Reaction of racemic ethyl trans-2-formyl-1-cyclopropane carboxylate (I) with tosylmethyl isocyanide in the presence of NaCN produced oxazoline (II) which, upon treatment with ethanolic ammonia at 120 C in a pressurized reactor afforded imidazole (III). Subsequent protection of the imidazole nucleus with dimethylsulfamoyl chloride gave (IV). Then, basic hydrolysis of ethyl ester of (IV) provided carboxylic acid (V). After activation of (V) as the mixed anhydride with ethyl chloroformate, treatment with NaN3 produced acyl azide (VI). Curtius rearrangement of (VI) in boiling toluene gave isocyanate (VII), which was converted to a mixture of diastereomeric carbamates (VIII) and (IX) using (R)-1-(2-naphthyl)ethanol. Finally, chromatographic separation of the required isomer, followed by hydrolysis in refluxing 30% HBr furnished the target compound.

Reaction of racemic ethyl trans-2-formyl-1-cyclopropane carboxylate (I) with tosylmethyl isocyanide in the presence of NaCN produced oxazoline (II) which, upon treatment with ethanolic ammonia at 120 C in a pressurized reactor afforded imidazole (III). Subsequent protection of the imidazole nucleus with dimethylsulfamoyl chloride gave (IV). Then, basic hydrolysis of ethyl ester of (IV) provided carboxylic acid (V). After activation of (V) as the mixed anhydride with ethyl chloroformate, treatment with NaN3 produced acyl azide (VI). Curtius rearrangement of (VI) in boiling toluene gave isocyanate (VII), which was converted to a mixture of diastereomeric carbamates (VIII) and (IX) using (R)-1-(2-naphthyl)ethanol. Finally, chromatographic separation of the required isomer, followed by hydrolysis in refluxing 30% HBr furnished the target compound.