Antifungal activity of novel organothiophosphonates

Antifungal activity of five newly synthesized organothiophosphonates namely N-(2-Methoxy-2-oxoethyl)-2-pyridinylidenamido (diethyl amido) (phenyl) thiophosphonate, N-(2-Ethoxy-2-oxoethyl)-2-pyridinylidenamido (diethyl amido) (phenyl) thiophosphonate, N-(2-Methoxy-2-oxoethyl)-2-pyridinylidenamido (diphenyl amido) (phenyl) thiophosphonate, N-(2-Methoxy-2-oxoethyl)-2-pyridinylidenamido (diisopropyl amido) (phenyl) thiophosphonate and N-(2-Methoxy-2-oxoethyl)-2-pyridinylidenamido (N-methyl cyclohexylamido) (phenyl) thio phosphonate incorporating the pyridine ring were evaluated against four seed-borne pathogens of Capsicum annuum namely, Alternaria alternata, Aspergillus flavus, A. niger and Fusarium oxysporum and compared with mancozeb and bavistin. All these compounds incorporate bulky substituents as well as a central phosphorus atom, which is electrophilic due to electron withdrawing groups (C₆H₅ & phenyl ester) in the vicinity. The compounds T-2, T-3, T-4, and T-5 exhibited significant antifungal activities at 100, 250 and 500 ppm.