Catalytic approach for the formation of optically active allyl alpha-aminoacids by addition of allylic metal compounds to alpha-imino esters

A new catalytic enantioselective approach for the formation of allyl alpha- amino acid derivatives by reaction of N-tosyl alpha-imino esters with allyl stannanes and silanes catalyzed by chiral copper(I) complexes has been dev eloped. A series of different BINAP and phosphine-oxazoline (P,N) ligands h ave, in combination with various Lewis acids, been tested as chiral catalys ts for allylation of N-tosyl alpha-imino esters. It has been found that bot h type of ligands, in combination with copper(I) salts, give highly valuabl e unsaturated alpha-amino acid derivatives. The reaction has been investiga ted for different allyl stannanes and silanes, and it has been found that t ri-n-butyl allyl stannane gives the best results of the simple allyl compou nds tested, leading to gamma,delta-unsaturated alpha-amino acid derivatives in up to 94% yield and with up to 83% ee, which can be improved to be >95% ee by recrystallization. The reaction has also been investigated using dif ferent acyclic and cyclic allyl stannanes leading to various types of unsat urated a-amino acid derivatives in very high yield (up to 95%) and with up to 98% ee. The stereochemistry and absolute configurations of the allyl alp ha-amino acid derivatives have been determined by X-ray analysis, and it is suggested that the reaction takes place as an ene-like reaction.