药物分子中的手性中心增加了合成,代谢,药理和临床研究的复杂性,另一个问题是可能缺乏构型稳定性。在这里,我们报告了用作模型化合物的七个5-单取代的氢化物(=咪唑烷-2,4-二酮)的氘化和外消旋化作用的详细动力学和机理研究。使用1测定了氘化和外消旋反应的1 H-NMR和手性RP-HPLC,反应速率和活化的热力学参数。通过在AM1水平上进行的分子轨道计算获得了去质子化的能量。已证明5-单取代乙内酰脲的氘化和外消旋化遵循一般的碱催化。氘化和消旋化的相同(在实验误差范围内)活化能表明,这两个反应共享相同的反应机理。氘的拟一级反应速率常数约为外消旋化的拟一级速率常数的事实表明,氘的发生是随着构型的反转而发生的。观察到这7种化合物之间的反应速率差异非常大,表明取代基对手性稳定性的显着影响。这些结果,加上观察到的小同位素效应,以及实验活化能与计算的去质子能之间的比较表明,S E 2推挽机制,用于5-单取代乙内酰脲的外消旋作用。
Dibutylphosphate (DBP) mediated synthesis of cyclic N,N′-disubstituted urea derivatives from amino esters: a comparative study
作者:Sumit K. Agrawal、Manisha Sathe、A.K. Halve、M.P. Kaushik
DOI:10.1016/j.tetlet.2012.08.083
日期:2012.11
The N,N′-disubstituted urea derivatives such as amino acid hydantoins and dihydrouracil derivatives were prepared starting from natural and unnatural amino acid esters using dibutylphosphate (DBP). During the attempted synthesis of N-heterocycles with larger than six-membered rings containing the N,N′-disubstituted urea functionalities, three unexpected products namely squamolone, N-methyl pyrrolidine-2-one
Revisiting the Urech Synthesis of Hydantoins: Direct Access to Enantiopure 1,5-Substituted Hydantoins Using Cyanobenziodoxolone
作者:Nina Declas、Franck Le Vaillant、Jerome Waser
DOI:10.1021/acs.orglett.8b03843
日期:2019.1.18
synthesis of enantiopure 1,5-substituted hydantoins was developed using a hypervalent iodine cyanation reagent (cyanobenziodoxolone, CBX) as a source of electrophilic carbon. Starting from inexpensive commercially available enantiopure protected amino acids, the method allowed the synthesis of various hydantoins without epimerization. Formation of hydantoins from dipeptides was also possible, but partial
Mechanochemical Preparation of Hydantoins from Amino Esters: Application to the Synthesis of the Antiepileptic Drug Phenytoin
作者:Laure Konnert、Benjamin Reneaud、Renata Marcia de Figueiredo、Jean-Marc Campagne、Frédéric Lamaty、Jean Martinez、Evelina Colacino
DOI:10.1021/jo5017629
日期:2014.11.7
eco-friendly preparation of 5- and 5,5-disubstituted hydantoins from various amino ester hydrochlorides and potassium cyanate in a planetary ball-mill is described. The one-pot/two-step protocol consisted in the formation of ureido ester intermediates, followed by a base-catalyzed cyclization to hydantoins. This easy-handling mechanochemical methodology was applied to a large variety of α- and β-amino esters
Hydantoin formation from alaninamide derivatives. Reactions with 5-amino-5-methylhydantoin
作者:Giancarlo Zanotti、Francesco Pinnen
DOI:10.1002/jhet.5570180829
日期:1981.12
The influence of the α-substitution on hydantoin formationfrom urethan protected alaninamide derivatives is investigated. Several 5-methyl-5-substituted hydantoins, obtained from 5-amino-5-methylhydantoin, are described.
Thermolysis reactions of N-alkyl-N′-CBZ amino acid amides. A route to substituted imidazolidine-2,4-diones
作者:Marc Casale、David A. Hunt
DOI:10.1016/j.tetlet.2018.01.086
日期:2018.3
Reaction of N-alkyl-N′-CBZ aminoacid amides under microwave conditions in water and in the presence of an acid catalyst results in the formation of N-substituted imidazolidine-2,4-diones in good yields.