N -Boc 2-乙酰氧基恶唑烷:对映体纯的1,2-二醇的有用前体,通过高度非对映选择性亲核加成反应
摘要:
N -Boc 2-乙酰基恶唑烷是由去氧麻黄碱和苯基甘醇合成的。该制备涉及:(i)将上述β-氨基醇转化为N。-Boc 2-乙氧基羰基恶唑烷,(ii)形成相应的Weinreb酰胺,和(iii)这些酰胺与有机金属试剂之间的反应。这样的非对映异构纯杂环与各种亲核试剂(格林纳德试剂,硼氢化钠和烯丙基硅烷)干净地反应,得到相应的醇。用三氟乙酸处理这些羟基恶唑烷,然后水解和还原中间体α-羟基醛,得到1,2-二醇。在大多数情况下,整体转化表现出完全的非对映选择性,这可以由用于亲核加成的螯合模型来解释。
Diastereoisomerically pure N-Boc 2-acyloxazolidines were synthesized from phenylglyoxal and ethyl glyoxylate. Reaction of these heterocycles with Grignard reagents is highly stereoselective. Homochiral 1,2-diols were ultimately obtained after N-deprotection, hydrolysis and reduction of the intermediate α-hydroxy aldehyde. The asymmetric induction can be explained by a chelated model.
phenylglycinol. This preparation involves: (i) a transformation of the above β-amino alcohols into N-Boc 2-ethoxycarbonyloxazolidines, (ii) the formation of the corresponding Weinreb amides and, (iii) a reaction between these amides and organometallic reagents. Such diastereomerically pure heterocycles react cleanly with various nucleophilic reagents (Grinard reagents, sodium borohydride and allylsilane) to afford
N -Boc 2-乙酰基恶唑烷是由去氧麻黄碱和苯基甘醇合成的。该制备涉及:(i)将上述β-氨基醇转化为N。-Boc 2-乙氧基羰基恶唑烷,(ii)形成相应的Weinreb酰胺,和(iii)这些酰胺与有机金属试剂之间的反应。这样的非对映异构纯杂环与各种亲核试剂(格林纳德试剂,硼氢化钠和烯丙基硅烷)干净地反应,得到相应的醇。用三氟乙酸处理这些羟基恶唑烷,然后水解和还原中间体α-羟基醛,得到1,2-二醇。在大多数情况下,整体转化表现出完全的非对映选择性,这可以由用于亲核加成的螯合模型来解释。