A highly stereoselective total synthesis of (+)-bourgeanic
acid has been accomplished by an enzymatic desymmetrization approach
to create two methyl chiral centers. Other key steps involved in
this approach are a Wittig reaction, a Gilman reaction, and TEMPO/iodobenzene
diacetate mediated selective oxidation of the 1,3-diol, Yamaguchi
lactonization and lithium hydroxide mediated partial hydrolysis
(saponification) of the eight-membered cyclic dilactone
enzymatic desymmetrization - aliphatic depside - (+)-bourgeanic
acid - bourgeanic lactone - (-)-hemibourgeanic
acid - Wittig reaction - Gilman reaction - Yamaguchi
lactonization