Stereocontrolled construction of rigid tricyclic bis(α-amino acid) derivatives by Ru(Ii)-catalyzed cascade and Diels–Alder reactions
作者:Jon Efskind、Christian Römming、Kjell Undheim
DOI:10.1039/b103254m
日期:2001.10.11
In the preparation of rigid and annulated tricyclic bis(α-amino acid) derivatives the key construction was effected by a Ru(II)-catalyzed RCM cascade reaction of gem-dienynes. The substrates were available by stepwise and stereocontrolled alkynylations and alkenylations of (2R)-2,5-dihydro-2-isopropyl-3,6-dimethoxypyrazine. The cascade products were bis-heterospiranes or symmetrical or unsymmetrical bis(α-amino acid) derivatives. Tricyclic DielsâAlder adducts were formed between diethyl acetylenedicarboxylate and the diene cascade products. Oxidative aromatization provided rigid tricyclic bis(α-amino acid) derivatives. X-Ray analysis was used to verify configurational assignments.
在制备刚性和环状三环双(δ-氨基酸)衍生物的过程中,关键的结构是通过 Ru(II)- 催化的 RCM 级联反应来实现的。底物可通过 (2R)-2,5-二氢-2-异丙基-3,6-二甲氧基吡嗪的逐步和立体控制的炔化和烯化反应获得。级联产物为双螺旋环烷或对称或不对称双(δ-氨基酸)衍生物。乙炔二甲酸二乙酯与二烯级联产物之间形成了三环 DielsâAlder 加合物。氧化芳香化反应产生了刚性三环双(δ-氨基酸)衍生物。X 射线分析被用来验证构型分配。