Here's a paper that discusses how to synthesize it, which was published because it's apparently easier than the synthesis of 4-HO-DMT, but with effects that would make it decent for clinical research. No idea if it's been done before this, though. http://www.erowid.org/references/texts/show/6535docid6064
Shulgin writes of "the acetate ester" of psilocin in his book in 1994. See the 4-HO-DMT entry. It very very likely goes back further than '94. Also check the references in that Nichols group paper. YOu might find what you're lookin' for.
