Readily available chiral 7-oxo-2-enimides have been converted into highlysubstituted pipecolic esters in moderate yields and excellent stereocontrol through a proline-catalyzed domino Mannich aza-Michael reaction.
Stereodivergent Synthesis of Enantiopure Tetrahydropyrans via the Silyloxy-Cope Rearrangement of Chiral Aldol Products
作者:Christoph Schneider
DOI:10.1055/s-1997-5748
日期:1997.7
A stereoselective synthesis of highly substituted and enantiopure tetrahydropyrans from chiral 7-hydroxy-2-alkenoic imides and esters is described. Depending on the carboxylic acid derivative the base-induced cyclization is kinetically or thermodynamically controlled to deliver either tetrahydropyran stereoisomer selectively.
oxa-conjugate addition has been employed in a stereoselective synthesis of enantiopure polyalkyl-substituted tetrahydropyrans, which are frequently found as substructures in many natural products. The requisite cyclization precursors, 7-hydroxy-2-enimides 3 and 7-hydroxy-2-enoates 6 were easily accessible by silyloxyCoperearrangements of the appropriate chiral syn-aldols. It was found that the stereoselectivity