Diethyl diazomalonate (III) was prepared by reaction of diethyl malonate (I) with p-tosyl azide (II) in the presence of Et3N. Subsequent coupling of (II) with 4-hydroxytetrahydropyran (IV) using dirhodium tetraacetate as the catalyst afforded ether (V). Alkylation of (V) with 3-(tert-butoxycarbonylamino)propyl bromide (VI) yielded adduct (VII). Finally, hydrolysis of ester groups of (VII) employing LiOH furnished the title dicarboxylic acid lithium salt.