Fluorescent sensors for lipids and hydrophobic amines in aqueous solution

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] A series of novel fluorescent sensors were designed and synthesized to detect lipids and hydrophobic amines in aqueous solutions. The closed allyl molecular tubes had fairly high affinity and selectivity towards lipids with fluorescence enhancements, but difficult synthesis was the limitation for further modifications to apply different targets. The carbazole open tube with easier synthesis and higher yield only bound hydrophobic amines including stimulants such as 2-aminoheptane, methylhexanamine, heptaminol, phenylethylamine, pseudoephedrine, driven by both hydrophobic effect and electrostatic interactions. The unexpected cyclic open tube selectively bound polyamines such as spermine and spermidine with fluorescence decreases. The binding mechanism of the cyclic open tube toward long chained alkylamines was not yet fully understood. The designed glycolipid sensors proved to be very acid sensitive, therefore base labile protecting groups for amine intermediates should be used. Other highly efficient reactions such as “copper catalyzed 1,3-dipolar cycloadditions” can also be used to couple phenylboronic acid in the future design.