The present invention provides a process for preparation of {(2E,4E,6E,8E)-9-(4-methoxy-2,3,6-trimethyl)phenyl-3,7-dimethyl-nona- 2,4,6,8}tetraenoate, an acitretin intermediate of formula (VI) with trans isomer >97%, comprising of reacting 3-formyl-crotonic acid butyl ester of formula (V), substantially free of impurities, with 5-(4-methoxy-2,3,6-trimethylphenyl)-3-methyl-penta-2,4-diene-l- triphenyl phosphonium bromide of formula (IV) and isolating resultant compound of formula (VI), treating the filtrate with iodine for isomerization of the undesired cis intermediate and finally obtaining acitretin (I), with desired trans isomer >97%.
