5-(2-methyl-3-oxobutyl)oxolan-2-one

5-(2-ethyl-3-oxohexyl)oxolan-2-one

5-(2-methyl-3-oxo-3-phenylpropyl)oxolan-2-one

5-[(2-oxocyclohexyl)methyl]oxolan-2-one

5-(3-oxobutyl)oxolan-2-one