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

• glycoprotein profile. Glycomics experiments are required to distinguish stereoisomers and the linkage information in order to obtain a full structural description about a glycan, whereas glycoproteomics are required to establish the glycan variability and occupancy at the glycosylation sites of the protein [43

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

• –carbon (C–C) bond-forming reactions play a key role in organic chemistry. Hereby the stereoselectivity of the reaction is highly important due to the different behavior of stereoisomers in human metabolism [1][2]. Stereocontrol was achieved either via an auxiliary [3][4][5][6][7] or a catalyst [8], both

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

Muyocopronones A and B: azaphilones from the endophytic fungus Muyocopron laterale

• Ken-ichi Nakashima,
• Junko Tomida,
• Tomoe Tsuboi,
• Yoshiaki Kawamura and
• Makoto Inoue

Beilstein J. Org. Chem. 2020, 16, 2100–2107, doi:10.3762/bjoc.16.177

• ) [25]. After conformational analysis, geometry optimization was performed for two possible stereoisomers with the (7S,10R,11R)- and (7S,10S,11S)-configurations using density functional theory (DFT) at the CAM-B3LYP/6-311+G(d,p) level of theory. In addition, the ECD spectra of the DFT-optimized

• experimental ECD spectra (black solid line) of 1 (A) and 2 (B) with the Boltzmann-weighted spectra computed for the (7S,10S,11S)- and (7S,10R,11R)-stereoisomers (green and red dashed lines, respectively) of the simplified models. (A) Synthesis of MTPA diesters 1a and 1b. (B) Δδ Values for the (S)- and (R)-MTPA

Convenient access to pyrrolidin-3-ylphosphonic acids and tetrahydro-2H-pyran-3-ylphosphonates with multiple contiguous stereocenters from nonracemic adducts of a Ni(II)-catalyzed Michael reaction

• Alexander N. Reznikov,
• Dmitry S. Nikerov,
• Anastasiya E. Sibiryakova,
• Victor B. Rybakov,
• Evgeniy V. Golovin and
• Yuri N. Klimochkin

Beilstein J. Org. Chem. 2020, 16, 2073–2079, doi:10.3762/bjoc.16.174

• reactions with aldehydes yielding tetrahydropyranylphosphonates as individual stereoisomers. These nonracemic heterocycles containing phosphoryl moieties are useful for designing new pharmacologically active compounds. Keywords: asymmetric catalysis; Michael addition; phosphonates; pyrrolidines

A complementary approach to conjugated N-acyliminium formation through photoredox-catalyzed intermolecular radical addition to allenamides and allencarbamates

• Olusesan K. Koleoso,
• Matthew Turner,
• Felix Plasser and
• Marc C. Kimber

Beilstein J. Org. Chem. 2020, 16, 1983–1990, doi:10.3762/bjoc.16.165

• ]+); this peak persisted at 15, 30, 60 and 120 min time intervals, respectively. Upon the oxidation of 41 two plausible iminium stereoisomers can be formed, Z-42 and E-42, respectively, with each of these iminium stereoisomers existing in two further conformers designated E-42’ and Z-42’. DFT calculations

One-pot and metal-free synthesis of 3-arylated-4-nitrophenols via polyfunctionalized cyclohexanones from β-nitrostyrenes

• Haruyasu Asahara,
• Minami Hiraishi and
• Nagatoshi Nishiwaki

Beilstein J. Org. Chem. 2020, 16, 1830–1836, doi:10.3762/bjoc.16.150

• efficiently to afford 5a in 61% yield even when the amount of iodine was decreased to 10 mol %. However further decreasing the iodine amount to 5 mol % was not effective for the conversion (Table 2, entries 4 and 5). In each case, both stereoisomers of 4a were completely consumed, and several unidentified

Pauson–Khand reaction of fluorinated compounds

• Jorge Escorihuela,
• Daniel M. Sedgwick,
• Alberto Llobat,
• Mercedes Medio-Simón,
• Pablo Barrio and
• Santos Fustero

Beilstein J. Org. Chem. 2020, 16, 1662–1682, doi:10.3762/bjoc.16.138

• affording the corresponding CF3-containing dehydropiperidine derivatives in excellent yields. Additionally, enynes 22 and 23 were evaluated as substrates in the intramolecular PKR, yielding the corresponding CF3-containing heterobicyclic derivatives in 68% (85:15 ratio of trans/cis stereoisomers) and 80

• % yield (18:82 ratio of trans/cis stereoisomers), respectively (Scheme 10). Ichikawa and co-workers described an attractive route to synthesize pyrrolidine ring-fused fluorinated cyclopentenone analogs via intramolecular PKR starting from 2-bromo-3,3,3-trifluoroprop-1-ene [50][51]. To this end, N

Facile synthesis of 7-alkyl-1,2,3,4-tetrahydro-1,8-naphthyridines as arginine mimetics using a Horner–Wadsworth–Emmons-based approach

• Rhys A. Lippa,
• John A. Murphy and
• Tim N. Barrett

Beilstein J. Org. Chem. 2020, 16, 1617–1626, doi:10.3762/bjoc.16.134

• T3P® [17], yielded olefin 15 in 93% yield as a 94:5 mixture of stereoisomers – presumably E/Z, although this is not conclusive from the 1H NMR spectrum. Based on LC–MS and 1H NMR spectroscopy observations, it is believed that aldehyde 5 exists predominantly as the corresponding hydrate and an excess

Diversity-oriented synthesis of 17-spirosteroids

• Benjamin Laroche,
• Thomas Bouvarel,
• Martin Louis-Sylvestre and
• Bastien Nay

Beilstein J. Org. Chem. 2020, 16, 880–887, doi:10.3762/bjoc.16.79

• of the obtained succinic anhydride derivative (16b) upon purification. Other unsymmetrical dienophiles (methyl acrylate, methyl propiolate) gave complex mixtures of regio- and/or stereoisomers. The reaction of lynestrenol enyne 6a with N-phenylmaleimide was also performed to furnish compound 17a in

• applied to the mestranol and lynestrenol cores. Notes: aIsolated among other unseparable stereoisomers (overall cycloadduct yields: 65% and 50%, for the respective reactions). Supporting Information Supporting Information File 38: General experimental details, compound descriptions, 1H and 13C NMR

Controlling alkyne reactivity by means of a copper-catalyzed radical reaction system for the synthesis of functionalized quaternary carbons

• Goki Hirata,
• Yu Yamane,
• Naoya Tsubaki,
• Reina Hara and
• Takashi Nishikata

Beilstein J. Org. Chem. 2020, 16, 502–508, doi:10.3762/bjoc.16.45

• examination, product isolation was difficult because of the formation of stereoisomers (E and Z stereoisomers of 5). The yields shown in Figure 2 were including isomers (We also put yield of pure E-5 as an NMR yield.). Although the chemical yields of 5 were moderate, the stereoselectivities in this reaction

• were good (the major stereoisomers of 5 produced were E). We tested compounds 2 possessing acyclic and cyclic structures and compounds 4 possessing MeO, F, and N-Et moieties as substrates for the reaction; however, no big differences were observed. The C–H cyclized products were not obtained from the

p-Pyridinyl oxime carbamates: synthesis, DNA binding, DNA photocleaving activity and theoretical photodegradation studies

• Panagiotis S. Gritzapis,
• Panayiotis C. Varras,
• Nikolaos-Panagiotis Andreou,
• Katerina R. Katsani,
• Konstantinos Dafnopoulos,
• George Psomas,
• Zisis V. Peitsinis,
• Alexandros E. Koumbis and
• Konstantina C. Fylaktakidou

Beilstein J. Org. Chem. 2020, 16, 337–350, doi:10.3762/bjoc.16.33

• 8.1 to 10.7 ppm and for the benzyl derivative 15 at 6.63 ppm. In the case of aldoxime carbamates three reactions gave mixtures of inseparable Z-stereoisomers ≈10% along with the major E-stereoisomer (products 25–27). It has been noted in the literature the preferable E-conformation for oxime

• carbamates [61][64][65] where 1H NMR spectroscopy has been used in order to distinguish between the two [61][65]. Thus, the imine benzylic proton of the E-stereoisomers shows a singlet in the area 8–8.7 ppm, whereas the ones belonging to a Z-conformation are upfield and appear between 7.3–7.6 ppm. Indeed

Self-assembled coordination thioether silver(I) macrocyclic complexes for homogeneous catalysis

• Zhen Cao,
• Aline Lacoudre,
• Cybille Rossy and
• Brigitte Bibal

Beilstein J. Org. Chem. 2019, 15, 2465–2472, doi:10.3762/bjoc.15.239

• of the two L2·(AgOTf)2 stereoisomers highlighted their different geometry. The catalytic activity of all silver(I) complexes was effective under homogeneous conditions in two tandem addition/cycloisomerization of alkynes using 0.5–1 mol % of catalytic loading. Keywords: coordination macrocycle

In water multicomponent synthesis of low-molecular-mass 4,7-dihydrotetrazolo[1,5-a]pyrimidines

• Irina G. Tkachenko,
• Sergey A. Komykhov,
• Vladimir I. Musatov,
• Svitlana V. Shishkina,
• Viktoriya V. Dyakonenko,
• Vladimir N. Shvets,
• Mikhail V. Diachkov,
• Valentyn A. Chebanov and
• Sergey M. Desenko

Beilstein J. Org. Chem. 2019, 15, 2390–2397, doi:10.3762/bjoc.15.231

• product is the 5-hydroxy-containing tetrahydro derivative. In our experiments, the three-component reaction of amine 1 with aldehyde 7b and compound 13 in water under microwave irradiation afforded tetrahydro derivative 14 as a mixture of two stereoisomers. Inspection of the mixture by 1H NMR revealed

• the final confirmation of the structure and to establish the relative stereochemistry of both stereoisomers. NOESY cross-peaks between signals of NH and OH protons revealed that A and B are in fact stereoisomers, rejecting the regioisomeric structure 14’. The different 3J values between 6-H and 7-H

Multiple threading of a triple-calix[6]arene host

• Veronica Iuliano,
• Roberta Ciao,
• Emanuele Vignola,
• Carmen Talotta,
• Patrizia Iannece,
• Margherita De Rosa,
• Annunziata Soriente,
• Carmine Gaeta and
• Placido Neri

Beilstein J. Org. Chem. 2019, 15, 2092–2104, doi:10.3762/bjoc.15.207

• stereoselective formation of endo-alkyl pseudo[n]rotaxane stereoisomers. Keywords: calixarene; multiple-threading; pseudo[n]rotaxane; stereoisomers; Introduction The self-assembly [1] of smaller components to larger aggregates represents one of the most spectacular phenomena in supramolecular chemistry [2][3][4

• pseudorotaxanes (endo-alkyl or endo-benzyl) for each calix[6]arene-wheel of 6, leading to a total of 4 possible stereoisomers, which are sketched in Figure 9. When 1 equiv of butylbenzylammonium cation 8+, as TFPB− salt, was added to a CDCl3 solution of 6, then the (endo-alkyl)-8+6 pseudo[2]rotaxane was formed as

• , DOSY, and ESI-FT-ICR MS/MS experiments. In addition, in the presence of a directional butylbenzylammonium axle, the stereoselective formation of endo-alkyl pseudorotaxane stereoisomers was observed. Experimental HR mass spectra were acquired on a FT-ICR mass spectrometer equipped with a 7T magnet. The

Characterization of two new degradation products of atorvastatin calcium formed upon treatment with strong acids

• Jürgen Krauß,
• Monika Klimt,
• Markus Luber,
• Peter Mayer and
• Franz Bracher

Beilstein J. Org. Chem. 2019, 15, 2085–2091, doi:10.3762/bjoc.15.206

• process (stereoisomers, products resulting from impure starting materials or side reactions), and only one of these impurities, lactone 2, is most likely a degradation product, resulting from acid-mediated lactonization of the 3,5-dihydroxyheptanoate side chain. A couple of previous publications deal with

α-Photooxygenation of chiral aldehydes with singlet oxygen

• Dominika J. Walaszek,
• Magdalena Jawiczuk,
• Jakub Durka,
• Olga Drapała and
• Dorota Gryko

Beilstein J. Org. Chem. 2019, 15, 2076–2084, doi:10.3762/bjoc.15.205

• by electronic circular dichroism spectroscopy’). Functionalization of 3,4-diphenylbutanal (1) at the α-position can lead to four stereoisomers, but photooxygenation catalyzed by secondary amines 16, 17 and 18 furnished only two of them. The diastereoisomeric ratio was always close to 2:1, the same as

• its rather simple structure diol 6 was not previously reported in the literature. The ratio of stereoisomers 6 was determined by HPLC analysis while the absolute configuration of the newly created stereocenter was established using a chiroptical spectroscopic method. Samples of stereoisomers syn-6 and

• based on the ECD spectra recorded for pure syn-6 and anti’-6 diols (Figure 1b) [29]. The comparison of the experimental ECD curves with the calculated ones for two possible stereoisomers (2R,3R) and (2R,3S) allowed for unambiguous assignment of (2R,3R) absolute configuration to the syn-6 isomer and (2R

Analysis of sesquiterpene hydrocarbons in grape berry exocarp (Vitis vinifera L.) using in vivo-labeling and comprehensive two-dimensional gas chromatography–mass spectrometry (GC×GC–MS)

• Philipp P. Könen and
• Matthias Wüst

Beilstein J. Org. Chem. 2019, 15, 1945–1961, doi:10.3762/bjoc.15.190

• stereoisomers α-ylangene and β-ylangene are formed via (R)-(+)-germacrene D. Furthermore, our results showed that the isomeric compounds α-cubebene and β-cubebene are also formed via (S)-(−)-germacrene D. In addition, 6 aromatic sesquiterpene hydrocarbons from the headspace of grape berry exocarp of the red

Synthesis of a [6]rotaxane with singly threaded γ-cyclodextrins as a single stereoisomer

• Jason Yin Hei Man and
• Ho Yu Au-Yeung

Beilstein J. Org. Chem. 2019, 15, 1829–1837, doi:10.3762/bjoc.15.177

• ). The 1H spectrum of 5R is much more complex. Ha of the anthracene stopper was observed as two overlapping doublets, and three triazole singlets and more than two sets of CB[6] signals were observed, showing that 5R was obtained as a mixture of stereoisomers with very different chemical environments at

• structural assignment of 5R may not be straightforward unless more detailed structural characterization such as X-ray crystal data is available. Nevertheless, the observation that 5R was obtained as different stereoisomers further strengthens the proposal that it is the full occupancy of the axle by the

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

• four stereoisomers with low (ca. 3:1) diastereoselectivity and in a non-enantioselective manner (Scheme 46) [21]. Undoubtedly, it was the 1,3-dipolar cycloaddition of the azomethine ylide 180 with an electron-rich alkene. Fortunately, cycloadducts (2R,3R,4S)-, (2S,3S,4R)-, (2R,3S,4R)- and (2S,3R,4S

• [110]. ʟ-1-Deoxynojirimycin ((2S,3S,4S,5R)-200) and five of its stereoisomers were synthesized in a unique approach using (2S,1'R)-5b as a starting material [88]. When the aziridine ketone (2S,1'R)-201 was treated with a NaBH4/ZnCl2 mixture the aziridine alcohol (2S,1'R,1''R)-202 was stereoselectively

Superelectrophilic carbocations: preparation and reactions of a substrate with six ionizable groups

• Sean H. Kennedy,
• Makafui Gasonoo and
• Douglas A. Klumpp

Beilstein J. Org. Chem. 2019, 15, 1515–1520, doi:10.3762/bjoc.15.153

• ), compound 9 undergoes two types of reactions. When the substrate is ionized in the presence of benzene and CF3SO3H, the arylation product 10 is formed as the major product (Scheme 3). Presumably, compound 10 is formed as a mixture of meso and dl stereoisomers. Similar reaction products were observed in our

Synthesis of pyrrolo[1,2-a]quinolines by formal 1,3-dipolar cycloaddition reactions of quinolinium salts

• Anthony Choi,
• Rebecca M. Morley and
• Iain Coldham

Beilstein J. Org. Chem. 2019, 15, 1480–1484, doi:10.3762/bjoc.15.149

• with triethylamine promoted the reaction of the resulting quinolinium ylides (formally azomethine ylides) with electron-poor alkenes by conjugate addition followed by cyclization or by [3 + 2] dipolar cycloaddition. The pyrroloquinoline products were formed as single regio- and stereoisomers. These

• with N-methylmaleimide in the presence of triethylamine in methanol to give the desired adducts 15a and 15b as single stereoisomers (Scheme 5). The stereochemistry of product 15a was confirmed by single crystal X-ray analysis (see Supporting Information File 1) and matches the relative configuration of

Introduction of an isoxazoline unit to the β-position of porphyrin via regioselective 1,3-dipolar cycloaddition reaction

• Xiujun Liu,
• Xiang Ma and
• Yaqing Feng

Beilstein J. Org. Chem. 2019, 15, 1434–1440, doi:10.3762/bjoc.15.143

• -generated nitrile oxide, which showed inferior selectivity and afforded regio-/stereoisomers [43]. NMR analysis assisted the identification of various isomeric isoxazoline-linked chlorin products. Here, we would like to report an artificial vinylporphyrin 2, which has been designed to control the

Borylation and rearrangement of alkynyloxiranes: a stereospecific route to substituted α-enynes

• Ruben Pomar Fuentespina,
• José Angel Garcia de la Cruz,
• Gabriel Durin,
• Victor Mamane,
• Jean-Marc Weibel and
• Patrick Pale

Beilstein J. Org. Chem. 2019, 15, 1416–1424, doi:10.3762/bjoc.15.141

• coupling reactions of either terminal or organometallic alkynes with vinyl halides or of alkynyl halides with vinylic organometallics [20]. However, both routes may lead to mixtures of stereoisomers and synthetic approaches to stereodefined substituted α-enynes remain scarce and thus still represent a

Synthesis of non-racemic 4-nitro-2-sulfonylbutan-1-ones via Ni(II)-catalyzed asymmetric Michael reaction of β-ketosulfones

• Alexander N. Reznikov,
• Anastasiya E. Sibiryakova,
• Marat R. Baimuratov,
• Eugene V. Golovin,
• Victor B. Rybakov and
• Yuri N. Klimochkin

Beilstein J. Org. Chem. 2019, 15, 1289–1297, doi:10.3762/bjoc.15.127

• cytotoxicity [9]. However, it is of great importance to obtain all stereoisomers for the study of biological activity. Therefore, the development of methods for the asymmetric synthesis of polyfunctional sulfones is valuable. The most notable of them are Ag- and Cu-catalyzed 1,3-dipolar cycloaddition reactions

• 8a or 9a. Оne of the stereoisomers can be formed directly during the reaction. To test this hypothesis, we decided to study the evolution of dr on the course of reaction by 1H NMR spectroscopy (Figure 3). The reaction of sulfone 5a with ω-nitrostyrene (6a) was chosen as the model reaction. Conversion