BINOL as a chiral element in mechanically interlocked molecules

• Matthias Krajnc and
• Jochen Niemeyer

Beilstein J. Org. Chem. 2022, 18, 508–523, doi:10.3762/bjoc.18.53

• )-38, featuring the BINOL unit on the axle, does not allow for higher stereoselectivities (19% ee), but interestingly gives the other product enantiomer as the main product (see Figure 9). In 2016, Takata and co-workers reported a pyridine-based rotaxane catalyst for the O-acylative asymmetric

The asymmetric Henry reaction as synthetic tool for the preparation of the drugs linezolid and rivaroxaban

• Martin Vrbický,
• Karel Macek,
• Jaroslav Pochobradský,
• Jan Svoboda,
• Miloš Sedlák and
• Pavel Drabina

Beilstein J. Org. Chem. 2022, 18, 438–445, doi:10.3762/bjoc.18.46

• oral anticoagulants). All these human drugs can be considered as modern medicaments, which were developed and approved during the past three decades [8]. The chirality of the mentioned oxazolidine-2-ones is a crucial factor for their therapeutic effect, because only a single enantiomer affords the

• desired biological activity. Hence, only the S-enantiomer of rivaroxaban (2) (sold under trade name Xarelto®) exhibits a strong inhibitory activity against coagulant factor Xa, whereas the R-enantiomer is almost inactive (IC50 = 0.7 nM for S vs 2300 nM for R) [7]. Similarly, in the case of the oxazolidine

• enantioselectivity was achieved with the copper(II) complexes of ligands Ia, IIa, IIIa, and IV. Fortunately, these catalysts provided the R-enantiomer of nitroaldol 21 as the major product, which can be subsequently transformed to S-linezolid (1) (the active stereoisomer). On the other hand, the catalysts derived

Organocatalytic asymmetric nitroso aldol reaction of α-substituted malonamates

• Ekta Gupta,
• Narendra Kumar Vaishanv,
• Sandeep Kumar,
• Raja Krishnan Purshottam,
• Ruchir Kant and
• Kishor Mohanan

Beilstein J. Org. Chem. 2022, 18, 217–224, doi:10.3762/bjoc.18.25

• on the screening of various bifunctional H-bonding catalysts, and in this regard, the reaction catalyzed by quinine-derived thiourea catalyst 3b furnished the product 4a in 55% yield and 71% ee (Table 1, entry 5). The other enantiomer was obtained when the reaction was carried out using the

Synthesis and late stage modifications of Cyl derivatives

• Phil Servatius and
• Uli Kazmaier

Beilstein J. Org. Chem. 2022, 18, 174–181, doi:10.3762/bjoc.18.19

• approach, 1 was mono-O-allylated to 2 under similar conditions reported previously for monobenzylation (Scheme 3) [50]. Iodination (3) and subsequent elimination of the iodide with zinc dust gave allylic alcohol 4 as a single enantiomer, which was esterified with Boc-protected glycine to allyl ester 5

Unsaturated fatty acids and a prenylated tryptophan derivative from a rare actinomycete of the genus Couchioplanes

• Shun Saito,
• Kanji Indo,
• Naoya Oku,
• Hisayuki Komaki,
• Masashi Kawasaki and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2021, 17, 2939–2949, doi:10.3762/bjoc.17.203

• -octadienoic acid (5), and one prenylated tryptophan derivative, 6-(3,3-dimethylallyl)-N-acetyl-ʟ-tryptophan (6). The enantiomer ratio of 4 was determined to be approximately S/R = 56:44 by a recursive application of Trost’s chiral anisotropy analysis and chiral HPLC analysis of its methyl ester. Compounds 1–5

• between the diastereomer pairs. The enantiomer ratio of 4 was estimated to be S/R = 56:44 or near by chiral phase HPLC analysis of 4' on a cellulose tribenzoate-coated silica gel column (Figure 4). Thus, 4 was concluded to be an enantiomeric mixture of (2E,4E)-7-hydroxy-2,4-dimethyl-2,4-octadienoic acid

• with an approximate enantiomer ratio of S/R = 56:44. The 1H and 13C NMR spectra of 5 were quite similar to those of 4 (Table 1 and Table 2), except for the lack of the oxymethine proton resonance and replacement of the doublet methyl resonance by a singlet signal with a six-proton intensity. These

Biological properties and conformational studies of amphiphilic Pd(II) and Ni(II) complexes bearing functionalized aroylaminocarbo-N-thioylpyrrolinate units

• Samet Poyraz,
• Samet Belveren,
• Sabriye Aydınoğlu,
• Mahmut Ulger,
• Abel de Cózar,
• Maria de Gracia Retamosa,
• Jose M. Sansano and
• H. Ali Döndaş

Beilstein J. Org. Chem. 2021, 17, 2812–2821, doi:10.3762/bjoc.17.192

• ligand rotamers were considered during the optimization process. Only one enantiomer was selected for running the calculations for simplicity. The obtained results are gathered in Figure 1 and Figure 2. These calculations show that for ligands L1 and L3, conformer A and conformer B, resulting from a free

Highly stereocontrolled total synthesis of racemic codonopsinol B through isoxazolidine-4,5-diol vinylation

• Lukáš Ďurina,
• Anna Ďurinová,
• František Trejtnar,
• Ľuboš Janotka,
• Lucia Messingerová,
• Jana Doháňošová,
• Ján Moncol and
• Róbert Fischer

Beilstein J. Org. Chem. 2021, 17, 2781–2786, doi:10.3762/bjoc.17.188

• were inactive towards the examined α-glucosidases. The enantiomer of 2 was the only one that still exhibited inhibitory activity against yeast α-glucosidase [2]. To our knowledge, the sole total synthesis of (−)-codonopsinol B and similar hydroxylated pyrrolidines to date was reported in the above

• )-enantiomer [18]. We have used ᴅʟ-proline for three reasons: first, it provides the target compounds 1 and 2 in their racemic form, second, it is able to catalyze the conjugate addition between N-EWG-protected hydroxylamines and enals effectively, and third, based on our experience, the products obtained by

Synthetic strategies toward 1,3-oxathiolane nucleoside analogues

• Umesh P. Aher,
• Dhananjai Srivastava,
• Girij P. Singh and
• Jayashree B. S

Beilstein J. Org. Chem. 2021, 17, 2680–2715, doi:10.3762/bjoc.17.182

• found that out of four stereoisomers, the β-configured ʟ-(−)-enantiomer 1 (EC50 = 0.02 µM) is more potent in primary human lymphocytes than the β-configured ᴅ-(+)-enantiomer 1a (EC50 = 0.2 µM) in CEM cells [14]. Similarly, the 5-fluoro-substituted analogue of cytidine, i.e., β-configured ʟ

• -(−)-enantiomer 2, exhibits potential antiviral activity against HIV-1 (EC50 = 0.009 µM) in CEM cells. However, the corresponding ᴅ-(+)-enantiomer is less active against HIV-1 (EC50 = 0.84 µM) [15]. The fusion of an appropriate sugar element, carbacycle, or heterocyclic equivalent with an activated base results

• higher antiviral activity and lower toxicity of the unnatural ʟ-(−)-enantiomer over the ᴅ-(−)-enantiomer. The enantiomers of natural nucleosides are known to have a greater biological activity since they possess structural and configurational similarity to naturally occurring counterparts. In turn, for

N-Sulfinylpyrrolidine-containing ureas and thioureas as bifunctional organocatalysts

• Viera Poláčková,
• Dominika Krištofíková,
• Boglárka Némethová,
• Renata Górová,
• Mária Mečiarová and
• Radovan Šebesta

Beilstein J. Org. Chem. 2021, 17, 2629–2641, doi:10.3762/bjoc.17.176

• /mismatched combination of chirality, we employed both enantiomers of tert-butyl sulfinamide with the (S)-enantiomer of the pyrrolidine building block. The introduction of green chemistry principles into chemical transformations is an important goal toward sustainable production and manufacturing. Asymmetric

• and enantiomeric purities (Table 1, entries 12 and 13). In terms of the stereochemical outcome, both sulfinylthioureas C1 and urea C2 afforded the same enantiomer as the main product. Furthermore, both diastereomers of both catalysts also directed the Michael addition toward the same enantiomer. These

• of adduct 8a dropped to 51%, when the excess of butanal (6a) was reduced from 3 to 1.5 equivalents. The diastereoselectivity increased to 93:7 and the enantioselectivity for the major enantiomer was 19:81 and 16:84 for the minor enantiomer, respectively (Table 3, entry 2). A base exchange had no

α-Ketol and α-iminol rearrangements in synthetic organic and biosynthetic reactions

• Scott Benz and
• Andrew S. Murkin

Beilstein J. Org. Chem. 2021, 17, 2570–2584, doi:10.3762/bjoc.17.172

• -substituents. For example, only the S enantiomer from a racemic mixture of 19 was capable of being rearranged; (R)-19 was recovered from the reaction mixture with 84% ee, whereas (S)-19 had been stereospecifically converted to 20 in 49% yield and 86% ee (Figure 5). The final example of asymmetric α-ketol

Strategies for the synthesis of brevipolides

• Yudhi D. Kurniawan and
• A'liyatur Rosyidah

Beilstein J. Org. Chem. 2021, 17, 2399–2416, doi:10.3762/bjoc.17.157

• following details: two reports present the unsuccessful syntheses of brevipolide H [13][14] and four reports cover the successful syntheses of brevipolide H [15] and its enantiomer [16], brevipolide M [17], and brevipolide N [17][18], respectively. To the best of our knowledge, this work presents the first

• synthesize brevipolide H (8), but unexpectedly ended up with the isolation of its enantiomer (ent-8) [16]. Common to the most of the reported retrosynthetic analyses of brevipolide, compound 8 is disconnected at the cinnamate ester bond giving β-hydroxy cyclopropyl intermediate 44 and (E)-p-methoxycinnamic

• compound 82. This molecule is expected to be available from cross metathesis of olefins 83 and 84. These two intermediates can then be readily prepared from optically active oxirane 85 and its enantiomer which can be derived through the Sharpless epoxidation of penta-1,4-dien-3-ol (86). In the synthesis

Base-free enantioselective S_N2 alkylation of 2-oxindoles via bifunctional phase-transfer catalysis

• Mili Litvajova,
• Emiliano Sorrentino,
• Brendan Twamley and
• Stephen J. Connon

Beilstein J. Org. Chem. 2021, 17, 2287–2294, doi:10.3762/bjoc.17.146

• of biological interest, as evidenced by the facile preparation of the (S)-enantiomer of a potent CRTH2 receptor antagonist. The importance of the 3,3-spirooxindole core and its access through enantioselective enolate alkylation. Substrate scope. aIsolated yield. bDetermined by CSP-HPLC. cValue in

Halides as versatile anions in asymmetric anion-binding organocatalysis

• Lukas Schifferer,
• Martin Stinglhamer,
• Kirandeep Kaur and
• Olga García Macheño

Beilstein J. Org. Chem. 2021, 17, 2270–2286, doi:10.3762/bjoc.17.145

• the seleniranium ring. Through favorable cation–π interactions with the catalyst, the (S,S)-intermediate reacts faster than its opposing enantiomer, allowing for excellent yields up to 95% and high enantioselectivities up to 91% ee. In contrast to the previous example, in which the chloride anion was

• between the catalyst and the substrate, which exclusively stabilize the transition state that forms the major enantiomer. Furthermore, Gouverneur and co-workers established an enantioselective nucleophilic fluorination protocol using a chiral bis-urea catalyst 41 and CsF as an inorganic fluoride source

Progress and challenges in the synthesis of sequence controlled polysaccharides

• Giulio Fittolani,
• Theodore Tyrikos-Ergas,
• Denisa Vargová,
• Manishkumar A. Chaube and
• Martina Delbianco

Beilstein J. Org. Chem. 2021, 17, 1981–2025, doi:10.3762/bjoc.17.129

Total synthesis of ent-pavettamine

• Memory Zimuwandeyi,
• Manuel A. Fernandes,
• Amanda L. Rousseau and
• Moira L. Bode

Beilstein J. Org. Chem. 2021, 17, 1440–1446, doi:10.3762/bjoc.17.99

• first total synthesis of the enantiomer of pavettamine, ent-pavettamine. The symmetrical structure of the molecule allows for the synthesis of a common C5 fragment that can be divergently transformed into two synthons for later convergent coupling to furnish the target carbon framework. Based on the

• developing a route for the synthesis of enantiomer 2 by modification of the established protocol used for the synthesis of 1. The plan was that the alternative strategy would lead to an improvement in the overall yield whilst eliminating some of the troublesome steps. Results and Discussion The synthetic

• , when compared to our original pavettamine synthesis [1]. This opposite functionalization ensured that the enantiomer would result from the synthesis. For purposes of comparison between the original route and the route described here, our efforts commenced with the synthesis of the common C5 unit 4

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

• Joseane A. Mendes,
• Paulo R. R. Costa,
• Miguel Yus,
• Francisco Foubelo and
• Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

• -butanesulfinyl ketimine condensation (Scheme 2) [21]. Mechanism of addition of nucleophiles to N-sulfinyl imines The p-toluenesulfinamide 5 was first described by Davis and co-workers in a racemic form [22], and subsequently, the compound was prepared and isolated as a single enantiomer [23][24], becoming an

• Grignard reagents to chiral aldimine (RS)-74, and an intramolecular oxidative cyclization of aminoalcohols derivatives 76, are key steps of this approach. Both diastereoisomers of aldimines 74 (RS and SS) were prepared from ᴅ-malic acid and the corresponding enantiomer of tert-butanesulfinamide

• influence on it the configuration of the sulfur atom of the sulfinyl unit. This methodology was applied to the asymmetric synthesis of (−)-CP-99,994 (128), the enantiomer of a promising clinical agent which displays a variety of biological activities, including neurogenic inflammation, pain transmission

Kinetics of enzyme-catalysed desymmetrisation of prochiral substrates: product enantiomeric excess is not always constant

• Peter J. Halling

Beilstein J. Org. Chem. 2021, 17, 873–884, doi:10.3762/bjoc.17.73

• the equilibrium constant where the enzymatic reaction was not completely irreversible [2]. A limitation of the enzymatic resolution is that the maximum yield of the desired enantiomer is the 50% contained in the starting racemate. This is one reason for the current greater interest in enzymatic

• desymmetrisation reactions, in which a prochiral substrate is used [3][4][5][6][7]. The reaction generates a new chiral centre, and the enzyme shows enantiospecifity in making predominantly one enantiomer as the product. In this case the yields of the favoured enantiomer can approach 100%. Some popular reactions

• favoured product are completely absent. In most of the applications the overall reaction is significantly reversible, with an equilibrium constant that is not enormously larger than 1. And in many cases there is a noticeable formation of the less favoured enantiomer, with product ee values of 0.98 or less

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

• Zhonglie Yang,
• Yutong Liu,
• Kun Cao,
• Xiaobin Zhang,
• Hezhong Jiang and
• Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

• enantiomer to diastereomer. A plausible mechanism is shown in Scheme 19. In the presence of acid, EDA complex 52 is formed by ketene 48 and diamine 51. Then, the ground state 52 transforms into excited state 53 or into unproductive charge-transfer excited state 54 that can restore ground state 52 by BET

Menthyl esterification allows chiral resolution for the synthesis of artificial glutamate analogs

• Kenji Morokuma,
• Shuntaro Tsukamoto,
• Kyosuke Mori,
• Kei Miyako,
• Ryuichi Sakai,
• Raku Irie and
• Masato Oikawa

Beilstein J. Org. Chem. 2021, 17, 540–550, doi:10.3762/bjoc.17.48

• Figure 1) [3][4], we found that 1) the (2R)-enantiomer is responsible for the neuroactivity and that 2) the activity is controlled by the structure of the ring C; the seven-membered azacyclic analog (2R)-TKM-107 (2) is moderately hypoactive, that is, it attenuates the voluntary movement of mice upon

• both enantiomers of MC-27, 4 and 4*, separately (see Figure 1 for the (2R)-enantiomer) and found that, as expected, the (2R)-enantiomer 4 is responsible for the neuroactivity (see above). Herein, we also report the enantiospecific synthesis and evaluation of the novel eight-membered azacyclic analog

• and Figure 2, were unambiguously determined later from crystallographic and spectroscopic studies of the 2R-derivative 9 (see below). Scheme 3 shows the synthesis of the (2R)-enantiomer of MC-27, 4. The deprotection of the PMB group of 9 (tR 11.5 min in Figure 2) by CAN proceeded smoothly at rt to

The synthesis of chiral β-naphthyl-β-sulfanyl ketones via enantioselective sulfa-Michael reaction in the presence of a bifunctional cinchona/sulfonamide organocatalyst

• Deniz Tözendemir and
• Cihangir Tanyeli

Beilstein J. Org. Chem. 2021, 17, 494–503, doi:10.3762/bjoc.17.43

• the product 12a with a final ee of 62% (Table 2, entry 18). This unexpected phenomenon could be linked to an enthalpic factor that favors the formation of the major enantiomer at higher temperature, or due to a change in the reaction mechanism when the temperature was altered. The most enantioenriched

CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

• occurred with 41% inversion (and 59% racemization, i.e., product 23f was obtained with an enantiomeric ratio of ca. 70:30 in favor of the (S)-enantiomer), while complete racemization was observed in more ionizing TFA or HFIP as the solvent (Figure 5b) [48]. These observations are in agreement with a

Regioselective chemoenzymatic syntheses of ferulate conjugates as chromogenic substrates for feruloyl esterases

• Olga Gherbovet,
• Fernando Ferreira,
• Apolline Clément,
• Mélanie Ragon,
• Julien Durand,
• Sophie Bozonnet,
• Michael J. O'Donohue and
• Régis Fauré

Beilstein J. Org. Chem. 2021, 17, 325–333, doi:10.3762/bjoc.17.30

• solid. [α]D20 0 (c 2.0, CH3OH). The NMR data (CD3OD) of the racemate 11 were consistent with those previously reported for the pure (S)-enantiomer [37] ([α]D20 −52 (c 2.0, CH3OH)). (±)-4-O-(2-Hydroxy-4-nitrophenyl)-1-O-trans-feruloyl-1,2,4-butanetriol (12). The application of the general procedure for

Progress in the total synthesis of inthomycins

• Bidyut Kumar Senapati

Beilstein J. Org. Chem. 2021, 17, 58–82, doi:10.3762/bjoc.17.7

• asymmetric aldol reaction in the presence of oxazaborolidinone derivative 68 and silyl ketene acetal 53 to produce the required α-hydroxy ester (+)-11 in 50% yield and 76% ee ((R)-stereochemistry of the major enantiomer). A competitive reduction of 71 was also observed to produce alcohol 72 in 43% yield

Circularly polarized luminescent systems fabricated by Tröger's base derivatives through two different strategies

• Cheng Qian,
• Yuan Chen,
• Qian Zhao,
• Ming Cheng,
• Chen Lin,
• Juli Jiang and
• Leyong Wang

Beilstein J. Org. Chem. 2021, 17, 52–57, doi:10.3762/bjoc.17.6

• DGG. In the CPL-active co-gels, noncovalent weak interactions might be formed between achiral fluorophores and a chiral gelator. So, the CPL emission of co-gels could be adjusted easily by external stimuli. The ᴅ-glutamic acid gelator DGG and its enantiomer LGG possess three hydrogen-bond sites, two

Recent progress in the synthesis of homotropane alkaloids adaline, euphococcinine and N-methyleuphococcinine

• Dimas J. P. Lima,
• Antonio E. G. Santana,
• Michael A. Birkett and
• Ricardo S. Porto

Beilstein J. Org. Chem. 2021, 17, 28–41, doi:10.3762/bjoc.17.4

• NMR, 13C NMR, MS) were identical to those of the natural product, and the specific rotation [α]D28 −11.4 (c 0.7, CHCl3) comparable to that found in the literature {[α]D20 −13 (CHCl3), [17]}. Yu synthesis – 2009 Yu et al. prepared (−)-adaline (1) and the nonnatural enantiomer (−)-euphococcinine (2) in

• approach consisted of a 3,3-sigmatropic rearrangement to give an all-carbon quaternary center, a ring-closing alkene metathesis to give an 8-membered ring, and the use of a single enantiomer of p-menthane-3-carboxaldehyde to make two natural alkaloids of opposite configuration. Firstly, (+)-euphococcinine