Choughuley A S, Subbaraman A S, Kazi Z A, Chadha M S
Biosystems. 1977 Sep;9(2-3):73-80. doi: 10.1016/0303-2647(77)90014-4.
When uracil is reacted with formaldehyde and formic acid in dilute aqueous solutions at 100-140 degrees C, 5-hydroxymethyluracil (5-HMU), methylenebiuracil (MBU) and thymine are formed. It has been shown that 5-HMU is an intermediate in the formation of MBU and thymine. In the presence of formic acid, 5-HMU gives MBU, thymine and in some cases uracil. The formation of thymine is generally favoured under acidic conditions, although small amounts of this base could also be obtained when the reactions were carried out under mildly basic conditions. A hydride ion transfer mechanism is suggested for some of these reactions. These results have relevance to the formation of thymine under prebiotic conditions.
当尿嘧啶在100 - 140摄氏度的稀水溶液中与甲醛和甲酸反应时，会生成5 - 羟甲基尿嘧啶（5 - HMU）、亚甲基双尿嘧啶（MBU）和胸腺嘧啶。已表明5 - HMU是MBU和胸腺嘧啶形成过程中的中间体。在甲酸存在下，5 - HMU会生成MBU、胸腺嘧啶，在某些情况下还会生成尿嘧啶。尽管在温和碱性条件下进行反应时也能获得少量胸腺嘧啶，但通常在酸性条件下更有利于胸腺嘧啶的形成。有人提出其中一些反应存在氢负离子转移机制。这些结果与在生命起源前条件下胸腺嘧啶的形成有关。
