Prostaglandins, synthesis biomimetic

Since the Diels-Alder reaction is both experimentally and theoretically well characterized, we now have a thorough understanding of this important transfonnation. This allowed one to influence rates and selectivities of this cycloaddition. An illustrative example is the selective synthesis of a key prostaglandine precursor (Scheme 2) in which all stereochemical information derives from the starting materials. Although the general mechanism of Diels-Alder reactions is well understood, it is still uncertain if these reactions occur in biosynthesis. An instructive example is represented by the total synthesis of optically active plagiospirohdes 1 and 2 (Scheme 3) -. These syntheses were considered to be biomimetic and are indications that Diels-Alder reactions may also occur in vivo. 

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