Molecular structure of anti-3,4-dihydroxy-1,2,3,4-tetrahydronaphthalene 1,2-oxide.

The molecular structure and conformation of anti-3,4-dihydroxy-1,2,3,4-tetrahydronaphthalene 1,2-oxide have been determined by X-ray crystallographic techniques. This compound has been identified as a urinary metabolite of naphthalene and also mimics various metabolites of carcinogenic polyaromatic hydrocarbons. The compound crystallizes in space group Pca2(1) with cell dimensions a = 8.120(3), b = 8.656(2), and c = 23.729(5) A. There are two unique molecules in the asymmetrical unit with similar conformations. The major difference between the two molecules is in the epoxide ring. One molecule shows symmetrical C--O bond lengths and the other shows unsymmetrical C--O bond lengths, due to steric variations in the environments of the epoxide oxygen atoms. Both molecules show a "twist-boat" conformation in the saturated portion of the carbon skeleton. Packing of the molecules in the unit cell results in alternate layers of hydrophobic and hydrophilic regions and an extensive intermolecular hydrogen bond network.