Synthesis of aromatic bis- and tris(amino acids) and chiral dendrimers

Abstract: A number of protected aromatic bis- and tris(amino acids) have been synthesised by catalytic asymmetric hydrogenation of the corresponding didehydroamino acid derivatives. The didehydroamino acid derivatives were prepared either by a Heck coupling of a 2-amidoacrylate with an aryl dihalide, or by Horner-Wadsworth-Emmons olefination of aromatic aldehydes with phosphonylglycine reagents. Excellent stereochemical purity could be achieved in most cases. The bis- and tris(amino acids) were then used as building blocks in a model study, the purpose of which was to assess the feasibility of constructing synthetic receptors from tris(amino acids). Several macrocyclic peptide-like compounds were prepared. Chiral dendrimers were also synthesised from the bis- and tris(amino acids). These dendrimers could be deprotected to yield water-soluble, polycationic or polyanionic macromolecules with a common structure. A chiroptical study of the protected dendrimers was undertaken, and it indicated that the solution shape is rather flat and sterically uncongested.