Synthesis and Biological Evaluation of Some New Coumarin Derivatives

Pyrimidino[5`,4`-6,5]-,pyridino[3`,2`-6,5]- and pyrrolo[3`,2`-5,6]4H-pyrano-[3,2-c][1]benzopyran-6-one derivatives (5-7 and 10) could be obtained via reaction of 2-amino-4-(p-bromophenyl)-3-cyano(carboethoxy)-4H,5H-pyrano[3,2-c][1]benzopyran-5-ones (3a,b)with a variety of reagents. Alkylation of (3b) with either 2-furoyl chloride or chloroacetyl chloride gave the 2-N-substituted derivatives (9a,b). Benzofurano[3,2-b]4H-pyran derivative (12) was also prepared. The antimicrobial activity of the prepared compounds was tested.


Introduction
Coumarins are nowadays an important group of organic compounds that are used as bactericides [1][2][3], fungicides [4], anti-inflammatory [5], anticoagulant [6] and antitumour agents [7,8]. These pharmacological properties of coumarins aroused our interest in synthesizing several new compounds featuring different heterocyclic rings fused onto the coumarin moiety with the aim of obtaining more potent pharmacologically active compounds.
Concerning the data of antifungal activity in Table 2, compound 5 showed excellent activity against Aspergillus niger, comparable to mycostatin , while compounds 7 and 8 exhibit good activity . Also, compound 9a displays moderate activity toward Penicillium italicum . In general, the data obtained from the microbiological screening showed that the activity of some synthesized compounds is equal to and sometimes greater than those of the reference drugs used.

General
Melting points were taken on an Electrothermal capillary melting point apparatus and are uncorrected. The microanalyses were done at Faculty of Scinece, King Khalid University. Infrared spectra were recorded on a Jasco FT/IR 460, using KBr disks. 1 H-NMR Spectra were recorded on JEOL EX-270 MHz NMR Spectrometer. Mass spectra were recorded on a Finnigan Mat SSQ-7000 mass spectrometer.

Biological Tests
Standard drugs (amoxicillin for bacteria and mycostatin for fungi) were used at a concentration of 1000 ppm for comparisons. The biological activity of these compounds have been evaluated by filter paper disc method [11] after dissolving them in N,N-dimethylformamide to obtain a 1mg/mL solution (1000 ppm). The inhibition zones of microbial growth surrounding the filter paper disc (5 mm) were measured in millimeters at the end of an incubation period of 3 days at 37°C for Echerichia coli and at 28°C for other bacteria and fungi. N,N-dimethylformamide alone showed no inhibation zone.
Compound 3a (3.9 g, 0.01 mole) was added to a mixture of formamide (10 mL), formic acid (5mL) and dimethylformamide (5mL). The reaction mixture was heated at reflux for 10h and then left to cool. The solid product was filtered off and recrystallised from benzene to produce 6 (cf.