Copper-catalyzed asymmetric conjugate addition of organometallic reagents to extended Michael acceptors

• Thibault E. Schmid,
• Sammy Drissi-Amraoui,
• Christophe Crévisy,
• Olivier Baslé and
• Marc Mauduit

Beilstein J. Org. Chem. 2015, 11, 2418–2434, doi:10.3762/bjoc.11.263

• it enables in a straightforward manner the sequential generation of two or more stereogenic centers. In the last decade, various chiral copper-based catalysts were evaluated in combination with different nucleophiles and Michael acceptors, and have unambiguously demonstrated their usefulness in the

• studied on a substrate scope. As shown in Scheme 2, tertiary and quaternary stereogenic centers could be generated using this methodology leading to products 19 in moderate to good yields and ees. In 2008, Alexakis and Mauduit evaluated a series of different chiral ligands in ACA reactions involving

• (CuTC) and (R)-Binap L4, which afforded the desired final products bearing two stereogenic centers with excellent diastereoselectivies (93–97%). N-Heterocyclic carbenes (NHCs) have emerged, in these last two decades, as a powerful and versatile class of ligands, and appeared to be potent in many

The marine sponge Agelas citrina as a source of the new pyrrole–imidazole alkaloids citrinamines A–D and N-methylagelongine

• Christine Cychon,
• Ellen Lichte and
• Matthias Köck

Beilstein J. Org. Chem. 2015, 11, 2029–2037, doi:10.3762/bjoc.11.220

• guanidine moiety). The relative configuration of the stereogenic centers C-9 and C-10 was identical as described for nagelamide B (8). In contrast to citrinamine C (3), a different connection of the monomeric units was found for citrinamine D (4). Furthermore, 3 and 4 have an additional methoxy group at C-9

Chiral Cu(II)-catalyzed enantioselective β-borylation of α,β-unsaturated nitriles in water

• Lei Zhu,
• Taku Kitanosono,
• Pengyu Xu and
• Shū Kobayashi

Beilstein J. Org. Chem. 2015, 11, 2007–2011, doi:10.3762/bjoc.11.217

• linkage can be transformed into C–O, C–N, as well as into C–C bonds, while retaining stereogenic centers [1][2][3][4]. The nitrile group can be transformed into a range of functional groups, such as amides [5], carboxylic acids [6], aldehydes [7], esters [8], alcohols [9], and amines [10

Investigation of the role of stereoelectronic effects in the conformation of piperidones by NMR spectroscopy and X-ray diffraction

• Cesar Garcias-Morales,
• David Ortegón-Reyna and
• Armando Ariza-Castolo

Beilstein J. Org. Chem. 2015, 11, 1973–1984, doi:10.3762/bjoc.11.213

• repulsion between the LPEs of the nitrogen. Although 3, 5, 6, and 8 have four stereogenic centers, however, there is a mirror plane that passes through N(3), C(9), and C(7), so these compounds do not exhibit optical activity. Compounds 4 and 7 have a methyl group on the C(1) carbon, where there is no mirror

New palladium–oxazoline complexes: Synthesis and evaluation of the optical properties and the catalytic power during the oxidation of textile dyes

• Rym Hassani,
• Mahjoub Jabli,
• Yakdhane Kacem,
• Jérôme Marrot,
• Damien Prim and
• Béchir Ben Hassine

Beilstein J. Org. Chem. 2015, 11, 1175–1186, doi:10.3762/bjoc.11.132

• structural features have been used in diverse reactions [8]. The importance of these ligands lies in the fact that the stereogenic centers are kept in close proximity to the metal and thereby having a strong and direct influence on the stereochemical course of the metal-catalyzed process. Oxazolines possess

Cathodic hydrodimerization of nitroolefins

• Michael Weßling and
• Hans J. Schäfer

Beilstein J. Org. Chem. 2015, 11, 1163–1174, doi:10.3762/bjoc.11.131

• configurations at the stereogenic centers. Hydrodimerization of 1 in dependence on the electrolyte composition. Hydrodimerization of 1a in dependence of temperature, conversion and cell type. Preparation of 1-aryl-2-nitroalkenes. Preparative hydrodimerization of nitroalkenes. δ-Values and multiplicities of the

Regioselective synthesis of chiral dimethyl-bis(ethylenedithio)tetrathiafulvalene sulfones

• Flavia Pop and
• Narcis Avarvari

Beilstein J. Org. Chem. 2015, 11, 1105–1111, doi:10.3762/bjoc.11.124

• by the combination of chirality with the TTF motif, a certain number of families of precursors have been reported. They possess various types of chirality, i.e., stereogenic centers, axial, planar, helical chirality, and supramolecular chirality [17][18][19][20][21]. Since methylated BEDT-TTF

The reactions of 2-ethoxymethylidene-3-oxo esters and their analogues with 5-aminotetrazole as a way to novel azaheterocycles

• Marina V. Goryaeva,
• Yanina V. Burgart,
• Marina A. Ezhikova,
• Mikhail I. Kodess and
• Viktor I. Saloutin

Beilstein J. Org. Chem. 2015, 11, 385–391, doi:10.3762/bjoc.11.44

• heterocycle 10. Compound 10 was isolated as one diastereomer, but the relative configuration of its stereogenic centers was not determined. Moreover, we studied the reaction of ethyl 2-ethoxymethylidenecyanoacetate (1f) with 5-AT. It has been found that this reaction does not occur either in refluxing ethanol

The unexpected influence of aryl substituents in N-aryl-3-oxobutanamides on the behavior of their multicomponent reactions with 5-amino-3-methylisoxazole and salicylaldehyde

• Volodymyr V. Tkachenko,
• Elena A. Muravyova,
• Sergey M. Desenko,
• Oleg V. Shishkin,
• Svetlana V. Shishkina,
• Dmytro O. Sysoiev,
• Thomas J. J. Müller and
• Valentin A. Chebanov

Beilstein J. Org. Chem. 2014, 10, 3019–3030, doi:10.3762/bjoc.10.320

• signals for the other terminal substituents. The relative stereochemistry of the stereogenic centers at positions 3 and 4 of compound 4a was established by 1D and 2D NMR spectra. Thus, a 3J coupling constant of 11.7 Hz accounts for a trans-orientation. The NOESY experiment showed only a quite weak

• stereogenic centers at positions 4 and 12 of compound 6a was first established by analysis of the 1D and 2D NMR spectra. Thus, a 3J coupling constant of 1.9 Hz corresponds with a cis-orientation and the NOESY experiment additionally supports the proximity of this pair of protons. The structure of compound 6a

• with relative stereochemistry of stereogenic centers was finally corroborated by an X-ray diffraction study (Figure 5). The heterocycles of the polycyclic fragment adopt a chair-like conformation (the puckering parameters [29] are: S = 0.78, Θ = 32.8°, Ψ = 1.0° and S = 0.83, Θ = 38.0°, Ψ = 1.8° for the

(2R,1'S,2'R)- and (2S,1'S,2'R)-3-[2-Mono(di,tri)fluoromethylcyclopropyl]alanines and their incorporation into hormaomycin analogues

• Armin de Meijere,
• Sergei I. Kozhushkov,
• Dmitrii S. Yufit,
• Christian Grosse,
• Marcel Kaiser and
• Vitaly A. Raev

Beilstein J. Org. Chem. 2014, 10, 2844–2857, doi:10.3762/bjoc.10.302

• isolated from a Streptomyces griseoflavus (strain W-384) fermentation broth by Zähner et al. in Tübingen, Germany and structurally identified by Zeeck et al. in Göttingen, Germany in 1989–1990 [3][4]. Once the absolute configuration of all the previously unassigned stereogenic centers in the

De novo macrolide–glycolipid macrolactone hybrids: Synthesis, structure and antibiotic activity of carbohydrate-fused macrocycles

• Richard T. Desmond,
• Anniefer N. Magpusao,
• Chris Lorenc,
• Jeremy B. Alverson,
• Nigel Priestley and
• Mark W. Peczuh

Beilstein J. Org. Chem. 2014, 10, 2215–2221, doi:10.3762/bjoc.10.229

• , stereogenic centers and stereoelectronic effects combine to dictate the “topology” or overall fold of a macrocycle. The structure of β-D-galactose-[13]-macrodiolide 3 [9], derived from X-ray data, originated this line of investigation. It showed that both esters and the epoxide unit are each composed of four

• this case the macrocyclic ring. In total it is the balancing of a number of small factors such as rigidification by multi-atom planar units, absolute configuration of stereogenic centers and stereoelectronic effects that dictate the observed structures. Minimum inhibitory concentrations (MICs) against

• work, however, relates the role of the exo-anomeric effect on the low-energy conformation of macrocycles linked through an anomeric center. This weak stereoelectronic effect should be listed with other factors such as ring size, multi-atom planar units, and stereogenic centers as determinants of

Application of cyclic phosphonamide reagents in the total synthesis of natural products and biologically active molecules

• Thilo Focken and
• Stephen Hanessian

Beilstein J. Org. Chem. 2014, 10, 1848–1877, doi:10.3762/bjoc.10.195

• α-alkyl phosphonamide, respectively [36]. Michael reactions The application of chiral, cyclic phosphonamides such as 28c in asymmetric Michael-type reactions has proven to be a powerful tool in natural product synthesis to generate up to three contiguous stereogenic centers in a single step with a

Rational design of cyclopropane-based chiral PHOX ligands for intermolecular asymmetric Heck reaction

• Marina Rubina,
• William M. Sherrill,
• Alexey Yu. Barkov and
• Michael Rubin

Beilstein J. Org. Chem. 2014, 10, 1536–1548, doi:10.3762/bjoc.10.158

• approach to palladium may also be responsible for the observed decrease in the reaction rate. Based on this analysis, we rationalized that the “wrong” relative configuration of the stereogenic centers in ligands L1, L2 and L3 could be responsible for the observed marginal enantioselectivity of the

cis–trans Isomerization of silybins A and B

• Michaela Novotná,
• Radek Gažák,
• David Biedermann,
• Florent Di Meo,
• Petr Marhol,
• Marek Kuzma,
• Lucie Bednárová,
• Kateřina Fuksová,
• Patrick Trouillas and
• Vladimír Křen

Beilstein J. Org. Chem. 2014, 10, 1047–1063, doi:10.3762/bjoc.10.105

• analogues are considered to be composed of two separate π-conjugated subsystems, the 3-hydroxyflavonone moiety (with the stereogenic centers C-2 and C-3), and the 1,4-benzodioxane moiety (C-10 and C-11) (see Figure 4). In this simplification we cannot avoid the adverse effects caused by neglecting the

• effects of local perturbations on specific stereogenic centers. Thus, the interpretation of our experimental ECD spectra is mainly based on empirical comparison and correlation to those of i) the dihydroflavonols taxifolin (15) and epitaxifolin (16) isolated from Thujopsis dolobrata [16] and ii) various

• obtained by the isomerization of 1 using BF3·OEt2 in EtOAc. ECD spectrum of silybin B (1b) and its separation (in a crude approximation) into two π-conjugated moieties (3-hydroxyflavonone with stereogenic centers C-2, C-3 (in blue) and 1,4-benzodioxane with C-10,C-11) (in red) according to [2]. Synthetic

Structure elucidation of female-specific volatiles released by the parasitoid wasp Trichogramma turkestanica (Hymenoptera: Trichogrammatidae)

• Armin Tröger,
• Teris A. van Beek,
• Martinus E. Huigens,
• Isabel M. M. S. Silva,
• Maarten A. Posthumus and
• Wittko Francke

Beilstein J. Org. Chem. 2014, 10, 767–773, doi:10.3762/bjoc.10.72

• (2E,4E)-4,6,8,10-tetramethyltrideca-2,4-diene (15), we had to assign the relative stereochemistry at the three stereogenic centers. Actually, we had to decide between 4 structures: syn,syn-, syn,anti-, anti,syn-, and anti,anti-configuration of the methyl groups at carbons 6, 8, and 10. Since

Organocatalytic asymmetric fluorination of α-chloroaldehydes involving kinetic resolution

• Kazutaka Shibatomi,
• Takuya Okimi,
• Yoshiyuki Abe,
• Akira Narayama,
• Nami Nakamura and
• Seiji Iwasa

Beilstein J. Org. Chem. 2014, 10, 323–331, doi:10.3762/bjoc.10.30

• the fluorination of α-branched aldehydes [7]. During the course of our study on the enantioselective construction of such fluorinated stereogenic centers, we developed a method for the enantioselective synthesis of α-chloro-α-fluoroaldehydes via the organocatalytic α-fluorination of α-alkyl-α

Tanzawaic acids I–L: Four new polyketides from Penicillium sp. IBWF104-06

• Louis P. Sandjo,
• Eckhard Thines,
• Till Opatz and
• Anja Schüffler

Beilstein J. Org. Chem. 2014, 10, 251–258, doi:10.3762/bjoc.10.20

• -dienoic acid unit was connected to the carbon at δC 79.0 (C-6). The relative configuration of the stereogenic centers was assigned based on NOESY data (Figure 1) and the previous work reported by Malmstrøm et al. on the stereochemistry of two related compounds, tanzawaic acids E and F [2]. The NOESY

• ). As in compounds 1–3, resonances of a (2E,4E)-penta-2,4-dienoic acid moiety as well as three additional CH groups, two CH2 groups and one CH3 for the completion of the decalin part were observed. The relative configuration of the stereogenic centers was determined by NOESY (Figure 4). Correlations

Boron-substituted 1,3-dienes and heterodienes as key elements in multicomponent processes

• Ludovic Eberlin,
• Fabien Tripoteau,
• François Carreaux,
• Andrew Whiting and
• Bertrand Carboni

Beilstein J. Org. Chem. 2014, 10, 237–250, doi:10.3762/bjoc.10.19

• three-component process (Scheme 3) [34]. Extension of this work to the intramolecular version is depicted in Scheme 4. The bicyclic lactone 1 was obtained stereoselectively from a diene-yne in a one-pot process with control of the relative stereochemistry of the five stereogenic centers [35]. Concerning

• boronated dienes 6, which were not isolated, but directly used in a one-pot Diels–Alder reaction/allylboration sequence. This efficiently generated, in high yields, tricyclic structures 7 with control of four stereogenic centers created (Scheme 8). In the presence of Grubbs II catalyst, a skeletal isomer 8

• with maleimides, as electron-poor dienophiles, followed by an allylboration (Scheme 21) [69]. This sequence proceeded with high stereocontrol, as already observed with the carbon and oxygen analogues. In addition, the absolute stereochemistry of the four new created stereogenic centers was controlled

Synthesis of new enantiopure poly(hydroxy)aminooxepanes as building blocks for multivalent carbohydrate mimetics

• Léa Bouché,
• Maja Kandziora and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2014, 10, 213–223, doi:10.3762/bjoc.10.17

• stereogenic center at the β-carbon (1,3-induction) has no or negligible influence. A few syn-selective additions of other nucleophiles to nitrones with two stereogenic centers similar to 6 or 8 were reported in the literature [38][39]. A preferred transition structure as depicted in Figure 1 plausibly

Synthesis of the B-seco limonoid core scaffold

• Hanna Bruss,
• Hannah Schuster,
• Rémi Martinez,
• Markus Kaiser,
• Andrey P. Antonchick and
• Herbert Waldmann

Beilstein J. Org. Chem. 2014, 10, 194–208, doi:10.3762/bjoc.10.15

• the thermodynamic enolate of 2-methylcyclohexanone (5) and the bicyclic electrophile 12 (Scheme 2). A challenging synthetic problem appears to be the construction of the stereochemically dense trans-fused C–D ring system 12, which possesses four stereogenic centers including two contiguous asymmetric

Studies on the interaction of isocyanides with imines: reaction scope and mechanistic variations

• Ouldouz Ghashghaei,
• Consiglia Annamaria Manna,
• Esther Vicente-García,
• Marc Revés and
• Rodolfo Lavilla

Beilstein J. Org. Chem. 2014, 10, 12–17, doi:10.3762/bjoc.10.3

• constitution of the azetidine 3a by spectroscopic methods (NMR, MS), the stereochemistry of the C=N bonds present in the structure remained unsolved. Furthermore, no conclusive nOe’s were observed to assign these stereogenic centers, and there were no reports in the literature regarding this point. A

Stereodivergent synthesis of jaspine B and its isomers using a carbohydrate-derived alkoxyallene as C₃-building block

• Volker M. Schmiedel,
• Stefano Stefani and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2013, 9, 2564–2569, doi:10.3762/bjoc.9.291

• sp. by Higa et al. [1]. In 2003 Debitus et al. were able to extract this natural product from the marine sponge Jaspis sp. [2]. Jaspine B (1) comprises a densely functionalized tetrahydrofuran ring, bearing three contiguous (2S,3S,4S)-configured stereogenic centers with a long alkyl chain at C-2 and

Gold(I)-catalyzed enantioselective cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2013, 9, 2250–2264, doi:10.3762/bjoc.9.264

• ], allowing the construction of six-membered adducts with up to three new stereogenic centers with complete diastereoselectivity and enantioselectivities of up to 91% ee (R1, R2 = Me, R4 = Ph, Scheme 11). With regard to the mechanism, it has been proposed that the activation of the allenamide by the gold

The chemistry of isoindole natural products

• Klaus Speck and
• Thomas Magauer

Beilstein J. Org. Chem. 2013, 9, 2048–2078, doi:10.3762/bjoc.9.243

• architecture and was first isolated from the fungus Aspergillus awamori in 2002 [74]. The highly functionalized pentacyclic skeleton comprises a unique 12-oxatricyclo[6.3.1.02,7]dodecane ring system and ten stereogenic centers. Its carbon framework is closely related to other members of the aspochalasin

Organocatalyzed enantioselective desymmetrization of aziridines and epoxides

• Ping-An Wang

Beilstein J. Org. Chem. 2013, 9, 1677–1695, doi:10.3762/bjoc.9.192

• [10][11][12] or epoxides [13][14][15] provides facile access to various chiral amines and alcohols and their derivatives with two adjacent stereogenic centers, which are widely used as building blocks in pharmaceutical and organic synthesis. The enantioselective catalytic desymmetrization of meso