SYNTHESIS AND CHARACTERIZATION OF RING-B CHOLESTANE 3-OXETANONES
SYNTHESIS AND CHARACTERIZATION OF RING-B CHOLESTANE 3-OXETANONES
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DOI：
10.1021/jo01270a057
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发表时间：
1968-01-01
影响因子：
3.6
通讯作者：
SCOTTSHO.T
中科院分区：
文献类型：
--
作者：
ROWLAND, AT;BENNETT, PJ;SCOTTSHO.T
研究了5，7/3-环氧-6-氧代-5/3-胆甾烷的合成。这些化合物是高度取代的3-氧杂环丁烷酮环系的实例，由C-3-取代的7 α-溴-5/3-羟基-6-氧代胆甾烷制备。当用氢氧化钾甲醇溶液在二甲基亚砜中处理时，带有3/3取代基（羟基、乙酰氧基或苯甲酰基氧基）的溴酮以良好的产率（> 70%）转化为3/3-羟基-5，7/3-环氧-5/3-胆甾烷-6-酮（7a）。在这些条件下，溴酮的C-3差向异构体以及3-脱氧溴酮（IIb）以非常低的产率转化为相应的氧杂环丁酮。使用碳酸氢钾水溶液代替甲醇氢氧化钾作为碱导致酰氧基保留，但氧杂环丁酮的产率较低。推测提出有关的转换机制，特别是关于在A/B类固醇环系统的反应过程中发生的构象变化的性质。通过NMR光谱检查n-溴酮和氧杂环丁酮，以准确表征起始材料和产物的结构。虽然进入3 η-取代的氧杂环丁烷酮系列受到从3 η-取代的η-溴酮获得的这些化合物的低产率的阻碍，但是已经开发了将3/3-羟基氧杂环丁烷酮（7a）转化为其3 η差向异构体（IOa）以及3-脱氧氧杂环丁烷酮12的简单方法。
The synthesis of 5, 7/3-epoxy-6-oxo-5/3-cholestanes has been investigated. These compounds, which are exam-ples of highly substituted 3-oxetanone ring systems, were prepared from C-3-substituted 7a-bromo-5/3-hydroxy-6-oxocholestanes. When treated with methanolic potassium hydroxide in dimethyl sulfoxide, the bromo ketones bearing 3/3 substituents (hydroxy, acetoxy, or benzoyloxy) were converted in good yields (> 70%) into 3/3-hydroxy-5, 7/3-epoxy-5/3-cholestan-6-one (7a). The C-3 epimers of the bromo ketones, as well as the 3-desoxybromo ketone (lib), were transformed in very poor yields into the corresponding oxetanones under these conditions. The use of aqueous potassium bicarbonate as the base instead of methanolic potassium hydroxide resulted in retention of acyloxy groups but gave lower yields of oxetanones. Speculation is raised concerning the mechanism of the transformation, especially regarding the nature of the conformational change in the A/B steroid ring system that occurs during the reaction. The «-bromo ketones and oxetanones were examined by nmr spectroscopy in order to characterize accurately the structure of starting materials and products. Although entrance into the 3 «-substituted oxetanone series was hindred by the poor yields of these compounds that were obtained from the 3 «-substituted «-bromo ketones, a simple method of converting the 3/3-hydroxyoxetanone (7a) into its 3 «epimer (10a), and also to the 3-desoxyoxetanone 12, has been developed.