DBU-catalyzed Michael additions of bulky glycine imine to β-arylfuryl substituted α,β-unsaturated esters

DBU-catalyzed Michael reactions between <i>tert</i>-butyl 2-((diphenylmethylene) amino)acetate and simple β-substituted α,β-unsaturated esters have been achieved in high yields (up to 95% yield) and diastereoselectivties (up to 99:1 dr) in the presence of 1.0 eq. of LiBr in acetonitrile under room temperature. The Michael adduct can be easily converted into <i>trans</i>-3-substituted pyroglutamic acid ester through <i>in-situ</i> acidic hydrolysis following lactamation.

本研究成功实现了DBU催化的叔丁基2-((二苯亚甲基氨基)乙酸酯与简单β-取代α,β-不饱和酯之间的迈克尔加成反应。该反应在乙腈溶剂中、室温条件下，以1.0当量溴化锂(LiBr)存在时，可获得最高95%的产率与最高99:1的非对映选择性(dr)。所得迈克尔加成产物可经原位酸性水解并伴随环酰胺化反应，便捷地转化为反式3-取代焦谷氨酸酯。