1-(4,5-Dihydro-2-thiazolyl)-3-azetidinethiol Hydrochloride is used as a reagent in the synthesis of Tebipenem Tetrahydrate (T012840); the active metabolite of Tebipenem Pivoxil (T012900) that shows excellent bactericidal activity against β-lactamase-nonproducing, ampicillin-resistant isolates.