TOTAL SYNTHESIS OF (+ -)-POROSIN, A NEOLIGNAN FROM OCOTEA-POROSA AND URBANODENDRON-VERRUCOSUM (LAURACEAE)/

Veratraldehyde was condensed with methyl 2-chloropropanoate to give a glycidic ester. This was hydrolyzed with aqueous sodium hydroxide and the resulting sodium salt was treated with lead(IV) tetraacetate to gi ve 1-acetoxy-1-(3,4-dimethoxyphenyl) propan-2-one(13). Condensation of 13 with dimethyl malonate, followed by acidic hydrolysis and sodium b orohydride reduction afforded oxyphenyl)-2-methoxycarbonyl-3-methyl-4- butanolide (7a). The gamma-lactone 7a was then converted into 5'-demet hoxyporosin (10) by means of a series of reactions: Michael reaction w ith methyl vinyl ketone, elimination of the methoxycarbonyl group, ace talization, allylation, deacetalization, and intramolecular aldol reac tion. Introduction of a hydroxyl group at the C-5' position in 10, fol lowed by methylation with diazomethane afforded racemic porosin. The s ynthetic porosin was further converted into 5-demethoxymegaphone aceta te.