Chiral anion recognition using calix[4]arene-based ureido receptors in a 1,3-alternate conformation

• Tereza Horáčková,
• Jan Budka,
• Vaclav Eigner,
• Wen-Sheng Chung,
• Petra Cuřínová and
• Pavel Lhoták

Beilstein J. Org. Chem. 2020, 16, 2999–3007, doi:10.3762/bjoc.16.249

• for N-acetyl-ʟ-phenylalaninate. The structures of some receptors were confirmed by single crystal X-ray analysis. Keywords: anion recognition; calixarene; chiral receptor; complexation; enantiodiscrimination; Introduction The recognition and complexation of anions has become undoubtedly one of the

A review of asymmetric synthetic organic electrochemistry and electrocatalysis: concepts, applications, recent developments and future directions

• Munmun Ghosh,
• Valmik S. Shinde and
• Magnus Rueping

Beilstein J. Org. Chem. 2019, 15, 2710–2746, doi:10.3762/bjoc.15.264

• and Lu investigated the enantioselective electrocarboxylation of 4-methylpropiophenone (27) on a stainless steel cathode in which the enantiodiscrimination was controlled by the nucleophilic quinuclidine nitrogen atom and the -OH group of the inductor alkaloid [35]. Mechanistically, cinchonine (CN

Mechanochemical enzymatic resolution of N-benzylated-β³-amino esters

• Mario Pérez-Venegas,
• Gloria Reyes-Rangel,
• Adrián Neri,
• Jaime Escalante and
• Eusebio Juaristi

Beilstein J. Org. Chem. 2017, 13, 1728–1734, doi:10.3762/bjoc.13.167

• presents a slight decrease in ee compared with the resolution reaction using the milled enzyme under solvent-free conditions. This observation suggests that the LAG additive increases to some extent the degree of denaturation of the enzyme, reducing the enantiodiscrimination (ee = 91%) although maintaining

• particular amount of enzyme can catalyze a larger amount of substrate, even up to nine equivalents, without loss of enantiodiscrimination (Table 4, entry 4). It appears that this high efficiency is a consequence of the highly-concentrated medium that is generated under solvent-free mechanochemical conditions

Molecular recognition of N-acetyltryptophan enantiomers by β-cyclodextrin

• Spyros D. Chatziefthimiou,
• Mario Inclán,
• Petros Giastas,
• Athanasios Papakyriakou,
• Konstantina Yannakopoulou and
• Irene M. Mavridis

Beilstein J. Org. Chem. 2017, 13, 1572–1582, doi:10.3762/bjoc.13.157

• cavity, taking into account that crystal lattice forces may introduce additional and more stringent parameters for the enantiodiscrimination [9][10]. However, the crystallographic structures of diastereomeric complexes of CDs with chiral guest molecules in the literature are scarce. For β-CD with

Addition of H-phosphonates to quinine-derived carbonyl compounds. An unexpected C9 phosphonate–phosphate rearrangement and tandem intramolecular piperidine elimination

• Łukasz Górecki,
• Artur Mucha and
• Paweł Kafarski

Beilstein J. Org. Chem. 2014, 10, 883–889, doi:10.3762/bjoc.10.85

• applied in organo- and metal-assisted catalysis [14][17][18][19][20] and NMR-monitored enantiodiscrimination [21]. According to our knowledge no example of formation of a direct C–P linkage between the quinine backbone and a phosphorus atom has been reported in the literature. Stimulated by this challenge

Synthetic scope and DFT analysis of the chiral binap–gold(I) complex-catalyzed 1,3-dipolar cycloaddition of azlactones with alkenes

• María Martín-Rodríguez,
• Luis M. Castelló,
• Carmen Nájera,
• José M. Sansano,
• Olatz Larrañaga,
• Abel de Cózar and
• Fernando P. Cossío

Beilstein J. Org. Chem. 2013, 9, 2422–2433, doi:10.3762/bjoc.9.280

• )-Binap·AuTFA]2. The alanine-derived oxazolone only reacts with tert-butyl acrylate giving anomalous regiochemistry, which is explained and supported by Natural Resonance Theory and Nucleus Independent Chemical Shifts calculations. The origin of the high enantiodiscrimination observed with maleimides and tert

• most appropriate solvent for these reactions (Table 1, entries 5–9), being the chemical yield high (90%) and the enantiodiscrimination excellent (99% ee). The presence of triethylamine as base is crucial for this transformation, it ensures both of the high conversions and enantioselections (Table 1

• -benzylamide in 76% yield and 96% ee was achieved after 17 h at 25 °C (Scheme 3) [18][19]. The study of the key points of the enantiodiscrimination step and mechanism for the 1,3-DC of azlactone 7aa and NPM can be originated by the presence of a more active homochiral dimer catalyst (Sa,Sa)-3 (X = TFA) with a

Chiral gold(I) vs chiral silver complexes as catalysts for the enantioselective synthesis of the second generation GSK-hepatitis C virus inhibitor

• María Martín-Rodríguez,
• Carmen Nájera,
• José M. Sansano,
• Abel de Cózar and
• Fernando P. Cossío

Beilstein J. Org. Chem. 2011, 7, 988–996, doi:10.3762/bjoc.7.111

• racemic samples identified when either AgSbF6 or AgTFA were employed as co-catalysts (Table 1, entries 19–21). Biphenol derived ligand (R,R)-12 generally furnished good yields of the cycloadduct 5b but with a low enantiodiscrimination (Table 1, entries 22–24). In many examples, although the reactions were

• 0 °C resulting in excellent enantiodiscrimination (99% ee) to the detriment of the reaction time, which had to be increased to 3 days (Table 2, entry 8). The result obtained in this last example was excellent but the enantiomeric excess achieved at room temperature in the reaction performed with (Sa

• enantiodiscrimination of the process. The temperature does not equally affect silver(I) and gold(I) catalysts. The effect of the heterocycle remains crucial in these transformations because, originally, the enantioselectivity of the reaction between methyl benzylideneiminoglycinate and alkyl acrylates failed in the

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

• 18 during complexation. Pyridino crown systems proved to be advantageous for enantiodiscrimination in the extensive studies of Izatt and Bradshaw. Other groups employed the principle for the preparation of other chiral receptors (Figure 12): A series of enantiomerically pure chiral pyridino-18-crown

• ligands and organic ammonium ions monitored by changes in their photophysical properties in acetonitrile [152]. With the enantiomerically pure (R,R)-ligand good binding and enantiodiscrimination in favor of the S-enantiomers of PEA (20b) [150] (Kass = 2.3 × 106 M−1) and NEA (Kass = 1.7 × 106 M−1) over the

• investigated and published in 1998 by the group of Naemura [179]. This system displayed, on investigation by UV–vis spectroscopy in chloroform, a good enantiodiscrimination ability in favor of (R)-phenylalaninol with an ΔR-SΔG = 6.4 kJ mol−1. In succession, Steensma et al. investigated thermodynamic data and

Towards practical biocatalytic Baeyer- Villiger reactions: applying a thermostable enzyme in the gram- scale synthesis of optically- active lactones in a two-liquid- phase system

• Frank Schulz,
• François Leca,
• Frank Hollmann and
• Manfred T. Reetz

Beilstein J. Org. Chem. 2005, 1, No. 10, doi:10.1186/1860-5397-1-10

• poor or even no activity with other compounds. This problem, however, can be considered to be solved as now various genetic tools are at hand with which enantiodiscrimination and the substrate spectrum of an enzyme can be controlled.[36][37][38] Along these lines we recently reported the directed