Abstract: A compound of D-phenylalanine derivative for hypoglycemic use, represented by the general formula ##STR1## R.sup.1 is selected from hydrogen, alkyl of 1 to 5 carbon atoms, aryl of 6 to 12 carbon atoms, aralkyl of 6 to 12 carbon atoms, ##STR2## --CH.sub.2 CO.sub.2 R.sup.3, --CH(CH.sub.3)--OCO--R.sup.3, and --CH.sub.2 --OCO--C(CH.sub.3).sub.3 ; R.sup.2 is selected from groups comprising aryl of 6 to 12 carbon atoms, a hetero six-membered ring, a hetero five-membered ring, cycloalkyl, or cycloalkenyl, any of which groups may have one or more substituents; and R.sup.3 is selected from hydrogen and alkyl of 1 to 5 carbon atoms; the salts thereof, and precursors which can be converted thereto in the human or animal body.Some of the compounds are novel per se.