Enol aldehydes are one type of key degradation and metabolic intermediates from a group of corticosteroids containing the 1,3-dihydroxyacetone side chain on their D-rings, such as betamethasone, dexamethasone, beclomethasone, and related compounds. The formation of enol aldehydes from these corticosteroids is via acid-catalyzed beta-elimination of water from the side chain, a process known as Mattox rearrangement. It was recently reported by our group that enol aldehydes could also be formed directly from the corresponding 17,21-diesters of these corticosteroids but only under alkaline condition, which was proposed to follow a variation pathway of the original Mattox rearrangement. In this paper, we report the results of a comparative study of enol aldehyde formation from these structurally similar corticosteroids (under the original acidic Mattox condition) and their 17,21-diesters (under the alkaline Mattox variation condition), respectively. In general, enol aldehydes were found to be formed under both conditions; however, the ratios of the E- and Z-isomers of the enol aldehyde were different in each case. The only exception was beclomethasone 17,21-diester under the alkaline condition, where a competing elimination of HCl from the 9,11-positions became predominant. These results can be explained by their structural differences with regard to the Mattox mechanism and its variation pathway. Lastly, solvent effect under acidic condition was studied between an aprotic and a protic solvent and the result suggests that enol aldehyde formation is greatly favored in an aprotic environment.

中文翻译：

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在酸性和碱性条件下由倍他米松，地塞米松，倍氯米松及相关化合物形成烯醇醛的比较研究。

烯醇醛是一组在其D环上含有1,3-二羟基丙酮侧链的皮质类固醇的关键降解和代谢中间体的一种，例如倍他米松，地塞米松，倍氯米松和相关化合物。由这些皮质类固醇形成烯醇醛是通过酸催化侧链水分的β-消除，这一过程称为Mattox重排。我们的小组最近报道，烯醇醛也可以直接由这些皮质类固醇的相应的17,21-二酯形成，但仅在碱性条件下才被提议，这是遵循原始Mattox重排的变化途径。在本文中，我们报告了分别由这些结构相似的皮质类固醇（在原始酸性Mattox条件下）和它们的17,21-二酯（在碱性Mattox变异条件下）形成烯醇醛的比较研究结果。通常，发现在两种条件下都会形成烯醇醛。然而，烯醇醛的E-和Z-异构体的比例在每种情况下是不同的。唯一的例外是在碱性条件下的倍氯米松17,21-二酯，其中竞争性地从9,11-位消除HCl成为主要问题。这些结果可以用它们在Mattox机理及其变异途径方面的结构差异来解释。最后，