Total Syntheses of (−) Epilupinine and (−)-Tashiromine Using Imino-Aldol Reactions

• Published in: Organic letters Vol. 13; no. 15; pp. 3988 - 3991
• Main Authors: Cutter, Amanda C, Miller, Iain R, Keily, John F, Bellingham, Richard K, Light, Mark E, Brown, Richard C. D
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 05-08-2011
• Subjects: Aldehydes - chemistry; Cyclization; Imines - chemistry; Indolizines - chemical synthesis; Molecular Structure; Sparteine - analogs & derivatives; Sparteine - chemical synthesis
• ISSN: 1523-7060; 1523-7052
• DOI: 10.1021/ol2015048

Short routes to enantiomerically pure indolizidine and quinolizidine alkaloids have been developed using imino-aldol reactions of enolates derived from phenyl 5-chlorovalerate. High levels of syn selectivity (dr ∼13–16:1) were obtained using lithium enolates of phenyl esters in combination with tert-butylsulfinyl imines. The imino-aldol adducts were deprotected and cyclized to afford (−)-epilupinine ((−)-2) and (−)-tashiromine ((−)-1) in two further steps.