The reaction of 4-acetoxy-3-[(1-(tert-butyldimethylsilyloxy)ethyl]azetidin-2-one (I) with benzyl-3-pyrrolidinocrotonate (II) gives the enimine ester (III), which is hydrolyzed with HCl to the corresponding ketoester (IV). The cyclization of (IV), through the diazo compound (V) by means of rhodium acetate, yields the bicyclic ketoester (VI). The condensation of (VI) with 1-(4-nitrobenzyloxycarbonyl)-3-mercaptopyrrolidine (VII) affords the protected carbapenem compound (VIII), which is deprotected by hydrogenation with H2 over Pd/C in THF giving 6-(1-hydroxyethyl)-2-(pyrrolidin-3-ylthio)-1-carbapen-2-em-2-carboxylic acid (IX). Finally, this compound is condensed with ethyl acetimidate (X) in a phosphate buffer.

The reaction of 4-acetoxy-3-[(1-(tert-butyldimethylsilyloxy)ethyl]azetidin-2-one (I) with benzyl-3-pyrrolidinocrotonate (II) gives the enimine ester (III), which is hydrolyzed with HCl to the corresponding ketoester (IV). The cyclization of (IV), through the diazo compound (V) by means of rhodium acetate, yields the bicyclic ketoester (VI). The condensation of (VI) with 1-(4-nitrobenzyloxycarbonyl)-3-mercaptopyrrolidine (VII) affords the protected carbapenem compound (VIII), which is deprotected by hydrogenation with H2 over Pd/C in THF giving 6-(1-hydroxyethyl)-2-(pyrrolidin-3-ylthio)-1-carbapen-2-em-2-carboxylic acid (IX). Finally, this compound is condensed with ethyl acetimidate (X) in a phosphate buffer.