Asymmetric Synthesis of l-Carbidopa Based on a Highly Enantioselective α-Amination
摘要:
A stereoselective synthesis of L-carbidopa in seven steps and 50% overall yield from commercial compounds is described. The key step involves a highly enantloselective alpha-amlnation reaction of an acyclic beta-ketoester with di-tert-butyl azodicarboxylate induced by europium and (R,R)-dlphenyl-pybox.
The enantioselective amination of α-alkylated β-keto esters with azodicarboxylates using a chiral dilithium binaphtholate as catalyst affords optically active α,α-disubstituted α-amino acid derivatives in high enantioselectivities of up to 95% ee. A stoichiometric amount of lithium hydroxide accelerates the amination. This method provides easy access to various chiral α,α-disubstituted α-amino acids