Free-radical approaches to stemoamide and analogues.
Two approaches allowing access to the tricyclic stemona backbone are presented. Both approaches rely on a free-radical cyclization reaction as the key step. In the formal synthesis of (+/-)-stemoamide, the construction of the A ring of the natural product was achieved via a 5-exo-trig radical cyclization with atom transfer. The two diastereoisomers issuing from this cyclization showed different reactivity while forming the seven-membered ring of the final product. In the second part of this study, a 7-exo-trig free radical cyclization was realized allowing access to the (+/-)-9,10-bis-epi-stemoamide. This reaction was highly stereoselective and allowed the control of three of the four contiguous stereocenters present in the molecule.
Bogliotti
Nicolas
N
Laboratoire de Chimie Organique, associé au CNRS, ESPCI, 10 rue Vauquelin, 75231, Paris Cedex 05, France.
Dalko
Peter I
PI
Cossy
Janine
J
D003500:Cyclization; D005609:Free Radicals / Q000737:chemistry*; D006575:Heterocyclic Compounds, 3-Ring / Q000737:chemistry*; D007783:Lactones / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D013055:Spectrophotometry, Infrared
D005609:Free Radicals; D006575:Heterocyclic Compounds, 3-Ring; D007783:Lactones; C519217:stemoamide