6’-Fluoro[4.3.0]bicyclo nucleic acid: synthesis, biophysical properties and molecular dynamics simulations

• Sibylle Frei,
• Andrei Istrate and
• Christian J. Leumann

Beilstein J. Org. Chem. 2018, 14, 3088–3097, doi:10.3762/bjoc.14.288

• to the hindrance of the difluorocarbene attack on the double bond. The stereochemistry around the cyclopropane ring (endo vs exo) could be assessed by the characteristic coupling pattern between the fluorine atom and the H-C(1) or C(7) in the endo-tricyclic sugars in the corresponding 1H and 13C NMR

A tutorial review of stereoretentive olefin metathesis based on ruthenium dithiolate catalysts

• Daniel S. Müller,
• Olivier Baslé and
• Marc Mauduit

Beilstein J. Org. Chem. 2018, 14, 2999–3010, doi:10.3762/bjoc.14.279

• metathesis the stereochemistry of the starting material is retained throughout the reaction: Z-alkenes starting materials lead to Z-alkene products and E-alkene starting materials lead to E-alkene products [1]. The first ruthenium dithiolate catalysts Ru-1 and Ru-2 were reported by Hoveyda in 2013 [2]. Ru-1

• previously discussed in the section "Mechanistic models". Cross metathesis utilizing the in situ methylene capping strategy with 1,1-disubstituted allylic alcohols Z-39 or E-39 afforded the products 40–42 in good yield and with excellent retention of stereochemistry independent of the configuration of the

Green synthesis of new chiral 1-(arylamino)imidazo[2,1-a]isoindole-2,5-diones from the corresponding α-amino acid arylhydrazides in aqueous medium

• Nadia Bouzayani,
• Jamil Kraїem,
• Sylvain Marque,
• Yakdhane Kacem,
• Abel Carlin-Sinclair,
• Jérôme Marrot and
• Béchir Ben Hassine

Beilstein J. Org. Chem. 2018, 14, 2923–2930, doi:10.3762/bjoc.14.271

• . The reaction is totally diastereoselective and gives access to the nitrogenated tricyclic core with a relative trans stereochemistry. Keywords: sodium dodecyl sulfate; totally diastereoselective; trans-stereochemistry; Introduction Tricyclic compounds, such as imidazo[2,1-a]isoindol-5-ones, are

• reaction described in this work occurred with high atom efficiency (atom economy of 90%) and produced only stoichiometric H2O as waste (E-factor of 0.1). Stereochemistry and mechanism The stereochemistries of 5a–m were ascribed by NOE NMR experiments. By example using 5a depicted in Figure 2, the 1H NMR

• in a trans-orientation with H(4). In addition, various crystallization tests were carried out in order to confirm the absolute stereochemistry by X-ray diffraction. The chiral 3-(2-(methylthio)ethyl)-1-(phenylamino)-1H-imidazo[2,1-a]isoindole-2,5(3H,9bH)dione (5f) crystallized [44][45][46][47][48][49

Pd-Catalyzed microwave-assisted synthesis of phosphonated 13α-estrones as potential OATP2B1, 17β-HSD1 and/or STS inhibitors

• Rebeka Jójárt,
• Szabolcs Pécsy,
• György Keglevich,
• Mihály Szécsi,
• Réka Rigó,
• Csilla Özvegy-Laczka,
• Gábor Kecskeméti and
• Erzsébet Mernyák

Beilstein J. Org. Chem. 2018, 14, 2838–2845, doi:10.3762/bjoc.14.262

• position, size and polarity are expected to have remarkable influence on the affinity for the target proteins. Investigation of the influence of the nature of the atom attached directly to the aromatic ring A of 13α-estrone and the stereochemistry of the introduced moiety would also be of high interest

Synthesis of pyrrolidine-based hamamelitannin analogues as quorum sensing inhibitors in Staphylococcus aureus

• Jakob Bouton,
• Kristof Van Hecke,
• Reuven Rasooly and
• Serge Van Calenbergh

Beilstein J. Org. Chem. 2018, 14, 2822–2828, doi:10.3762/bjoc.14.260

• which the cationic character of the pyrrolidine nitrogen is removed, were also synthesized. The correct stereochemistry of the synthesized analogues was unequivocally proven via X-ray structural analysis of compound 3a (Figure 2). Biological evaluation The synthesized analogues were tested in a S

Copolymerization of epoxides with cyclic anhydrides catalyzed by dinuclear cobalt complexes

• Yo Hiranoi and
• Koji Nakano

Beilstein J. Org. Chem. 2018, 14, 2779–2788, doi:10.3762/bjoc.14.255

• stereochemistry of the copolymer prepared from enantiomerically pure (S)-PO. Because a ring opening at the methine carbon results in both a regioerror and the inversion of stereochemistry at the stereocenter, the enantiomeric excess (ee) of the repeating unit in the copolymer should reflect the regioregularity

Ring-opening metathesis of some strained bicyclic systems; stereocontrolled access to diolefinated saturated heterocycles with multiple stereogenic centers

• Zsanett Benke,
• Melinda Nonn,
• Márton Kardos,
• Santos Fustero and
• Loránd Kiss

Beilstein J. Org. Chem. 2018, 14, 2698–2707, doi:10.3762/bjoc.14.247

• Zsanett Benke Melinda Nonn Marton Kardos Santos Fustero Lorand Kiss Institute of Pharmaceutical Chemistry, University of Szeged, Eötvös u. 6, H-6720 Szeged, Hungary MTA-SZTE Stereochemistry Research Group, Hungarian Academy of Sciences, Eötvös u. 6, H-6720 Szeged, Hungary Departamento de Química

Non-native autoinducer analogs capable of modulating the SdiA quorum sensing receptor in Salmonella enterica serovar Typhimurium

• Matthew J. Styles and
• Helen E. Blackwell

Beilstein J. Org. Chem. 2018, 14, 2651–2664, doi:10.3762/bjoc.14.243

• -libraries were designed to test the effects of lactone stereochemistry, substitution of a variety of more structurally diverse and non-native functional groups on the acyl tail (e.g., alkyl, cycloalkyl, and aryl), and alkyl linker length between the head group and these functional groups [51]. The C and E

• head group to a phenyl or cyclohexane was not well tolerated; however, cyclopentane, thiolactones, and the alternative stereochemistry, D-lactone were generally tolerated. Interestingly, 1-octanoyl-rac-glycerol (23) showed no agonism in this reporter assay, suggesting it does not act as an AHL signal

Synergistic approach to polycycles through Suzuki–Miyaura cross coupling and metathesis as key steps

• Sambasivarao Kotha,
• Milind Meshram and
• Chandravathi Chakkapalli

Beilstein J. Org. Chem. 2018, 14, 2468–2481, doi:10.3762/bjoc.14.223

• 121 was accomplished with PCC to provide the corresponding diones 120 (79%) and 122 (76%) with trans geometry. The stereochemistry was confirmed on the basis of the coupling constant (J = 15.0 Hz, 1H NMR spectrum) of the olefinic protons (Scheme 18). A variety of macrocycles were synthesized through

Non-metal-templated approaches to bis(borane) derivatives of macrocyclic dibridgehead diphosphines via alkene metathesis

• Tobias Fiedler,
• Michał Barbasiewicz,
• Michael Stollenz and
• John A. Gladysz

Beilstein J. Org. Chem. 2018, 14, 2354–2365, doi:10.3762/bjoc.14.211

• of the key alkene metathesis steps in Scheme 2 and Scheme 5. Steps that set the in,in/out,out vs in,out stereochemistry of 2·2BH3 in Scheme 2 and Scheme 5. Another non-metal-templated approach to dibridgehead diphosphorus compounds. Previously synthesized dibridgehead diphosphine diboranes. Alkene

Stereoselective total synthesis and structural revision of the diacetylenic diol natural products strongylodiols H and I

• Pamarthi Gangadhar,
• Sayini Ramakrishna,
• Ponneri Venkateswarlu and
• Pabbaraja Srihari

Beilstein J. Org. Chem. 2018, 14, 2313–2320, doi:10.3762/bjoc.14.206

• esters showed a positive chemical shift difference ∆δ for the protons at C7 and C8 indicating the R configuration at C6 in compound 25 (see Figure 2). Having determined the stereochemistry at the newly generated carbon center in intermediate 25, we proceeded further to extend the chain at the right hand

Synthesis of 1,4-imino-L-lyxitols modified at C-5 and their evaluation as inhibitors of GH38 α-mannosidases

• Maroš Bella,
• Sergej Šesták,
• Ján Moncoľ,
• Miroslav Koóš and
• Monika Poláková

Beilstein J. Org. Chem. 2018, 14, 2156–2162, doi:10.3762/bjoc.14.189

• -5 stereocenter. This elongation led to about 25-fold decrease in inhibition activity against GMIIb in comparison with 1a. It is interesting that the increase of IC50 values was essentially not influenced by the stereochemistry at C-5 in 4a and 5a. On the contrary, the introduction of a halogen atom

Studies towards the synthesis of hyperireflexolide A

• G. Hari Mangeswara Rao

Beilstein J. Org. Chem. 2018, 14, 2106–2111, doi:10.3762/bjoc.14.185

• product was isolated from these bis-alkylation reactions due to favorable attack from the less hindered convex face of 6 [10] to give α,α'-cis stereochemistry. Now the stage has been set for allylation of γ-lactone fused cyclopentanone 6. Treatment of 6 with K2CO3 in the presence of allyl bromide at 0 °C

• -lactone fused cyclopentanone 10 in excellent yield (Scheme 4). Allylation and methylation both were occurred stereoselectively from the convex face to give α,α'-cis stereochemistry. The allyl derivative 10 was then subjected to cross metathesis reaction with ethyl vinyl ketone. Initially, the reaction

Synthesis of spirocyclic scaffolds using hypervalent iodine reagents

• Fateh V. Singh,
• Priyanka B. Kole,
• Saeesh R. Mangaonkar and
• Samata E. Shetgaonkar

Beilstein J. Org. Chem. 2018, 14, 1778–1805, doi:10.3762/bjoc.14.152

• -substituted phenol 126 to tricyclic spiroketals 127a,b in 56% yield using PIDA (15) as electrophilic species in acetonitrile at room temperature (Scheme 47). The mixture of both isomers was separated by flash column chromatography and the stereochemistry of major isomer 127a was assigned on the basis of NOE

Heterogeneous acidic catalysts for the tetrahydropyranylation of alcohols and phenols in green ethereal solvents

• Ugo Azzena,
• Massimo Carraro,
• Gloria Modugno,
• Luisa Pisano and
• Luigi Urtis

Beilstein J. Org. Chem. 2018, 14, 1655–1659, doi:10.3762/bjoc.14.141

• , successfully catalyzes the protection of a variety of functionalized and non-functionalized alcohols and phenols, including an optically pure alcohol with no detrimental effects on its stereochemistry. Due to a particularly simple work-up procedure, NH4HSO4@SiO2 can be easily recovered and recycled several

Glycosylation reactions mediated by hypervalent iodine: application to the synthesis of nucleosides and carbohydrates

• Yuichi Yoshimura,
• Hideaki Wakamatsu,
• Yoshihiro Natori,
• Yukako Saito and
• Noriaki Minakawa

Beilstein J. Org. Chem. 2018, 14, 1595–1618, doi:10.3762/bjoc.14.137

• reaction of trans-cyclobutane sulfoxide 59. The authors concluded that the stereochemistry of the sulfoxide and the nature of the protecting groups had no significant effect on the yield of the Pummerer-type glycosylation [47] (Scheme 8). Pummerer-type glycosylation, which was developed by our group

An unusual thionyl chloride-promoted C−C bond formation to obtain 4,4'-bipyrazolones

• Gernot A. Eller,
• Gytė Vilkauskaitė,
• Algirdas Šačkus,
• Vytas Martynaitis,
• Ashenafi Damtew Mamuye,
• Vittorio Pace and
• Wolfgang Holzer

Beilstein J. Org. Chem. 2018, 14, 1287–1292, doi:10.3762/bjoc.14.110

• and elemental analysis confirmed the molecular formula. The non-equivalence of the OCH2 protons of the ester functions can be smoothly explained by the presence of an asymmetric carbon atom at pyrazole C4/C4'. As the NMR spectra displayed a single set of signals, regarding the stereochemistry a

Stereoselective nucleophilic addition reactions to cyclic N-acyliminium ions using the indirect cation pool method: Elucidation of stereoselectivity by spectroscopic conformational analysis and DFT calculations

• Koichi Mitsudo,
• Junya Yamamoto,
• Tomoya Akagi,
• Atsuhiro Yamashita,
• Masahiro Haisa,
• Kazuki Yoshioka,
• Hiroki Mandai,
• Koji Ueoka,
• Christian Hempel,
• Jun-ichi Yoshida and
• Seiji Suga

Beilstein J. Org. Chem. 2018, 14, 1192–1202, doi:10.3762/bjoc.14.100

• give the disubstituted piperidine derivatives in an excellent diastereoselective manner (Scheme 1). This result inspired us to investigate the stereochemistry of the N-acyliminium ions by means of NMR spectroscopy, which is challenging to achieve without using cation pool methods. The current report

• stereochemistry of the N-acyliminium ions and the reaction products is in agreement with common interpretation and further synthetic applications and more detailed investigations of the reaction mechanism are in progress in our laboratory. (a) 1H NMR of N-acyliminium ion C1 in CD2Cl2 at −80 °C (600 MHz). (b

Synthetic avenues towards a tetrasaccharide related to Streptococcus pneumonia of serotype 6A

• Aritra Chaudhury,
• Mana Mohan Mukherjee and
• Rina Ghosh

Beilstein J. Org. Chem. 2018, 14, 1095–1102, doi:10.3762/bjoc.14.95

• 100.1 (1JC1-H1 = 169.2 Hz), respectively. The values are indicative of α-stereochemistry at all the anomeric centers [42]. Moreover, the chemical shifts were found to be in fair agreement with the reported C-1 chemical shifts at δ 99.5, 95.6, and 100.3, exhibited in D2O corresponding to the anomeric

Recent advances in synthetic approaches for medicinal chemistry of C-nucleosides

• Kartik Temburnikar and
• Katherine L. Seley-Radtke

Beilstein J. Org. Chem. 2018, 14, 772–785, doi:10.3762/bjoc.14.65

• maneuver stereochemistry as well as to incorporate structural modifications. In this review, we describe recent reports on the modular synthesis of C-nucleosides with a focus on D-ribonolactone and sugar modifications that have resulted in potent lead molecules. Keywords: C-nucleosides; convergent

• that is also based on the nucleophilic substitution of ribonolactone. Review Nucleophilic addition to D-ribonolactone and its stereochemistry Two prominent methods of C-nucleoside syntheses involve either i) the linear construction of a (hetero)aryl moiety on a C1'-functionalized ribose or ii) coupling

• in turn, is affected by the nature of the C2', C3' and C5' substituents [80][81]. Codée and coworkers elaborated on the mechanism and stereochemistry of this reaction by calculating the energies of different oxocarbenium conformers using a free energy surface (FES) mapping method [80][81]. These

Stepwise radical cation Diels–Alder reaction via multiple pathways

• Ryo Shimizu,
• Yohei Okada and
• Kazuhiro Chiba

Beilstein J. Org. Chem. 2018, 14, 704–708, doi:10.3762/bjoc.14.59

• adduct 3 was an approximately cis/trans = 1:2 mixture, the reaction must proceed in a stepwise fashion. This stereochemistry was confirmed when the E-form 1E also gave the same synthetic outcome. Namely, the Diels–Alder adduct 3 was obtained as an approximately cis/trans = 1:2 mixture, indicating that

• reaction of the aryl vinyl ether 1 (Scheme 7). On the basis of the oxidation potentials, oxidative SET would selectively take place from the aryl vinyl ether 1 even in the presence of 2,3-dimethyl-1,3-butadiene (2) to generate the radical cation 1·+, in which the stereochemistry derived from the starting

Liquid-assisted grinding and ion pairing regulates percentage conversion and diastereoselectivity of the Wittig reaction under mechanochemical conditions

• Kendra Leahy Denlinger,
• Lianna Ortiz-Trankina,
• Preston Carr,
• Kingsley Benson,
• Daniel C. Waddell and
• James Mack

Beilstein J. Org. Chem. 2018, 14, 688–696, doi:10.3762/bjoc.14.57

• the reaction in comparison to completely solvent-free conditions. Finally, we observed that there was an effect of the dielectric constant of the solvent used in LAG on the stereochemistry of the product [27]. Although previously we were able to generate high yields of Wittig products under liquid

Mannich base-connected syntheses mediated by ortho-quinone methides

• Petra Barta,
• Ferenc Fülöp and
• István Szatmári

Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43

• Petra Barta Ferenc Fulop Istvan Szatmari Institute of Pharmaceutical Chemistry and Research Group for Stereochemistry, Hungarian Academy of Sciences, University of Szeged, Eötvös u. 6, H-6720 Szeged, Hungary 10.3762/bjoc.14.43 Abstract This article provides an overview about specifically modified

Latest development in the synthesis of ursodeoxycholic acid (UDCA): a critical review

• Fabio Tonin and
• Isabel W. C. E. Arends

Beilstein J. Org. Chem. 2018, 14, 470–483, doi:10.3762/bjoc.14.33

• containing 5β-steroids. Their structure contains multiple hydroxy substituents: the position and the stereochemistry of these OH groups influence the solubility and biochemical properties of the compounds. In CA, for example, the OH groups on the steroidal ring are all in α-position with respect to the ring

• are related to the position and stereochemistry of the hydroxy groups attached to the steroid ring. A general structure with the names of several bile acids is reported in Figure 2. Deconjugation Free bile acids can be obtained from the corresponding bile amides (with glycine and taurine) through a

Syn-selective silicon Mukaiyama-type aldol reactions of (pentafluoro-λ⁶-sulfanyl)acetic acid esters with aldehydes

• Anna-Lena Dreier,
• Andrej V. Matsnev,
• Joseph S. Thrasher and
• Günter Haufe

Beilstein J. Org. Chem. 2018, 14, 373–380, doi:10.3762/bjoc.14.25

• : aldol reaction; ester enolate; fluorine; SF5 compounds; stereochemistry; Introduction The classical acid- or base-catalyzed directed cross aldol reaction of an aldehyde and an enolizable second carbonyl compound is one of the most powerful and reliable carbon–carbon bond-forming transformations in

• oils and could not be crystallized. Thus, in order to determine the relative stereochemistry, we analyzed the vicinal coupling constants of the protons attached to the stereocenters. In the syn-isomers 2 these protons are anti to each other, while in the anti-isomers 3 these protons are in a syn