Enantioselective Catalytic Addition of HCN to Ketoimines. Catalytic Synthesis of Quaternary Amino Acids
摘要:
Highly enantioselective addition of HCN to ketoimines has been achieved for the first time using readily accessible and recyclable Schiff base catalysts. Essentially quantitative isolated yield and enantioselectivity of up to 95% ee was obtained. Furthermore, some of the Strecker adducts could be recrystallized in high recovery, yielding optically pure materials. Conversion of the alpha-aminonitrile adducts to the corresponding alpha-quaternary alpha-amino acids was effected in high yield by a formylation/hydrolysis sequence.
A general asymmetric Strecker-type reaction is reported, catalyzed by the Lewis acid-Lewis base bifunctionalcatalyst 1. The reaction of trimethylsilyl cyanide (TMSCN) with various fluorenyl imines, including n-aldimines and alpha,beta-unsaturated imines, proceeds with good to excellent enantioselectivities in the presence of a catalytic amount of phenol as additive (20 mol%) (catalytic system 1).
The Strecker reaction coupled to Viedma ripening: a simple route to highly hindered enantiomerically pure amino acids
作者:Iaroslav Baglai、Michel Leeman、Klaus Wurst、Bernard Kaptein、Richard M. Kellogg、Willem L. Noorduin
DOI:10.1039/c8cc06658b
日期:——
The Strecker reaction is broadly used for the preparation of α-amino acids. However, control of enantioselectivity remains challenging. We here couple the Strecker reaction to Viedma ripening for the absolute asymmetricsynthesis of highly sterically hindered α-amino acids. As proof-of-principle, the enantiomerically pure α-amino acids tert-leucine and α-(1-adamantyl)glycine were obtained.
A novel synthesis of tert-leucine via a Leuckart type reaction
作者:Brian M. Adger、Ulrich C. Dyer、Ian C. Lennon、Peter D. Tiffin、Simon E. Ward
DOI:10.1016/s0040-4039(97)00269-4
日期:1997.3
An efficient synthesis of racemic tert-leucine from trimethylpyruvic acid using a Leuckart type reaction is described. A facile resolution of an intermediate with α-methylbenzylamine allows entry into either (R)-or (S)-tert-leucine.