合成路线1

3) The cyclization of (R)-(+)-citronellal (XVIII) with ZnBr2 followed by reaction with diborane and H2O2 gives the diol (XI), which is selectively benzylated with benzyl chloride and NaH to the monobenzyl ether (XX). The oxidation of (XX) with the Jones reagent yields the cyclohexanone (XXI), which is condensed with 3-(trimethylsilyl)-3-buten-2-one (XXII) by means of lithium diisopropylamide to the dione (XXIII). The cyclization of (XXIII) by means of Ba(OH)2 and oxalic acid affords the benzylated octahydronaphthalenone (XXIV), which by reduction with NaBH4 followed by reoxidation with the Jones reagent gives the decalinone (XXV). The Grignard methylation of (XXV) with methylmagnesium iodide yields the tertiary alcohol (XXVI), which is dehydrated with p-toluenesulfonic acid to the octahydronaphthalene (XXVII). The debenzylation of (XXVII) with sodamide, followed by oxidation with the Jones reagent and methylation with diazomethane affords the ester (XXVIII), which is ozonolyzed with O3 to the formyl ketone (XXIX). Selective protection of the ketone group with propane-1,3-dithiol (XXX) and p-toluenesulfonic acid gives the substituted 1,3-dithiane (XXXI), which is treated with methyl orthoformate and p-toluenesulfonic acid to yield the methoxymethylene derivative (XXXII). The elimination of the dithiane group with HgCl2 in aqueous acetonitrile affords the ketoester (XXXIII), which is submitted to a photochemical oxidation using rose bengal as catalyst in methanol, giving the peroxide (XXXIV). Finally, this compound is cyclized by means of HClO4 and OsO4. 4) The benzylated octahydronaphthalenone (XXIV) can also be obtained by benzylation of the ketone (VIII) with benzyl bromide by means of NaH in DMF.

合成路线2