Importance of Planning in a Synthesis

We now find ourselves familiar with methods of constructing a carbon skeleton for an organic molecule, how to introduce and transform functional groups, and how to achieve the required selectivity. One could almost expect the rich arsenal of contemporary methods to enable the chemist to solve practically any problem of synthetic chemistry. Yet it is not quite so simple. It is imperative to be skillful in planning a synthesis, to be able not only to master its tactics, but its overall strategy as well. 

How to ensure the natural trans-anti-trans configuration of all ring junctions. 

How to create the functionality pattern required for the preparation of the final targets, 2-7. 

We will follow the basic idiosyncracies of this synthesis that led to the solution of these tasks, 

The tetracyclic skeleton was assembled by constructing the rings in sequence, C + D + B + A, with 5-methoxy-2-methylbenzoquinone 8 as the precursor for ring C. The infallible Diels-Alder reaction was used as a pathway leading eventually to the construction of the five-membered ring D. Actually, the immediate result was the attachment of a six-membered D ring, but the 

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