Iterative rearrangements

When 2-methoxy-3-methyl-l,3-butadiene and alcohol (153) are the reacting partners, the unsaturated ketone (157) results. In this instance, the R group is isopropenyl, and the stereochemistry of the isolated double bond is of the (E)-configuration. Reduction of the ketone (equation 20) provides a new secondary allylic alcohol (158) that can undergo iterative rearrangements. Each rearrangement introduces the equivalent of an isoprene unit in a head-to-tail fashion. 

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