4-Nitrobenzyl (1S,5R,6S)-2-[7-(2-bromoethyl)thioimidazo[5,1-b]thiazol-2-yl]-6-((1R)-1-hydroxyethyl)-1-methyl-1-carbapen-2-em-3-carboxylate (128 mg) was dissolved in 3 ml of acetonitrile and 0.5 ml of DMF. Thiourea (222 mg) was added to the solution. The mixture was stirred at 50° C. for 18 hr. The reaction solution was concentrated under the reduced pressure. The residue was purified by column chromatography on Sephadex LH-20 (dichloromethane:methanol=1:1), followed by a reaction and purification in the same manner as in Example 1c). Thus, 14.5 mg of the title compound was prepared.
