Piezoactive amino acid derivatives containing fragments of planar- chiral ortho- carboranes

A series of novel (S)-amino acid derivatives bearing planar-chiral (3-acylamino-1,2-dicarba-closo-dodecaboran-1-yl)acetyl substituents was synthesized. Carboranyl amino esters were obtained in a diastereomerically pure form (according to chiral HPLC). Single crystals of individual diastereomers were studied by optical microscopy, X-ray diffraction analysis and piezoresponse force microscopy. The piezoelectric activity of some compounds was shown to exceed that of most known organic piezoelectrics.