quaternary amino acidderivatives from inexpensive bulk chemicals. In that way highly enantioenriched acyclic α‐amino acids, α‐alkyl proline, and α‐alkyl pyroglutamic acidderivatives could be prepared in diastereomerically pure form. In addition, a unique way is presented to prepare diastereomerically pure bicyclic dipeptides in just two steps from unprotected tertiary α‐amino acids.
描述了作为活化氨基酸衍生物的氮杂内酯的第一次催化不对称共轭加成反应向烯酮的发展和进一步发展。第一代方法是从孤立的氮杂内酯开始的,而第二代方法中的氮杂内酯可以从外消旋的N开始原位生成。苯甲酰化氨基酸。第三个进化阶段可以利用外消旋未保护的α-氨基酸直接形成高度对映体富集和非对映体纯的带掩蔽季铵氨基酸产物,并带有一个附加的叔立体中心。通过使用稳固的平面手性bis-Pd催化剂,布朗斯台德酸(HOAc或BzOH; Ac =乙酰基,Bz =苯甲酰基)和布朗斯台德碱(NaOAc),通过协同活化来实现逐步经济转型。特别是第二代和第三代方法提供了快速而多样化的途径,可从廉价的散装化学品中获得生物学上令人感兴趣的非天然季氨基酸衍生物。这样,可以以非对映体纯形式制备高度对映体富集的无环α-氨基酸,α-烷基脯氨酸和α-烷基焦谷氨酸衍生物。此外,
Catalytic Asymmetric Synthesis of Functionalized α,α-Disubstituted α-Amino Acid Derivatives from Racemic Unprotected α-Amino Acids via in-situ Generated Azlactones
作者:Manuel Weber、Wolfgang Frey、René Peters
DOI:10.1002/adsc.201200085
日期:2012.5.21
Masked and activated highly enantioenriched α,α‐disubstituted α‐amino acids with an additional adjacent stereocenter were formed by a tandem reaction involving five steps using racemic unprotected amino acid substrates. Key step is the 1,4‐addition of in‐situ generated azlactones to a broad number of enones. The products of this step‐economic route can, e.g., be useful for a divergent and rapid access
Organocatalytic Enantioselective Conjugate Addition of Azlactones to Enolizable Linear and Cyclic Enones
作者:Chao-Ming Wang、Jun-An Xiao、Jing Wang、Sha-Sha Wang、Zhao-Xu Deng、Hua Yang
DOI:10.1021/acs.joc.6b01356
日期:2016.9.2
Highly diastereo- and enantioselective conjugateadditions of azlactones to enolizable cyclic and linear enones were conducted by employing proline aryl sulfonamide as the organocatalyst in trifluorotoluene. The conjugate adducts bearing contiguous quaternary and tertiarystereocenters were obtained in moderate to good yields with excellent diastereoselectivities and moderate to good enantioselectivities
Brønsted Acid Catalyzed Highly Diastereoselective Michael-Type Addition of Azlactones to Enones
作者:Eloah P. Ávila、Amanda C. de Mello、Renata Diniz、Giovanni W. Amarante
DOI:10.1002/ejoc.201300076
日期:2013.4
A highly regio- and diastereoselective 1,4-addition of azlactones to enones catalyzed by a Bronsted acid is described. The Michael adducts were prepared in moderate to good yields and with complete control of the relative stereochemistry. In addition, two consecutive stereogenic centers were created, one of which was a quaternary stereocenter. The method was successfully extended to the first highly