Total Syntheses of (+)-α-Allokainic Acid and (-)-2- epi-α-Allokainic Acid Employing Ketopinic Amide as a Chiral Auxiliary.

Asymmetric Michael reaction of iminoglycinate 4 to α,ß-unsaturated esters had been developed with >98:<2 diastereoselectivity. A reverse of diastereoselectivity for Michael reaction could be achieved by the replacement of lithium enolate with magnesium enolate. This methodology was applied to the total syntheses of (+)-α-allokainic acid 1 and (-)-2- epi-α-allokainic acid 6 each in 11 synthetic steps starting from 4 in 17.8 and 18.0% yields, respectively.

A turn-on and reversible Schiff base fluorescence sensor for Al3+ ion.

A simple Schiff-base receptor 2 was prepared. It exhibits an "off-on-type" mode with high sensitivity in the presence of Al3+. The receptor 2 exhibited a high association constant with submicromolar detection for Al3+ in EtOH­H2O (95:5 v/v) solution. The addition of EDTA quenches the fluorescence of the receptor 2·Al3+ complex offering receptor 2 as a reversible chemosensor.

A fluorescence enhancement-based sensor for hydrogen sulfate ion.

Sugar-aza-crown ether-based cavitand 1 can act as a selective turn-on fluorescence sensor for hydrogen sulfate ion in methanol among a series of tested anions. Spectroscopic studies, particularly NMR spectroscopy, revealed that the C-H hydrogen bonding between 1,2,3-triazole ring of cavitand 1 and hydrogen sulfate ion is crucial for the high selectivity of the receptor for hydrogen sulfate.