When its 4 phenyl phenapromide or or 4 phenyl propiram.
Now, if you have software to view/compare the above & fentanyl, one will realize that their minimum energy conformations are IDENTICAL. The LogP of the others isn't quite as good but affinity seems identical and they really do overlay the 4 important class of moieties are IDENTICAL thus x60 M.
I am not a fan of the class but I'm sure that with some research, even more potent analogs are possible. Potency is simple, euphoria is HARD. I have experienced that latter problem MANY times. I am still amazed that something that has such a huge retail price has to be surprisingly cheap & simple to make in bulk. I think U-47700 cost $16000/Kg for the first order (a key) but went down. I wish people could try and demand the euphoric stuff.
Now, if you have software to view/compare the above & fentanyl, one will realize that their minimum energy conformations are IDENTICAL. The LogP of the others isn't quite as good but affinity seems identical and they really do overlay the 4 important class of moieties are IDENTICAL thus x60 M.
I am not a fan of the class but I'm sure that with some research, even more potent analogs are possible. Potency is simple, euphoria is HARD. I have experienced that latter problem MANY times. I am still amazed that something that has such a huge retail price has to be surprisingly cheap & simple to make in bulk. I think U-47700 cost $16000/Kg for the first order (a key) but went down. I wish people could try and demand the euphoric stuff.