A series of new carbapenem compounds, which have a pyrrolidin-3′-ylthio group substituted with various aminocarbonyl group at C-5′ position as C-2 side chain, have been prepared. The antibacterial activity and the stability to renal dehydropeptidase-I of these compounds were investigated, and the structure-activity relationships were discussed. In this series, SM-7338; (1R,5S,6S)-2-[(3S,5S)-5-dimethylaminocarbonylpyrrolidin-3-ylthio]-6-[(R)-1-hydroxyethyl]-1-methylcarbapen-2-em-3-carboxylic acid (5a) was the most interesting compound. © 1990, JAPAN ANTIBIOTICS RESEARCH ASSOCIATION. All rights reserved.