The synthesis of (&)-gibberone, a tetracyclic degradation product of gibberellic acid, is described. THE bicyclo[3,2,l]octane ring system comprising rings c and D of gibberellic acid (I) is still present in the degradation product gibberone (11; X = 0), although here the configuration of the two-carbon bridge has been inverted during the degradation sequence by the mechanistic requirement of the change from allogibberic to gibberic acid.4The same bridged-ring system occurs also in the phyllocladene group of diterpenes, and its biogenesis there has been discussed by \Venkert.5 Previous syntheses of bicyclo-[3,2,l]octanes have been based on rearrangements of isomeric bicyclo[2,2,2]octanes or, as in the case of phyllocladene itself, on the cyclisation of a dicarboxylic acid which is not easily accessible.* The elegant ring closure described by Masamune should also be mentioned. Substituted bicyclo[2,2,2]octanes can be synthesised in a reasonably rational manner, but their rearrangement to substituted bicyclo[3,2,l]octanes seems to be limited in scope, because it depends on delicate stereochemical factors and there seems little to choose between the relative stabilities of the isomeric ring systems.lOWe decided to start from 4-methyl-l-oxoindan-2-ylacetic acid (111; R = R' = H).Attempts to alkylate 4-methylindan-l-one with methyl bromoacetate through an enamine or by reaction with the enolate of the ketone did not lead to the desired product, but reaction of the corresponding a-bromo-ketone with di-t-butyl sodiomalonate followed by acid hydrolysis and decarboxylation gave the expected keto-acid in good yie1d.l' Its 9 4 5 6 7 8 1960,
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