Asymmetric Chelated Claisen Rearrangements in the Presence of Chiral Ligands—Scope and Limitations

Recent progress on the stereoselective synthesis of cyclic quaternary α-amino acids

“…Thus, treatment of 581a–c with LiHMDS and Al( i -OPr) 3 in the presence of quinine under Kazmaier's conditions,233 gave the rearrangement products 582a–c in good yield as single diastereo-isomers through the transition state A . Interestingly, the Claisen rearrangement only occurred in the presence of quinine.…”

Peptidomimetics, a synthetic tool of drug discovery

“…The absolute stereochemical control of the β-substituent can be achieved by metal chelation with use of chiral ligands [21,22], chirality transfer from available chiral sources [23,24], or by chiral auxiliaries [25,26]. For example, optically active syn β-substituted γ,δ-unsaturated amino acids can be synthesized via chelate-Claisen rearrangement in the presence of chiral quinine [21,22]. On the other hand, Eschenmoser-Claisen rearrangement can be employed for the synthesis of anti β-substituted γ,δ-unsaturated amino acids [27] and incorporation of a C 2 -symmetric chiral auxiliary in the Eschenmoser-Claisen rearrangement can provide optically active amide analogues with various β-substituents [26].…”

A modular toolkit to inhibit proline-rich motif–mediated protein–protein interactions

“…The preparation of the required building blocks was achieved on a multigram scale by exploiting, as a key step, either the Cu-catalyzed 1,4-addition of vinyl-MgBr to a cyclic dehydro-amino acid derivative (A1 and A4, respectively) (27), diastereoselective vinylation (formylation/ methylenation) of the protected proline A2 (28), or the enantioselective Claisen rearrangement of the glycine derivative A3 (29). The Fmoc-protected ProMs can subsequently be used for ligand synthesis, exploiting established protocols for peptide coupling.…”