A process for the preparation of a carbapenem antibacterial compound of the following formula (4) having a 1-alkylpyrrolidine structure or a salt thereof, a useful synthetic intermediate of the following formula (1) or a salt thereof, and a process for the preparation thereof: ##STR1##

wherein R¹ represents a C₁-C₃ alkyl group, R² and R³ each independently represents a hydrogen atom or an organic residue or R² and R³ together with the nitrogen atom they are attached to form a ring.