Intramolecular amidofuran cycloadditions across an indole pi-bond: an efficient approach to the aspidosperma and strychnos ABCE core.
[reaction: see text] The intramolecular Diels-Alder reaction between an amidofuran moiety tethered onto an indole component was examined as a strategy for the synthesis of Aspidosperma and Strychnos alkaloids. Furanyl carbamate 13 was acylated using the mixed anhydride 16 to provide amidofuran 12 in 68% yield. Further N-acylation of this indole furnished 17 in 88% yield. Cyclization precursors were prepared by removing the carbamate moiety followed by N-alkylation with the appropriate alkyl halides. Thermolysis of 25 provided the novel tetracyclic ketone 26 in 74% yield.
Lynch
Stephen M
SM
Department of Chemistry, Emory University, Atlanta, Georgia 30322, USA.
Bur
Scott K
SK
Padwa
Albert
A
D000470:Alkaloids / Q000138:chemical synthesis*; D030009:Aspidosperma / Q000737:chemistry*; D003500:Cyclization; D007211:Indoles / Q000737:chemistry; D031451:Strychnos / Q000737:chemistry*
D000470:Alkaloids; D007211:Indoles