Carpanone total synthesis

Scheme 8.42 Total synthesis of Carpanon utilizing resin-bound reagents and polymers.

Chapman s (O. L. Chapman, then at Iowa State and later at UCLA) classic total synthesis of ( )-carpanone is so remarkably simple that it is used as an imdergraduate laboratory preparation. It is modeled on a possible biosynthetic route for this lignan-derived natural product. Phenol oxidations figure prominently in many such bios)mtheses of natural products. In one step, this reaction creates no less than five contiguous chiral centers, all in the correct relative configuration. 

Finally, an intramolecular cyclization of a bis-o-quinonemethide (32) was employed by Chapman in the total synthesis of the lignan carpanone (31). In this remarkably facile synthesis the required o-quinonemethide was generated situ by phenolic coupling of two molecules of 2-(trans-l-propenyl)-H,5 methylenedio henol (33) with palladium dichloride. This procedure led directly to carpanone (33.) in 46% yield and involves the introduction of five asymmetric centers in a single step. 

Chapman et al. reported elegant total synthesis of carpanone 94, a lignan obtained from the bark of the carpano tree, by the palladium-mediated coupling reaction... 

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