Stereodivergent Mannich reaction of bis(trimethylsilyl)ketene acetals with N-tert-butanesulfinyl imines by Lewis acid or Lewis base activation, a one-pot protocol to obtain chiral β-amino acidsElectronic supplementary information (ESI) available. CCDC 1523513. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7ob01853c

• Main Authors: Cantú-Reyes, Margarita, Alvarado-Beltrán, Isabel, Ballinas-Indilí, Ricardo, Álvarez-Toledano, Cecilio, Hernández-Rodríguez, Marcos
• Format: Journal Article
• Language: English
• Published: 20.09.2017
• ISSN: 1477-0520; 1477-0539
• DOI: 10.1039/c7ob01853c

We report a one-pot synthesis of chiral β 2,2,3 -amino acids by the Mannich addition of bistrimethylsilyl ketene acetals to N-tert -butanesulfinyl imines followed by the removal of the chiral auxiliary. The synthesis and isolation of pure β-amino acid hydrochlorides were conducted under mild conditions, without strong bases and this method is operationally simple. The stereoselective reaction was promoted by two different activation methods that lead to different stereoisomers: (1) Lewis Acid (LA) catalysis with boron trifluoride diethyl etherate and (2) Lewis Base (LB) catalysis with tetrabutylammonium difluorotriphenylsilicate. The reaction presented good diastereoselectivity with LB activation and moderate to good dr with LA catalysis. The exceptions in both protocols were imines with electron donating groups in the aromatic ring. Synthesis of chiral β 2,2,3 -amino acids. Either Lewis acid or Lewis base promote the reaction, surprisingly, each activation afford different enantiomer.