Synthesis of complex intermediates for the study of a dehydratase from borrelidin biosynthesis

• Frank Hahn,
• Nadine Kandziora,
• Steffen Friedrich and
• Peter F. Leadlay

Beilstein J. Org. Chem. 2014, 10, 634–640, doi:10.3762/bjoc.10.55

• preferentially accepts the 2D,3D-configured precursor, if all four potential stereoisomers of 3-hydroxy-2-methyl-SNAc-pentanoate model substrates are presented [7]. A commonly accepted model suggests that DHs from PKS I systems catalyze the removal of water by syn-dehydration and that a 2D,3D-configured

One-pot three-component synthesis and photophysical characteristics of novel triene merocyanines

• Christian Muschelknautz,
• Robin Visse,
• Jan Nordmann and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 599–612, doi:10.3762/bjoc.10.51

• flexible and fixed acceptor moieties. DFT-computed energy differences of the stereoisomers of 2Z,4Z-8a and 2Z,4E-8a. DFT-computed energy differences of the stereoisomers of 10a and 10h. DFT-computed (B3LYP functional, 6-31G* basis set) HOMO (left) and LUMO (right) of merocyanine 8a. Absorption and emission

Self-assembly of metallosupramolecular rhombi from chiral concave 9,9’-spirobifluorene-derived bis(pyridine) ligands

• Rainer Hovorka,
• Sophie Hytteballe,
• Torsten Piehler,
• Georg Meyer-Eppler,
• Filip Topić,
• Kari Rissanen,
• Marianne Engeser and
• Arne Lützen

Beilstein J. Org. Chem. 2014, 10, 432–441, doi:10.3762/bjoc.10.40

• -protected [(dppp)Pd]2+ and [(dppp)Pt]2+ ions. The self-assembly process of the racemic ligand preferably occurs in a narcissistic self-recognising manner. Hence, a mixture of all three possible stereoisomers [(dppp)2M2{(R)-L}2](OTf)4, [(dppp)2M2{(S)-L}2](OTf)4, and [(dppp)2M2{(R)-L}{(S)-L}](OTf)4 was

• (Figure 2a,b). In principle, three stereoisomers of the dinuclear metallosupramolecular rhombi can form from racemic ligands upon coordination to [(dppp)Pd(OTf)2] or [(dppp)Pt(OTf)2] – a racemic mixture of two enantiomeric homochiral assemblies and an achiral heterochiral complex. These are expected to

• heterochiral one in both cases – the palladium and the platinum complexes and independent of the solvents we used. This corresponds to an amplification of the homochiral stereoisomers via self-recognition by a factor of approximately three. Although these NMR spectra already provide a very good proof for the

Concise, stereodivergent and highly stereoselective synthesis of cis- and trans-2-substituted 3-hydroxypiperidines – development of a phosphite-driven cyclodehydration

• Peter H. Huy,
• Julia C. Westphal and
• Ari M. P. Koskinen

Beilstein J. Org. Chem. 2014, 10, 369–383, doi:10.3762/bjoc.10.35

• Abstract A concise (5 to 6 steps), stereodivergent, highly diastereoselective (dr up to >19:1 for both stereoisomers) and scalable synthesis (up to 14 g) of cis- and trans-2-substituted 3-piperidinols, a core motif in numerous bioactive compounds, is presented. This sequence allowed an efficient synthesis

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

• involves a sequential double isocyanide incorporation into the C=N bond. The final step is a nucleophilic 4-exo-dig cyclization, and the anti addition modes likely lead to less stable stereoisomers which spontaneously isomerize to the observed compounds. Furthermore, we have determined the scope of the

Plakilactones G and H from a marine sponge. Stereochemical determination of highly flexible systems by quantitative NMR-derived interproton distances combined with quantum mechanical calculations of ¹³C chemical shifts

• Simone Di Micco,
• Angela Zampella,
• Maria Valeria D’Auria,
• Carmen Festa,
• Simona De Marino,
• Raffaele Riccio,
• Craig P. Butts and
• Giuseppe Bifulco

Beilstein J. Org. Chem. 2013, 9, 2940–2949, doi:10.3762/bjoc.9.331

• ). Over 200 conformers were found for each of the stereoisomers for 2a–h (see Experimental), and their geometries were optimized at the DFT theoretical level by using the MPW1PW91 functional and 6-31G(d) [26] basis set (Gaussian 09 Software Package [27]). From the DFT-optimized geometries interproton

• -calculated interproton distances for 2a,b,e,f differed by more than 0.03 Å (≈ 1%) from each other. The data reported in Table 3 clearly show that the diastereoisomer 2b represents the best fit with the experimentally derived distances (MAE 4.1% and standard deviation (STD) 5.0%). The stereoisomers 2a, 2e and

• 2f poorly agree with the NOE-derived distances. The maximum error shown by the calculated distances for 2b is 9.4%, whereas the other stereoisomers have at least three calculated distances with an associated error higher than 10%. The largest errors (>10%) are relative to protons around the

Synthesis and determination of the absolute configuration of (−)-(5R,6Z)-dendrolasin-5-acetate from the nudibranch Hypselodoris jacksoni

• I. Wayan Mudianta,
• Victoria L. Challinor,
• Anne E. Winters,
• Karen L. Cheney,
• James J. De Voss and
• Mary J. Garson

Beilstein J. Org. Chem. 2013, 9, 2925–2933, doi:10.3762/bjoc.9.329

• individual stereoisomers (see below). The 3:1 ratio of E/Z-isomers was confirmed via analytical HPLC. In principle, the rearrangement of 6 could afford either [1,2]-rearranged products (e.g. 7a/b or 8) or [2,3]-rearranged products such as 9 or 10 depending on which site adjacent to the ether oxygen is

Novel supramolecular affinity materials based on (−)-isosteviol as molecular templates

• Christina Lohoelter,
• Malte Brutschy,
• Daniel Lubczyk and
• Siegfried R. Waldvogel

Beilstein J. Org. Chem. 2013, 9, 2821–2833, doi:10.3762/bjoc.9.317

• ) provides an open side to access the concave regime. As anticipated, two stereoisomers are formed in this condensation reaction of 5b with 4. After separation via column chromatography, these products were identified as the all-syn- and anti,anti,syn-isomers of the desired product 8, which were obtained in

Multigramme synthesis and asymmetric dihydroxylation of a 4-fluorobut-2E-enoate

• James A. B. Laurenson,
• John A. Parkinson,
• Jonathan M. Percy,
• Giuseppe Rinaudo and
• Ricard Roig

Beilstein J. Org. Chem. 2013, 9, 2660–2668, doi:10.3762/bjoc.9.301

• enantiomers 29a and 29b was excellent, with over 6 minutes separating the stereoisomers in the chromatograms. Due to the robust nature of the dibenzoylation chemistry and the excellent chromatograms produced, the derivatisation/chiral HPLC assay was used routinely. However, direct measurement of the ee's of

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

• Volker M. Schmiedel Stefano Stefani Hans-Ulrich Reissig Institut für Chemie und Biochemie, Freie Universität Berlin, Takustr. 3, D-14195 Berlin, Germany 10.3762/bjoc.9.291 Abstract Herein we present the synthesis of the anhydrophytosphingosine jaspine B and three of its stereoisomers using a

• therefore leads to a stereodivergent approach to the natural product and its enantiomer. The gold-catalyzed 5-endo-cyclization affords the corresponding dihydrofurans, which after separation, azidation of the enol ether moiety and two subsequent reduction steps give the natural product and its stereoisomers

• synthesis of stereoisomers of the natural product [4][12][16][17][19][26][27][28] because these compounds also showed comparable biological activities [4][5]. During our current studies on the synthesis of highly functionalized heterocycles utilizing alkoxyallenes as versatile C3-building blocks we chose

Gold(I)-catalyzed 6-endo hydroxycyclization of 7-substituted-1,6-enynes

• Ana M. Sanjuán,
• Alberto Martínez,
• Patricia García-García,
• Manuel A. Fernández-Rodríguez and
• Roberto Sanz

Beilstein J. Org. Chem. 2013, 9, 2242–2249, doi:10.3762/bjoc.9.263

• subsequent Friedel–Crafts reaction (Scheme 6). Both compounds were isolated as single stereoisomers with a high overall yield [43]. In this case, the 5-exo pathway was more competitive compared to the result of model substrate 1a, probably due to the Thorpe–Ingold-type effect caused by the methyl group at

Flow synthesis of phenylserine using threonine aldolase immobilized on Eupergit support

• Jagdish D. Tibhe,
• Hui Fu,
• Timothy Noël,
• Qi Wang,
• Jan Meuldijk and
• Volker Hessel

Beilstein J. Org. Chem. 2013, 9, 2168–2179, doi:10.3762/bjoc.9.254

• four isomers is depicted in Figure 13. The correct elution of the different stereoisomers was elucidated by injecting pure sample of each compound and comparison with literature [43][44][45]. In all experiments, 20% of diastereomeric excess of phenylserine was observed and a >99% enantiomeric excess

Microflow photochemistry: UVC-induced [2 + 2]-photoadditions to furanone in a microcapillary reactor

• Sylvestre Bachollet,
• Kimitada Terao,
• Shin Aida,
• Yasuhiro Nishiyama,
• Kiyomi Kakiuchi and
• Michael Oelgemöller

Beilstein J. Org. Chem. 2013, 9, 2015–2021, doi:10.3762/bjoc.9.237

• acetone and irradiation with UVB light) gave an incomplete conversion of approximately 60%. A complex mixture of various stereoisomers of 3 and several unknown byproducts was obtained, which could not be separated satisfactory. Direct irradiation conditions were thus chosen for all further investigations

Synthesis of enantiomerically pure (2S,3S)-5,5,5-trifluoroisoleucine and (2R,3S)-5,5,5-trifluoro-allo-isoleucine

• Holger Erdbrink,
• Elisabeth K. Nyakatura,
• Susanne Huhmann,
• Ulla I. M. Gerling,
• Dieter Lentz,
• Beate Koksch and
• Constantin Czekelius

Beilstein J. Org. Chem. 2013, 9, 2009–2014, doi:10.3762/bjoc.9.236

• stereoisomers of Ile are less hydrophobic than Aha. F6Leu is similar to Aha in hydrophobicity, while exhibiting a much larger volume. In a free energy perturbation study, the hydration energy of F6Leu was shown to be 1.1 kcal/mol higher than that of leucine [29]. This, together with our previous and new

An approach towards azafuranomycin analogs by gold-catalyzed cycloisomerization of allenes: synthesis of (αS,2R)-(2,5-dihydro-1H-pyrrol-2-yl)glycine

• Jörg Erdsack and
• Norbert Krause

Beilstein J. Org. Chem. 2013, 9, 1936–1942, doi:10.3762/bjoc.9.229

• were published [2][5][6][7][8] as well as numerous reports dedicated to derivatives and stereoisomers [9][10][11][12][13][14][15][16][17][18][19][20]. Examination of structure–activity relationship (SAR) revealed a loss of antibiotic activity upon shifting of the methyl group to different positions

Topochemical control of the photodimerization of aromatic compounds by γ-cyclodextrin thioethers in aqueous solution

• Hai Ming Wang and
• Gerhard Wenz

Beilstein J. Org. Chem. 2013, 9, 1858–1866, doi:10.3762/bjoc.9.217

• the dominant factor, but rather the pre-organization of the guest molecules in the CD cavity prior to excitation has the greatest effect. The distribution of the stereoisomers appears to be mainly topochemically [5] controlled because of the short lifetime of the excited state of COU. Quantum

Self-assembly of 2,3-dihydroxycholestane steroids into supramolecular organogels as a soft template for the in-situ generation of silicate nanomaterials

• Valeria C. Edelsztein,
• Andrea S. Mac Cormack,
• Matías Ciarlantini and
• Pablo H. Di Chenna

Beilstein J. Org. Chem. 2013, 9, 1826–1836, doi:10.3762/bjoc.9.213

• key to the directed design of new organogels. We report herein the organogelating property of four stereoisomers of the simple steroid 2,3-dihydroxycholestane. Only the isomer with the trans-diaxial hydroxy groups had the ability to gelate a broad variety of liquids and, thus, to be a super

• the stereoisomers 2–4 bearing equatorial hydroxy groups (Figure 1). The gelation ability of 1 is discussed in terms of the Hansen solubility parameters and Kamlet–Taft parameters based on its behavior in a set of 33 solvents. We also report on the sol–gel polymerization of TEOS carried out with gels

• fibrillar network of the gel. Tubular nanostructured materials, such as these presented here, may offer alternatives over spherical nanoparticles for some biomedical and biotechnological applications [30][31]. Conclusion In summary, we have studied the organogelating behavior of the four stereoisomers of

α-Bromodiazoacetamides – a new class of diazo compounds for catalyst-free, ambient temperature intramolecular C–H insertion reactions

• Åsmund Kaupang and
• Tore Bonge-Hansen

Beilstein J. Org. Chem. 2013, 9, 1407–1413, doi:10.3762/bjoc.9.157

• exo-5a–f). The stereochemistry of the obtained β-lactams was determined based on the previously published NMR data for endo/exo-5b [45], as well as on the characteristic magnitude of the couplings and chemical shift values of the α-protons of the endo/exo stereoisomers [46][47][48][49]. The high

Efficient regio- and stereoselective access to novel fluorinated β-aminocyclohexanecarboxylates

• Loránd Kiss,
• Melinda Nonn,
• Reijo Sillanpää,
• Santos Fustero and
• Ferenc Fülöp

Beilstein J. Org. Chem. 2013, 9, 1164–1169, doi:10.3762/bjoc.9.130

• 9 in good yield (Scheme 2). The synthetic route presented above could be extended to the preparation of other 4-fluorinated cyclohexane amino acid derivatives, stereoisomers of 7 or 9. Ethyl trans-2-aminocyclohex-4-enecarboxylate 10 [57] was analogously transformed to its cis counterpart through

Study on the total synthesis of velbanamine: Chemoselective dioxygenation of alkenes with PIFA via a stop-and-flow strategy

• Huili Liu,
• Kuan Zheng,
• Xiang Lu,
• Xiaoxia Wang and
• Ran Hong

Beilstein J. Org. Chem. 2013, 9, 983–990, doi:10.3762/bjoc.9.113

• -exo-trig cyclization is the favorable pathway during the PIFA-mediated amide-cyclization of alkene. Two isomers after cyclization were then attributed to the stereoisomers of the C=N double bond in the iminolactone C. This notion is also consistent with numerous reports on the iodocyclization with

Highly stereocontrolled synthesis of trans-enediynes via carbocupration of fluoroalkylated diynes

• Tsutomu Konno,
• Misato Kishi and
• Takashi Ishihara

Beilstein J. Org. Chem. 2012, 8, 2207–2213, doi:10.3762/bjoc.8.249

• enediynes 14a–c in high to excellent yields. In all cases, other stereoisomers were not detected at all and 14a–c were generated as the sole products in a pure form. Conclusion In summary, we have established a convenient as well as efficient access to the trifluoromethylated diyne by Sonogashira cross

• . Finally, the thus-obtained iodide underwent a smooth Sonogashira cross-coupling reaction to afford the various desired trans-enediyne derivatives in high yields. trans-Enediyne. Regio- and stereoisomers. Synthetic strategy for the preparation of trifluoromethylated diynes. Preparation of various enynes. A

The multicomponent approach to N-methyl peptides: total synthesis of antibacterial (–)-viridic acid and analogues

• Ricardo A. W. Neves Filho,
• Sebastian Stark,
• Bernhard Westermann and
• Ludger A. Wessjohann

Beilstein J. Org. Chem. 2012, 8, 2085–2090, doi:10.3762/bjoc.8.234

• pursued. The advantages of the MCR protocol are speed, variability, insensitivity to steric crowding, safe peptoid-moiety formation, and access to equally distributed stereoisomers (which can be a disadvantage though, once the most active isomer is identified). The improved classical approach gave the

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

A new approach toward the total synthesis of (+)-batzellaside B

• Jolanta Wierzejska,
• Shin-ichi Motogoe,
• Yuto Makino,
• Tetsuya Sengoku,
• Masaki Takahashi and
• Hidemi Yoda

Beilstein J. Org. Chem. 2012, 8, 1831–1838, doi:10.3762/bjoc.8.210

• appealing performance observed in the above synthetic process, this reaction protocol has the major disadvantage of low stereoselectivity causing operational inconvenience associated with the laborious chromatographic separation of the two stereoisomers. From the practical considerations, we next explored a

Exploring chemical diversity via a modular reaction pairing strategy

• Joanna K. Loh,
• Sun Young Yoon,
• Thiwanka B. Samarakoon,
• Alan Rolfe,
• Patrick Porubsky,
• Benjamin Neuenswander,
• Gerald H. Lushington and
• Paul R. Hanson

Beilstein J. Org. Chem. 2012, 8, 1293–1302, doi:10.3762/bjoc.8.147

• on multigram scale through the use of three efficient steps, namely sulfonylation, Mitsunobu alkylation and SNAr, to generate both stereoisomers of each core [37] (Scheme 2). The bridged benzofused sultam scaffolds were prepared by a sulfonylation intramolecular SNAr protocol, reported previously [32

• composed of the entire spectrum of possible stereoisomers, and library II (5–8) was composed of two sets of benzofused sultams having an H or Me group at the R1 position. The use of all possible stereoisomers provides the opportunity to generate stereochemical SAR (SSAR) for each building block combination