29.6 g of glyoxylic acid of 50% by weight are heated in water under reduced
pressure until elimination of 80% of the water present, whereupon, after
cooling, 84.1 g of 3,4,5-trimethoxy acetophenone are introduced into the
reaction mixture. Heating is effected for 2 h at 95°-100°C under reduced
pressure (about 50 mm/Hg), at the same time distilling off the residual water
present.
After cooling of the medium, 120 ml of water containing 11.6 g of sodium
carbonate and ether are introduced, the aqueous phase is decanted and
washed with : ether, whereupon the aqueous phase is acidified to a pH of 1
with 50% hydrochloric acid. The desired product is extracted with ethyl
acetate. After elimination of the extraction solvent 31.5 g of the 4-(3,4,5-
trimethoxyphenyl)-4-oxo-2-hydroxy butanoic acid, melting point 119°-120° are obtained (recrystallization from 1,2-dichloroethane).
15.8 g of 4-(3,4,5-trimethoxyphenyl)-4-oxo-2-hydroxy butanoic acid, 20 ml of
acetic acid and 20 ml of concentrated hydrochloric acid (d-1.18) are heated
for 2.5 h under reflux. The reaction medium is cooled and precipitated by
water. The precipitate formed is filtered off. 10.5 g of the (E)-4-(3,4,5-
trimethoxyphenyl)-4-oxo-2-butenoic acid, melting point 140°C are obtained
(recrystallization from ethanol-water 1:1).
