An enantioselective total synthesis of (+)-geissoschizine.
[formula: see text] A concise asymmetric synthesis of the indole alkaloid (+)-geissoschizine (1) has been completed. The synthesis features the highly diastereoselective vinylogous Mannich reaction of 3 with 4 to give 5, which is elaborated into the key tetracyclic intermediate 7 in two steps. Following the stereoselective introduction of the ethylidene moiety to give 9, reduction of the lactam and radical decarboxylation via an acyl selenide gave 12, which was converted into (+)-geissoschizine by formylation. The synthesis requires only 11 chemical operations and proceeds in an overall yield of 17%.
Martin
S F
SF
Department of Chemistry and Biochemistry, University of Texas at Austin 78712, USA. sfmartin@mail.utexas.edu
Chen
K X
KX
Eary
C T
CT
D000470:Alkaloids / Q000138:chemical synthesis*; D002243:Carbolines / Q000138:chemical synthesis*; D003653:Decarboxylation; D008352:Mannich Bases; D013237:Stereoisomerism
D000470:Alkaloids; D002243:Carbolines; D008352:Mannich Bases; C410326:geissoschizine