azlactones
Oxazol-5(4H)-ones I, compounds derived by cyclization of N-acyl α-amino carboxylic acids, RC(=O)NHCR2C(=O)OH, through formal loss of the elements of water. 4-Hydrocarbylideneazlactones II are often referred to as 'unsaturated azlactones'.
A00559-2
Source:
PAC, 1995, 67, 1307 (Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1321