Binding abilities of a chiral calix[4]resorcinarene: a polarimetric investigation on a complex case of study

• Marco Russo and
• Paolo Lo Meo

Beilstein J. Org. Chem. 2017, 13, 2698–2709, doi:10.3762/bjoc.13.268

• occurring in host–guest complex formation processes involving calixarenes in general. This can be particularly useful, even because CAP and structurally related ligands might find various interesting applications, due to their amphiphilic character, chirality and coordination ability towards metal cations

Synthesis of 1,3-cis-disubstituted sterically encumbered imidazolidinone organocatalysts

• Jan Wallbaum and
• Daniel B. Werz

Beilstein J. Org. Chem. 2017, 13, 2577–2583, doi:10.3762/bjoc.13.254

• subtle differences in the substitution pattern a modular approach for their preparation is highly desirable. A simple retrosynthetic cut of the five-membered ring delivers an amino acid methyl amide and a carbaldehyde as starting materials. Chirality is commonly introduced by the use of derivatives of

Asymmetric synthesis of propargylamines as amino acid surrogates in peptidomimetics

• Matthias Wünsch,
• David Schröder,
• Tanja Fröhr,
• Lisa Teichmann,
• Sebastian Hedwig,
• Nils Janson,
• Clara Belu,
• Jasmin Simon,
• Shari Heidemeyer,
• Philipp Holtkamp,
• Jens Rudlof,
• Lennard Klemme,
• Alessa Hinzmann,
• Beate Neumann,
• Hans-Georg Stammler and
• Norbert Sewald

Beilstein J. Org. Chem. 2017, 13, 2428–2441, doi:10.3762/bjoc.13.240

• Supporting Information File 1). Independent on the substituent, solvent and Lewis acid used, the direction of the nucleophilic attack of (trimethylsilyl)ethynyllithium was always the same, forming the new centers of chirality of all N-sulfinyl propargylamines 7 configured as expected. As already described by

• ], it provides a versatile protective group for the amine during the conversion of the alkyne. Additionally, it’s chirality indicates epimerization and, for example in the Pauson–Khand reaction [14], allows the determination of the stereoselectivity of asymmetric conversions by simple 1H NMR experiments

Phosphonic acid: preparation and applications

• Charlotte M. Sevrain,
• Mathieu Berchel,
• Hélène Couthon and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2017, 13, 2186–2213, doi:10.3762/bjoc.13.219

• chiral auxiliary to control the chirality of the carbon atom in α-position of the phosphorus atom as exemplified by the alkylation of the phosphonodiamide 88 (Figure 27). Furthermore, phosphonodiamide can be purified by different methods including chromatography and their transformation to phosphonic

Remarkable functions of sn-3 hydroxy and phosphocholine groups in 1,2-diacyl-sn-glycerolipids to induce clockwise (+)-helicity around the 1,2-diacyl moiety: Evidence from conformation analysis by ¹H NMR spectroscopy

• Yoshihiro Nishida,
• Mengfei Yuan,
• Kazuo Fukuda,
• Kaito Fujisawa,
• Hirofumi Dohi and
• Hirotaka Uzawa

Beilstein J. Org. Chem. 2017, 13, 1999–2009, doi:10.3762/bjoc.13.196

• Yoshihiro Nishida Mengfei Yuan Kazuo Fukuda Kaito Fujisawa Hirofumi Dohi Hirotaka Uzawa Nanobiology Course in Graduate School of Advanced Integration Science & Molecular Chirality Research Center, Chiba University, Matsudo 271-8510, Chiba, Japan Nanomaterials Research Institute, National Institute

• used. From the 1H NMR analysis, the helical conformational properties around the 1,2-diacyl moiety conformed to a simple empirical rule, which permitted the proposal of a conformational diagram for 1,2-dipalmitoyl-sn-glycerols in the solution states. Keywords: cell membrane; chirality; conformation

• chiral biomolecules have an asymmetric sn-glycerol backbone. Although sn-glycerol is symmetric, an sn-3 phosphate group makes it chiral with an (R)-configuration at the sn-2 position [4]. Such molecular chirality is crucial to not only their biological activities but also for their metaphysical

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

• the enhancement of solubility, bioavailability and stability of drugs [2][3][4][5]. Moreover, being oligomers of α-D-glucopyranose, CDs possess an intrinsic chirality, thus they form diastereomeric inclusion complexes with enantiomeric pairs and frequently they exhibit enantioselectivity in aqueous

• The molecular models of D-NAcTrp complexes were based (a) on the geometry of the major orientation of β-CD–L-NAcTrp by changing the chirality of the Cα atom and (b) on β-CD non-hydrogen atoms of the corresponding lattice. To relieve steric clashes, restrained energy minimization of D-NAcTrp have been

• cavity with the aliphatic part protruding from its primary side towards the empty space formed by three neighboring β-CD monomers of the lattice (Figure 4b), whereas for the β-CD–D-NAcTrp dimer model the crystallographic coordinates of the β-CD–L-NAcTrp dimer were employed after changing the chirality of

Bifunctional organocatalysts for the asymmetric synthesis of axially chiral benzamides

• Ryota Miyaji,
• Yuuki Wada,
• Akira Matsumoto,
• Keisuke Asano and
• Seijiro Matsubara

Beilstein J. Org. Chem. 2017, 13, 1518–1523, doi:10.3762/bjoc.13.151

• . Moderate to good enantioselectivities were afforded with a range of benzamide substrates. Mechanistic investigations were also carried out. Keywords: axial chirality; benzamide; bifunctional organocatalyst; molecular conformation; multipoint recognition; Introduction Bifunctional organocatalysts have

• resolution [42][43][44][45][46][47], desymmetrization [48][49][50][51][52][53][54], de novo annulation [55][56][57][58][59][60][61], and point-to-axial chirality transfer [58][59] (for reviews, see references [31][62][63]), motivated us to expand on the utility of this class of small-molecule catalysts. We

• axial chirality [36][37]. Thus, we assumed that this method could be further applied to the enantioselective synthesis of a range of axially chiral compounds. In this study, we present the enantioselective synthesis of 3-hydroxybenzamides via aromatic electrophilic bromination [28][29]. The 3

Base-promoted isomerization of CF₃-containing allylic alcohols to the corresponding saturated ketones under metal-free conditions

• Yoko Hamada,
• Tomoko Kawasaki-Takasuka and
• Takashi Yamazaki

Beilstein J. Org. Chem. 2017, 13, 1507–1512, doi:10.3762/bjoc.13.149

• the toluene refluxing temperature, and utilization of the corresponding optically active substrates unambiguously demonstrated that this transformation proceeded in a highly stereoselective fashion. Keywords: allylic alcohols; chirality; computation; 1,3-proton shift; trifluoromethyl; Introduction

• chirality transmission (CT) on the basis of the chiral HPLC analysis (Table 4, entries 1, 4, and 5). Unanimous formation of (R)-stereoisomers at the 3 position of 7 from (R,E)-6 led to confirmation that the proton attached to C1 was migrated to C3 from its si face, thus from the same back side if (R,E)-6

• tractable tertiary amine as DBU, thus under metal-free conditions like the cases of the Ando [14] and Martín-Matute groups [15]. Moreover, this intriguing proton shift was clarified to be applied for optically active allylic alcohols whose chirality was transmitted almost in a perfect fashion. These results

Synthesis of alkynyl-substituted camphor derivatives and their use in the preparation of paclitaxel-related compounds

• M. Fernanda N. N. Carvalho,
• Rudolf Herrmann and
• Gabriele Wagner

Beilstein J. Org. Chem. 2017, 13, 1230–1238, doi:10.3762/bjoc.13.122

• the addition of organometallic reagents to the camphor carbonyl group allows for selective introduction of additional substituents and functional groups (e.g., as in [7]). Camphor was the source of chirality in Holton’s taxol synthesis [8] and other approaches to the taxane group of compounds [9][10

Cycloheximide congeners produced by Streptomyces sp. SC0581 and photoinduced interconversion between (E)- and (Z)-2,3-dehydroanhydrocycloheximides

• Li Yang,
• Ping Wu,
• Jinghua Xue,
• Huitong Tan,
• Zheng Zhang and
• Xiaoyi Wei

Beilstein J. Org. Chem. 2017, 13, 1039–1049, doi:10.3762/bjoc.13.103

• geometries around torsion angles (C1–C6–Cα–Cβ, Φ) of 90° and −90° in the S1 surface, for which optimizations failed to converge. Due to the presence of the stereogenic center C4 in 2a and 3a, the twisted structures around Φ 90º and −90° are diastereomeric in chirality [15]. Thus, two twisted minima, P and P

Inclusion complexes of β-cyclodextrin with tricyclic drugs: an X-ray diffraction, NMR and molecular dynamics study

• Franca Castiglione,
• Fabio Ganazzoli,
• Luciana Malpezzi,
• Andrea Mele,
• Walter Panzeri and
• Giuseppina Raffaini

Beilstein J. Org. Chem. 2017, 13, 714–719, doi:10.3762/bjoc.13.70

• compound 1. Compounds 1 and 2 are not planar and the exocyclic double bond prevents the free rotation of the side chain with respect to the ring system. Consequently, 1 and 2 show inherent chirality [9] as lacking of symmetry elements. The main purpose of the work is the comparison of the structural

Studies directed toward the exploitation of vicinal diols in the synthesis of (+)-nebivolol intermediates

• Runjun Devi and
• Sajal Kumar Das

Beilstein J. Org. Chem. 2017, 13, 571–578, doi:10.3762/bjoc.13.56

• Runjun Devi Sajal Kumar Das Department of Chemical Sciences, Tezpur University, Napaam, Tezpur, Assam-784028, India 10.3762/bjoc.13.56 Abstract While the exploitation of the Sharpless asymmetric dihydroxylation as the source of chirality in the synthesis of acyclic molecules and saturated

• that a large number of racemic and asymmetric syntheses of nebivolol and their intermediates have been described in the literature, however, the Sharpless asymmetric dihydroxylation has never been employed as the sole source of chirality for this purpose. Keywords: dihydroxylation; epoxide-ring

• Sharpless asymmetric dihydroxylation as the sole source of chirality [27]. For the synthesis of chroman derivative 2, first a base-mediated intramolecular SNAr reaction was envisioned for the aryl C–O bond formation under transition-metal-free conditions [28][29][30]. The additional benefit of this strategy

Polyketide stereocontrol: a study in chemical biology

• Kira J. Weissman

Beilstein J. Org. Chem. 2017, 13, 348–371, doi:10.3762/bjoc.13.39

• controlling the configurational outcomes. Finally, where chirality is introduced, post-PKS processing reactions also proceed with defined stereochemistry, although this aspect will also not be discussed in this article. The following sections will address the role of each of the principal PKS domains in

New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation

• Pavel Nagorny and
• Zhankui Sun

Beilstein J. Org. Chem. 2016, 12, 2834–2848, doi:10.3762/bjoc.12.283

• form the corresponding salts, and these generated in situ ion pairs were treated with silyl enol ethers in the presence of chiral catalysts L2–L4 to form chiral addition products. High levels of chirality transfer were generally observed for various 6-membered nitrogen-containing heterocyclic

• as potential catalysts, and chiral catalyst L25 was identified as the catalyst of choice. Although no chirality transfer was observed during the reduction of 2-phenylquinoline, L25 was found to be a very active catalyst promoting transfer hydrogenation of a C=N group containing heterocycles and

Biomimetic synthesis and HPLC–ECD analysis of the isomers of dracocephins A and B

• Viktor Ilkei,
• András Spaits,
• Anita Prechl,
• Áron Szigetvári,
• Zoltán Béni,
• Miklós Dékány,
• Csaba Szántay Jr,
• Judit Müller,
• Árpád Könczöl,
• Ádám Szappanos,
• Attila Mándi,
• Sándor Antus,
• Ana Martins,
• Attila Hunyadi,
• György Tibor Balogh,
• György Kalaus (†),
• Hedvig Bölcskei,
• László Hazai and
• Tibor Kurtán

Beilstein J. Org. Chem. 2016, 12, 2523–2534, doi:10.3762/bjoc.12.247

• conjugates of racemic naringenin ((±)-1) with pyrrolidine-2-one with C-6–C-5” and C-8–C-5” linkage, respectively. Due to the two chirality centers, four possible stereoisomers exist for each regioisomer, and accordingly, the isolated substances were verified to be 1:1 mixtures of two diastereoisomeric

A new and expeditious synthesis of all enantiomerically pure stereoisomers of rosaprostol, an antiulcer drug

• Wiesława Perlikowska,
• Remigiusz Żurawiński and
• Marian Mikołajczyk

Beilstein J. Org. Chem. 2016, 12, 2234–2239, doi:10.3762/bjoc.12.215

• (−)-1a obtained herein has the absolute configuration R at the C-2 stereogenic center. As the chirality at this carbon atom remains unchanged in the four-step conversion of (+)-3 into (−)-1a, the same chirality has to be assigned to the corresponding carbon atom (now C-3) in (+)-3. Taking into account a

Determination of the absolute stereostructure of a cyclic azobenzene from the crystal structure of the precursor containing a heavy element

• Reji Thomas and
• Nobuyuki Tamaoki

Beilstein J. Org. Chem. 2016, 12, 2211–2215, doi:10.3762/bjoc.12.212

• ; cyclic compound; enantiomer; stereostructure; X-ray crystal analysis; Introduction Chirality is a topic of fundamental importance in several branches of science [1][2][3][4][5]. Homochirality in nature was one of the most important challenges for researchers and the origin is still unsolved [6][7][8

• pharmaceutical ingredients [11]. In addition to the special interest in molecular chirality in diverse fields of biology and pharmaceutical chemistry, several chiral molecules have been synthesised and studied for their stereostructure-dependent physical properties such as optical activity [12][13][14][15][16

• chirality methods [28][29], NMR spectroscopy [30][31][32], X-ray diffraction [33][34][35], etc. In addition to these methods, many researchers explored a combination of vibrational circular dichroism and quantum mechanical calculations to determine the absolute stereostructures [36][37][38]. Among various

Varioloid A, a new indolyl-6,10b-dihydro-5aH-[1]benzofuro[2,3-b]indole derivative from the marine alga-derived endophytic fungus Paecilomyces variotii EN-291

• Peng Zhang,
• Xiao-Ming Li,
• Xin-Xin Mao,
• Attila Mándi,
• Tibor Kurtán and
• Bin-Gui Wang

Beilstein J. Org. Chem. 2016, 12, 2012–2018, doi:10.3762/bjoc.12.188

• Cotton effects (CEs) had the same sign for conformer A and B, while the lower-wavelength (<250 nm) CEs were significantly different. The hindered rotation along the biaryl linkage may have implied an additional stereogenic element, which would have enabled atropodiastereomers with axial chirality. In

• order to explore the possibility of axial chirality, torsional angle scans were performed on the lowest-energy M (conformer A) and P (conformer B) helicity gas-phase conformers or atropodiastereomers. Rotational energy barriers between the two isomers were estimated to be ca. 35–42 kJ/mol for TS1 (ωC12

• showed that there is no axial chirality in 1, and equilibrating conformers with M and P helicity are present in solution as obtained in the conformational analysis. The Boltzmann-weighted ECD spectra calculated for both the gas-phase and the solvent model conformers of (2R,3R)-1 at B3LYP/TZVP, BH&HLYP

Enantioselective addition of diphenyl phosphonate to ketimines derived from isatins catalyzed by binaphthyl-modified organocatalysts

• Hee Seung Jang,
• Yubin Kim and
• Dae Young Kim

Beilstein J. Org. Chem. 2016, 12, 1551–1556, doi:10.3762/bjoc.12.149

• properties [5], enzyme inhibition [6], peptide mimetic function [7], and herbicidal properties [8]. Since the biological activity of α-aminophosphonate derivatives is dependent upon the chirality of the α-position to the phosphorus atom, asymmetric synthesis of α-aminophosphonates has received considerable

Stereodynamic tetrahydrobiisoindole “NU-BIPHEP(O)”s: functionalization, rotational barriers and non-covalent interactions

• Golo Storch,
• Sebastian Pallmann,
• Frank Rominger and
• Oliver Trapp

Beilstein J. Org. Chem. 2016, 12, 1453–1458, doi:10.3762/bjoc.12.141

• ][6], palladium [7][8], platinum [9][10] and gold [11][12][13] in combination with chiral co-ligands or counter ions that are used after alignment of the ligand’s axial chirality. One major advantage of stereodynamic ligands is that there is no need for separate preparation of one ligand enantiomer as

• long as their chirality can be controlled by chiral additives or auxiliaries. In addition, the simultaneous presence of both axially chiral BIPHEP enantiomers can be beneficial as this allows bidirectional control of enantioselectivity depending on temperature [14][15]. In this approach, both product

A practical way to synthesize chiral fluoro-containing polyhydro-2H-chromenes from monoterpenoids

• Oksana S. Mikhalchenko,
• Dina V. Korchagina,
• Konstantin P. Volcho and
• Nariman F. Salakhutdinov

Beilstein J. Org. Chem. 2016, 12, 648–653, doi:10.3762/bjoc.12.64

• -fluorohexahydro-2H-chromenes under the developed conditions, the reaction occurs with inversion of configuration. Keywords: chirality; fluorine; halo-Prins reaction; isopulegol; monoterpene; Introduction Recently, we have found that a reaction between para-mentha-6,8-dien-2,3-diol (1) and aromatic aldehydes in

New synthetic strategies for xanthene-dye-appended cyclodextrins

• Milo Malanga,
• Andras Darcsi,
• Mihaly Balint,
• Gabor Benkovics,
• Tamas Sohajda and
• Szabolcs Beni

Beilstein J. Org. Chem. 2016, 12, 537–548, doi:10.3762/bjoc.12.53

• scaffold. Because of the chirality of the cyclodextrin part, the two phenyl rings of the xanthene moiety are formally diastereotopic, and consequently, anisochronous even without any complexation. This fact can be proven by recording the 1H NMR spectrum of the Rho-β-CD in deuterated DMSO, a solvent known

The aminoindanol core as a key scaffold in bifunctional organocatalysts

• Isaac G. Sonsona,
• Eugenia Marqués-López and
• Raquel P. Herrera

Beilstein J. Org. Chem. 2016, 12, 505–523, doi:10.3762/bjoc.12.50

• ; bifunctional; organocatalysis; hydrogen bonding; Introduction The structural and chemical properties of the 1,2-aminoindanol scaffold 1 have transformed aminoindanol derivatives into versatile building blocks for the construction of catalysts and the efficient induction of chirality in asymmetric processes

• amino groups. Although the aminoindanol scaffold appears in the structure of different catalysts (providing a suitable way to induce chirality), it is not always directly involved in the bifunctional activation of the substrates [17]. Herein, we show only those cases where the aminoindanol moiety

• through an organocatalyzed asymmetric domino-Michael addition/Henry reaction (Scheme 8) [36]. These heterocyclic products are important chiral building blocks for the synthesis of organocatalytic frameworks and ligands for chiral metal complexes, both with the potential ability to induce chirality. They

Effective in silico prediction of new oxazolidinone antibiotics: force field simulations of the antibiotic–ribosome complex supervised by experiment and electronic structure methods

• Jörg Grunenberg and
• Giuseppe Licari

Beilstein J. Org. Chem. 2016, 12, 415–428, doi:10.3762/bjoc.12.45

• enantioselectivity (it is well known that (S)-linezolid is the only active enantiomer) of the recognition process [16][42]. Again, the working-shell was used for this purpose as starting structure. The chirality of linezolid was inverted in place inside the receptor. (R)-Linezolid was rotated by 180° around an

Self and directed assembly: people and molecules

• Tony D. James

Beilstein J. Org. Chem. 2016, 12, 391–405, doi:10.3762/bjoc.12.42

• group were developing carbohydrate receptors from what looked like simple molecules requiring just one or two steps to synthesize. Therefore, while working with the late Takaaki Harada, we developed a simple colorimetric system able to “read-out” the chirality of sugars. The system we developed used the

• colour of liquid crystals to determine chirality and was quickly prepared in just two steps. The addition of our D-glucose boronate complex to a liquid crystal system the colour changed from green to red, however for the L-glucose system the colour changed from green to blue [11][12] (Figure 2 depicting

• acid spontaneously self-assemble to quantitatively form a stable complex. Interestingly, when the chirality of the binol or amine was fixed the 1H NMR of the complexes formed using a scalemic mixture of the other chiral partner (diol or amine) results in a 1H NMR where signals due to both