Structural revision of sesbagrandiflorains A and B, and synthesis and biological evaluation of 6-methoxy-2-arylbenzofuran derivatives

Sesbagrandiflorains A (1) and B (2), isolated from the stem bark of the Indonesian fabaceous plantSesbania grandiflora, were reported to be 6-methoxy-2-(2 ',3 '-dihydroxy-5 '-methoxyphenyl)-1-benzofuran-3-carbaldehyde and 6-hydroxy-2-(2 ',3 '-dihydroxy-5 '-methoxyphenyl)-1-benzofuran-3-carbaldehyde, respectively. However, based on reevaluation of their 1D and 2D NMR data, the chemical structures of 1 and 2 have been revised to 4-hydroxy-2-(4 '-hydroxy-2 '-methoxyphenyl)-6-methoxybenzofuran-3-carbaldehyde and 4-hydroxy-2-(4 '-hydroxy-2 '-hydroxyphenyl)-6-methoxybenzofuran-3-carbaldehyde, respectively. In addition, seven new derivatives of1have been synthesized from the natural product in good yields (65 - 93%). The chemical structures of the synthetic compounds-one diester (6), four ethers (7-10), one secondary amine (11), and one oxime (12)-were confirmed by MS and NMR analysis. Compound 6 exhibited moderate antibacterial activity against the plant pathogenRhodococcus fascianswith a MIC of 0.1 mg/mL. Compounds 8 and 12 demonstrated respectable cytotoxicity against A375 melanoma cancer cells line with the relative IC(50)values of 22.8 and 32.7 mu M, respectively.

Automated summary

The chemical structures of two compounds isolated from Sesbania grandiflora have been revised, and seven new derivatives have been synthesized. Compound 6 showed moderate antibacterial activity, while compounds 8 and 12 exhibited cytotoxicity against melanoma cancer cells.