Chiral GC-MS analysis of CrISY and AmISY products. a, synthesis of nepetalactol and iridodial standards by DIBAL reduction of nepetalactones (11, 21, 24). b, reaction products of CrISY and AmISY with 8-oxogeranial substrate were analyzed on a chiral GC-MS column. The intensity axis of all chromatograms was normalized to the tallest peak. In the CrISY reaction, ten products could be identified (red) in comparison with authentic standards. AmISY products, which have the opposite chirality (blue), were matched to the CrISY products based on electron impact fragmentation spectra (supplemental Fig. S3). Product 8′ is presumably hidden under a larger peak in the AmISY chromatogram. The matching of CrISY and AmISY spectra (left inset) and the matching of CrISY and standard spectra (right inset) was verified by calculating pairwise similarity scores for all combinations, where a score of 1 signifies identity. The presence of similarity scores close to one on the diagonal confirms the peak assignment. c, circular dichroism spectra of 7S-cis-trans nepetalactol standard (black, 2 mm in hexane) and of the extracted CrISY (red) and AmISY (blue) reaction products from a reaction conducted in water without buffer. Water without buffer was used because buffer resulted in an attenuated CD signal.