First Efficient Synthesis of Chlorogenic Acid
The first efficient synthesis of chlorogenic acid (1) was achieved in four steps (three purifications) from quinic acid (2). The overall yield was 65%. The key intermediate was quinic acid bisacetonide (6), selectively prepared by a modified kinetic acetalization protocol. Esterification of 6 with caffeic acid chloride (3) afforded ester 12. Cleavage of all the protecting groups of 12 was accomplished in one step under acidic conditions. The progress of the hydrolysis was monitored by MALDI-MS.