Corey, enantioselective prostaglandin synthesis

Lest you should imagine that all effective auxiliaries are oxazolidinones, here is a different one— 8-phenylmenthol—used by Corey in enantioselective prostaglandin synthesis. 8-Phenylmenthol is made from the natural product pulegone (Chapter 51). Even in the starting material the role of the phenyl group is clearly to crowd one face of the dienophile. 

Because the Corey synthesis has been extensively used in prostaglandin research, improvements on the various steps in the procedure have been made. These variations include improved procedures for the preparation of norbomenone (24), alternative methods for the resolution of acid (26), stereoselective preparations of (26), improved procedures for the deiodination of iodolactone (27), alternative methods for the synthesis of Corey aldehyde (29) or its equivalent, and improved procedures for the stereoselective reduction of enone (30) (108—168). For example, a catalytic enantioselective Diels-Alder reaction has been used in a highly efficient synthesis of key intermediate (24) in 92% ee (169). 

Auxiliary-controlled diastereoselective and enantioselective Diels-Alder reactions (Corey) and diastereoselective three-component reactions (Noyori), examples of which were tested for the first time in the total synthesis of prostaglandins, enriched the arsenal of methods in modem preparative organic chemistry. 

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