β-hydroxy-α,α-disubstituted amino acid derivatives from cyclic orthoamide is reported. The first step is the orthoamide-type Overman rearrangement of an α,β-unsaturated ester to give a sterically hindered α,α-disubstituted amidoester. The α,β-unsaturated ester is known to be a challenging substrate in the conventional Overman rearrangement due to the competitive aza-Michael reaction. However, suppression
                                    报道了从环状原酰胺中两步合成 β-羟基-α,α-二取代
氨基酸衍
生物的发展。第一步是 α,β-不饱和酯的邻酰胺型 Overman 重排,得到位阻的 α,α-二取代酰胺酯。由于竞争性 aza-Michael 反应,已知 α,β-不饱和酯是常规 Overman 重排中具有挑战性的底物。然而,aza-Michael 反应的抑制是通过两个因素实现的:1) 反应温度高,和 2) α-位有烷基取代基。第二步是立体发散分子内SN2'反应,用于在β-位安装羟基。通过简单地改变反应条件,无论是同型还是反型 SN2' 反应都是可能的。