Processes for the preparation of diastereomerically and enantiomerically enriched oxazolines

A process for the preparation of a diastereomerically and enantiomerically enriched mixture of an amino acid of general formula (IV) or a salt thereof:

• said process comprising the following synthetic operations:
• a) preparing a diastereomerically and enantiomerically enriched mixture of the oxazoline of general formula (II) by reacting a benzaldehyde (I) with an isocyanoacetate (V) in the presence of a catalytic system comprising a 9-amino(9-deoxy)epi Cinchona alkaloid derivative (VIII) and a salt of silver or gold or a mixture thereof:
• wherein:
• R1 is a C6-C10 aryl or a substituted C6-C10 aryl;
• R2 is a C1-C6 linear or branched alkyl, a C6-C10 aryl or a C1-C6 linear or branched alkyl substituted with a C6-C10 aryl;
• R3 is H, OH, or a C1-C6 linear or branched alkoxy;
• R4 is
• and
• R5 is an ethyl or a vinyl group;
• b) converting said enriched mixture of the oxazoline of general formula (II) into a diastereomerically and enantiomerically enriched mixture of the protected amino acid of general formula (III):
• c) converting the enriched mixture of the protected amino acid of general formula (III) into a diastereomerically and enantiomerically pure mixture of the amino acid of general formula (IV):