has functional parent penam penem (5R)-4-thia-1-azabicyclo[3.2.0]hept-2-en-7-one 127.009 127.16534 2,3-didehydropenam An organic heterobicyclic compound that consists of (5R)-4-thia-1-azabicyclo[3.2.0]hept-2-ene bearing a 7-keto substituent. The parent of the class of penems. C5H5NOS CHEBI:35994 HHXMXAQDOUCLDN-RXMQYKEDSA-N InChI=1S/C5H5NOS/c7-4-3-5-6(4)1-2-8-5/h1-2,5H,3H2/t5-/m1/s1 [H][C@@]12CC(=O)N1C=CS2 chebi_ontology penems