Neoliacinic acid

In several natural product syntheses, it has been demonstrated that a tandem ylide formation/rearrangement sequence provides a convenient method to construct synthetic key intermediates containing a oxabicyclo[5.3.1]undecane ring system (e.g., neoliacinic acid and labiatin). This transformation also served to prepare the oxabicyclo[6.2.1]undecane system of ( )-vigulariol (Scheme 79) <2007AGE437>. 

Scheme 16.27 Model study toward neoliacinic acid by Clark and coworkers.

Scheme 16.28 Second-generation approach to neoliacinic acid by Clark and coworkers. 16.2.4.2 Litophynins E and I... 

Keto esters such as acetoacetate without a substituent at the a-carbon. namely with two acidic protons, first attack the central carbon of the allenylpal-ladium to form the zr-allyl complex 89. Then intramolecular attack of the enolate oxygen of the 0-keto ester at the rr-ully l system takes place to form the nieihv-lenedihydrofuran 90 as a primary product, which is easily isomerized to the turn 91. The /3-diketone 92 reacts similarly to give the furan 93[40], The reaction can be applied to the synthesis of the phenyIthiomethyl-substituted furan 94. which is useful for the synthesis of natural products such as neoliacine. [41]... 

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