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
作者:Regine Riess、Michael Schön、Sabine Laschat、Volker Jäger
DOI:10.1002/(sici)1099-0690(199803)1998:3<473::aid-ejoc473>3.0.co;2-v
日期:1998.3
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, H2-Pd/BaSO4, 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
研究了 3-羟基异恶唑-5-酯 1 在 O- 与 N-烷基化方面的区域选择性。3-O-烷基产物 2 受苄基、二苯甲基和烯丙基溴 (≥ 91:9) 的青睐,这与 5-烷基-3-羟基异恶唑的已知用途或使用重氮甲烷(或甲基碘)进行甲基化形成对比. 甲氧基甲基化仅产生 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%)。为了去除苄基保护基团,发现三种变体(HBr/HOAc、H2-Pd/BaSO4、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 3-羟基-5-甲醛 9,即 GABA 激动剂 muscimol 的假定毒性代谢物。