Diastereoselective Synthesis of Carbohydrate Conjugates: Pyrano[3,2-c]quinolones

Abstract

Abstract A facile and efficient protocol for the diastereoselective synthesis of pyrano[3,2-c]quinolone carbohydrate derivatives from Perlin aldehydes and 4-hydroxyquinolones has been developed using a one-pot condensation at room temperature. In this investigation, glucose and galactose were employed as inexpensive starting materials to synthesize two sets of pyrano[3,2-c]quinolone-based carbohydrate conjugates. A total of sixteen novel compounds were successfully synthesized using this methodology in good to excellent yields. The reaction exhibited remarkable diastereoselectivity, resulting in a single diastereomeric product with a diastereomeric excess (dr) 97:3 for glucose, while a diastereomeric mixture with a diastereomeric excess (dr) 67:33 was obtained for galactose. The structural characterization of all sixteen compounds was carried out using various analytical techniques, including IR, 1H NMR, 13C NMR, 1H-1H COSY, 1H-13C HETCOR experiments, 2D NOESY NMR, and HRMS data. Additionally, the scalability of the protocol was successfully demonstrated by synthesizing one of the compounds on a gram scale, highlighting its potential for large-scale production.