To obtain a new compound having excellent antibacterial effect and absorbability through the digestive tract, and useful as a propylactic and/or therapeutic agent or the like for microbism.

This compound is a compound of formula I (R1 is a modification group hydrolyzable in organism; R2 and R3 are each a lower alkyl; R4 and R5 are each H or a lower alkyl; R6 is a 1-10C alkyl), pref. pivaloyloxymethyl (1R,5S,6S)-2-[(3S,5S)-(5-N,N-dimethylaminocarbonyl-1- propionyloxymethyloxycarbonyl) pyrrolidin-3-ylthio]-6-[(1R)-1-hydroxyethyl]-1- methylcarbapen-2-em-3-carboxylate or the like. The compound of formula I is obtained, for example, by reacting a compound of formula II with a compound of the formula R1-X (X is a halogen or the like) (e.g. pivaloyloxymethyl iodide), in the presence of a base, in a solvent not inhibiting the reaction.