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首页> 外文期刊>European journal of organic chemistry >Evaluation of Protecting Groups for 3-Hydroxyisoxazoles - Short Access to 3-Alkoxyisoxazole-5-carbaldehydes and 3-Hydroxyisoxazole-5-carbaldehyde, the Putative Toxic Metabolite of Muscimol
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Evaluation of Protecting Groups for 3-Hydroxyisoxazoles - Short Access to 3-Alkoxyisoxazole-5-carbaldehydes and 3-Hydroxyisoxazole-5-carbaldehyde, the Putative Toxic Metabolite of Muscimol

机译：评估3-羟基异恶唑的保护基团-短距离获得3-麝香酚的假定有毒代谢产物3-烷氧基异恶唑-5-甲醛和3-羟基异恶唑-5-甲醛

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摘要

The regioselectivity of the 3-hydroxyisoxazole-5-ester 1 is studied with respect to O- versus N-alkylation. 3-O-Alkyl products 3 are highly favoured with benzyl, benzhydryl, and allyl bromide (≥ 91:9), in contrast to known uses of 5-alkyl-3-hydroxyisoxazoles or when methylation with diazomethane (or methyl iodide) is effected. Methoxymethylation leads to the N-substituted isoxazolinone 3e only. On reduction with DIBAH, the esters 2 afford 3-O-protected 3-hydroxyisoxazole-5-carbaldehydes 4 (75-98%). For removal of the benzyl protecting groups, three variations (HBr/HOAc, H_2/Pd/BaSO_4, NBS/AIBN) were found useful with 5-ester, 5-formyl, and 5-hydroxymethyl derivatives. The free 3-hydroxy-5-carbaldehyde 9, the putative toxic metabolite of the GABA agonist muscimol, is prepared accordingly. The O-protected 3-hydroxyisoxazole-5-carbaldehydes 5 constitute versatile intermediates in various routes to analogues of CNS-active amino acids and can now be obtained in a highly efficient manner.
机译：关于O-对N-烷基化，研究了3-羟基异恶唑-5-酯1的区域选择性。与5-烷基-3-羟基异恶唑的已知用途或与重氮甲烷（或碘代甲烷）进行甲基化反应相反，3-O-烷基产品3非常受苄基，苯甲酰基和烯丙基溴（≥91：9）青睐。 。甲氧基甲基化仅导致N-取代的异恶唑啉酮3e。用DIBAH还原后，酯2得到3-O-保护的3-羟基异恶唑-5-甲醛4（75-98％）。为了除去苄基保护基，发现三种变体（HBr / HOAc，H_2 / Pd / BaSO_4，NBS / AIBN）可用于5-酯，5-甲酰基和5-羟甲基衍生物。相应地制备了游离的3-羟基-5-甲醛9，它是GABA激动剂麝香酚的有毒代谢产物。 O-保护的3-羟基异恶唑-5-甲醛在各种途径中构成了中枢神经系统活性氨基酸类似物的通用中间体，现在可以以高效的方式获得。

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