There are thousands of high-boiling ketones to be found *everywhere*, so maybe a substance like MDP2P has better usages, don't you think...
A low yield was obtained by using DMSO ; DMSO/Cu-chelate ; DMSO/acetone and turpentine/dill oil. I thought the latter was the most promising, after Student's research, but since L-Trp is completely insoluble in the hot turp you need to have really good stirring, especially when working with larger amounts, or this reaction is going to take days.
My dill oil (french seed oil) contains 40% carvone. Maybe DMSO/carvone would be better (solubility) ?
"There are many things under the sun."