The mono-Boc protected amino cyclopentenecarboxylate (I) is converted to the di-Boc derivative (II) by means of di-tert-butyl dicarbonate and DMAP. Dipolar cycloaddition of the nitrile oxide generated from ethyl 2-chloro-2-(hydroxyimino)acetate (III) to cyclopentene (II) gives the cis-fused cyclopentaisoxazole (IV) as a diastereomeric mixture. After cleavage of the acidic Boc groups, the desired isomer (V) can be isolated by column chromatography. Finally, alkaline hydrolysis of the ethyl ester functions of (V) affords the target dicarboxylic acid.