L. carbon = charcoal. Penem see Penicillin.

Carbapenems are a group of antibiotics that are of the class of beta-lactams, and are therefore quite similar to penicillin (penem), however instead of having a sulfur atom on the pentane ring, they have a carbon atom (carba). Note that this additional carbon causes a double bond on that pentane ring, which therefore becomes a pentene ring, and so -penem is used instead of -penam.