Stereoselective synthesis of bicyclic tetrahydrofuran-fused ?-lactams and their conversion into methyl cis-3-aminotetrahydrofuran-2-carboxylates
摘要:
cis-3-Benzyloxy-4-(2-mesyloxyethyl)azetidin-2-ones were shown to be useful starting products for the synthesis of cis-2-oxa-6-azabicyclo[3.2.0]heptan-7-ones in high overall yields and purity upon hydrogenolysis of the benzyl ether substituent followed by intramolecular nucleophilic substitution using sodium hydride in THF. These unconventionally C-fused bicyclic beta-lactams were easily converted into the corresponding methyl cis-3-aminotetrahydrofuran-2-carboxylates via acidic methanolysis. This methodology constitutes a convenient alternative for the known preparation of cis-4,4-dimethy1-2-oxa-6-azabicyclo[3.2.0]heptan-7-ones and methyl cis-3-amino-4,4-dimethyltetrahydrofuran-2-carboxylates, as their 4,4-nor-dimethyl variants are usually considered to be more promising compounds within the field of drug design. (C) 2012 Elsevier Ltd. All rights reserved.
首次评估了通过一氯丙烷还原和相应的β-内酰胺甲磺酸化获得的2-(2-甲氧基氧乙基)氮杂环丁烷对不同亲核试剂的反应性,从而立体选择性地制备了多种新的4-乙酰氧基-,4-羟基-,4-溴-和4-甲酰氧基哌啶。在这些反应过程中,短暂的1-azoniabicyclo [2.2.0]己烷易于经历S N 2型开环,以提供最终的氮杂杂环,这可以通过详细的计算分析加以合理化。该方法构成了已知制备3,4-二取代的5,5-二甲基哌啶的方便替代方法,可轻松获得5,5-去甲二甲基类似物,作为药物化学中的重要模板。此外,顺式通过脱氢溴化然后酸水解,将-4-溴-3-(苯氧基或苄氧基)哌啶精制到哌啶-3-酮骨架中。