Synthesis of Novel Indole Schiff Base Compounds and Their Antifungal Activities.

A series of novel indole Schiff base derivatives ( 2a - 2t ) containing a 1,3,4-thiadiazole scaffold modified with a thioether group were synthesized, and their structures were confirmed using FT-IR, 1 H NMR, 13 C NMR, and HR-MS. In addition, the antifungal activity of synthesized indole derivatives was investigated against Fusarium graminearum ( F. graminearum ), Fusarium oxysporum ( F. oxysporum) , Fusarium moniliforme ( F. moniliforme ), Curvularia lunata (C. lunata ), and Phytophthora parasitica var. nicotiana ( P. p. var. nicotianae ) using the mycelium growth rate method. Among the synthesized indole derivatives, compound 2j showed the highest inhibition rates of 100%, 95.7%, 89%, and 76.5% at a concentration of 500 μg/mL against F. graminearum , F. oxysporum , F. moniliforme , and P. p. var. nicotianae , respectively. Similarly, compounds 2j and 2q exhibited higher inhibition rates of 81.9% and 83.7% at a concentration of 500 μg/mL against C. lunata . In addition, compound 2j has been recognized as a potential compound for further investigation in the field of fungicides.