DEOXYGENATION REACTIONS OF C19-DITERPENOID ALKALOIDS

Article abstract of DOI:10.1016/S0040-4020(01)86133-0

Efficient methods for deoxygenation of secondary and tertiary alcohols of some C₁₉-diterpenoid alkaloids are presented.Delphisine (12) was converted to 1-deoxydelphisine (19) via either 1,2-pyrodelphisine (17) or phenyl thionocarbonate 20.The following alkaloids were deoxygenated via their thiocarbonylimidazolyl derivatives: 14-acetyldelcosine (13) to 14-acetyl-1-deoxydelcosine (22); alkaline hydrolysis of 22 gave 1-deoxydelcosine (23); aconitine (24) to 3-deoxyaconitine (27); yunaconitine (25) to crassicauline A (28).Deoxygenation of 14-acetyldictyocarpine (30) via the chloro-derivate 31 gave 14-acetyl-10-deoxydictiocarpine (34).Reduction of 31 with LiAlH4 gave the unusual elimination product 32.An improved partial synthesis of hypaconitine (35) from aconitine (24) is also presented.