The intended product is ornithine-δ-isonicotinamide, alkylated on the pyridine nitrogen with a 5-carbon chain terminating in a carboxylic acid. We have been trying to remove a 4-methoxybenzylester used to protect the carboxylic acid on this chain (the carboxylic acid of the ornithine moiety is unprotected). In the deprotection reaction excess phenol was the scavenger (TFA was present also), and we are not certain whether or not the group was removed. The next step was to extract away the phenol, and my student mistakenly extracted using 1 M KOH versus ethyl acetate. Our presumed product is in the aqueous layer, and it is the last product of a six-step synthesis. I have thought of several things we might do.
1. Add a large excess of Dowex-50 (not that we have a great deal in lab right now). Once we added sufficient excess, we would bind all of the potassium ion to the Dowex resin, and we would then elute our product with ammonia.
2. Try to purify using some sort of reverse-phase. The KOH should go right through (as long as it stays soluble in water -organic mixtures), but our compound of interest, having some hydrophobic regions, should bind.
3. Go back one or two steps and try again.