Synthesis of a Polyhydroxyquinolizidine bearing a Polyhydroxylated Carbon Side-Chain
作者:Christophe Schaller、Pierre Vogel
DOI:10.1055/s-1999-3164
日期:1999.8
Asymmetric Syntheses of New Polyhydroxylated Quinolizidines: Cross-Aldol Reactions of 7-Oxabicyclo[2.2.1]heptan-2-one and 3a,4a,7a,7b-Tetrahydro[1,3]dioxolo[4,5]furo[2,3-d]isoxazole-3-carbaldehyde Derivatives
Protocols were found for highly diastereoselective condensation giving the four possible aldols (+)-27 ('anti'), (+)-28 ('syn). 29 ('anti'). and (-)-30 ('syn') resulting from the exclusive exo-face reaction of the bicyclic lithium enolate of (-)-25 and bicyclic silyl ether (-)-31. Steric factors can explain the selectivities observed. Aldols (+)-27 (+)-28, 29, and (-)-30 were converted stereoselectively