α-(Aminomethyl)acrylates as acceptors in radical–polar crossover 1,4-additions of dialkylzincs: insights into enolate formation and trapping

• Angel Palillero-Cisneros,
• Paola G. Gordillo-Guerra,
• Fernando García-Alvarez,
• Olivier Jackowski,
• Franck Ferreira,
• Fabrice Chemla,
• Joel L. Terán and
• Alejandro Perez-Luna

Beilstein J. Org. Chem. 2023, 19, 1443–1451, doi:10.3762/bjoc.19.103

• levels of chiral induction, paving the way to enantioenriched β2-amino acids and β2,2-amino acids. Keywords: β-amino acids; tandem reactions; radical–polar crossover; tert-butanesulfinamide; zinc radical transfer; Introduction Dialkylzinc reagents react in aerobic medium with a range of α,β-unsaturated

• view, the reported protocols are relevant as they offer a new, direct and modular route to enantioenriched α-mono- and α,α-disubstituted β-amino acids (β2-amino acids and β2,2-amino acids), with, for the latter, the noteworthy stereocontrolled construction of an all-carbon quaternary stereocenter

2-Phenyl- tetrahydropyrimidine- 4(1H)-ones – cyclic benzaldehyde aminals as precursors for functionalised β²-amino acids

• Markus Nahrwold,
• Arvydas Stončius,
• Anna Penner,
• Beate Neumann,
• Hans-Georg Stammler and
• Norbert Sewald

Beilstein J. Org. Chem. 2009, 5, No. 43, doi:10.3762/bjoc.5.43

• serve as universal precursors for the asymmetric synthesis of functionalised β2-amino acids containing acid-labile protected side chains. Diastereoselective alkylation of the tetrahydropyrimidinone is followed by a chemoselective two step degradation of the heterocycle to release the free β2-amino acid

• . In the course of this study, an L-asparagine derivative was condensed with benzaldehyde and subsequently converted to orthogonally protected (R)-β2-homoaspartate. Keywords: β2-amino acids; cyclocondensation; diastereoselective alkylation; N,N-acetals; peptidomimetics; ring opening; self-regeneration

• of stereocentres (SRS); Introduction Monosubstituted β-amino carboxylic acids can be classified according to their substitution pattern into α-substituted “β2-amino acids” and β-substituted “β3-amino acids” [1]. Oligomers of these β-amino acids are called “β-peptides” and tend to form distinct and