Distribution behavior of potential bioactive 1-azabicyclo[3,3,1]nonane derivatives in some organic solvent/buffer pH 7.4 systems

The apparent distribution coefficients of the potential bioactive compounds of the N-aryl-(3-sulfur-1-azabicyclo[3,3,1] non-2-ylidene) amine series in organic solvent/buffer pH 7.4 systems at five temperatures from 293.15 to 315.15 K have been determined by the shake-flask method. The logDO/B values of substances between 1-octanol and the aqueous phase range from 1.76 to 2.06 and at 298 K decrease depending on the chemical nature of the substituents of the phenyl fragment in the following order: cyan- > ethyl- > acetyl- > methyl-, chloro- > isopropyl-. The replacement of 1-octanol by hexane shifts the equilibrium of the substances from the organic phase to the buffer and the resulting values logDH/B < 1. According to the obtained partition coefficients (logPO/B), bicyclic derivatives with alkyl substitutents are the most lipophilic ones. The logPO/B values are consistent with those calculated using the HyperChem program (RMSE = 0.5 log units). It is shown that the lipophilicity of the studied compounds with an azabicyclo[3,3,1]nonane fragment is higher than that of their structural analogues with a spiro-bicycle. The transfer process of compounds from the aqueous phase to the organic one is characterized as spontaneous, endothermic and entropy-driven. The effect of solvation enthalpies of the studied compounds in buffer pH 7.4, 1-octanol and hexane on partition coefficients has been revealed.