合成路线1

The reaction of 3-methyl-2-trans-penten-4-yn-1-ol (I) with ethyl vinyl ether (II) by means of p-toluenesulfonic acid gives 1-(1-ethoxyethoxy)-3-methyl-4-trans-penten-1-yne (III), which is condensed with 2,6,6-trimethyl-3-isobutoxycyclohex-2-en-1-one (IV) by means of butyllithium in ether at -60 C to afford 5-(2,6,6-trimethyl-3-oxocyclohexen-1-yl)-3-methyl-2-trans-penten-4-yn-1-ol (V). The reduction of (V) with H2 over a Lindlar catalyst in toluene yields 5-(2,6,6-trimethyl-3-oxocyclohexen-1-yl)-3-methyl-2,4-pentadien-1-ol (VI), which is converted into the corresponding pentadienyl bromide (VII) by reaction with PBr3 in ether. The reaction of (VII) with triphenylphosphine in refluxing benzene affords 5-(2,6,6-trimethyl-3-oxocyclohexen-1-yl)-3-methyl-2,4-pentadien-1-triphenylphosphonium bromide (VIII) , which is finally condensed in a Wittig reaction with 2,7-dimethyl-2,4,6-octatriene-1,8-dial (IX) by means of sodium methoxide in dichloromethane.