Access to 2-Alkyl/Aryl-4-(1H)-Quinolones via Orthogonal "NH3" Insertion into o-Haloaryl Ynones: Total Synthesis of Bioactive Pseudanes, Graveoline, Graveolinine, and Waltherione F.

An efficient one-pot synthesis of 4-(1H)-quinolones through an orthogonal engagement of diverse o-haloaryl ynones with ammonia in the presence of Cu(I), involving tandem Michael addition and ArCsp2-N coupling, is presented. The substrate scope of this convenient protocol, wherein ammonium carbonate acts as both an in situ ammonia source and a base toward diverse 2-substituted 4-(1H)-quinolones, has been mapped and its efficacy validated through concise total synthesis of bioactive natural products pseudanes (IV, VII, VIII, and XII), graveoline, graveolinine, and waltherione F.

Synthesis, in vitro and in vivo biological evaluation of novel graveolinine derivatives as potential anti-Alzheimer agents.

A novel series of graveolinine derivatives were synthesized and evaluated as potential anti-Alzheimer agents. Compound 5f exhibited the best inhibitory activity for acetylcholinesterase (AChE) and had surprisingly potent inhibitory activity for butyrylcholinesterase (BuChE), with IC50 values of 0.72 µM and 0.16 µM, respectively. The results from Lineweaver-Burk plot and molecular modeling study indicated non-competitive inhibition of AChE by compound 5f. In addition, these derivatives showed potent self-induced ß-amyloid (Aß) aggregation inhibition. Moreover, 5f didn't show obvious toxicity against PC12 and HepG2 cells at 50 µM. Finally, in vivo studies confirmed that 5f significantly ameliorates the cognitive performances of scopolamine-treated ICR mice. Therefore, these graveolinine derivatives should be thoroughly and systematically studied for the treatment of Alzheimer's disease.

Design and synthesis of new triazoles linked to xanthotoxin for potent and highly selective anti-gastric cancer agents.

Two series of xanthotoxin-triazole derivatives were designed, synthesized, and studied for their antiproliferative properties. The in vitro cytotoxicity of the compounds in the AGS cancer cell line and the L02 normal cell line was evaluated via MTT assay. Among the synthesized compounds, 9-((1-(4-(trifluoromethyl)phenyl)-1H-1,2,3-triazol-4-yl)methoxy)-7H-furo[3,2-g]chromen-7-one (6p) was found to have the greatest antiproliferative activity against AGS cells (IC50=7.5µM) and showed better activity than the lead compound (xanthotoxin, IC50>100µM) and the reference drug (5-fluorouracil, IC50=29.6µM) did. The IC50 value of 6p in L02 cells was 13.3 times higher than that in the AGS cells. Therefore, the compound exhibited better therapeutic activity and specificity compared with the positive control 5-fluorouracil. Cell cycle analysis revealed that compound 6p inhibited cell growth via the induction of S/G2 phase arrest in AGS cells. Compound 6p was identified as a promising lead compound for the further development and identification of 1,2,3-triazole-based anticancer agents.

Graveoline Analogs Exhibiting Selective Acetylcholinesterase Inhibitory Activity as Potential Lead Compounds for the Treatment of Alzheimer's Disease.

This study designed and synthesized a series of new graveoline analogs on the basis of the structural characteristics of acetylcholinesterase (AChE) dual-site inhibitors. The activity of these analogs was also evaluated. Results showed that the synthesized graveoline analogs displayed stronger inhibitory activity against AChE and higher selectivity than butyrylcholine esterase (BuChE) (Selectivity Index from 45 to 486). When the two sites in the graveoline parent ring substituting phenyl and amino terminal had six chemical bonds (n = 3) and the terminal amino was piperidine, compound 5c showed the best activity. Furthermore, the mechanism of action and binding mode were explored by enzyme kinetic simulation, molecular docking, and thioflavin T-based fluorometric assay. Cytotoxicity assay showed that the low concentration of the analogs did not affect the viability of the neurocyte SH-SY5Y.

Synthesis of [7-(14) C]bergapten.

Bergapten (1) is a furocoumarin natural product and currently employed to treat skin disorders. Since past attempts to radiolabel 1 with (14) C were limited to only its 5-methoxy group, a synthesis of the required ring [7-(14) C]1 is now described. The literature reported precursor 4-methoxy-6-hydroxybenzofuran-5-carboxaldehyde (3) was Wittig reacted with stabilized [carbonyl-(14) C]methoxycarbonylmethylenetriphenylphosphorane (4) to obtain [7-(14) C]1 in 47% radiochemical yield, with the desired product being characterized by thin-layer chromatography, HPLC, m.p. and proton NMR.

Total syntheses of the coumarin-containing natural products pimpinellin and fraxetin using Au(I)-catalyzed intramolecular hydroarylation (IMHA) chemistry.

The title natural products (1 and 2, respectively) have been synthesized by Au(I)-catalyzed intramolecular hydroarylation (IMHA) of the relevant aryl propiolate esters (e.g., 13), which were themselves formed by reaction of the corresponding phenols with either 3-(trimethylsilyl)propiolic acid or propiolic acid and N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride or dicyclohexylcarbodiimide. (±)-Purpurasol (3) was readily derived from fraxetin (2) by established procedures.

Synthesis and evaluation of graveoline and graveolinine derivatives with potent anti-angiogenesis activities.

A series of graveoline and graveolinine derivatives were synthesized. The biological results showed that most of graveoline derivatives possessed higher cytotoxicity and better inhibitive effect against the adhesion and migration of human umbilical vein endothelial cell (HUVEC) than graveolinine derivatives. Among these compounds, 8d was the most potent agents that also showed significant anti-angiogenesis activities in chick embryo chorioallantoic membrane (CAM) assay.

Formation of 6-formyl-7-hydroxy-8-methoxycoumarin and 5,8-dioxopsoralen by reaction of 8-methoxypsoralen with H2O2 and potassium superoxide (KO2) catalyzed by halogenated or perhalogenated 5,10,15,20-tetraarylporphyrinatoiron(III) chlorides.

The oxidation of 8-methoxypsoralen (2) with hydrogen peroxide and potassium superoxide catalyzed by 5,10,15,20-(2,4,6-trimethylphenyl)porphyrinatoiron(III) chlorides [Me12TPPFe(III)Cl] (1a) and 5,10,15,20-(2,6-dichlorophenyl)porphyrinatoiron(III) chlorides [Cl8TPPFe(III)Cl] (1b) in dichloromethane gives 6-formyl-7-hydroxy-8-methoxycoumarin (3) in moderate yields, whereas the oxidation of (2) with H2O2 catalyzed by 5,10,15,20-(2,6-dichlorophenyl)-beta-octahaloporphyrinatoiron(III) chlorides [Cl8betaX8TPPFe(III)Cl] (X=Cl, Br) (1c, 1d) gives specifically 5,8-dioxopsoralen (4) in moderate yields.

New tetracyclic analogues of photochemotherapeutic drugs 5-MOP and 8-MOP: synthesis, DNA interaction, and antiproliferative activity.

The synthesis of new tetrahydrobenzo- and benzopsoralen derivatives carrying at position 5 or 8 of the furocoumarin moiety a methoxy, hydroxy, or dimethylaminopropoxy side chain is reported. The study of their photoantiproliferative activity and ability to induce erythema on guinea pig skin allows us to state that the derivatives carrying the dimethylaminopropoxy side chain exhibit a very interesting photobiological pattern. Indeed, if compared with the lead compounds 5-MOP and 8-MOP, they exert a higher cytotoxic activity devoid of significant skin phototoxicity. Between them, the more interesting appears to be 16, a nonphototoxic compound whose antiproliferative activity on HeLa cells is 2 orders of magnitude higher than that of the reference drug 8-MOP. Photoreaction experiments have revealed that, like classic furocoumarins, A-T is the preferred nucleic base pair in its photobinding. Moreover, the extent of covalent photoaddition to DNA correlates well with the photobiological activity. For this compound a certain effect was also observed in the dark. Evaluation of the ability to induce DNA cleavage in the presence of human topoisomerase II has suggested that this enzyme is probably the target accountable for this effect.

4-tert-butylperoxymethyl-9-methoxypsoralen as intercalating photochemical alkoxyl-radical source for oxidative DNA damage.

We describe the synthesis of a novel psoralen peroxide 1 that generates on irradiation (350 nm) alkoxyl radicals, namely tert-butoxyl radicals, as confirmed by electron spin resonance studies with the spin trap 5,5-dimethyl-pyrroline-N-oxide. The radical source intercalates into the DNA, which has been demonstrated by linear-flow-dichroism measurements. Thus, the alkoxyl radicals are formed advantageously directly in the DNA matrix. In supercoiled pBR322 DNA, the generation of strand breaks by the photochemically or metal-catalyzed generated alkoxyl radicals is demonstrated. Photosensitization by the psoralen chromophore was excluded because similar substances that do not release radicals caused no DNA damage, nor were the photoproducts of the peroxide 1 active. With calf thymus DNA, 8-oxoGua and small amounts of guanidine-releasing products, e.g. oxazolone, were observed. However, in these reactions the photoproduct also displayed some DNA-oxidizing capacity.

Some new methyl-8-methoxypsoralens: synthesis, photobinding to DNA, photobiological properties and molecular modelling.

The tricyclic structure of known natural photochemotherapeutic drugs such as 8-methoxypsoralen and 5-methoxypsoralen is often taken as a model in the search of new photosensitizer agents with less phototoxic and mutagenic effects. This paper describes the synthesis, characterization, photobinding to DNA, photobiological properties and computational chemistry of some 8-methoxypsoralen derivatives bearing two or three methyl groups at the key positions of the two photoactive double bonds. Results showed that photoreactivity and photobiological behaviour depend on the pattern of methyl substitutions. Antiproliferative activity in cell lines shows good correlation with DNA interaction data.

1-Thiomethoxsalen and 1-thiopsoralen: synthesis, photobiological properties, and site specific reaction of thiopsoralens with DNA.

The sulfur analogues of psoralen and 8-methoxypsoralen (8-MOP) in the pyrone moiety were synthesized and compared to the parent compounds in terms of photoreactivity with viral M13mp19 RF DNA. The damaged viral DNA was transfected into Escherichia coli and scored for infectivity toward Ca-treated wild-type E. coli. This allowed a comparative study of the sulfur and oxygen analogues to be made in terms of photoreactivity. Furthermore, the DNA sequence specificity for the formation of monoadducts and cross-links of the four analogues was determined with 32P-labeled oligonucleotides containing thymidine in different sequences. The most site specific of the studied psoralens is 8-MOP, while 1-thiopsoralen is the most reactive analogue. This new thio analogue of psoralen leads to the efficient formation of monoadducts and cross-links in any pyrimidine-purine site.

The phototoxicity of 8-methoxythionepsoralen and 6-methylthionecoumarin.

The phototoxicity of 8-methoxythionepsoralen (8-MOTP) and 6-methylthione coumarin (6-MTC) when activated by UV-A has been investigated using a variety of Escherichia coli strains, Haemophilus influenzae transforming DNA and Escherichia coli pBR322 plasmid DNA. The results demonstrate that 8-MOTP is a strictly oxygen independent photosensitizer that is about 500-fold less efficient in forming lesions leading to equivalent lethality than is the parent compound from which it is derived (8-MOP). As is true for 8-MOP, 8-MOTP is capable of inducing histidine independent mutations in E. coli and inactivating transforming DNA consistent with DNA being a target for lesions induced by this molecule in the presence of UV-A. 6-MTC is a strongly oxygen dependent photosensitizer activated by UV-A when tested with either E. coli cells or transforming DNA in contrast to the parent compound (6-methylcoumarin; 6-MC) which is not phototoxic when treated with UV-A. These results imply that the membrane may be an important target leading to lethality. 6-MTC in the presence of UV-A can inactivate pBR322 plasmid and Haemophilus influenzae transforming DNA activity in vitro suggesting that DNA is a potential target for this molecule when activated by UV-A.

Synthesis of some bergapten and ammajin derivatives with potential antibacterial activity.

The reaction of bergapten and ammajin with chlorosulfonic acid i shown to give the sulfonyl chlorides 1 and 11 which react with aliphatic, aromatic, and heterocyclic amines to give the corresponding sulfonamides. Phenols also react with 1 and 11 to give the sulfonate esters 5 and 15. Interaction of bergapten with phosphorous(V)sulfide gave the thione 7 which on reaction with amines gave 9. The antibacterial activity of the products is reported.