Stereoselective total syntheses of atrochrysone, torosachrysone and related 3,4-dihydroanthracen-1(2H)-ones

The total synthesis of the pre-anthraquinones atrochrysone 1 and torosachry sone 2 in both enantiomeric forms is described. The synthesis relies on the regioselective Tebbe methylenation of a chiral diester followed by an intr amolecular enol ether acylation with N-triflyl-4-(dimethylamino)pyridinium triflate. The resulting 3-methoxycyclohex-2-enone 9 is condensed with suita ble orsellinic acid derivatives to yield after deprotection the optically a ctive 3,4-dihydroanthracen-1(2H)-ones 1 and 2. This flexible approach can b e used for the synthesis of C-13-labelled compounds and should provide acce ss to a series of analogues.