An enantioselective synthesis of cis-dihydropyrans as the formal HDA reaction products was achieved through the catalyst-controlled anti-selective conjugate addition of aldehydes to β,γ-unsaturated α-keto esters. The observed unusual cis-selectivity could be attributed to the stabilization of the less favorable transition state for anti-conjugate adducts by the hydrogen bonding between the hydroxy
                                    通过醛控制的反选择性共轭醛加成到β,γ-不饱和α-
酮酯中,可以实现顺式-二氢
吡喃类化合物作为对映体H
DA反应产物的对映选择性合成。观察到的异常的顺式选择性归因于
氨基二醇催化剂的羟基与β,γ-不饱和α-
酮酯之间的氢键,使抗共轭加合物的较不利的过渡态稳定。