Catalytic Asymmetric Synthesis of a Nitrogen Analogue of Dialkyl Tartrate by Direct Mannich Reaction under Phase-Transfer Conditions

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[reaction: see text] Phase-transfer-catalyzed direct Mannich reaction of glycinate Schiff base 3 with alpha-imino ester 4 has been accomplished with high enantioselectivity by the utilization of N-spiro C(2)-symmetric chiral quaternary ammonium bromide 2 as a catalyst. This methodology enables the catalytic asymmetric synthesis of differentially protected 3-aminoaspartate, a nitrogen analogue of dialkyl tartrate. The product (syn-5) was converted into a precursor (6) of streptolidine lactam.