Enantioselective Construction of Vicinal Stereogenic Quaternary Centers by Dialkylation: Practical Total Syntheses of (+)- and meso-Chimonanthine.
All three stereoisomers of the hexacyclic 3a,3a'-bispyrrolidino[2,3-b]indoline moiety found in complex indole alkaloids can be prepared, as illustrated by total syntheses of meso-chimonanthine (1) and (+)-chimonanthine (2). A rare example of high diastereoselectivity arising from the combination of a prostereogenic enolate with a chiral electrophile containing a sp(3) carbon atom is the key feature of the asymmetric synthesis of the C(2) stereoisomer.
Overman
LE
Department of Chemistry University of California, Irvine 516 Rowland Hall, Irvine, CA 92697-2025 (USA).
Larrow
JF
Stearns
BA
Vance
JM