Stereocontrolled total synthesis of (-)-vincamajinine and (-)-11-methoxy-17-epivincamajine.
The first total syntheses of (-)-vincamajinine (5) (from Na-methyl-d-tryptophan methyl ester) and (-)-11-methoxy-17-epivincamajine (6) (from Na-methyl-6-methoxy-d-tryptophan ethyl ester) are described. The syntheses have been completed in a highly stereocontrolled manner (>98% ee). Key steps included the asymmetric Pictet-Spengler reaction, enolate-mediated palladium cross-coupling reaction, and acid-catalyzed formation of the C(7)-C(17) bond. In addition, the triethylsilane/TFA-mediated incorporation of the 2alpha-H (11 to 12) and the borohydride generation of the C(17) hydroxyl function (R) were also stereospecific. The unique highly conjested carbon skeletons of the two alkaloids were completed in a concise manner and in regiospecific fashion.
Yu
Jianming
J
Department of Chemistry, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, USA.
Wearing
Xiangyu Z
XZ
Cook
James M
JM
D031051:Alstonia / Q000737:chemistry; D026121:Indole Alkaloids / Q000138:chemical synthesis*; D013237:Stereoisomerism
C485202:11-methoxy-17-epivincamajine; D026121:Indole Alkaloids; C485203:vincamajinine