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Description:
The objective of this work was to synthesize the quaternary stereocenter containing spirocycles, (+)-Canangone and beta-Chamigrene. Michael acceptor was prepared in three steps. The Robinson annulation of enamino lactone and Michael acceptor followed by hydrolysis provided the spirolactone. Subsequent deprotection, Luche reduction and oxidation gave (R*,R*) Canangone and (5R*,6S*)-epi-Canangone. Following the same strategy, optically active (+)-Canangone and (-)-Canangone, and their epimers were synthesized. As a second target, the synthesis of -Chamigrene was attempted but unfortunately, attempts to synthesize the -Chamigrene precursor completely failed.An alternative route was proposed, in which -Chamigrene could be synthesized in only four steps. The Diels-Alder reaction of methyl vinyl ketone and isoprene gave acetyl cyclohexene and alkylation of this product using prenyl iodide provided the mono alkylated product but unfortunately, attempts to cyclize it failed completely to give the desired spirocyclic compound.