Synthesis and bioactivity of fluorine compounds containing isoxazolylamino and phosphonate groups

A series of α-amino (2, or 4)-fluorobenzyl-phosphonates containing isoxazole moiety were synthesized by the reaction of fluorobenzoaldehyde, 3-amino-5-methylisoxazole and dialkyl phosphite under unltrasound irradiation without solvent and catalyst. Their structures were established by elemental analysis, IR, 1H NMR and 13C NMR. The bioassay tests showed that these title compounds exhibit moderate anticancer activity in vitro by MTT method. The crystal structure of 4c has been determined by X-ray diffraction. It crystallizes in the monoclinic system, space group P2(1)/n, with unit cell parameters: a = 0.9335(3), b = 1.3067(4), c = 1.6552(6) nm, β = 104.801(6)°, Z = 4, V = 1.9521(11) nm3, Dc = 1.260 g/cm3, μ = 0.172 mm−1, F(000) = 784. The crystal structure was solved by direct methods and refined by full-matrix least squares to final values of R = 0.0524 and w R = 0.1592 with 9902 reflections (I > 2σ(I)). The dihedral angle between the plane of isoxazole group and the plane of the benzene is 77.27°.