PEG, yeah, just what I was thinking. With fewer hydroxyls, it won't bump into Lilienthal's objection as badly as glycol, or say, glycerine would. Naphthalene, hm, who knows -- with this "solvent", how could you ever get your Tryp out? Sounds like you're in a worse fix than with DMSO! Any way a vegetable cooking oil could dissolve tryptophan? Aqueous acid would sure pull the basic tryptamine out of that, a lot easier than it would the amphoteric amino acid. But for a catalyst, try benzoquinone! Betcha that would work.
Turning science fact into <<science fiction>>