It would also be possible to decarboxylate Dopa or Tyrosine, for example by using any of these procedures:
Post 416740 (https://www.thevespiary.org/talk/index.php?topic=13012.msg41674000#msg41674000)
(Rhodium: "Novel amino acid decarboxylation via the nitrile", Tryptamine Chemistry)
Post 285716 (https://www.thevespiary.org/talk/index.php?topic=6574.msg28571600#msg28571600)
(foxy2: "Tyramine", Chemistry Discourse)
Both tyrosine and L-Dopa are fairly available. I know at least tyrosine can be purchased in a powder form for something like $10/oz. L-dopa can be extracted from some kind of plant which is also rather available. TFSE or Google should turn up the information. These could then be decarboxylated (to tyramine and dopamine resp.) by heating with a ketone catalyst in a high boiling point solvent. Look at student's spearmint catalyzed decarboxylation of tryptophan in turpentine on Rhodium's site. I expect that it should work similarly for phenylalanines like tyrosine. The only concern which comes to mind is that the hydroxyl group(s) might oxidize at those temperatures (at least on L-dopa this seems likely). I think that none of this is necessary, though, since tyrosine is part of the biosynthesis of mescaline, at least in peyote. See this site. (http://www.usm.maine.edu/~newton/Chy251_253/Lectures/AminesII/alkaloids.html)
(http://www.usm.maine.edu/~newton/Chy251_253/Lectures/AminesII/alkaloids.html)
Be sure to wait a long time before harvesting, since otherwise you'll get mainly whatever you injected into the cactus :P . Tyrosine has its purposes (for example, it seems to help with amphetamine hangovers), but certainly lacks the sparkle of mescaline ;D
Edit: n/m there are easier methods posted above.
Dopamine is 3,4-dihydroxy-phenethylamine.
Why not demethylate the 3-methoxy group on vanillin via the pyridine.hcl/microwave method.
(https://www.thevespiary.org/rhodium/Rhodium/chemistry/methylenation.html (https://www.thevespiary.org/rhodium/Rhodium/chemistry/methylenation.html)
)
then condense via nitomethane
reduce via your favorite reducing agent.