Gibberellic acids rearrangement

Secondly, this epimerization does not occur in gibberellic acid (I). Instead (Figure 9) allylic rearrangement of the lactone occurs giving the 1 3 lactone... 

Diels-Alder reaction with cyclopentadienes. An improved synthesis of a key intermediate (6) to gibberellic acid (7) begins with the cycloaddition of 1 to a 2 1 mixture of 2- and l-(2-bromoallyl)cyclopentadiene (2) to give the adduct 3 in which the acetyl group has the enr/o-orientation. The silyl enol ether of 3 when heated undergoes a Cope rearrangement to give a eis-hydrindene (4), which was converted... 

Several aspects of the chemistry of gibberellic acid have been studied. The 3-hydroxy-group has been shown100 to participate in the rearrangement of A1<2>-gibberellin 19-10-lactones to the isomeric A1(1°)-gibberellin 19-2-lactone (67). 

The antheridium-inducing factor of the fern Anemia phyllitidis has been shown to have a gibberellin-like structure (101), reminiscent of the rearrangement products of gibberellic acid in concentrated sulphuric acid. ... 

Treatment of gibberellic acid with dilute alkali yields an inactive isomer (X) resulting from an allylic rearrangement. 

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