Single-Step Synthesis of Racemic Di- and Tripeptides Derived from Unnatural β-Hydroxy and β-Mercapto α-Amino, Acids by the Ugi Reaction
作者:M. Hatam、D. Tehranfar、J. Martens
DOI:10.1055/s-1994-25535
日期:——
An efficient single-step selective synthesis of oligopeptide analogues, which contain amino acid analogues and are derivatives of 3-thiazolidines and 3-oxazolidine, through the use of hydrochloric acid as the protecting agent is described. These compounds are prepared based on the Ugi four component condensation (4CC) reaction.
Concept of Improved Rigidity: How to Make Enantioselective Hydrophosphonylation of Cyclic Imines Catalyzed by Chiral Heterobimetallic Lanthanoid Complexes Almost Perfect
The catalytic and enantioselective hydrophosphonylation of cyclic iminesusing cyclic phosphites is described for the first time. In contrast to the application of acyclic phosphites, significant improvements are presented arising from the concept of improved rigidity by utilization of cyclic phosphites in the lanthanoid BINOL complex catalyzed hydrophosphonylation of 3-thiazolines. Cyclic phosphites
首次描述了使用环亚磷酸酯催化的环亚胺催化和对映选择性的氢膦酰化反应。与无环亚磷酸酯的应用相反,通过在镧系元素的BINOL配合物催化3-噻唑啉的氢膦酰化反应中利用环状亚磷酸酯提高了刚性,提出了显着改进。环状亚磷酸酯在催化循环中显示出一定的改进作用。研究了诸如催化剂和亚磷酸酯的浓度之类的参数对催化的影响以及取代基对起始原料的影响。以高达99%ee的出色光学纯度和高达99%的高化学产率合成了具有药理学意义的噻唑烷基膦酸酯。所需的催化剂量减少到2.5mol%。使用催化体系“ 2.5 mol%(S)-YbPB / 2.5当量的亚磷酸酯/ 50摄氏度/ 48 h / THF-甲苯(1:7)”可获得涉及环亚磷酸酯的最高反应效率。基于结果,提供了所提出的催化循环的改进。为了比较,将环状亚磷酸酯与手性钛催化剂用于氢膦酰基化。
Highly diastereoselective hydrophosphonylation of cyclic imines using BINOL as source of chirality
The first highly diastereoselective (dr up to > 95:5) hydrophosphonylation of heterocyclic imines by a chiral phosphorus nucleophile is introduced. Addition of binaphthol ester of phosphorus acid towards BF3-activated 3-thiazolines gives the corresponding (aR*,4R*)-4-thiazolidinylphosphonates almost exclusively as elucidated by X-ray analysis. (C) 2000 Elsevier Science Ltd. All rights reserved.
Thiel et al., Justus Liebigs Annalen der Chemie, 1958, vol. 611, p. 131,137
作者:Thiel et al.
DOI:——
日期:——
Diastereoselective Lewis acid mediated hydrophosphonylation of heterocyclic imines: a stereoselective approach towards α-amino phosphonates
of new chiral α-amino phosphonates by the Lewisacidmediated addition of bisesters of phosphonic acid to 3-thiazolines (2,5-dihydro-1,3-thiazoles), is described. The diastereoselectivity of the reaction using chiral reactants was systematically investigated. The chiral BINOL-phosphonate 1 was found to be a highly stereoselective phosphonylating agent towards 3-thiazolines. Structural aspects of the