Sulfinyl-Directed Diastereoselective [5 + 2] Pyrone−Alkene Cycloadditions: A Practical Route to Enantiopure 8-Oxabicyclo[3.2.1]octane Derivatives
作者:Fernando López、Luis Castedo、José L. Mascareñas
DOI:10.1021/ol005724u
日期:2000.4.1
[GRAPHICS]Introduction of a homochiral p-tolylsulfinyl group at an appropriate position in the alkene accelerates the thermal [5C + 2C] intramolecular cycloaddition to beta-silyloxy-gamma-pyrones and, most importantly, leads to excellent levels of diastereodifferentiation. The resulting adducts can be easily desulfinylated to give optically active 8-oxabicyclic[3.2.1]octane intermediates which by virtue of their rich functionalization might he susceptible to elaboration into enantiomerically pure natural products containing seven-membered carbocycles and tetrahydrofurans.
A Practical Route to Enantiopure, Highly Functionalized Seven-Membered Carbocycles and Tetrahydrofurans: Concise Synthesis of (+)-Nemorensic Acid
those obtained from the sulfinyl precursors. Cleavage of the oxa-bridge on the desulfurated adducts yields highlyfunctionalized seven-membered carbocyclic derivatives in enantiopure form. Alternative cleavage of the seven-membered carbocycle provides enantiomerically enriched tetrahydrofurans. We have exploited this reaction pathway for the synthesis of the naturally occurring enantiomer of nemorensic