Naphthalene trans-dihydrodiols

Abstract

The currently used GC-MS method for analysis of PAH metabolites in fish bile only focus on phenols; 1-naphthol, 2-naphthol, 1-hydroxyphenanthrene, and alkylated derivatives. 1- Hydroxypyrene is also included, but not alkylated forms. However, since trans-naphthalene dihydrodiol and methylated derivatives are formed in vivo and are known carcinogens, their presence in fish bile should be further investigated. Due to the absence of commercially available standards of trans-dihydro diols and their methylated derivatives, these compounds need to be synthesized. trans-1,2-Dihydronaphthalene-1,2-diol (13±), trans-6-methyl-1,2-dihydronaphthalene-1,2- diol (19±), trans-5,7-dimethyl-1,2-dihydronaphthalene-1,2-diol (20±) and trans-4,6,7- trimethyl-1,2-dihydronaphthalene-1,2-diol (21±) were synthesized from commercially available starting materials, and their overall yield were 40%, 59%, 28% and 3%, respectively. The compunds were prepared from 1,2-naphthoquinone, 6-methyl-1-tetralone, 5,7-dimethyl-1- tetralone, 1,2-dihydroxybenzene and 2,3-dimethyl-1,3-butadiene, and oxidation was performed by using 2-iodoxybenzoic acid (IBX) or Laccase-catalyzed Diels-Alder reaction, following reduction by sodium borohydride (NaBH4) to give the trans-naphthalene dihydrodiols.

Fish bile samples obtained from Atlantic cod (Gadus morhua), exposed to dispersed crude oil, were prepared by de-conjugation, extraction and derivatisation, following standard procedure in order to prepare the samples for GC-MS analysis.