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在研究雪胆甲素(1)的过程中,试图用氢氧化钾的乙醇溶液进行皂解,以期得到雪胆乙素(2)。但所得为另一物质,与甲素、乙素的突出区别是具有紫外光谱270nm(3.98)与红外光谱1615cm~(-1)(强)等峰,推测可能产生了β-二羰体系的烯醇式结构(-CO-C=C-OH),~1H核磁共振谱82.24(3H,s)表明仍保留乙酰基。雪胆甲素(1)为叔醇酯,皂解反应的速度较低。但12及23位碳在碱性条件下均易形成碳负离子,其中23位的碳负离子对乙酰羰基进行分子内部的进攻(形成五元环中间体),可远超过皂解的反应速度,从而使乙酰基由氧向碳转移。结合光谱数据,可以判定产
In the study of hectaretin (1), an attempt was made to soapize with a solution of potassium hydroxide in ethanol to obtain hectare (2). However, the obtained product is another substance with the prominent difference from A and B in that it has the peaks at 270 nm (3.98) and 1615 cm -1 (strong) in the infrared spectrum, presumably resulting in the formation of β-dicarbonyl ene The alcoholic structure (-CO-C = C-OH), ~ 1HNMR 82.24 (3H, s) indicates that acetyl groups remain. Snow hyacinth A (1) for the tertiary alcohol ester, soap reaction speed lower. However, both carbons 12 and 23 are easy to form carbanions under alkaline conditions. The carbanions at position 23 attack intramolecular acetyl-carbonyls (forming five-membered ring intermediates), which can greatly exceed the reaction speed of soap hydrolysis The acetyl group is transferred from oxygen to carbon. Combined with the spectral data, you can determine the production