- Which base would be a great choice?
- How much time does it take for tryptophan to fully decarboxylate?
- What is the ideal temperature for this type of reaction?
Just heating with base is ineffective. Laval and Golding  describe a general procedure for the decarboxylation of α-amino acids using N-bromosuccinimide and Ni(0) in aqueous solution. The yields are pretty good.
- Laval, G.; Golding, B. T. One-Pot Sequence for the Decarboxylation of α-Amino Acids. Synlett 2003, No. 4, 0542–0546. DOI: 10.1055/s-2003-37512.