Process for producing phosphinylamino acid derivatives

A process for producing a phosphinylamino acid derivative of the formula:

• ##STR21## wherein R.sup.1 is a lower alkyl group, R.sup.2 is a hydrogen atom, a lower alkyl group, a halo-lower alkyl group or a substituted or unsubstituted phenyl group, and R.sup.3 is a substituted or unsubstituted alkyl group or a substituted or unsubstituted phenyl group, which comprises reacting a compound of the formula:
• ##STR22## wherein R.sup.1 and R.sup.2 are as defined above, and/or a compound of the formula:
• ##STR23## wherein R.sup.1 and R.sup.2 are as defined above, with a compound of the formula:
• R.sup.3 CONH.sub.2 (IV)
• wherein R.sup.3 is as defined above, carbon monoxide and hydrogen in the presence of a catalyst containing a metal of Group VIII of the Periodic Table, and then separating the catalyst containing a Group VIII metal from the reaction solution by oxidizing the catalyst in the reaction solution in the presence of a mineral acid and adsorbing it on a cation exchange resin.