Interesting, hmm ..., it most definitely is.
This ethyl 4-phenyl-1-(3-phenylpropyl)-piperidine-4-carboxylate seems to be a hybrid between pethidine (the phenyl & the ethyl carboxylate on the 4 position in the piperidine ring) and phenoperidine (the 3-phenylpropyl group on the N of the piperidine ring - although it is a 3-phenyl-3-hyrdroxy-propyl group in the case of phenoperidine). Phenoperidine, which is a kind of pethidine reversed esther, is 25 - 50 times as powerfull as morphine. Hence, I think that the reversed esther of 4-phenyl-1-(3-phenylpropyl)-piperidine-4-carboxylate would be more powerfull than the 14 x pethidine. It would be the phenoperidine minus the 3-hydroxy. Reversed esters are always more potent than the corresponding pethidine analog.
The only problem with this patent would be the synthesis of the ethyl 4-phenylpiperidine-4-carboxylate hydrochloride precursor. This is not like a easy thing to do
.
For mor information about pethidine & analogs see:
http://www.undcp.org/bulletin/bulletin_1957-01-01_4_page006.html#s12
