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A novel synthesis of optically active anti-beta-substituted gamma,delta-unsaturated amino acids via a thio-Claisen rearrangement has been achieved. A 2,5-diphenylpyrrolidine was used as a C2-symmetric chiral auxiliary to control the stereochemistry, giving good yields and excellent diastereoselectivities and enantioselectivities.
A substituted hydropyrazino[1,2-a]pyrimidin-6-one derivative was synthesized stereoselectively via the intramolecular N-acyliminium ion cyclization between an amide nitrogen and an N(α)-acetal derived from Cbz-protected aminopropyl-phenylalaninamide in very good yields. The formation of a single diastereomer is due to the low energy chairlike conformation… (More)
Parallel synthesis of peptides and peptidomimetics has been an important approach to search for biologically active ligands. A novel systematic synthesis of different size bicyclic dipeptide mimetics was developed on solid-phase supports. By taking advantage of the enantioselective synthesis of omega-unsaturated amino acids and their N-methylated… (More)
Optically active anti-beta-substituted gamma,delta-unsaturated amino acids are important synthetic building blocks in organic synthesis and for peptidomimetics. A novel asymmetric Eschenmoser-Claisen rearrangement with use of a C2-symmetric chiral auxiliary was developed to generate this type of amino acid. Excellent diastereoselectivities and high… (More)
Anti-beta-substituted gamma,delta-unsaturated amino acids have been synthesized via a novel design of the Eschenmoser-Claisen rearrangement. The rearrangement gives good isolated yields and excellent diastereoselectivity due to (Z)-N,O-ketene acetal formation and the pseudochairlike conformations of the reaction intermediates. Upon reductive hydrolysis,… (More)