Synthesis of (E,E)-Germacrane Sesquiterpene Alcohols via Enolate-Assisted 1,4-Fragmentation.

摘要: An efficient method has been developed for the synthesis of (E,E)-germacrane sesquiterpene alcohols. The key step in these syntheses involves enolate-assisted 1,4-fragmentation properly functionalized perhydro-1-naphthalenecarboxaldehydes with 1 equiv sodium tert-amylate as base, to give corresponding aldehydes. These aldehydes are not very stable, and situ reduction aldehyde function Red-Al is required obtain high yields desired germacrane This procedure led successful 15-hydroxygermacrene B (4) 15-hydroxyhedycaryol (35) from mesylates 6 33, respectively. When KHMDS used instead fragmentation reaction 6, isomerization initially formed C(4)-C(5) E double bond cannot be avoided results, after Red-Al, formation (E,Z)-germacrane alcohol 24. 15-hydroxy-(E,E)-germacranes excellent starting materials selective 4,5-epoxides, which turn can perfectly well studies on biomimetic guaiane sesquiterpenes.