21 SYNTHETIC STUDIES OF OPTICALLY ACTIVE MAHUBA LACTONES AND RELATED COMPOUNDS
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The total synthesis of (-)-dihydromahubanolide B (1a) and (-)-isodihydromahubanolide B (1b), two components of the amazonian Lauraceae, Licaria mahuba (Samp.) Kosterm. has been accomplished starting from natural L-(+)-tartaric acid. Synthetic efforts directed toward the synthesis of obtusilactone A (2a) and iso-obtusilactone A (2b), structurally related compounds isolated from the Japanese Lauraceae, Lindera obtusiloba Blume. have been also described. Thus, natural L-(+)-tartaric acid was converted to the known hydroxy ester 3 which gave in several steps the keto benzoate 6, a key intermediate of the route. Keto benzoate 6 was transformed into (-)-dihydromahubanolide B (1a) and (-)-isodihydro-mahubanolide B (1b) by the reaction sequence involving the Wittig reaction, oxidation and acid treatment. The hydroxy ester 3 afforded the lactones 4a and 4b according to the sequence similar to that described above. Conversion of these lactones into 2a and 2b is now under investigation.
