Boc或Cbz保护的L-脯氨醇衍生物的稳定性

Stability of Cbz or Boc Protected L-Prolinol Derivatives

近年来,L-脯氨醇衍生物催化的不对称Michael加成反应已经成为手性催化研究领域的热点.而在L-脯氨醇衍生物的合成中,常常涉及到L-脯氨醇氨基的保护.为此,研究了Boc和Cbz保护的脯氨醇衍生物的稳定性,发现Boc保护的L-脯氨醇在羟基被取代为易离去基团时,就变得不稳定,在67℃就发生分子内环合生成化合物γ-丁内酯;而Cbz保护的L-脯氨醇衍生物的稳定性要好得多,在140℃且有三乙胺存在时,才会发生类似的分子内环合反应.

Recently,the asymmetric Michael addition mediated by the derivatives of L-prolinol has been a big hit in the field of asymmetric synthesis.However,the protection of the amino group of L-prolinol is a key step and often involved in the synthesis of L-prolinol derivatives.Thus,the stability of Cbz or Boc pro-tected L-prolinol derivatives is investigated.It was found that when the hydroxyl group of Boc protected L-prolinol is replaced by easily leaving group,it is unstable and cyclization proceeds effectively to give γ-butyrolactone at 67 ℃;however,Cbz protected L-prolinol derivatives are more stable,similar cyclization will happen at 140 ℃ in the presence of triethylamine.