Department of Pharmaceutical Chemistry, School of Pharmacy, University of California, San Francisco, CA, USA.
Photochem Photobiol. 2011 Jul-Aug;87(4):802-17. doi: 10.1111/j.1751-1097.2011.00932.x. Epub 2011 May 10.
Previous studies of the photochemical reaction of 1-methylthymine (MeT) in frozen aqueous solution have indicated that four cyclobutane type dimers are formed. We have restudied this system and have found that, in addition to cyclobutane dimers, both a (5-4) adduct and a (6-4) adduct of MeT are formed in significant amounts. Upon standing in aqueous solution, the (5-4) adduct is susceptible to reaction to form an isomeric form of the parent adduct, possibly via ring-opening and closure reactions at C-6 of the saturated pyrimidine ring component of the adduct. Irradiation of each of these three adducts with UVB light produces a pair of Dewar-type adducts. The nine products were individually characterized by mass spectrometry, proton NMR spectroscopy and UV spectroscopy. A less comprehensive study showed that irradiation of thymidine in frozen aqueous solution produces a diastereomeric pair of (5-4) adducts, along with the previously known diastereomeric pair of (6-4) adducts.
先前对 1-甲基胸腺嘧啶（MeT）在冷冻水溶液中的光化学反应的研究表明，形成了四种环丁烷型二聚体。我们重新研究了该体系，发现除了环丁烷二聚体外，还大量形成了（5-4）加合物和（6-4）加合物。在水溶液中放置时，（5-4）加合物易发生反应，形成母体加合物的异构形式，可能通过加合物饱和嘧啶环成分的 C-6 的开环和闭环反应。用 UVB 光照射这三种加合物中的每一种都会产生一对 Dewar 型加合物。这九个产物分别通过质谱、质子 NMR 光谱和 UV 光谱进行了表征。一项不那么全面的研究表明，在冷冻水溶液中辐照胸腺嘧啶会产生一对非对映异构体的（5-4）加合物，以及先前已知的一对非对映异构体的（6-4）加合物。
