Preparative chromatographic enantioseparation of putative melatonin receptor agents, using cellulose chiral stationary phases

In order to obtain milligram amounts of the enantiomers of two tetrahydrona phthalenic derivatives 1 and 2, to be tested for binding to the melatonin s ites, preparative HPLC was set up with a mobile phase consisting of n-hexan e-alcohol and a silica-based cellulose tris-3,5-dimethylphenylcarbamate (Ch iralcel OD-H), or tris-methylbenzoate (Chiralcel OJ) using isocratic condit ions and multiple repetitive injections. The preparative separation was opt imized by adjusting the sample size from a scale-up of the analytical metho d. The purity obtained were sufficient for a first screen of their biochemi cal affinity. A reversal of the enantiomeric elution order by the change-ov er of the carbamate type phase (Chiralcel OD-H) towards the benzoate type p hase (Chiralcel OJ) was observed. The optical rotation and the circular dic hroism spectra of the single enantiomers were determined after separation a nd their absolute configuration.