L-Pyrohomoglutamic acid (S-6-oxopiperidine-2-carboxylic acid) is a δ-lactam formed the head-to-tail cyclisation of L-homoglutamic acid. Unlike pyroglutamic acid, L-pyrohomoglutamic acid has not been reported as a pyrolysis product but is re-named to better reflect the compound’s structural relationship to L-homoglutamic acid. L-Pyrohomoglutamic acid has been reported as a secondary metabolite of Nocardia lactamdurans and a co-metabolite of penicillin V from Penicillium chrysogenum but its pharmacological properties have not been extensively investigated.