Chemoselective Synthesis of<i>N</i>-Protected Alkoxyprolines under Specific Solvation Conditions
作者:Voichita Mihali、Francesca Foschi、Michele Penso、Gianluca Pozzi
DOI:10.1002/ejoc.201402429
日期:2014.8
N-Protected hydroxyprolines (Hyp) were transformed chemoselectively into alkoxyproline derivatives by direct O-alkylation. The starting Hyp was transformed into the corresponding dianion in a mixture of dimethyl sulfoxide and tetrahydrofuran (1:16 v/v) as solvent. Under these conditions, the carboxy-anion showed reduced nucleophilicity because it was specifically solvated, and the more reactive oxy-anion
N-保护的羟脯氨酸 (Hyp) 通过直接 O-烷基化被化学选择性地转化为烷氧基脯氨酸衍生物。在作为溶剂的二甲基亚砜和四氢呋喃 (1:16 v/v) 的混合物中,起始的 Hyp 被转化为相应的二价阴离子。在这些条件下,羧基阴离子显示出降低的亲核性,因为它被特异性地溶剂化,而更具反应性的氧阴离子被选择性地烷基化。N-保护的反-4-烷氧基-、顺-4-烷氧基-和反-3-烷氧基脯氨酸因此以非常高的总产率和立体中心构型的完全稳定性在单个步骤中获得。