Enantioselective synthesis of α,β-diamino ester derivatives: memory of chirality in imino-aldol reactions

Memory of Chirality Concept in Asymmetric Intermolecular Michael Addition of α-Amino Ester Enolates to Enones and Nitroalkenes

A highly stereoselective asymmetric intermolecular conjugate addition of α-amino ester derivatives to cyclic enones via the memory of chirality (MOC) concept in high yields with excellent diastereo- and enantioselectivity (dr >99:1, up to 99% ee) is reported. The applicability and the generality of the strategy was demonstrated by its further exploration to acyclic α,β-unsaturated ketone and aromatic nitroalkenes, resulting in the formation of δ-keto-α-amino ester derivative and γ-nitro-α-amino ester derivatives, respectively, with excellent ee and dr.

Group-Assisted Purification Chemistry for Asymmetric Mannich-type Reaction of Chiral N-Phosphonyl Imines with Azlactones Leading to Syntheses of α-Quaternary α,β-Diamino Acid Derivatives †

An asymmetric Mannich-type reaction between chiral N-phosphonyl imines and azlactones [oxazol-5(4H)-ones] has been established under convenient conditions at room temperature. The reaction was performed without using any bases, additives, or catalysts to achieve up to excellent chemical yields and diastereoselectivity for 32 examples. The α-quaternary syn-α,β-diamino acid products were purified simply by washing the crude mixtures with cosolvents, following the group-assisted purification chemistry/technology, without involving traditional chromatography or recrystallization methods. The auxiliary can be readily removed and recycled for reuse. The absolute configuration was unambiguously assigned by X-ray structural analysis.

Memory of chirality (MOC) concept in imino-aldol reaction: enantioselective synthesis of α,β-diamino esters and aziridines

A simple strategy for the synthesis of chiral α,β-diamino- and α-amino,β-hydroxy ester derivatives in high yields with moderate to high ee has been developed via asymmetric imino-aldol and aldol reactions, respectively, starting from protected aminoesters employing memory of chirality concept for chiral induction. This strategy has been extended for the enantioselective synthesis of aziridines (ee up to 92%). The absolute configuration of the imino-aldol adducts has been determined. The stereochemical outcome of the products has been explained by a suitable mechanism and supported by computational studies.

Memory of chirality in cascade rearrangements of enediynes

The cascade rearrangement of chiral enediynes 1c-e, involving successively 1,3-proton shift, Saito-Myers cyclization, 1,5-hydrogen atom transfer, and intramolecular coupling of the resulting biradical, proceeded at 80 °C to form tri- and tetracyclic heterocycles possessing a quaternary stereogenic center with a very high level of memory of chirality.