Synthesis of sulfonate derivatives of carvacrol and thymol as anti-oomycetes agents

Two series of sulfonate derivatives of carvacrol and thymol were synthesized and screened in vitro for their anti-oomycete activity against Phytophthora capsici, respectively. Among all of 32 derivatives, five compounds 3a, 4a, 4k, 3n, and 4n exhibited more potent anti-oomycete activity against P. capsici with EC50 values of 66.66, 62.94, 68.65, 61.24, and 52.91 mg/L, respectively. This suggested that introduction of different substitutions at the hydroxyl position of 1/2 could have remarkable effect on anti-oomycete activity. Overall, when R1 = isopropyl and R2 = methyl, the anti-oomycete activities of the compounds were higher than that of the corresponding compounds of R1 = methyl and R2 = isopropyl.