To neutralize the pungent odor of skunk spray, which arises mainly from mercaptans, Du and coworkers reported a chemoreactive fungal metabolite of Tolypocladium sp. termed pericosine A. With the help of a Michael acceptor-methoxycarbonyl group-on C 4 and chlorine atom on C 6 position, the pericosine A scaffold can act as an electron sink during its reaction with the nucleophilic mercaptan. The reaction between phenylethyl mercaptan and pericosine A (shown in Fig. ) was reported to follow two potential mechanisms: syn-S N 2 and The EDC plot in Fig. showed the main density changes for the syn-S N 2 reaction mechanism. During the transition from the reactant to TS, the C 5 -C 6 π bond lost some electron density (shown in magenta in Fig. ), and the new S-C 5 bond was partially formed (shown in blue). From the TS to product, the S-C 5 bond was completely formed, along with a π bond migration from C 5 -C 6 to C 6 -C 1 in Fig. . Notably, the C 1 -Cl bond was broken (shown in magenta) only after the TS, leading to the release of a chloride ion. This is also consistent with the change of bond lengths shown in Fig. .