J.C.S. CHEM. COMM., 1981 Optical Resolution of Mutagenic and Carcinogenic Derivatives of Polyaromatic Hydrocarbons by High Pressure Liquid Chromatography on a Chiral Support By YOUNG HWAN KIM, A. TISHBEE, and E. GIL-AV (Department of Organic CJzemistry, The Weizrnann Institute of Science, Rehovot, Israel) 75 Summary Optically active diols of benzo [alpyrene and benz [alanthracene, and a benzo [alpyrene diol-epoxide, were resolved by h.p.1.c. on (R)-( -)-2-(2,4,5,7-tetranitro- 9-fluorylideneamino-oxy)propionic acid (TAPA) bonded to silica gel. COVALENT binding of activated metabolites of the highly carcinogenic polyaromatic hydrocarbons (PAH) to DNA is widely considered to be the initiating step in their muta- genic and carcinogenic action, and is hence of considerable topical interest. Compounds to which attention has been drawn in this context are diols, epoxides, and diol-epoxides of PAH’s, such as benzo[a]pyrene (BP),benz[a]anthracene (BA), and 7,12-dimethylbenz [alanthracene. The forma- tion of these derivatives generates chiral centres in the molecule, and it has been shown recently that the muta- genic and carcinogenic activity is enantiose1ective.l l2 It has thus become of considerable importance to develop methods for the resolution of these oxygen-containing PAH deri- vatives. Diastereomeric derivatives have been used successfully for the h.p.1.c. separation of these optical isomer^.^^^ For instance, the trans-7,8-dihydroxybenzo [alpyrene (1) was resolved via the di- ( + )-a-methoxy-a-trifluoromethylphenyl- a~etate.~ We now report a procedure which permits efficient separation of the enantiomers of a number of oxidized PAH’s without the need for an esterification step. Chiral 2- (2,4,5,7-tetranitro-9-fluorylideneamino-oxy)pro- pionic acid (TAPA) is a well known resolving agent for optically active aromatic compounds capable of interacting with the former through charge transfer complexation.5 Some years ago it was shown that this reagent can also be used in h.p.1.c. with the TAPA coated on, or covalently linked to, silica For the present work the support was prepared as follows: (3)-(-)-TAPA was first coupled to 3-aminopropyltriethoxysilane with NN’-dicyclohexylcarbo- di-imide; the silane formed was then bonded to Lichrosorb Si 100 (5~), and finally the remaining unchanged silanol groups were ‘end-capped’ with trimethylsilyl chloride. The slurry packing method was employed for column preparation. MeOH-CH,Cl, was used as the mobile phase. Solvent composition and other chromatographic conditions em- ployed are given in the Table. TAPA was shown to manifest stereoselectivity for all compounds studied. Hydrocarbons (1)-(6) differ from each other by one or more structural features, e.g., the molecular skeleton and position of the nonaromatic ring, the functionality, or the position or geometry of the vicinal diols. Correspondingly, the a-values vary quite consider- ably (Table), 0 10 20 R ~ / min FIGURE 1. Resolution of ( -J-)-trans-4,5-dihydroxy-4,5-dihydro- benzo[a]pyrene (2) ; see the Table for experimental conditions. TABLE. Resolutions of diols and diol-epoxides of polyaromatic hydrocarbons by h.p.1.c. on silica gel linked to (I?)-( -)-TAPA. PAHb Mobile phase (MeOH : CH,Cl,) k; ad (1) trans-7,8-dihydroxy-7,8-dihydrobenzo [alpyrenec 4: 11 3-43 3.86 1.125 (2) trans-4,5-dihydroxy-4,5-dihydrobenzo[a]pyrene 4: 11 3.54 4-67 1.319 (3) cis-4,5-dihydroxy-4,5-dihydrobenzo[u]pyrene 5: 95 4.12 4.46 1.083 (4) r-7,t-8-dihydroxy-t-9,10-epoxy-7,8,9,10-tetra- hydrobenzo [alpyrene 1:4 3.65 4.06 1.112 (5) cis-5,6-dihydroxy-5,6-dihydrobenz [alanthracenec 5 : 95 1.98 2-14 1.081 (6) trans-3,4-dihydroxy-3,4-dihydrobenz[a]anthracene 5:95 5.85 6.22 1.063 * Chromatographic conditions: column dimensions = 15 x 0-46 cm; flow rate = 0.7 ml/min; ambient temperature. b For number- d a = resolution ing, see the general formulae (A) and (B). factor = ki/ki = ratio of capacity factors of the two enantiomers. C Both the racemic and (-)-enantiomeric compounds were available. Published on 01 January 1981. Downloaded by Universitat Politècnica de València on 25/10/2014 08:58:59. View Article Online / Journal Homepage / Table of Contents for this issue