what about this idea?

[SPISSHAK]

take 1mol of koh, one mole of alanine, and two moles bezaldehyde  and reac them in absolute alchol to give a phenylserine now issote the seriene and subject it to boiling water as thier potassium caroxylic acid base pairs
water will decarboxlate them as in the other examples here where it is done on a nitro-acid, and others too
 reflux to decrboxylate the serine to something like ppa?

[SPISSHAK]

basically, create a addition product of alanine and benzaldehyde in alcohol solution using a base as in the phenyl serine synthesis, then boil the Sodium or Potassium salt of the "serine" in water to decarboxylate it to yeild PPA, and NaHCO3, Or KHCO3.
The decarboxlation reaction is analagous to another decarboxlyation found here:

Post 238118

(Aurelius: "Re: What can be done to improve the performance of clandestine nitroethane synth?", Chemistry Discourse)
That uses a Sodium salt of a nitro acid and water to decarboxylate the nitroacid.
The reason me thinks this is that the addition product of alanine and bezaldehyde would be a beta amino acid and hencewould'nt decarboxylate in the prescence of a ketone as readily as say tryptophan which is an alpha amino acid because of the carbon between the amino group and the carboxyl function.