ELSEVIER Journal of Chromatography A, 752 (1996) 131-146 JOURNAL OF CHROMATOGRAPHY A Resolution of enantiomers of uridine analogs, potential antiviral agents • a :g • a a Shulamit Levm ' , Marina Sterln , Amir Magora , Anne Popescu b aThe School of Pharmacy, P.O.B. 12065, The Hebrew University, Jerusalem, Israel hChemieal Center, Organic Chemistry 1, BOX 124, $22100 Lund, Sweden Received 10 July 1995; revised 15 May 1996; accepted 23 May 1996 Abstract Racemic mixtures of 5-substituted carbocylic analogs of uracil nucleosides, 2"- and 3"-furyl, 2"- and 3"-thienyl and 2"-selenienyl, potentially anti-viral agents, were resolved using amylose tris(3,5-dimethylphenyl)carbamate as the stationary phase. The mobile phase was n-hexane with ethanol or 2-propanol. Effects of some structural features on the extent of discrimination between the enantiomers were examined through the selectivity and resolution factors as well as the elution order. The structural features were as follows; the type and position of the hetero-atom O, S or Se, in the cyclopentadienyl substituent 5 of the uracil and hydroxymethyl vs. acetoxymethyl groups on the cyclopentene moiety of the uridine analogs. It appeared that effects of the structural features on the separation were solvent dependent, with some very unusual solvent effects. For example, average retention, which did not follow the polarity of the mobile phase modifiers, was much higher when ethanol was used compared to 2-propanol. Also, the elution order of the two enantiomers of several pairs was reversed when ethanol was changed to 2-propanol. In general, ethanol affected higher selectivity and resolution of all the enantiomeric pairs. Keywords: Enantiomer separation; Uridine; Uracil nucleosides 1. Introduction Carbocyclic analogs of nucleosides have shown antiviral properties and can potentially serve as candidates for anti-human immunodeficiency virus (HIV) drugs [1,2]. Many of these analogs are chiral and can exhibit stereoselectivity in their biological activity [3]. A well known example of stereoselec- tivity in drug action is exhibited by the drug Car- bovir (CBV), a carbocyclic analog of 2',3'-dideoxy- guanosine that exhibits potent and selective in vitro activity against HIV. It has been shown [4,5] that its *Corresponding author. antiviral activity is associated with only the (-)- enantiomer. These findings imply that other enantio- mers of the carbocyclic analogs of nucleosides are expected to differ in their biological activity and that just one of the enantiomers would be therapeutic. The enantiomeric purity of the therapeutic form of the candidate drug should be established before using it for anti-HIV purposes, to prevent possible side effects. Any future development of these compounds as antiviral or anti-HIV drugs would require that it is possible to analyze them, as enforced by health regulatory agencies for newly developed chiral drugs [6-8]. A literature search linking chiral carbocyclic ana- 0021-9673/96/$15.00 © 1996 Elsevier Science B.V. All rights reserved PII S0021-9673(96)00507-9