Hee Cho

Efficient resolution of the dihydrodiol derivatives of benzo[a]pyrene by high-pressure liquid chromatography of the related (−)-dimenthoxyacetates

The diastereomeric (−)-dimenthoxyacetate derivatives of (±)-trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene were efficiently resolved by high-pressure liquid chromatography (HPLC) on silica gel. Treatment with methanolic ammonia under mild conditions removed the menthoxyacetate groups to furnish the optically pure (+) and (−) enantiomers of the trans-dihydrodiol. Epoxidation of each of the latter with m-chloroperbenzoic acid gave the corresponding (−) and (+) anti-diolepoxides. The speed and efficiency of resolution of these relatively sensitive compounds by HPLC demonstrates the potential utility of this technique for resolution of all types of carcinogen-derived arene dihydrodiols.

Synthesis of hydroquinone diacetates from polycyclic aromatic quinones

A convenient general synthesis of hydroquinone diacetates from polycyclic aromatic quinones through reduction with sodium borohydride in dimethylformamide is described. Improved methods for the synthesis and chromatographic separation of the 1,6-, 3,6-, and 6,12-diones of benzo[a]pyrene are also described. 270 MHz N.m.r. spectroscopy is employed to confirm the structural assignments of the latter and the use of this technique is proposed for the characterization of carcinogen metabolites.

Synthesis of “K-region” quinones and arene oxides of polycyclic aromatic hydrocarbons

A new general synthesis of arene oxides recently reported’ from this laboratory has allowed the synthesis of the previously inaccessible “K-region” oxides (@, ,b) of the potent carcinogens ‘7,12-dimethylbenzraY anthracene (‘7.1 P-DMBA) and benzola] pyrene2. This approach, however, still suffers from the limitation of requiring the use of osmium tetroxide in the initial step. This reagent is both costly and hazardous, affords only moderate yields, and necessitates time-consuming operations in handling the air sensitive products6. As a consequence, the quantities of the oxides available for biological studies remain severely limited.

Improved synthesis of benzo[a]pyren-1-ol and isolation of a covalent benzo[a]pyrene–lead compound

A two-step synthesis of benzo[a]pyren-1-ol from 6-bromobenzo[a]pyrene via consecutive reactions with lead tetra-acetate and n-butyl-lithium is described.