Anthracene Derivatives Bearing Thiourea and Glucopyranosyl Groups for the Highly Selective Chiral Recognition of Amino Acids:  Opposite Chiral Selectivities from Similar Binding Units

Two new anthracene thiourea derivatives, 1 and 2, were investigated as fluorescent chemosensors for the chiral recognition of the two enantiomers of α-amino carboxylates. Especially, host 2 displayed K_l/K_d values as high as 10.4 with t-Boc alanine. Furthermore, the d/l selectivity of hosts 1 and 2 is opposite, even though both hosts bear the same glucopyranosyl units. These intriguing opposite d/l binding affinities by 1 and 2 were obtained without/with H-π interaction between anthrancene moiety and the methyl groups, which were explained by extensive high-level theoretical investigations taking into account the dispersion energy as well as the 2D-NMR chemical shifts.