Process for producing keto nitrile derivative

A process for producing a (2S)-2-(N,N-dibenzyl)amino-5-amino-1,6-diphenyl-4-hexen-3-one derivative represented by formula (VI):

• ##STR16## wherein Bn represents a benzyl group, Ph represents a phenyl group, and C* represents an asymmetric carbon atom,
• which comprises reacting a (2S)-2-(N,N-dibenzyl)aminophenylalanine ester derivative represented by formula (I):
• ##STR17## wherein R.sub.1 represents a lower alkyl group or a benzyl group, and Bn, Ph and C* are as defined above,
• with acetonitrile in the presence of a benzylmagnesium halide or a benzyllithium.

A process for producing a (4S)-4-(N,N-dibenzyl)amino-5-phenyl-3-oxo-pentanenitrile derivative represented by formula (II):

• ##STR18## wherein Bn represents a benzyl group, Ph represents a phenyl group, and C* represents an asymmetric carbon atom,
• which comprises reacting a (2S)-2-(N,N-dibenzyl aminophenylalanine ester derivative represented by forumla (I):
• ##STR19## wherein R.sub.1 represents a lower alkyl group or a benzyl group, and Bn, Ph and C* are as defined above,
• with acetonitrile in the presence of a lithium compound or a magnesium compound, wherein said lithium compound is an organolithium compound represented by formula (III):
• ##STR20## wherein R.sub.2 and R.sub.3, which are the same or different, each represent a hydrogen atom, a lower alkenyl group, a phenyl group or a benzyl group, provided that they do not simultaneously represent a hydrogen atom, or when taken together form a 5- or 6-membered ring together with a nitrogen atom and wherein said magnesium compound is an organomagnesium compound represented by formula (IV):
• R.sub.4 MgX (IV)
• wherein X represents a halogen atom and R.sub.4 represents a lower alkyl group, an aralkyl group, a phenyl group or a vinyl group,
• or an organomagnesium compound represented by formula (V):
• ##STR21## wherein X is as defined above and R.sub.5 and R.sub.6, which are the same or different, each represents a hydrogen atom, a lower alkyl group, a lower alkenyl group, a phenyl group or a benzyl group, provided that they do not simultaneously represent a hydrogen atom, or when taken together form a 5- or 6-membered ring together with a nitrogen atom.