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[摘要]：Mander reductive alkylation of Me 2-methoxybenzoate with prenyl bromide and hydrolysis of the enol ether afforded Me 6-oxo-1-prenyl-2-cyclohexenecarboxylate. This was converted in five steps (redn. of the ketone, sapon., iodolactonization, ozonolysis, and intramol. aldol reaction) to a spiro lactone cyclopentenal I. An efficient first synthesis of (?-vibralactone (II) was completed by retro-iodolactonization with activated Zn, formation of the b-lactone (vibralactone C), and redn. of the aldehyde. Except for the novel use of an iodolactone to protect both the prenyl double bond and carboxylic acid, no protecting groups were used. A similar sequence starting with asym. reductive alkylation of the (2S)-2-[(methoxymethoxy)methyl]pyrrolidine amide of 2-methoxybenzoic acid with prenyl bromide afforded (-)-vibralactone confirming the abs. stereochem. assignment that was based on computational methods. |
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