On the cyclobutyl ring (four-membered), each carbon initially carries an exocyclic double bond to an oxygen atom. Replace three of these groups as follows: one oxygen replaced by a double-bonded sulfur (=S), one oxygen replaced by a methyl substituent (-CH3), and one oxygen replaced by an imine group (=NH). Arrange them so that the only remaining double-boned oxygen is located on the carbon directly opposite the methyl substituent.