Well, it's not clear why it failed exactly. It might have been because it never existed before, but it seems more likely to me that it was because Harry didn't know what it was exactly. He didn't try to transmute "this molecular structure I have in my mind", he tried to transmute "a substance I know nothing about except that it cures Alzheimer's". That was probably not specific enough for the spell. (Otherwise, why not transmute a black-box device with a big red "kill Voldemort where-ever he is" button, or a mysterious "bring a dead body back to life" device?)
In any case there are things who physical properties we know, and which exist or have existed, but would be very valuable to create in laboratories. Like creating a string of DNA to order, which can then replicate itself into ordinary non-transmuted matter - very valuable in 1993!
This is a new thread to discuss Eliezer Yudkowsky’s Harry Potter and the Methods of Rationality and anything related to it. This thread is intended for discussing chapter 97. The previous thread is at nearly 500 comments.
There is now a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author’s Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.)
The first 5 discussion threads are on the main page under the harry_potter tag. Threads 6 and on (including this one) are in the discussion section using its separate tag system.
Also: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25.
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: