(7,8-Dicarba-nido-undecaboran-7-yl)acetic acid: synthesis of individual enantiomers and the first example of the determination of the absolute configuration of chiral monosubstituted nido-carborane

Abstract

Individual (R_P)- and (S_P)-enantiomers of planar-chiral (7,8-dicarba-nido-undecaboran-7-yl)acetic acid were obtained for the first time by deboronation of the derivatives of achiral (1,2-dicarba-closo-dodecaboran-1-yl)acetic acid containing residues of natural amino acids and ethylenediamine, followed by separation and hydrolysis of diastereomeric derivatives. An alternative route for the preparation of enantiopure (nido-carboran-7-yl)acetic acid starting from an enantiopure amino ester based on closo-carborane of known configuration made it possible for the first time to assign the absolute configuration of structurally simple C-monosubstituted nido-carborane derivatives. Using the example of introducing an amino group into position 10 of the carborane fragment of (7,8-dicarba-nido-undecaboran-7-yl)acetic acid, we have demonstrated the possibility of obtaining planar-chiral functional derivatives of nido-carborane.