Elisabethin C Yamada

Me2C=CHCH2Br 2. LDA, HCHO Me 2. TBSCI, imidazole. . J 3. MOMCI. /Pr2EtN vie. YC 0M0M 

The diene fragment in the form of iodide 87 was synthesized from commercially available (+)-Roche ester 90 by tritylation, LAH reduction, and Swern 

In contrast to Nicolaou s model system, the IMDA reaction of quinone 86 to adduct 85 proceeded through an exo transition state geometry. This difference is due to the two additional substitutes attached to the diene side chain of quinone 86. A more detailed analysis (molecular modeling) of the four theoretically possible transition states (Fig. 10) reveals that an enophilic endolexo 

The significance of this IMDA reaction lies firstly in the use of a tethered (E,Z)-diene - the first case that has been successfully developed - secondly, in the unusually mild and virtually biomimetic conditions (aqueous medium, ambient temperature), and thirdly in the high yield and stereoselectivity. 

---