text: Most natural lipase inhibitors differ only in the structure of the side chains and the nature of the linked amino acids, but have the same β-lactone ring in (S)-configuration as a primary structure.
  Besides the role of the β-lactone ring in structure-activity relationship, the nature of the functional groups (e.g. ester or ether and the chain length at the β-site) also matter. However a trans-position of the side-chains on the β-lactone ring is crucial for its activity.