Fragmentation – Juvenile hormone synthesis

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An important demonstration of the use of fragmentation is the synthesis of juvenile hormone. Juvenile hormone contains three trisubstituted double bonds (one of which ends up as an epoxide), and the initial target was to make the related ketone which contains two of them. It was reasoned that if this methyl ketone could be made stereospecifically by fragmenting a cyclic starting material, the (hard-to-control) double bond stereochemistry would derive directly from the (easier-to-control) relative stereochemistry of the cyclic compound.

The formation of the related methyl ketone is demonstrated on this page, showing how the desired stereochemistry is produced. Subsequent steps lead to the formation of juvenile hormone.

R. Zurflueh, E. N. Wall, J. B. Siddall and J. A. Edwards, J. Am. Chem. Soc., 1968, 90, 6224–6225.