The condensation of salicylaldehydes and malononitrile revisited: synthesis of new dimeric chromene derivatives.
The reaction of salicylic aldehydes with malononitrile was reinvestigated, and the reaction pathway was followed by 1H NMR spectroscopy. A delicate control of the experimental conditions allowed the synthesis of 2-imino-2H-chromene-3-carbonitriles 1, (2-amino-3-cyano-4H-chromen-4-yl)malononitriles 2, 4-amino-5-imino-2,7-dimethoxy-5H-chromeno[3,4-c]pyridine-1-carbonitrile 12, and (4,5-diamino-1-cyano-1,10b-dihydro-2H-chromeno[3,4-c]pyridin-2-ylidene)malononitrile 13. Two novel 2-iminochromene dimers, with structures 8 and 9, were isolated and fully characterized. The activity of compound 8a on Aspergillus spp. growth and on ochratoxin A production was evaluated. The results of the bioassays indicate that compound 8a, applied at concentrations of 2 mM, totally inhibited the growth of the fungi tested. Ochratoxin A production by Aspergillus alliaceus was reduced by about 93% with a 200 microM solution of this compound. A moderate inhibitory effect was observed for the analogous structure 8b, and no inhibition was registered for compounds 2 and 1, used as synthetic precursors of the dimeric species 8.
Costa
Marta
M
Centro de Química, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
Areias
Filipe
F
Abrunhosa
Luís
L
Venâncio
Armando
A
Proença
Fernanda
F
D000447:Aldehydes / Q000737:chemistry*; D001230:Aspergillus / Q000378:metabolism; D001578:Benzopyrans / Q000737:chemistry*; D019281:Dimerization; D009682:Magnetic Resonance Spectroscopy; D009570:Nitriles / Q000737:chemistry*; D009793:Ochratoxins / Q000096:biosynthesis; D020156:Salicylic Acid / Q000737:chemistry*; D013055:Spectrophotometry, Infrared
D000447:Aldehydes; D001578:Benzopyrans; D009570:Nitriles; D009793:Ochratoxins; C025589:ochratoxin A; C000945:dicyanmethane; D020156:Salicylic Acid