Novel synthetic approach to non-natural conformationally rigid spiro-linked amino acids

Abstract

1-Aminospiro[2.3]hexane-1,5-dicarboxylic and 1-ammo-5-(ammomethyl)spiro[2.3]hexane-1-carboxylic acids, which are the conformationally rigid analogues of glutamic acid and lysine, respectively, were synthesized from 3-methylidenecyclobutanecarbonitrile. The synthetic route includes a catalytic [1+2]-cycloaddition of ethyl 2-diazo-2-nitroacetate to a double bond of the unsaturated nitrile, a subsequent chemoselective reduction of the nitro and cyano groups, and a hydrolysis of the ester moiety.