Steroselective total syntheses of ([plus-minus])-longicyclene, ([plus-minus])- longicamphor, and ([plus-minus])-longiborneol
Date
1974
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Abstract
Stereoselective total syntheses of (±)-longicyclene (1), ([plus-minus])-longicamphor (2A), and ([plus-minus])-longiborneol (2B) from tetrahydroeucarvone (21) via intermediate aldehyde 23 are discussed. The synthetic approach contains a reductive-cyclization reaction utilizing di isobutyl aluminum hydride to convert an enol-lactone to a bicyclic ketol. A new sequence of reactions is used to convert a cyclopropyl ketone intermediate to ([plus-minus])-longicyclene (1) without fragmentation. An attempt to apply a modification of the synthetic scheme used in the ([plus-minus])-longicyclene synthesis to the synthesis of (+)-cyclosativine (.5) is also presented.