Synthesis of Conformationally Constrained Diaminodicarboxylic Acid Derivatives

Functionally protected forms of three conformationally constrained diaminodicarboxylic acids were synthesized and characterized. 2,2′-Diaminospiro[3.3]heptane-2,2′-dicarboxylic acid, an analogue of diaminopimelic acid, was prepared in racemic form and the structure established by X-ray crystallographic analysis of the methyl ester hydrochloride. trans-1,4-Diaminocyclohexane-1,4-dicarboxylic acid was prepared and its structure established by X-ray crystallographic analysis of the corresponding Cbz-protected ethyl ester. cis- and trans-2,6-diamino-1,2,3,5,6,7-hexahydro-s-indacene-2,6-dicarboxylic acids were synthesized and the structures assigned by X-ray crystallographic analysis of the corresponding Boc-protected ethyl ester and Cbz-protected ethyl ester, respectively.