Ring‐chain tautomerism provides a route to 7a‐hydroxy‐3a‐methyl‐2,7‐dioxoperhydrobenzofuran. Synthesis of the hydroxy γ‐lactone substructure of myrocin and other bioactive natural products

Abstract

Abstract(2‐Oxocyclohexyl)acetic acid 10 was converted into bicyclic alkoxy γ‐lactones 12a–d via intermediate chloro lactone 11 and alkanolysis. Similarly, lactones 15a, b and 18 were prepared. In contrast, simple ring‐chain tautomerism directly afforded the title heterocycle 28, a crystalline, stable and well‐defined compound. The angular methyl group seems essential for the spontaneous lactonization. 5,5‐Dialkoxy‐4‐oxocarboxylic acids 26a, b without an angular methyl group did not cyclize to bicyclic hydroxy γ‐lactones.