Trans—trans nepetalactone was not found in any Nepeta plant in sufficient quantities and had to be synthesized by epimerization of cis—cis nepetalactone under basic conditions (21). In a 50-ml flask equipped with a reflux condenser, 500 mg of cis—cis nepetalactone (1 eq, 3.0 mmol) was dissolved in toluene and refluxed. Progress of the reaction was controlled by GC-MS, and the reaction was stopped when the equilibrium was reached at a 9:1 cis–cis:trans–trans ratio after 6 h. The reaction mix was evaporated under reduced pressure and separated by silica flash chromatography as described for cis—cis nepetalactone. Fractions were checked for the nepetalactone diastereomers by TLC (anisaldehyde stain, 20% ethyl acetate in hexane as eluent), where trans–trans (Rf = 0.65) and cis–cis nepetalactone (Rf = 0.59) were well separated. The 1H NMR was identical to a spectrum published previously (21).