Tetrahydrofurane und γ‐Lactone, V[1,2] Optisch aktive δ‐Hydroxy‐γ‐lactone aus Cyclooctin und Furan — Synthese von (—)‐(R,R)‐ und (+)‐(S,S)‐Muricatacin sowie verwandter Verbindungen

Tetrahydrofurans and γ‐Lactones, V[1,2]. — Optically Active δ‐Hydroxy‐γ‐lactones from Cyclooctyne and Furan — Synthesis of (—)‐(R,R)‐ and (+)‐(S,S)‐Muricatacin and Related Compounds The γ‐lactone 1a, easily available from cyclooctyne and furan is converted to enantiomerically pure (—)‐(R,R)‐ and (+)‐(S,S)‐muricatacin (2e). Compound 2e was isolated recently as a biologically active (R,R/S,S) mixture from the seeds of Annona muricata. Optically active compounds were obtained by chromatographic separation of the diastereomeric camphanoates (4R)‐4a and (4S)‐4b and subsequent highly diastereoselective reduction with L‐Selectride≫ to give finally (4R,5R)‐ and (4S,5S)‐2c. The necessary side chain was introduced via Wittig reaction of the aldehyde 3c. Absolute configuration of all new products were established by X‐ray structural analysis of the δ‐lactone 7a and by comparison of (–)‐2f with its known dextrorotatory enantiomer as well. According to Mosher ester analysis of (—)‐2c and (—)‐2e the ee is ≥98%. The synthesis of rac‐muricatacin is also described. The scope of this new approach to functionalized dodecane (di)acid derivatives 3a–3c with (4R,5R) and (4S,5S) configuration is discussed.