合成路线1

The condensation of phenylboronic acid (I) with methyl 2-bromo-5-nitrobenzoate (II) by means of palladium tetrakis(triphenylphosphine) gives the biphenyl-2-carboxylic ester (III), which is treated with KOH in ethanol/THF to afford the corresponding free acid (IV). The reaction of (IV) with SOCl2 yields the acyl chloridde (V), which is cyclized by means of AlCl3 to provide the dibenzopyranone (VI). The reduction of the nitro group of (VI) with Zn and CaCl2 in refluxing ethanol gives the corresponding amino derivative (VII), which is cyclized with acetone and I2 at 125-35 C yielding the tetracyclic ketone (VIII). The reaction of (VIII) with 3-chlorophenyllithium (IX) in THF affords the tetracyclic hemiketal (X), which is dehydroxylated with boron trifluoride ethearate and triethylsilane in dichloromethane to give the target compound as a racemic mixture (XI). Finally, this racemate is optically resolved by chiral HPLC over a Whelk-O column.