METATHESIS REACTION INVOLVING THE UNSATURATED SIDE CHAIN OF AN ALPHA, ALPHA-DISUBSTITUTED AMINO ACID

摘要

The invention relates to a process for amino acid synthesis, i.e., the preparation of side chain unsaturated alpha,alpha-disubstituted-alpha-amino acid derivatives with formula (1) wherein: * denotes a stereogenic C-atom PG represents an N-protecting group or the C-terminal part of an optionally protected amino acid or peptide chain; X represents an optionally substituted amine group or an alkoxy group; R<1> represents an optionally substituted alkyl group; R represents R<2> or R<3>; if R = R<2> then R = R<5> and if R = R<3> then R = H; R<2>, R<3> and R<5> each independently represent H, an optionally substituted (cyclo)alkyl, (hetero)aryl, acyl, alkoxycarbonyl, cyano, di-alkylphosphonyl, oxiranyl group, a CHO group optionally protected as its acetal, or a group derived from an O-protected carbohydrate, or R<2> and R<5> may form together with the C-atorn to which they are attached an optionally substituted hydrocarbon ring, with the proviso that R<2> , R<3> and R<5> do not all represent H at the same time. R<4> represents H, an alkyl group or an aryl group; n represents an integer larger than or equal to 0, via a cross metathesis reaction between the corresponding amino acid derivative precursor and an (eventually substituted) alkene.