Synthesis of the First Axially Dissymmetric,Cα,α-Disubstituted Glycine Containing a Crown Ether Receptor, and the Conformational Preferences of a Model Peptide
作者:Jean-Paul Mazaleyrat、Yolaine Goubard、Maria-Vittoria Azzini、Michel Wakselman、Cristina Peggion、Fernando Formaggio、Claudio Toniolo
DOI:10.1002/1099-0690(200204)2002:7<1232::aid-ejoc1232>3.0.co;2-i
日期:2002.4
esterification and Nα-Boc protection, gave (RS)-, (R)- and (S)-Boc-[HO]2-Bip-OMe. Cyclization with Cs2CO3/DMF and pentaethylene glycol ditosylate afforded the crown-carrier Cα,α-disubstituted glycines (RS)-Ia, (R)-Ia and (S)-Ia, possessing only axial dissymmetry. Although (R)-Ia and (S)-Ia are enantiomerically stable in solution at 110 °C, they were obtained with only 64% ee and 48% ee, respectively, because
外消旋和对映体富集的 Nα-保护的甲基 6-amino-1,11-(20-crown-6)-6,7-dihydro-5H-dibenzo[a,c]cycloheptene-6-carboxylates (Boc-[20-C -6]-Bip-OMe) (RS)-Ia、(R)-Ia 和 (S)-Ia 是通过甘氨酸叔丁酯的 4-氯亚苄基衍生物的相转移二烷基化合成的,具有外消旋和拆分(两种对映异构体)2,2'-双(溴甲基)-6,6'-二甲氧基-1,1'-联苯用作烷化剂。将所得 (RS)-、(R)- 和 (S)-H-[MeO]2-Bip-OtBu 脱甲基化,然后进行酯化和 Nα-Boc 保护,得到 (RS)-、(R)- 和 ( S)-Boc-[H2O]2-Bip-OMe。用 Cs2CO3/DMF 和五乙二醇二甲苯磺酸环化得到仅具有轴向不对称性的冠载体 Cα,α-二取代甘氨酸 (RS)-Ia、(R)-Ia