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 prepar
ed by a modified kinetic acetalization protocol. Esterification of 6 with c
affeic acid chloride (3) afforded ester 12. Cleavage of all the protecting
groups of 12 was accomplished in one step under acidic conditions. The prog
ress of the hydrolysis was monitored by MALDI-MS.