Volume 20, Issue 5

Dibenzo[ b , f ][1,4]oxazepine (DBO) derivatives possess an array of pharmacological activities, and are of growing pharmaceutical interest. Twelve recent synthetic protocols to construct DBO and DBO derivatives have been described in this review. The reported methods include cyclocondensation with two precursors exemplified by substituted 2-aminophenols and substituted 2-halobenzaldehydes, substituted 2-nitro-1-bromobenzene and substituted 2-triazolylphenols, substituted 2-nitro-1-bromobenzene and substituted 2-hydrazonamidophenol, substituted 2-nitro-1-bromobenzene and substituted 2-(aminomethyl)phenol, and 2-aminobenzonitrile and 1,4-dichloro-2-nitrobenzene. Other methods include copper catalysis, 1,3-dipolar cycloaddition, domino elimination-rearrangement-addition sequence, and an Ugi four-component reaction followed by an intramolecular O -arylation. These methods will serve as a guide to chemists in developing DBO derivatives of pharmacological interest.

New approaches to synthesis of five- and six-membered heterocyclic compounds utilizing dimethyl N- cyanodithioiminocarbonate are surveyed. The scope and limitation of the most important approaches are discussed.

The new radical scavenger 12T061C (C 20 H 22 O 7 ) has been identified from a culture of Streptomyces species. Spectroscopic elucidation showed that this compound is a new Julichrome family compound. 12T061C shows a potent radical-scavenging activity with an ED 50 of 18 μ m that is similar to those of the known antioxidant compounds α-tocopherol (ED 50 16 μ m ) and quercetin (ED 50 3 μ m ).

Several derivatives of the novel pyrimido[4′,5′:2,3][1,4]thiazepino[7,6- b ]quinoline ring system have been synthesized through cyclocondensation of 5-amino-6-methylpyrimidine-4-thiols 5a,b and 2-chloroquinoline-3-carbaldehydes 6a–c in the presence of K 2 CO 3 in DMF.

Potassium fluoride-catalyzed solvent-free multicomponent reaction of aldehydes, N , N ′-dialkyl barbiturates and malononitrile results in the fast (15 min) and efficient (yields 89–95%) formation of substituted pyrano[2,3- d ]pyrimidines. The improved synthetic methodology for this class of bioactive compounds is important from the viewpoint of diversity-oriented large-scale processes and represents an environmentally benign solvent-free synthetic concept for multicomponent reactions strategy.

An expeditious method to prepare pyranocoumarins containing an aroyl group by the three-component reaction of 4-hydroxycoumarin with arylglyoxals and malononitrile is described. The reaction is efficiently catalyzed by Mohr’s salt, and the products were obtained in good to excellent yields with high purity. The method is simple, inexpensive, and environmentally friendly.

Novel triazole Schiff-base derivative 3 bearing a coumarin unit was synthesized by the reaction of 4-formylbenzocoumarin ( 1 ) with 3,5-diphenyl-4-amino-1,2,4-triazole ( 2 ). The structure of the product was characterized by means of IR, MS, 1 H NMR, 13 C NMR, and elemental analysis. The UV-vis absorption and fluorescence emission spectra of compound 3 exhibit blue-shifted absorption and fluorescent enhancement upon chelation to cupric ion. Fluorometric titration revealed a 2:1 ligand to metal ratio in the complex and the binding constant of 4.62×10 6 m -1 .

Hybrid compounds are relevant products in the structure-activity relationships analysis. A new series of hybrid compounds containing coumarin, 1,2,3-triazole, and chalcone substructures were synthesized and screened for their antimicrobial activity. The structures of the synthesized compounds have been established on the basis of analytical and spectral data.

A one-pot synthesis of 3,4-dihydro-3-hydroxyisochroman-1-one (lactol) 3 by oxidation of indene using tungstic acid-hydrogen peroxide is reported. The synthesized lactol was converted into acetal derivatives 5a–h , which were evaluated for their in vitro antibacterial activity against Staphylococcus aureus , Streptococcus pyogenes (Gram-positive), Escherichia coli , Pseudomonas aeruginosa (Gram-negative) strains, and antifungal activity against Candida albicans and Aspergillus niger by broth dilution method. The compounds show potent activity against S. aureus in comparison with ampicillin and exhibit modest antifungal activity.

Two series of s -triazine derivatives were synthesized by copper-catalyzed Ullmann reaction. Facile route was adopted to achieve amination of s -triazines for the first time. The C-N coupling reactions were conducted in water under ligand-free and oxygen-free conditions. The synthesized compounds were screened for their in vitro antibacterial and antifungal activity. Compounds were further subjected to in vitro antitubercular screening against the H37Rv strain. Compared with standard drugs, compound 5b was found to be the most active antimicrobial and antitubercular agent that inhibits Staphylococcus aureu s and H37Rv strain with minimum inhibitory concentration of 1.56 and 6.25 μg/mL, respectively.