyl chloride were investigated using ZnCl₂ based ionic liquid (ILs) Lewis acid catalysts. Multi-component Lewis acid catalysts of ZnCl₂ and ionic liquids such as 1-butyl-3-methylimidazolium bromide, 1-butylpyridinium bromide, cholin chloride and tetrabutylammonium bromide were prepared, supported on silica gel, and compared for alkylation reactions with various alkylating agents. Among the IL-based catalysts, 1-butyl-3-methyl imidazolium-bromide-ZnCl₂ and 1-butylpyridinium bromide-ZnCl₂ are highly active.     

Synthesis and regioselective N- and O-alkylation of 3-alkyl-5-phenyl-3H-[1,2,3]triazolo[4,5-d]pyrimidin-7(6H)-ones and 2-phenyl-9-propyl-9H-purin-6(1H)-one with evaluation of antiviral and antitumor activities

3-Alkyl-5-phenyl-3H-[1,2,3]triazolo[4,5-d]pyrimidin-7(6H)-ones were prepared by nitrosative cyclization of the appropriate 5,6-diamino-2-phenylpyrimidin-4(3H)-ones with nitrous acid and were subjected to regioselective alkylation with several alkylating agents in aprotic solvent at different temperature. Simultaneous 6-N- and 7-O-alkylation were observed and the regioselectivity varied remarkably with size and shape of the alkylating agents as well as with the reaction temperature. Similarly, N- and O-alkylation as well as selectivity was also observed in the case of 2-phenyl-9-propyl-9H-purin-6(1H)-one. Some of the synthesized compounds showed moderate antiviral and antitumor activities.     

Alkylating potential of α,β-unsaturated compounds

Alkylation reactions of the nucleoside guanosine (Guo) by the α,β-unsaturated compounds (α,β-UC) acrylonitrile (AN), acrylamide (AM), acrylic acid (AA) and acrolein (AC), which can act as alkylating agents of DNA, were investigated kinetically. The following conclusions were drawn: i) The Guo alkylation mechanism by AC is different from those brought about the other α,β-UC; ii) for the first three, the following sequence of alkylating potential was found: AN > AM > AA; iii) A correlation between the chemical reactivity (alkylation rate constants) of AN, AM, and AA and their capacity to form adducts with biomarkers was found. iv) Guo alkylation reactions for AN and AM occur through Michael addition mechanisms, reversible in the first case, and irreversible in the second. The equilibrium constant for the formation of the Guo-AN adduct is K(eq) (37 °C) = 5 × 10(-4); v) The low energy barrier (≈10 kJ mol(-1)) to reverse the Guo alkylation by AN reflects the easy reversibility of this reaction and its possible correction by repair mechanisms; vi) No reaction was observed for AN, AM, and AA at pH < 8.0. In contrast, Guo alkylation by AC was observed under cellular pH conditions. The reaction rate constants for the formation of the α-OH-Guo adduct (the most genotoxic isomer), is 1.5-fold faster than that of γ-OH-Guo. vii) a correlation between the chemical reactivity of α,β-UC (alkylation rate constants) and mutagenicity was found.     

Synthesis of phenethylamines from phenylacetonitriles obtained by alkylation of cyanide ion with mannich bases from phenols and other benzylamines

Benzylamines, obtained by the Mannich reaction on phenols or by reductive alkylation of aldehydes, have been used in place of benzyl chlorides to alkylate cyanide ion to obtain nitriles which may be reduced to phenethylamines. Yields of 4-hydroxy-3-methoxyphenylacetonitrile were about the same from the primary, secondary, and tertiary amines. Benzylamines not having either an ortho or para OH group did not function as alkylating agents. With such compounds it was necessary to prepare the quaternary salts before alkylation could be achieved. 6-Hydroxydopamine was prepared from 2,4,5-trimethoxybenzaldehyde utilizing the latter approach. 3,5-Dimethoxy-4-hydroxyphenethylamine was cyclized to the corresponding dihydroisoquinoline. The isoquinoline and tetrahydroisoquinoline analogs were also prepared. 4-Hydroxy-3-methoxyphenylacetonitrile was hydrolysed to homovanillic acid, the naturally occurring metabolite of dopamine.     

Evaluation of the DNA Alkylation Properties of a Chlorambucil-Conjugated Cyclic Pyrrole-Imidazole Polyamide

Hairpin pyrrole-imidazole polyamides (hPIPs) and their chlorambucil (Chb) conjugates (hPIP-Chbs) can alkylate DNA in a sequence-specific manner, and have been studied as anticancer drugs. Here, we conjugated Chb to a cyclic PIP (cPIP), which is known to have a higher binding affinity than the corresponding hPIP, and investigated the DNA alkylation properties of the resulting cPIP-Chb using the optimized capillary electrophoresis method and conventional HPLC product analysis. cPIP-Chb conjugate 3 showed higher alkylation activity at its binding sites than did hPIP-Chb conjugates 1 and 2 . Subsequent HPLC analysis revealed that the alkylation site of conjugate 3 , which was identified by capillary electrophoresis, was reliable and that conjugate 3 alkylates the N3 position of adenine as do hPIP-Chbs. Moreover, conjugate 3 showed higher cytotoxicity against LNCaP prostate cancer cells than did conjugate 1 and cytotoxicity comparable to that of conjugate 2 . These results suggest that cPIP-Chbs could be novel DNA alkylating anticancer drugs.     

合成2-芳基-3-烷基-7-硝基-1,4-氧硫杂萘-4,4-二氧化物的新方法

在K₂CO₃－TEBA－DNIF体系中,2－(2-氧-4-硝基苯磺酰基)－1-芳基乙酮与各种烷基化试剂发生烷基化-环化反应,得到一系列3-位取代的1,4-氧硫杂萘4,4-二氧化物,并讨论了反应机理和反应条件.     

Nucleosome Assembly Alters the Accessibility of the Antitumor Agent Duocarmycin B2 to Duplex DNA

To evaluate the reactivity of antitumor agents in a nucleosome architecture, we conducted in vitro studies to assess the alkylation level of duocarmycin B₂ on nucleosomes with core and linker DNA using sequencing gel electrophoresis. Our results suggested that the alkylating efficiencies of duocarmycin B₂ were significantly decreased in core DNA and increased at the histone‐free linker DNA sites when compared with naked DNA conditions. Our finding that nucleosome assembly alters the accessibility of duocarmycin B₂ to duplex DNA could advance its design as an antitumor agent.     

Synthesis and Antimicrobial Evaluation of Some New Spiroindolinone Derivatives

In an attempt to find a new class of antimicrobial agents, a series of spiroindolinone compounds containing pyridine, pyrimidine, benzopyrans, pyrido, naphtodiazepines, pyrazole, and isoxazole ring systems were prepared via the reaction of 3‐(2‐oxo‐2‐(3‐oxo‐3H‐benzo[f]chromen‐2‐yl)ethylidene)indolin‐2‐one ( 4 ) with an appropriate nucleophilic reagent. Newly synthesized compounds were characterized by elemental analysis and spectral data (IR, ¹H‐NMR, ¹³C‐NMR, and mass spectra). Representative compounds were tested and evaluated as antimicrobial agents.