The compounds of formula I where R1 is other than H can be prepared by reacting a cinnamoyl chloride of the formula ##STR4## or a mixed anhydride of the formula ##STR5## where R2 is t-butyl or ethoxy with an N-substituted hydroxylamine in an inert solvent in the presence of a base at about -30??? C. to about 40??? C. for about 0.25-16 hours.