Carpanone

[1][2] Carpanone itself is limited in its pharmacologic and biologic activities, but related analogs arrived at by variations of the Brophy-Chapman approach have shown activities as tool compounds relevant to mammalian exocytosis and vesicular traffic,[5] and provided therapeutic "hits" in antiinfective, antihypertensive, and hepatoprotective areas.

A particular conformation of this dimer then places a 4-electron enone of one ring over the 2-electron enol of the other (shown adjacent in image for clarity), setting the state for a variant of the Diels-Alder reaction termed an inverse demand Diels-Alder reaction (see curved arrows in image), which closes the 2 new rings and generates the 5 contiguous stereocenters.

[1][6] The Chapman approach has been applied in a variety of ways since its original report, varying substrates, oxidants,[7] and other aspects (and so synthesis of carpanone has subsequently been achieved by "quite a few research groups");[1][3] the actual mechanism of Pd(II) action is likely more complex than the original conjecture, and there is evidence that the mechanism, broadly speaking, depends on actual conditions (specific substrate, oxidant, etc.).

[3] Various groups, including the laboratories of Steve Ley, Craig Lindley, and Matthew Shair, have succeeded in extending the Chapman method to solid-supported synthesis, i.e., phenolic starting materials on polymeric supports, thus allowing the generation of libraries of carpanone analogs.

[1][5] A hetero-8-8' oxidative coupling system akin to the Chapman approach has been developed that uses IPh(OAC)2, and that allows for preparation of more electron rich homodimers, and for hetero-tetracyclic analogs of carpanone.

Carpacin, an ortho -methoxy styrene , and a more common type of phenolic plant phenylpropanoid whose structure was recognized as being dimerized in carpanone
Biomimetic transformation of desmethylcarpacin into carpanone in one pot, via a tandem oxidative coupling–Diels Alder reaction sequence. [ 6 ] Note, in the second image in the scheme, the two lines crossing at the top are the two molecules overlapping each other (and do not imply chemical bonds). In this scheme, Pd (II) is shown forming a complex between two monomers of carpacin, then mediating oxidative 8-8' (β-β') phenolic coupling of their alkene tails to generate a dimer , a trans - ortho - quinone methide intermediate, followed immediately by an endo -selective inverse electron-demand hetero- Diels-Alder reaction (see Diels–Alder reaction#Mechanism ), [ 1 ] to close the rings and generates the stereocenters .