Stereodivergent Asymmetric Reactions of α-Isothiocyanato Ester with Ketimines

Significance

Until the disclosure of this work, there have been no reports on the catalytic asymmetric preparation of β-tetrasubstituted α,β-diamino acids or their surrogates, which represent an interesting structural motif in light of biological activity. The methodology reported herein employs the Mannich-type reaction of ketimines with α-methyl-α-isothiocyanato ester 1 mediated by Mg and Sr complexes of 2, which are notable for inducing the opposite enantiofacial selectivities leading to syn- and anti-diastereomers, respectively. Desulfurization as well as a Dpp removal-desulfurative coupling sequence were carried out on certain products demonstrating their synthetic utility.