A biomimetic approach to b-amino acids

The feasibility of a 1,2-radical mediated migration reaction of the imino group has been investigated as a novel route to p-amino acids. Previously only one example of this reaction had been reported. This study describes a further five examples of this reaction (shown below) which together with analogous studies within our group have allowed us to determine the factors (steric and electronic) important for the migration. The synthesis of p-functionalised a-amino acids and their derivatives via a new strategy involving the C-alkylation of salicylaldehyde imines is also reported. [diagram] R1 = H, Me : R2 = Me, CH(CH3)2, CH2CH(CH3)2 : Ar = 2-hydroxy benzene, pyridoxal, C6F5. The synthesis of enantiopure p-phenylseleno a-amino acids via bis-lactim chemistry was also investigated and the first example of these types of compounds is reported. In addition a number of functionalised imines have been synthesised (shown below) to investigate the nature of the radical intermediates involved in the migration reaction and the results from these studies are described. [diagram] Finally the novel ring opening reaction of an aziridine employing A/-bromosuccinimide and benzoyl peroxide chemistry to give an a-brominated-p-iminoester is also reported and the mechanistic relevance to the studies above is discussed.