Molecular Recognition by Inclusion Crystals of Chiral Host Molecules Having Trityl and Related Bulky Groups

Abstract

Molecular recognition by inclusion phenomena is a useful application of organic crystals. So, in this research, first, we discuss how several recent examples of inclusion crystal methods have been overviewed in the optical resolution field. Then, we focus on the installation of trityl and related bulky groups, which enable compounds possible to settle guest molecules to form inclusion crystals. Some hosts of amines and amino-acid derivatives having trityl or 9-phenyl-9-xanthenyl groups include several neutral guests to construct inclusion crystals and achieve structural isomer separation and optical resolution. Finally, we report how salts between N-trityltyrosine and tert-butylamine include 1-(1-naphtyl)ethanol with high enantioselectivity of 96% ee (R). Through this review, we recognize trityl and related bulky groups as crystal engineering tools that conduct inclusion ability to host candidates. Single-crystal X-ray analyses of these inclusion crystals show us that inclusion with low enantioselectivity is often due to the statistically disordered structure of guests. The method of suppressing this statistic disorder to reach high enantioselective inclusion remains unknown.