Synthesis, resolution and assignment of absolute configuration of trans 3-amino-1-oxyl-2,2,5,5-tetramethylpyrrolidine-4-carboxylic acid (POAC), a cyclic, spin-labelled β-amino acid
作者:Karen Wright、Laurence Dutot、Michel Wakselman、Jean-Paul Mazaleyrat、Marco Crisma、Fernando Formaggio、Claudio Toniolo
DOI:10.1016/j.tet.2008.02.058
日期:2008.5
absolute configuration of the asymmetric C3, C4 carbons of POAC were assigned from the induced circular dichroism of a flexible biphenyl probe present in the terminally protected dipeptide derivatives Boc-Bip-(+)-POAC-OMe and Boc-Bip-(−)-POAC-OMe (Bip, 2′,1′:1,2;1″,2″:3,4-dibenzcyclohepta-1,3-diene-6-amino-6-carboxylic acid). This assignment was confirmed by X-ray diffraction analysis of the diastereomeric
通过常规方法制备的外消旋反式3-(9-芴基甲氧基羰基氨基)-1-氧基-1,2,2,5,5-四甲基吡咯烷-4-羧酸(Fmoc-POAC-OH)经(a R)酯化后拆分-2,2'-二羟基-1,1'-联萘基。通过结晶/色谱法分离获得的非对映体单酯Fmoc-(±)-反式-POAC- O-(a R)-联萘酚,并通过对芳基酯官能进行皂化除去手性助剂,提供了两种对映体(+)-( 3 R,4 R)-Fmoc-POAC-OH和(-)-(3 S,4 S)-Fmoc-POAC-OH。不对称C 3,C 4的绝对构型POAC的碳是由存在于末端保护的二肽衍生物Boc-Bip-(+)-POAC-OMe和Boc-Bip-(-)-POAC-OMe中的柔性联苯探针的诱导圆二色性分配的(Bip,2' ,1':1,2; 1'',2'':3,4-dibenzcyclohepta-1,3-diene-6-amino-6-羧酸)。该分配