The analysis of the CrISY diastereomeric profile, as described above, revealed that the majority of the product forms the cis–trans isomer, or 4aS,7S,7aR. The stereochemistry of this isomer matches that of the downstream iridoid products in C. roseus. The major isomer found in the AmISY product profile must then correspond to 4aR,7R,7aS (cis–trans), which is the enantiomer of 4aS,7S,7aR. However, downstream A. majus iridoids are derived from the 4aR,7S,7aR isomer (cis–cis), which is found in only ∼5% of the cyclic AmISY products. Therefore, although AmISY generates the correct stereochemistry at the C7 position, the required cis–cis isomer is not the major product.