That's simply not a fact, only a theory. There's no solid proof that every ester of the 4-sub-Ts simply converts to its 4-HO-counterpart. Personally I don't buy it since some of the 4-AcO-Ts (like 4-AcO-DMT and 4-AcO-DiPT) bear only a small resemblance to their 4-HO cousins. I've talked about this a lot in this forum, though probably not in this particular thread. There's not even any absolute proof that 4-PO-DMT simply converts to 4-HO-DMT in vivo either, only educated speculation.
I think it would be silly to try to say that the esters don't convert at ALL to their 4-HO counterparts, but personally I think they're able to cross the BBB in some individuals, or perhaps given enough time. I'm sure it has to do with each individual's unique biochemistry. The comparison that led me to this conclusion is my considerable experience with both 4-AcO-DMT and pure, synthetic 4-HO-DMT (in separate trials of course). In my body, 4-AcO-DMT actually begins to come on
faster than 4-HO-DMT (by a good 5 minutes), and it's over a full hour sooner, about 2-2.5 hours total in duration. 4-HO-DMT is pretty close to mushrooms, though significantly different still (MUCH less body-oriented and more cerebral vs emotional/spiritual), but 4-AcO-DMT feels exactly like smoked DMT, but slower to unfold and less intense overall. The high-frequency buzzing is exactly the same along with the ringing/whining in the ears, and the visuals are jewelled. 4-HO-DMT, on the other hand, has a much slower, more smooth buzz like mushrooms do, earthy but crisp visuals, and a tremendously more evolved mental change. It doesn't resemble smoked n,n-DMT at all other than in the way that everything with a DMT base does.
People seem to fall into roughly two camps with 4-AcO-DMT. They either find it similar to the way I described my own experience with it, or they find it substantially like mushrooms except with a longer total duration of each stage. And in both cases, people seem to find it MUCH less anxiety- and bodyload-producing than 4-HO-DMT or mushrooms, which is a common thread with acetoxy esters of 4-sub tryptamines. I believe that those like me who find it to be like an oral version of smoked DMT are not breaking it down very much into 4-HO-DMT and mostly it's the 4-AcO-DMT crossing the BBB to produce unique effects. And the other group is primarily breaking it down into 4-HO-DMT before it crosses the BBB, leading to effects mostly like psilocin.
Of course my theory is full of speculation as well, but it's the conclusion I've come to based on considerable experience and considerable reading and discussion of the topic with others in the online community. If someone has strong evidence to the contrary or that points toward another theory entirely, I'd love to see it because the truth is what I seek.
Also, it's true that it's not uncommon for people to confuse 4-HO-XXX and 4-AcO-XXX (or particularly 4-PO-DMT and 4-HO-DMT), but I think that's primarily due to people who do not have the background of research on these substances seeing both names and simply getting mixed up or thinking they're two names for the same thing or something.
