Here's a great mini-history of the discovery of artificial sweeteners
It suggests that these kinds of discoveries actually usually DON'T come from rational scientists saying "well if we mix a substance with property 2 with one of property 3 we'll get a substance with property 23"
Instead they come from some guy spilling some unknown chemicals on his hand then tasting them in his hamburger. Or just: "Test? I
thought you said taste!"
So I'm trying to picture the kind of error that would produce this botox discovery