SYNTHESIS OF NEOLIGNANS VIA A PROPOSED BIOSYNTHETIC INTERMEDIATE - TOTAL SYNTHESIS OF (+/-)-FUTOENONE

The attempted spectroscopic observation of a quinone methide proposed to be an intermediate in the biosynthesis of neolignans is reported. The results afforded substantial indirect evidence for the formation of quinone methide 3. The synthesis of racemic bicyclo[3.2.1]octenedione 22, a natural product, is proposed to occur through a similar quinone methide intermediate. The synthesis of (+/-)-futoenone via a benzylic cation intermediate related to quinone methide 3 is reported. The results provide support for Gottlieb's proposal that several different neolignans arise from a common biosynthetic precursor. The efficient synthesis of (+/-)-futoenone and related spiro[5.5]undecanoids using a Buchi quinone ketal cycloaddition is also described.