Synthesis and antifungal properties of (4-tolyloxy)-pyrimidyl-α-aminophosphonates chitosan derivatives

A novel class of α-aminophosphonate chitosan derivatives was investigated. These chitosan derivatives consist of (4-tolyloxy)-pyrimidyl-dimethyl-α-amino-phosphonate chitosan (α-ATPMCS) and (4-tolyloxy)-pyrimidyl-diethyl-α-aminophosphonate chitosan (α-ATPECS). Their structures were well defined. Antifungal activity of them against some crop-threatening pathogenic fungi was tested in vitro. The derivatives were found to have a broad-spectrum antifungal activity that was obviously enhanced compared with chitosan. At 250 mg/L, both α-ATPMCS and α-ATPECS even inhibited growth of Phomopsis asparagi (Sacc.) (P. asparagi) and Fusarium oxysporum (F. oxysporum) at 100%, which was even stronger than polyoxin whose antifungal index was 37.2% and 32.1%, respectively. Additionally, the initial mechanism of the chitosan derivatives in F. oxysporum model was studied. It was found that the derivatives may have an effect on membrane permeability of the fungi. The results demonstrated the derivatives may serve as attractive candidates in crop protection.