Specific Solvation as a Tool for theN-Chemoselective Arylsulfonylation of Tyrosine and (4-Hydroxyphenyl)glycine Methyl Esters
作者:Michele Penso、Domenico Albanese、Dario Landini、Vittoria Lupi、Giovanni Tricarico
DOI:10.1002/ejoc.200300366
日期:2003.12
The methyl esters of L-tyrosine and D-(4-hydroxyphenyl)glycine were directly transformed into the corresponding 2-arylsulfonamido esters with arylsulfonyl chlorides, without protecting the phenolic hydroxy group. The reaction is conducted in a THF/DMF (8:1) mixture as solvent, and using lyophilized solid sodium carbonate as base. The N-arylsulfonylation takes place with good yields (62−85%) in a chemoselective
L-酪氨酸甲酯和D-(4-羟基苯基)甘氨酸甲酯与芳基磺酰氯直接转化为相应的2-芳基磺酰氨基酯,无需保护酚羟基。该反应在作为溶剂的 THF/DMF (8:1) 混合物中进行,并使用冻干的固体碳酸钠作为碱。N-芳基磺酰化以化学选择性方式以良好的产率(62-85%)发生,没有立体碳中心的外消旋化。DMF(2.6 mol/mol 氨基酯)特异性地溶解形成的 N,O-二价阴离子的氧原子,降低其亲核性并显着提高 N-取代的化学选择性。相反,在没有高度配位添加剂的情况下,酚盐阴离子与 2-氨基竞争亲核攻击,而 N、O-二磺酰酯以相应的产率生产。(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)