Extreme Convergence in Plans

The conventional practice is to state the overall yield with respect to the longest branch, which in this case is Bl. Note that the chain of reaction yields is easily linked using these synthesis tree diagrams B2 links to Bl, B3 links to Bl, B4 links to Bl, B5 links to B4 which in turn links to Bl, and B6 links to B4 which in turn links to Bl. A general rule is that the number of branches is equal to the number of points of convergence plus one. The reader can easily verify that the 

FIGURE 11.27 Abbreviated synthesis tree diagram for the Khorana-Todd (1961) plan for coenzyme A. 

FIGURE 11.28 Abbreviated synthesis tree diagram for the Myles (1997) plan for (-)-discodermolide. 

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