PURPOSE: To obtain the subject compound having a carbonate group, easily synthesized, stable and useful as an intermediate for carbapenem as an antimicrobial agent.

CONSTITUTION: This carbapenem-based compound is a compound of formula I [R1 is a (protected) hydroxy-substituted lower alkyl; R2 is H or a lower alkyl; R3 is a protecting group for carboxyl; R4 is an alkyl, an alkenyl, an alkynyl or an aryl which may have a substituting group], e.g. 4-nitrobenzyl(4R,5R,6S)-3- methoxycarbonyloxy-6-[(R)-1-hydroxyethyl]-4-methyl-7-oxo-1- azabicyclo[3,2,0]hepto-2-ene-2-carboxylate. Further, the compound of formula II is reacted with the compound of the formula XC(=0)OR4 (X is a halogen) of 1-5 fold mol in the presence of a base (e.g.; diethylamine) of 1-10 fold mol in a solvent such as toluene, at (-)30-50°C reaction temperature for 10min to several days to obtain the objective compound.