Definition: Cyclic esters of hydroxy carboxylic acids, containing a 1-oxacycloalkan-2-one structure. Large cyclic lactones of over a dozen atoms are MACROLIDES.
pyran-2-ones: index PYRONES + LACTONES but BENZOPYRAN-2-ONES is available; for cyclic lactones over 12 atoms consider MACROLIDES
clasto-lactacystin beta-lactone [ c-lact compound,clasto-lactacystin beta-lactone, (1R-(1alpha(S*),4beta,5alpha))-isomer ] active metabolite of lactacystin; inhibits 20 S proteasome; structure in first source