Complex sentence: The isomerization of brasofensine is not between the alpha and beta positions on the 2 position of the tropane ring but rather the E/Z isomerization of the imine (i.e. "methyl-aldoxime").
Split into simpler sentences: The isomerization of brasofensine is not between the alpha and beta positions on the 2 position of the tropane ring. They are merely talking about E/Z isomerization of the imine (i.e. "methyl-aldoxime").