Could X-Ray Analysis Explain for the Differing Antimicrobial and Antioxidant Activity of Two 2-Arylamino-3-Nitro-Coumarins?

Abstract

Abstract X-Ray analyses of 4-(naphthalen-1-ylamino)-3-nitro-chromen-2-one and 3-nitro-4-phenylamino-chromen-2-oneshowedthatthementionedcompoundscrystallizeinthespace groups P1- (triclinic crystal system; unit cell parame-ters: a = 8.087(2) A˚, b = 9.241(3) A˚, c = 10.911(3) A˚,a = 93.77(3) , b = 102.51(3) , c = 106.44(2) ,V=756.4(4) A˚ 3 and Z = 2) and P2 1 2 1 2 1 (orthorhombic crystalsystem; unit cell parameters: a = 4.9274(9) A˚, b =14.725(3) A˚, c = 17.866(4) A˚, a = b = c = 90 ,V=1296.3(5)A˚ 3 andZ = 4),respectively.Theanalysesofcrystalstructures and gas phase conformations, inferred from singleX-ray crystallographic and molecular modeling experiments,respectively, showed that the changes in p delocalizationof the farmacoactive formal 3-amino-2-nitro-acrylic acidderivatives might explain the observed significant differenceof the antimicrobial and antioxidant activities and spectralproperties of two 4-arylamino-3-nitro-coumarin derivatives.Keywords 4-Arylamino-3-nitro-coumarins Synthesis X-ray analysis Conformation Antimicrobial activity Antioxidant capacityIntroductionIn the continuation of our investigation [1] of biologi-cally active coumarin derivatives we synthesized two2-arylamino-3-nitro-coumarins: 4-(naphthalen-1-ylamino)-3-nitro-chromen-2-one (1) and 3-nitro-4-phenylamino-chromen-2-one (2), Fig. 1. Previous research has shownthat 4-amino-3-nitrocoumarins, tested for pharmacologicalactivity in mice and rabbits, had neurotropic activity, gen-erally inhibiting spontaneous locomotor activity, decreasinghyperactivity induced by phenamine, and prolonging thio-pental sleep [2]. The same study [2] also pointed out to themost active of the derivatives containing a secondary aminogroup, compound 2, that inhibited phenamine hyperactivity2-5-fold and prolonged thiopental sleep 2-fold. Compoundspossessing a 4-amino-3-nitrocoumarin moiety were alsointeresting due to the previously noted steric inhibition ofresonance of the C-3 NO