title: Synthesis of pyridine-carboxylate derivatives of hydroxysteroids for liquid chromatography-electrospray ionization-mass spectrometry.
abstract: Synthesis and liquid chromatography-electrospray ionization-mass spectrometric (LC-ESI-MS) behaviors of the picolinoyl, 6-methylpicolinoyl, nicotinoyl, 2-methoxynicotinoyl and isonicotinoyl derivatives of the hydroxysteroids estrone, estradiol, 3beta-hydroxyandrost-5-en-17-one (dehydroepiandrosterone) and testosterone in positive mode were investigated. Each steroid was converted to the corresponding pyridine-carboxylate derivative by the acyl chloride method or the mixed anhydride method using the corresponding free acids and 2-methyl-6-nitrobenzoic anhydride; in each case, the latter method principally gave a better yield. The pyridine-carboxylate derivative of each steroid exhibited a clear single peak in liquid chromatography with a reversed phase column and CH(3)CN-0.1% CH(3)COOH as a mobile phase. The positive-ESI-mass spectra of the picolinoyl, 6-methylpicolinoyl and 2-methoxynicotinoyl derivatives showed a predominance of [M+H](+), whereas [M+H+CH(3)CN](+) was observed with high intensity in the nicotinoyl and isonicotinoyl derivatives. Even in the case of estradiol, with its two hydroxyl groups, a single charged ion of [M+H](+) or [M+H+CH(3)CN](+) was observed in the positive-ESI-mass spectrum of each derivative. The results revealed that picolinoyl derivatization is a simple and versatile method suitable for the sensitive and specific determination of hydroxysteroids by LC-ESI-MS (selected reaction monitoring).
authors.affiliation: Faculty of Pharmaceutical Science, Tohoku Pharmaceutical University, 4-1 Komatsushima 4-Chome, Aoba-ku, Sendai 981-8558, Japan. kyama@tohoku-pharma.ac.jp
authors.forename: Kouwa
authors.initials: K
authors.lastname: Yamashita
authors.forename: Sayuri
authors.initials: S
authors.lastname: Kobayashi
authors.forename: Satoshi
authors.initials: S
authors.lastname: Tsukamoto
authors.forename: Mitsuteru
authors.initials: M
authors.lastname: Numazawa
mesh_terms: D002138:Calibration; D002264:Carboxylic Acids / Q000138:chemical synthesis* / Q000737:chemistry; D002853:Chromatography, Liquid / Q000379:methods*; D004355:Drug Stability; D006914:Hydroxysteroids / Q000032:analysis* / Q000737:chemistry*; D011725:Pyridines / Q000138:chemical synthesis* / Q000737:chemistry; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D002264:Carboxylic Acids; D006914:Hydroxysteroids; D011725:Pyridines