the question is, would it help to add it? It is naturally formed as a part of the yeast's metabolism, (and virtually any organism that uses sugars to provide energy) but is the rate of production equal the rate of PDC production? If PDC was being produced in excess to the proportion of pyruvic acid, we could probably squeeze more out of it (?) If not, the whole line of thought is worthless... unless we can get PDC out of yeast somehow perhaps, or if it is commercially available. or... maybe there's some way to make pyruvic acid useful here somehow (chlorinate it and react with benzyl chloride perhaps?)
(just looking at molecules) oh i see decarboxylate tartaric acid one time and remove one hydrogen (or add an oxygen) and you get *tada* pyruvic acid.
I've been trying to nut out how exactly the PDC goes about joining these things together and what i've figured out is this: The pyruvic acid decarboxylates, and the free carbon bond remaining of what used to be pyruvic acid reacts with the aldehyde, which bonds by saturating the carbon with the acetaldehyde which is lacking a hydrogen (which is floating around from the decarboxylation), and the hydrogen goes onto the now single-bonded oxygen at the first carbon on the now phenylacetylcarbinol.
If one created reaction conditions of pyruvate decarboxylating in the presence of benzaldehyde, it doesn't make any difference how it is done so long as the process allows the freshly decarboxylated pyruvic acid take up the carbon bond. or am i missing some vital point here? The stereoselectivity is inherent in this reaction because of the way it reacts via the production of an aldehyde with an extra proton on the carbon with the aldehyde on it, because the keto group has some kind of interaction with the oxygen with a free electron. I think in this case we always want the OH and keto group to end up opposite each other, and i suspect that is exactly what they do. One could imagine that there would be some kind of interaction leading to a fairly predictable bonding formation.
Tricky thing is, how do we get the pyruvic acid to decarboxylate with benzaldehyde around? perhaps a high boiling ketone? pressure (*ducks flamethrower blasts*) ? *wince* ... ooh, maybe something simple like a natural organic ketone, eg carvone or something similar... That would dissolve the benzaldehyde well enough but the determining factor for the best ketone solvent/matrix/decarboxylation catalyst would be good solubility of pyruvic acid.