合成路线1

1) The Diels-Alder cyclization of butadiene (I) with 2-methylbenzophenone (II) by means of acetic acid in refluxing toluene followed by oxidation with ceric ammonium nitrate gives 2-methyl-1,4-naphthoquinone (III), which by a new Diels-Alder cyclization with cyclopentadiene (IV) yields 4aalpha-methyl-1,4,4a,5,8,9a-hexahydro-1alpha,4alpha-methanoanthraquinone (V). The alkylation of (V) with 3,7,11,15-tetramethyl-2(E),6(E),10(E),14-hexadecatetraeanyl bromide (VI) by means of potassium tert-butoxide in THF affords the alkylated anthraquinone (VII), which is submitted to a retro Diels-Alder reaction in refluxing toluene containing dichlorodicyanobenzoquinone (DDQ) in order to obtain a simultaneous dehydrogenation. 2) The Diels-Alder cyclization of 1,4-naphthoquinone (VIII) with cyclopentadiene as before gives 1,4,4a,9a-tetrahydro-1,4-methanoanthraquinone (IX), which is alkylated with the alkyl bromide (VI) as before to yield the alkylated anthraquinone (X). The methylation of (X) with methyl iodide and potassium tert-butoxide affords the 9a-methylated anthraquinone (XI), which is finally submitted to a retro Diels-Alder reaction in refluxing toluene.