Myers retrosynthetic planning for the synthesis of -neocarzinostatin

From a tactical perspective, early retrosynthetic removal of the epoxy dienediyne core must dominate all synthetic planning for (+ )-neocarzi-nostatin, since its presence in any intermediate will render that molecule highly susceptible to nucleophilic attack, and will jeopardise the success of all the remaining chemistry. In essence, it would be strategically advisable to install the epoxy dienediyne unit late in a forward total synthesis of ( + )-neocarzinostatin. 

Good retrosynthetic planning for ( + )-neocarzinostatin would also make every effort to identify nine-membered carbocycle precursors that were considerably less strained. Such molecules should be far easier to 

Sound strategic planning would also attempt to pinpoint those features, already present in the epoxydienediyne core, which could greatly assist in assembly of the nine-membered carbocycle. Clearly, such structural elements would have to be retained in any prospective cycli-sation precursor. With these things in mind, we will now examine Myers retrosynthetic plan for this target. 

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Scheme 8,1 Myers retrosynthetic plan for the synthesis of (+)-neocarzinostatin.

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