CATALYTIC ASYMMETRIC-SYNTHESIS OF BIS-ARMED AROMATIC AMINO-ACID DERIVATIVES - PROBLEMS RELATED TO THE SYNTHESIS OF ENANTIOMERICALLY PURE BIS-METHYL ESTER OF THE (S,S)-PYRIDINE-2,6-DIYL BIS-ALANINE

(S,S)-Pyridine-2,6-diyl bis-alanines 8 and 9 carrying protecting group s suitable for peptide synthesis have been synthesised Rom 2,6-pyridin edicarbaldehyde by the phosphonoglycine condensation route followed by catalytic by hydrogenation with Rh{(COD)[(R,R)-DIPAMP]}BF4. The alter native route via double Heck coupling of 2,6-dibromopyridine and benzy l Boc-amidoacrylate was unsuccessful although mono-coupling could be a chieved. The reasons for this failure are discussed as well as the fai lure of two mono-armed didehydroamino acid derivatives to undergo hydr ogenation with Rh-bisphosphine catalysts. The CuCl2 and RhCl3 complexe s of the bis-amino derivative 9 were prepared; a 20% e.e. was achieved in the cyclopropanation of styrene with ethyl diazoacetate using the Cu(II)-complex as a catalyst.