Efficient Assembly of an Indole Alkaloid Skeleton by Cyclopropanation: Concise Total Synthesis of (±)‐Minfiensine

Abstract

Members of the akuammiline [1] alkaloids such as echitamine, [2] vincorine, [3] and corymine, [4] like indole alkaloid minfiensine, [5] possess a highly congested pentacyclic ring system (Figure 1). These alkaloids exhibit a number of [*] L.

Ring-opening, cycloaddition and rearrangement reactions of nitrogen-substituted cyclopropane derivatives

“…Direct aminal formation from tryptamine and tryptophane derivatives via an aminocyclopropane intermediate 199. A subsequently developed fully intramolecular version of the method has been applied to a total synthesis of the indole alkaloid (±)-minfiensine (Scheme 79) 200. Scheme 79.…”

Asymmetric Total Syntheses of Kopsia Indole Alkaloids

“…To improve the yield of 20,[ Cu(hfacac) 2 ]w as then used as the catalyst in further screening of the solvent and temperature.T he yield of 20 was enhanced to 38 %w hen microwave irradiation conditions (120 8 8C) were applied in DCE (entry 9). Further screening revealed that chlorobenzene was the best solvent for the cyclopropanation reaction when heating at 120 8 8Cf or 30 minutes (entries [10][11][12][13][14]. Diazo decomposition of 21 on a5gram scale with 20 mol %o f [Cu(hfacac) 2 ]provided 20 in an acceptable 52 %yield and 30 in 13 %y ield (entry 12).…”

It All Began with an Error: The Nomofungin/Communesin Story

“…A related strategy was used by Qin and co‐workers in their recent synthesis of the indole alkaloid minfiensine ( 75 ; Scheme ) 14. In this case, in a one‐pot cascade reaction, diazoketoester 71 was first converted into the labile cyclopropane ester 72 , which isomerized to zwitterion 73 under the ring strain.…”