The Synthesis of (S)-(+)-2-Amino-3-(1-adamantyl)-propionic Acid (L-(+)-Adamantylalanine, Ada) as a ?Fat? or ?Super? Analogue of Leucine and Phenylalanine

Enantioselective synthesis of adamantylalanine and carboranylalanine and their incorporation into the proteasome inhibitor bortezomib

The incorporation of adamantylalanine and carboranylalanine at the P2 site of bortezomib is well tolerated and provided potent cell permeable proteasome inhibitors with increased off-rates compared to bortezomib. Adamantylalanine and carboranylalanine were synthesized enantioselectively by an asymmetric Strecker reaction on Ellmans tert-butyl sulfinimines.

Synthesis of gamma-methyl-L-leucine (neopentylglycine, Neo) and derivatives suitable for peptide synthesis

The modified Strecker synthesis of Patel & Worsley was combined with an enzymatic deamidation in the final step, to produce the title compound. The amino acid is a member of the family of the "fat" amino-acids with high lipophilicity and space-filling properties, as estimated by its Hansch hydrophobicity constant pi and its Charton steric parameter v. It can be used for qualitative and quantitative studies of structure-activity relationships in biologically active peptides. Three of its derivatives suitable for peptide synthesis are also described.

Electronic, steric, and hydrophobic factors influencing the action of enkephalin-like peptides on opiate receptors

The requirements of opiate receptors for electronic, steric, and hydrophobic properties of the amino acids in Pos. 4 and 5 of enkephalin-like peptides were studied. A series of [D-Ala2]-enkephalins containing carboranylalanine, adamantylalanine, t-butylglycine and p-nitrophenylalanine were synthesized and their pharmacological activities in the guinea pig ileum and their naloxone displacement in rat brain homogenates determined. An electronegative (-E) aromatic character of the amino acid in Pos. 4 strongly enhanced potency, overruling steric effects. The enhancement was not caused by exceptional enzyme resistance. Amino acid in Pos. 5 contributed to potency mainly through its effect on overall hydrophobicity. The two C-terminal amino acids seem to function as potentiator and address elements in the enkephalins.

Unusually strong lipophilicity of 'fat' or 'super' amino-acids, including a new reference value for glycine

Lipophilic, steric, electronic, and enzyme resistance characteristics of carboranylalanine, adamantylalanine, neopentylglycine and tert-butylglycine are described. The first 2 amino-acids display lipophilicities 2 orders of magnitude higher than tryptophan.