The synthesis of unusual isocoumarin derivatives: the chemistry of homophthalic acid

Hauser-Kraus Annulation Initiated Multi-Cascade Reactions for Facile Access to Functionalized and Fused Oxazepines, Carbazoles and Phenanthridinediones

The Hauser-Kraus (H-K) annulation of N-unsubstituted 3-olefinic oxindoles with 3-nucleophilic phthalides triggers a cascade of ring expansion and ring contraction reactions through several regioselective steps in one pot. While oxazepines were isolated in the presence of stoichiometric amounts of base at room temperature, carbazoles and phenanthridinediones were the products in the presence of excess base and microwave irradiation. Mechanistic studies guided by stepwise reactions and control experiments revealed that the isolable oxazepine intermediate, formed via ring expansion of the H-K adduct, is the key precursor to carbazole and phenanthridinedione via decarboxylative regioselective cyclizations.

Synthesis of Disulfide-Bridged N-Phenyl-N'-(alkyl/aryl/heteroaryl)urea Derivatives and Evaluation of Their Antimicrobial Activities

The discovery of new antimicrobial agents is extremely needed to overcome multidrug-resistant bacterial and tuberculosis infections. In the present study, eight novel substituted urea derivatives (10a-10h) containing disulfide bond were designed, synthesized and screened for their in vitro antimicrobial activities on standard strains of Gram-positive and Gram-negative bacteria as well as on Mycobacterium tuberculosis. According to the obtained results, antibacterial effects of the compounds were found to be considerably better than their antimycobacterial activities along with their weak cytotoxic effects. Molecular docking studies were performed to gain insights into the antibacterial activity mechanism of the synthesized compounds. The interactions and the orientation of compound 10a (1,1'-((disulfanediylbis(methylene))bis(2,1-phenylene))bis(3-phenylurea)) were found to be highly similar to the original ligand within the binding pocket E. faecalis β-ketoacyl acyl carrier protein synthase III (FabH). Finally, a theoretical study was established to predict the physicochemical properties of the compounds.

Synthesis of 4-hydroxyindole fused isocoumarin derivatives and their fluorescence “Turn-off” sensing of Cu(ii) and Fe(iii) ions

A simple and efficient protocol has been developed for the synthesis of 4-hydroxyindole fused isocoumarins from easily available starting materials.

Total synthesis of cytotoxic metabolite ( ± )-desmethyldiaportinol from Ampelomyces sp

A concise total synthesis of ( ± )-desmethyldiaportinol isolated from Ampelomyces sp. is described. Microwave-assisted cyclocondensation of 3,5-dimethoxyhomopthalic acid with 3,4-dibromobutanoyl chloride afforded the 3-(2,3-dibromopropyl)-6, 8-dimethoxyisocoumarin in 2-3 min as the pivotal step. The 3,4-dibromobutanoyl chloride was itself synthesised from 3-butenoic acid via bromination in carbon tetrachloride at room temperature to yield 3,4-dibromobutanoic acid followed by reaction with thionyl chloride. The replacement of bromo- by hydroxyl substituent was achieved under mild conditions involving the refluxing in a mixture of acetone and water to provide ( ± )-3-(2,3-dihydroxypropyl)-6,8-dimethoxyisocoumarin which on complete demethylation furnished the title natural product.

Silica sulfuric acid: a reusable solid catalyst for one pot synthesis of densely substituted pyrrole-fused isocoumarins under solvent-free conditions

A convenient and efficient methodology for the synthesis of densely substituted pyrrole-fused isocoumarins, which employs solid-supported silica sulfuric acid (SSA) as catalyst, has been developed. When the mixture of ninhydrin adducts of acetylacetone/ethyl acetoacetate and primary amines was heated on the solid surface of SSA under solvent-free conditions, the pyrrole-fused isocoumarins were formed in good yields. This synthetic method has several advantages such as the employment of solvent-free reaction conditions without the use of any toxic reagents and metal catalysts, the ease of product isolation, the use of a recyclable catalyst, the low cost, the easy availability of the starting materials, and the excellent yields of products.

Total synthesis and antibacterial screening of ( ± )-7-butyl-6,8-dihydroxy-3-pentyl-3,4-dihydroisochromen-1-one

A new total synthesis of ( ± )-7-butyl-6,8-dihydroxy-3-pentyl-3,4-dihydroisochromen-1-one, isolated as R-enantiomer from Geotrichum sp., has been described. Reaction of 4-butyl-3,5-dimethoxyhomophthalic anhydride with hexanoyl chloride in the presence of 1,1,3,3-tetramethyl guanidine and triethyl amine afforded 7-butyl-6,8-dimethoxy-3-pentylisochromen-1-one, which was converted into corresponding 3,4-dihydroisochromen-1-one by successive ring opening and reduction. Final demethylation to furnish the natural product was achieved using anhydrous aluminum chloride in ethanethiol. The target compound and the intermediates were subjected to antibacterial evaluation against 10 bacterial strains using levofloxacin as standard.

Reaction discovery using microfluidic-based multidimensional screening of polycyclic iminium ethers

Polycyclic iminium ethers are ambident electrophilic intermediates that react with a range of nucleophiles in a highly condition-dependent manner to afford densely functionalized lactams. In an effort to expand the scope of reactivity and assist in the generation of new chemotypes from these intermediates, several iminium ethers were subjected to reaction screening using an automated microfluidics reaction platform. Application of this approach led to the discovery of several interesting reaction pathways involving the iminium ether intermediates that will be described.

Synthesis and in vitro and in vivo evaluation of a series of dihydroisocoumarin derivatives conjugated with fatty acids, alcohols, and amines as potential anticancer agents

In this paper, we report the synthesis and biological activity of a series of dihydroisocoumarin analogues conjugated with fatty acids, alcohols, or amines, of varying hydrocarbon chain length and degree of unsaturation, to the dihydroisocoumarins, kigelin and mellein, at the C-7 and C-8 positions on the core dihydroisocoumarin structure. These compounds were evaluated for their antiproliferative activity against human breast cancer (MCF-7 and MDA-MB-468) and melanoma cells (SK-MEL-28 and Malme-3M) using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. Two compounds conjugated with gamma-linolenyl alcohol (18:3 n-6) demonstrated potent antiproliferative activity in vitro with one of these 4-hydroxy-3-oxo-1,3-dihydro-isobenzofuran-5-carboxylic acid octadeca-6,9,12-trienyl ester, demonstrating significant antitumor activity in vivo in a number of human tumor xenograft models.

Formation of 3-Aryl-5-nitroisocoumarins from 5-Nitroisocoumarins and Aromatic Acyl Chlorides under Friedel−Crafts Conditions

Treatment of 5-nitroisocoumarin with aromatic acyl chlorides under Friedel-Crafts conditions gives 3-aryl-5-nitroisocoumarins, rather than the expected 4-acyl-5-nitroisocoumarins. This procedure was optimized for reaction temperature (150 degrees C), solvent (nitrobenzene), and Lewis acid (SnCl4). Reaction of 5-nitroisocoumarin with [13C]-carbonyl benzoyl chloride under the optimum conditions gave 5-nitro-3-phenylisocoumarin in which the 13C is located at the 3-C of the heterocycle, indicating that the benzoyl carbon framework is incorporated intact.