Stereoselective synthesis and transformation of pinane-based 2-amino-1,3-diols

• Ákos Bajtel,
• Mounir Raji,
• Matti Haukka,
• Ferenc Fülöp and
• Zsolt Szakonyi

Beilstein J. Org. Chem. 2021, 17, 983–990, doi:10.3762/bjoc.17.80

• , POB 35, 40351 Jyväskylä, Finland Stereochemistry Research Group of the Hungarian Academy of Sciences, H-6720 Szeged, Eötvös u. 6, Hungary, Interdisciplinary Centre of Natural Products, University of Szeged, Szeged, Hungary 10.3762/bjoc.17.80 Abstract A library of pinane-based 2-amino-1,3-diols was

• synthesised in a stereoselective manner. Isopinocarveol prepared from (−)-α-pinene was converted into condensed oxazolidin-2-one in two steps by carbamate formation followed by a stereoselective aminohydroxylation process. The relative stereochemistry of the pinane-fused oxazolidin-2-one was determined by 2D

• , two main synthetic strategies are used to prepare these analogues. One requires the insertion of the alcohol and amino groups in the α,β position with the correct stereochemistry [17][18][19][20]. The second strategy involves a bond formation between two chiral centers to produce the targeted 2-amino

Prins cyclization-mediated stereoselective synthesis of tetrahydropyrans and dihydropyrans: an inspection of twenty years

• Asha Budakoti,
• Pradip Kumar Mondal,
• Prachi Verma and
• Jagadish Khamrai

Beilstein J. Org. Chem. 2021, 17, 932–963, doi:10.3762/bjoc.17.77

• (−)-blepharocalyxin D29 [45] and the macrolide leucascandrolide A [46]. In another type, the triflic acid-catalyzed Prins cyclization was used for the synthesis of 2,4,5,6-tetrasubstituted tetrahydropyran with complete control of stereochemistry, which is an important core of a variety of natural products, such as

• -stereochemistry in the major product. Asymmetric Prins cyclization Mullen and Gagné reported a first catalytic asymmetric Prins cyclization reaction between 2-allylphenol 292 and glyoxylate ester 293 using (R)-[(tolBINAP)Pt(NC6F5)2][SbF6]2 (294) as chiral catalyst [110]. An optimization study revealed that the

Beyond ribose and phosphate: Selected nucleic acid modifications for structure–function investigations and therapeutic applications

• Christopher Liczner,
• Kieran Duke,
• Gabrielle Juneau,
• Martin Egli and
• Christopher J. Wilds

Beilstein J. Org. Chem. 2021, 17, 908–931, doi:10.3762/bjoc.17.76

• aluminum 2-methoxyethoxide, which attacks and inserts at the 2'-position, opening the ring and producing the nucleoside with the correct stereochemistry (Scheme 5) [117]. Conveniently, this 2'-O-MOE uridine can be converted to the cytidine derivative by 4-nitrophenylation, 3',5'-trimethylsilylation and

Simulating the enzymes of ganglioside biosynthesis with Glycologue

• Andrew G. McDonald and
• Gavin P. Davey

Beilstein J. Org. Chem. 2021, 17, 739–748, doi:10.3762/bjoc.17.64

• it is possible to infer that all of the enzymes of the model are all configuration-inverting, rather than configuration-retaining. This inversion of configuration refers to the stereochemistry of the anomeric carbon in the acceptor product, which has the opposite configuration to that of the donor

α,γ-Dioxygenated amides via tandem Brook rearrangement/radical oxygenation reactions and their application to syntheses of γ-lactams

• Mikhail K. Klychnikov,
• Radek Pohl,
• Ivana Císařová and
• Ullrich Jahn

Beilstein J. Org. Chem. 2021, 17, 688–704, doi:10.3762/bjoc.17.58

• of diverse N-allylic α-(aminoxy)amides 9 from various epoxides 7 and a range of N-allylic α-silylamides 8. α-(Aminoxy)amides 9 serve well for the synthesis of polysubstituted γ-lactams 10 with moderate diastereoselectivities. The stereochemistry of the initial cyclization products can be however

Designed whole-cell-catalysis-assisted synthesis of 9,11-secosterols

• Marek Kõllo,
• Marje Kasari,
• Villu Kasari,
• Tõnis Pehk,
• Ivar Järving,
• Margus Lopp,
• Arvi Jõers and
• Tõnis Kanger

Beilstein J. Org. Chem. 2021, 17, 581–588, doi:10.3762/bjoc.17.52

• synthetic schemes starts with natural steroids, taking advantage of the appropriate stereochemistry of existing stereogenic centres [16][17][18][19][20]. However, the synthesis of target compounds is a multistep procedure, often including several protections and deprotections of functional groups. Our

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

• * and 21 (see below). The PMB group of 20* and 20 was then independently removed by CAN at −10 °C to give 21* and 21 in 88% and 80% yield, respectively (Scheme 6). With 21* and 21, the stereochemistry was determined on the basis of the NOESY data in combination with the conformational analyses by

• , and the stereochemistry of 20 and 21 is 2R, as described in Figure 6, Scheme 5, and Scheme 6. The assignments were undoubtedly verified by the PGME amide analysis [22][23] (see the Supporting Information File 7). The stereochemical analyses carried out here and in our previous study [4] have been

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

Diels–Alder reaction of β-fluoro-β-nitrostyrenes with cyclic dienes

• Savva A. Ponomarev,
• Roman V. Larkovich,
• Alexander S. Aldoshin,
• Andrey A. Tabolin,
• Sema L. Ioffe,
• Jonathan Groß,
• Till Opatz and
• Valentine G. Nenajdenko

Beilstein J. Org. Chem. 2021, 17, 283–292, doi:10.3762/bjoc.17.27

• activation parameters. Furthermore, the synthetic utility of the cycloadducts obtained was demonstrated. Keywords: Diels–Alder reaction; fluorine; nitrostyrene; norbornene; stereochemistry; Introduction Organofluorine compounds play an exceptionally important role in various fields of science and

• , the ratio of endo/exo was 2:1. The stereochemistry of the products 2a–l can be unambiguously assigned using 1H NMR spectroscopy. According to the literature data [59] the dienophile-derived proton at C6 resonates at lower field in the exo-form than the corresponding proton of the endo-isomer. For

A sustainable strategy for the straightforward preparation of 2H-azirines and highly functionalized NH-aziridines from vinyl azides using a single solvent flow-batch approach

• Michael Andresini,
• Leonardo Degannaro and
• Renzo Luisi

Beilstein J. Org. Chem. 2021, 17, 203–209, doi:10.3762/bjoc.17.20

• observed. The relative stereochemistry was assigned by NOESY experiments (see Supporting Information File 1). Unfortunately, when the protocol was applied to 1-(1-azidovinyl)-2,3,4,5,6-pentafluorobenzene (1k), only a complex mixture was recovered likely because of the instability of the corresponding 2H

Insight into functionalized-macrocycles-guided supramolecular photocatalysis

• Minzan Zuo,
• Krishnasamy Velmurugan,
• Kaiya Wang,
• Xueqi Tian and
• Xiao-Yu Hu

Beilstein J. Org. Chem. 2021, 17, 139–155, doi:10.3762/bjoc.17.15

• stereochemistry as catalysts [27]. The stereochemical properties were sensitive to the linker size and length, and the yield of the syn-head-to-tail-9,10:9',10'-cyclodimer could reach 97–98%. Traditional thiol-functionalized organic ligands decorated on the surface of gold nanoclusters (AuNCs) tend to generate a

Facile preparation and conversion of 4,4,4-trifluorobut-2-yn-1-ones to aromatic and heteroaromatic compounds

• Takashi Yamazaki,
• Yoh Nakajima,
• Minato Iida and
• Tomoko Kawasaki-Takasuka

Beilstein J. Org. Chem. 2021, 17, 132–138, doi:10.3762/bjoc.17.14

• to proceed under the action of a catalytic amount of a base, and only 2 mol % of t-BuOK led to the formation of the desired adduct 3aa as a sole stereoisomer in 84% isolated yield under the same reaction conditions (Table 2, entries 6−8). The E-stereochemistry of 3aa was deduced from the NMR data of

Direct synthesis of anomeric tetrazolyl iminosugars from sugar-derived lactams

• Michał M. Więcław and
• Bartłomiej Furman

Beilstein J. Org. Chem. 2021, 17, 115–123, doi:10.3762/bjoc.17.12

• widely used as organocatalysts. Such moieties are employed in a number of important synthetic transformations, including the aldol reaction [30], Michael addition [31], Mannich reaction [32], and hydrogenation [33]. We plan to test these possibilities in the near future. Stereochemistry and configuration

• conformer. Therefore, once the ground conformer of the oxocarbenium ion is established, this logic may be used to predict the reaction’s stereochemistry. The same principle may be successfully applied to reactions of iminium cations. We have previously shown that in the case of glucose- and galactose

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

• concluded that (+)-69 must have (3R)-stereochemistry and they had completed a formal total synthesis of the Zeeck−Taylor [2][21] stereostructure for inthomycin C ((+)-3). To remove any doubt, Stille cross-coupling of 48 with (+)-69 was performed under Ryu’s conditions [50] to give the desired product (+)-11

• C (+)-3 (See Scheme 7 and Scheme 10). Soon after, a subsequent collaboration between the Hale and Hatakeyama groups demonstrated that inthomycin C ((–)-3) has (3R)- and not (3S)-stereochemistry [57]. Careful reappraisal of the previously published work [21][22][50][60] now strongly recommends that

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

• conditions to afford alkene (±)-39. Hydroboration of (±)-39 with the borane–THF complex followed by oxidation of the obtained intermediate led to the mixture of alcohols (±)-40 + (±)-41 with yields of 31% and 39%, respectively. The 1H NMR spectrum confirmed the structure and stereochemistry of alcohol (±)-41

• in 65% yield and complete stereochemistry retention. When isocyanate (−)-84 was treated with copper chloride in water and THF, the (+)-euphococcinine (2) was obtained in 63% yield. A similar sequence was used to synthesize natural (−)-adaline (1, Scheme 10). In this case, vinyl iodide 86 was obtained

Fluorine effect in nucleophilic fluorination at C4 of 1,6-anhydro-2,3-dideoxy-2,3-difluoro-β-D-hexopyranose

• Danny Lainé,
• Vincent Denavit,
• Olivier Lessard,
• Laurie Carrier,
• Charles-Émile Fecteau,
• Paul A. Johnson and
• Denis Giguère

Beilstein J. Org. Chem. 2020, 16, 2880–2887, doi:10.3762/bjoc.16.237

• approach using Et3N·3HF as an alternative to the DAST reagent. We controlled the stereochemistry of the nucleophilic fluorination at C4 of 1,6-anhydro-2,3-dideoxy-2,3-difluoro-4-O-triflate-β-ᴅ-talopyranose using Et3N·3HF or in situ generated Et3N·1HF. The influence of the fluorine atom at C2 on reactivity

• 3 is the stereochemistry of the fluorine atom at C2. Finally, only decomposition originated from the use of mannose analogue 5 as substrate. The difference in terms of reactivity between 5 and 2 was unexpected since they only differ from the stereochemistry of the fluorine atom at C2 (distal to the

• reactive site at C4). Although rather disappointing in terms of yields, these results shed some light on the fact that both the stereochemistry of the fluorine atom at C2 and the C4 hydroxy group could influence the outcome of the fluorodeoxygenation at C4 for 1,6-anhydro-hexopyranose systems in the

Easy access to a carbohydrate-based template for stimuli-responsive surfactants

• Thomas Holmstrøm,
• Daniel Raydan and
• Christian Marcus Pedersen

Beilstein J. Org. Chem. 2020, 16, 2788–2794, doi:10.3762/bjoc.16.229

• metal-binding event. This study was carried out by having pyrene fluorophores attached to the two non-chelating positions, giving rise to excimer fluorescence when the distance between them was decreased due to the ring flip [12]. Carbohydrates with gluco stereochemistry have also been used as templates

Nocarimidazoles C and D, antimicrobial alkanoylimidazoles from a coral-derived actinomycete Kocuria sp.: application of ¹J_C,H coupling constants for the unequivocal determination of substituted imidazoles and stereochemical diversity of anteisoalkyl chains in microbial metabolites

• Md. Rokon Ul Karim,
• Enjuro Harunari,
• Amit Raj Sharma,
• Naoya Oku,
• Kazuaki Akasaka,
• Daisuke Urabe,
• Mada Triandala Sibero and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 2719–2727, doi:10.3762/bjoc.16.222

• -enantiomers with a ratio of 73:27, 4 is the pure (S)-enantiomer, and 5 is the (S)-enantiomer with 98% ee. The present study illustrates the diversity in the stereochemistry of anteiso branching in bacterial metabolites. Compounds 1−4 were moderately antimicrobial against Gram-positive bacteria and fungi, with

• , and 5) and even with a compound (in terms of having the common planar structure) from different organisms (e.g., 5). This lesson not only warrants the insufficiency of assigning the stereochemistry of the synthesized anteiso-chained natural products only by comparison of the optical rotation values

A consensus-based and readable extension of Linear Code for Reaction Rules (LiCoRR)

• Benjamin P. Kellman,
• Yujie Zhang,
• Emma Logomasini,
• Eric Meinhardt,
• Karla P. Godinez-Macias,
• Austin W. T. Chiang,
• James T. Sorrentino,
• Chenguang Liang,
• Bokan Bao,
• Yusen Zhou,
• Sachiko Akase,
• Isami Sogabe,
• Thukaa Kouka,
• Elizabeth A. Winzeler,
• Iain B. H. Wilson,
• Matthew P. Campbell,
• Sriram Neelamegham,
• Frederick J. Krambeck,
• Kiyoko F. Aoki-Kinoshita and
• Nathan E. Lewis

Beilstein J. Org. Chem. 2020, 16, 2645–2662, doi:10.3762/bjoc.16.215

• stereochemistry (>80%). (B) The maximum common substructure (MCS) associated with each cluster. (C) An example to illustrate the modifications needed to reach one monosaccharide to another, as identified by the complete monosaccharide reachability network (Table S6, Supporting Information File 1). (D) The

Synthesis of novel fluorinated building blocks via halofluorination and related reactions

• Attila Márió Remete,
• Tamás T. Novák,
• Melinda Nonn,
• Matti Haukka,
• Ferenc Fülöp and
• Loránd Kiss

Beilstein J. Org. Chem. 2020, 16, 2562–2575, doi:10.3762/bjoc.16.208

• , Eötvös u. 6, Hungary MTA-SZTE Stereochemistry Research Group, Hungarian Academy of Sciences, H-6720 Szeged, Eötvös u. 6, Hungary Department of Chemistry, University of Jyväskylä, FIN-40014, Jyväskylä, Finland 10.3762/bjoc.16.208 Abstract A study exploring halofluorination and fluoroselenation of some

• compounds, we selected some functionalized (to obtain valuable building blocks), cyclic (to obtain better insight into the stereochemistry), and usually symmetrical olefins (to eliminate regioselectivity issues). The first substrate, the cyclohexene diester (rac)-1, has a twofold rotational symmetry, that

• with NBS/Deoxo-Fluor® and NIS/Deoxo-Fluor® systems in anhydrous CH2Cl2 afforded the compounds (rac)-2a and (rac)-2b as single products. The stereochemistry of (rac)-2a and (rac)-2b was determined using NOESY experiments. The reactions proceeded smoothly, although the yields were moderate (Scheme 2

Leveraging glycomics data in glycoprotein 3D structure validation with Privateer

• Haroldas Bagdonas,
• Daniel Ungar and
• Jon Agirre

Beilstein J. Org. Chem. 2020, 16, 2523–2533, doi:10.3762/bjoc.16.204

• ], glycosidic linkage stereochemistry [14] and torsion [15][16], and most recently, ring conformation [17]. Most of these issues have now been addressed as part of ongoing efforts to provide better software tools for structure determinations of glycoproteins, although the most difficult cases remain hard to

• stereochemistry [14], incorrect torsion [15][16], and unlikely high-energy ring conformations [17]. Early efforts in the validation of carbohydrate structures saw the introduction of online tools such as PDB-CARE [37] and CARP [16]; more recently, we released the Privateer software [24], which was the first

• terminal Man-(1→3)-GlcNAc [14]. Moreover, the proposed model contained systematic errors in the anomer annotations and carbohydrate stereochemistry. To this day, there is still no experimental evidence reported for these types of linkages and capping in an identical context. The new version of Privateer

Hierarchically assembled helicates as reaction platform – from stoichiometric Diels–Alder reactions to enamine catalysis

• David Van Craen,
• Jenny Begall,
• Johannes Großkurth,
• Leonard Himmel,
• Oliver Linnenberg,
• Elisabeth Isaak and
• Markus Albrecht

Beilstein J. Org. Chem. 2020, 16, 2338–2345, doi:10.3762/bjoc.16.195

• auxiliary, Lewis acid or catalyst. In the previously reported system two different induction pathways were conceivable: (1) A chiral ligand is located close to the diene and controls the stereochemistry of the cycloaddition. (2) The chiral ligand controls the helicity of the helicate (ΔΔ or ΛΛ) and the

• reaction yielded the racemic product after purification. Scheme 3 is showing that the induction of stereochemistry of the Diels–Alder reaction depends on the chirality at the chiral ligand and not at the helix. This allows improvement of the stereoselectivity by using more appropriate sterically hindered

• formed helicates with mixtures of ligands as platforms to control the stereochemistry of C–C bond-forming reactions. However, it would be of great advantage to transfer the findings to catalytic C–C bond-forming reactions which are catalyzed by hierarchical helicates containing chiral ligands for

Chan–Evans–Lam N1-(het)arylation and N1-alkеnylation of 4-fluoroalkylpyrimidin-2(1H)-ones

• Viktor M. Tkachuk,
• Oleh O. Lukianov,
• Mykhailo V. Vovk,
• Isabelle Gillaizeau and
• Volodymyr A. Sukach

Beilstein J. Org. Chem. 2020, 16, 2304–2313, doi:10.3762/bjoc.16.191

• ) as a reagent; the thus obtained N1-styryl-substituted 4-trifluoromethylpyrimidin-2(1H)-one 5a obviously has considerable synthetic potential [49][50]. The stereochemistry of compound 5a was confirmed by a NOE NMR experiment, which demonstrated significant spatial interaction between the H6 and Hb

Styryl-based new organic chromophores bearing free amino and azomethine groups: synthesis, photophysical, NLO, and thermal properties

• Anka Utama Putra,
• Deniz Çakmaz,
• Nurgül Seferoğlu,
• Alberto Barsella and
• Zeynel Seferoğlu

Beilstein J. Org. Chem. 2020, 16, 2282–2296, doi:10.3762/bjoc.16.189

• , and HRMS analyses (Figures S1–S40 in Supporting Information File 1). Moreover, the stereochemistry of the double bonds was determined on the basis of the coupling constants of the vinylic hydrogens in the 1H NMR spectra (J ≈ 15–16 Hz) and revealed that the dyes are stable as E-stereoisomers [31

Reactions of 3-aryl-1-(trifluoromethyl)prop-2-yn-1-iminium salts with 1,3-dienes and styrenes

• Thomas Schneider,
• Michael Keim,
• Bianca Seitz and
• Gerhard Maas

Beilstein J. Org. Chem. 2020, 16, 2064–2072, doi:10.3762/bjoc.16.173

• -(1-phenylvinyl)indene 12 through an intramolecular iminium ion-induced 1,5-cyclization. The same cyclization type together with oxidative aromatization converts dihydronaphthalenes 16 into benzo[a]fluorenes 13. The stereochemistry of 12d can be explained by a stereoselective formation of trans-3,4