Lipophilicity Of The 1-aryl-2-iminoperhydro-pyrimidine Derivatives Measurement
LIPOPHILICITY OF THE 1-ARYL-2-IMINOPERHYDRO-PYRIMIDINE DERIVATIVES MEASUREMENT
BY MEANS OF SPECTROPHOTOMETRIC
"PASSAGE HALF TIME - t1/2" METHOD
A. Persona1, D. Matosiuk2, U. Kijkowska-Murak2,
G. Wroński1, Z. Fekner1
1Faculty of Chemistry, Maria Curie-Sklodowska University,
Maria Curie-Sklodowska sq. 3, 20-031 Lublin, Poland
2Department of Synthesis and Technology of Drugs, Medical University,
Staszica st. 6, 20-081 Lublin, Poland
Lipophilicity is one of the structure and electron distribution dependent feature of the biologically active compounds, which can be easily correlated with the activity factors. Lipophilicity is one of the most important properties of active compounds, affecting not only its pharmacological action but in fact, its capacity to act as drug in the living organism. Lipophilicity affects distribu- tion, metabolism, blood-tissue barrier penetration, plasma-protein binding, and other phenomena – increased lipophilicity usually results in an increase in all these properties.
The role of the lipophilicity leads to the importance of its measurement. The most frequently used methods are currently chromatographic ones, both TLC (RP-TLC) and HPLC (RP-HPLC). Their advantages are mainly fast and easy procedures, and possibility of simultaneous analysis of large number of samples, but there are some disadvantages as well.
The new method for lipophilicity assessment could be the spectrophoto-metric "passage half time – t1/2" method, using UV/VIS detected time of the passage of half amount of the analyte through the water/n-octanol interfacial barrier. This method was used for assessing lipophilicity factor (logP) of the large group of the 2-arylsulphonyliminoperhydropyrimidines bearing different substituents in position 1 (aryl, alkyl, arylalkyl, cycloalkyl). Correlation of the spectrophotometric logPt with the respective chromatographic logPTLC values gave the experimental lipophilicity calculated from the correlation equation:
logPEXP = 1.0949logPTLC – 0.4023
(r2 = 0.8112, n = 28)
The presence or lack of the aliphatic chain fragments in the investigated compounds affects the experimental lipophilicity. For respective groups (aryl, alkyl/arylalkyl/cycloalkyl) distingue equation can be drawn:
logPEXPAR = 1.2163logPTLCAR – 0.6159
(r2 = 0.8581, n = 14)
logPEXPALK = 1.0125logPTLCALK – 0.1649
(r2 = 0.9034, n = 14)
The discussion of the substitution effects on the lipophilicity will be presented.
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