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The total synthesis of (+-)-prezizanol and (+-)-prezizaene

University of British Columbia

This thesis describes work leading to the completion of a total synthesis of the sesquiterpenoids (±)-prezizanol (188) and (±)-prezizaene (6). The known alcohol 128 was transformed, in three steps, into the endo-monochloride 156. The commercially available alcohol 129 was converted, in a two step sequence, into the vinyl iodide 127. Palladium catalyzed coupling of the vinyl iodide 127 with an organozinc compound derived from the chloride 156 provided the bicyclo[3.1.0]hexane 165. The bicyclo[3.1.0]hexane 165 was elaborated, in three steps, into the ester 172. Treatment of this ester with lithium diisopropylamide, followed by kinetic protonation of the resultant enolate anion, provided the endo-(1-alkenyl)-bicyclo[3.1.0]hex-2-ene 123, which cleanly underwent a Cope rearrangement to provide the bicyclo[3.2.1]octadiene 121. An attempt to cleanly synthesize 121 via the Cope rearrangement of the exo-(1-alkenyl)bicyclo-[3.1.0]hex-2-ene 122 was unsuccessful. A six step sequence was used to synthesize the mixture of silyl ethers 186 and 187 (88:12, respectively) from the bicyclo[3.2.1]octadiene 121. (±)-Prezizanol (188) was prepared, in a series of seven steps, from the silyl ether 186. Dehydration of (±)-prezizanol (188) provided (±)-prezizaene (6) in 2.2% overall yield from the alcohol 128. [Formula Omitted]

Text

2010-08-16

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http://hdl.handle.net/2429/27441

Chemistry

University of British Columbia

Graduate