Highly diastereoselective allylation and reduction of chiral camphor-derived α-ketoamides

The diastereoselective allylation and reduction of camphor-derived α-ketoamides to give optically enriched α-hydroxyl amides with high to excellent stereoselectivities are described. Allylation was carried out using allyltributylstannane in the presence of a stoichiometric amount of a Lewis acid to afford the desired homoallylic alcohols in relatively high chemical yields (up to 98%) and stereoselectivities (up to 98% de). Diastereoselective reductions were performed with the relatively bulky hydride K-Selectride at -78°C to give the corresponding α-hydroxy amides in excellent chemical yields (up to 98%) and stereoselectivities (up to 98% de). The absolute configuration of the new stereogenic center of the major diastereomer was established by X-ray crystallographic analysis. Finally, stereochemical induction and the Lewis acid dependent reversal of stereoselectivity is described.