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

• ], and at the preparatory scale by lipase-catalyzed discrimination [4][5]. However, chromatographic separation of 2,3-cis- and 2,3-trans-silybins is feasible after their C-23 O-acetylation, which can be accomplished with Novozym 435 in an acetone/vinyl acetate mixture, giving a nearly quantitative yield

Addition of H-phosphonates to quinine-derived carbonyl compounds. An unexpected C9 phosphonate–phosphate rearrangement and tandem intramolecular piperidine elimination

• Łukasz Górecki,
• Artur Mucha and
• Paweł Kafarski

Beilstein J. Org. Chem. 2014, 10, 883–889, doi:10.3762/bjoc.10.85

• catalysis, transition metal complexing, molecular recognition, chromatographic separation and analysis of enantiomers [2][3][4][5]. Synthetic modifications of the basic structure, motivated by an improved stereoselectivity potential of quinine, are an issue of ongoing trials [6][7][8][9]. Surprisingly

Isocyanide-based multicomponent reactions towards cyclic constrained peptidomimetics

• Gijs Koopmanschap,
• Eelco Ruijter and
• Romano V.A. Orru

Beilstein J. Org. Chem. 2014, 10, 544–598, doi:10.3762/bjoc.10.50

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

• –5.2 Å. Since the introduction of nitrobenzyl esters as protecting groups for the (−)-isosteviol carboxylic acid moiety obviously does not have an enhanced effect on the polarity of the two isomers and, as a consequence, the chromatographic separation procedure does not correlate with the nature of the

• ), employing the 2nd generation Grubbs catalyst in refluxing dichloromethane. Even after prolonged reaction times, complete conversion of the starting material could not be achieved. However, the formation of a sole product was observed. Upon chromatographic separation, the product was obtained, exhibiting a

The total synthesis of D-chalcose and its C-3 epimer

• Jun Sun,
• Song Fan,
• Zhan Wang,
• Guoning Zhang,
• Kai Bao and
• Weige Zhang

Beilstein J. Org. Chem. 2013, 9, 2620–2624, doi:10.3762/bjoc.9.296

• retrosynthetic analysis of I and I′ is presented in Scheme 1. Diol II and II′ arose from a Sharpless asymmetric dihydroxylation that form the C2 stereogenic center. The installation of the C3 stereocenter on vinyl ether III was proposed to utilize a Grignard reaction followed by chromatographic separation

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

• of the desired intermediates. Difficulties of the separation of the diastereomeric tetrahydrofuranols were successfully overcome by protection of the C-3 hydroxy group as carbonate, which enabled an easy chromatographic separation of the diastereomers and a global deprotection/reduction leading to

Micro-flow synthesis and structural analysis of sterically crowded diimine ligands with five aryl rings

• Shinichiro Fuse,
• Nobutake Tanabe,
• Akio Tannna,
• Yohei Konishi and
• Takashi Takahashi

Beilstein J. Org. Chem. 2013, 9, 2336–2343, doi:10.3762/bjoc.9.268

• CCX-1200 (Tokyo Rikakikai Co., Ltd.). Chromatographic separation was performed using a Purif®-α2 (Shoko Scientific Co., Ltd.). Experimental details General procedure for the preparation of imidochlorides: The mixture of N-(1-naphthyl)benzamide and SOCl2 (2 mL/mmol amide) was stirred at 65 °C for 4 h

Elucidation of the regio- and chemoselectivity of enzymatic allylic oxidations with Pleurotus sapidus – conversion of selected spirocyclic terpenoids and computational analysis

• Verena Weidmann,
• Mathias Schaffrath,
• Holger Zorn,
• Julia Rehbein and
• Wolfgang Maison

Beilstein J. Org. Chem. 2013, 9, 2233–2241, doi:10.3762/bjoc.9.262

• to start with diastereomerically pure theaspirane (trans-1) that was obtained by chromatographic separation of the commercial diastereomeric mixture of cis- and trans-theaspirane (1). As depicted in Scheme 4, trans-theaspirane (trans-1) was converted to the corresponding epoxides 4a and 4b following

• ) in good yield [48]. Overall, this improved protocol gave racemic vitispirane (23) in three steps from theaspirane (trans-1) in excellent 72% overall yield. It should be noted that the gas chromatographic separation of racemic vitispirane (23) has been reported by Schreier [45]. In addition, we have

A concise enantioselective synthesis of the guaiane sesquiterpene (−)-oxyphyllol

• Martin Zahel and
• Peter Metz

Beilstein J. Org. Chem. 2013, 9, 2028–2032, doi:10.3762/bjoc.9.239

• completion of the synthesis of (−)-oxyphyllol (1) from 4. To our delight, a direct regio- and diastereoselective Co(II)-catalyzed hydration [12] of the olefin in 4 succeeded to give the required α-stereoisomer 3 in 58% isolated yield after chromatographic separation of the minor β-alcohol. Compared to the

The preparation of several 1,2,3,4,5-functionalized cyclopentane derivatives

• André S. Kelch,
• Peter G. Jones,
• Ina Dix and
• Henning Hopf

Beilstein J. Org. Chem. 2013, 9, 1705–1712, doi:10.3762/bjoc.9.195

• halogenated derivatives of 16 had been produced; their chromatographic separation failed. In order to avoid working in solution and subjecting the presumably reactive 5 to extended work-up and purification conditions, we next tried to prepare the xanthate 20 and the acetate 21 from 16, derivatives that could

The diketopiperazine-fused tetrahydro-β-carboline scaffold as a model peptidomimetic with an unusual α-turn secondary structure

• Francesco Airaghi,
• Andrea Fiorati,
• Giordano Lesma,
• Manuele Musolino,
• Alessandro Sacchetti and
• Alessandra Silvani

Beilstein J. Org. Chem. 2013, 9, 147–154, doi:10.3762/bjoc.9.17

• synthesis of peptidomimetic 1a (Scheme 1). Starting from L-tryptophan methyl ester and N-Cbz-aminoacetaldehyde dimethyl acetal [43], tetrahydro-β-carboline 2 was obtained in good yield and high diastereoselectivity (dr 70% from 1H NMR) by means of Pictet–Spengler reaction [44] and subsequent chromatographic

• separation. The 6S,12aS-configuration of the prevailing diastereoisomer was easily ascertained by application of the protocol of Ungemach et al. [45] on the 13C NMR spectrum of compound 2 and, conclusively, by the observation of an intense NOE contact between H-6 and H-12a in the 2D NOESY spectrum

Polar reactions of acyclic conjugated bisallenes

• Reiner Stamm and
• Henning Hopf

Beilstein J. Org. Chem. 2013, 9, 36–48, doi:10.3762/bjoc.9.5

• , i.e., the fully alkylated biallenyl 7 can be isolated, possibly formed via the dilithiated intermediate 6 (up to 15% depending on the exact alkylation conditions). However, since the purification of this product required gas-chromatographic separation, a stepwise approach was adopted to prepare it

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

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

• chromatographic separation and purification [38]. Biallenyl 2 is also produced when 1,5-hexadiyne is treated with sodium ethoxide in ethanol at 65 °C for 24 h. But again this is not a practical preparative method since it results in the formation of too many other isomers of the substrate and 2 [39]. Alkylated

• reaction. In this case the diketone 107 was obtained by a Zn/Cu-couple-induced coupling reaction between excess phenacyl bromide (105) and the enyne 106 (Scheme 27) [83]. Besides 107 its diyne and propargylallene dimers were produced, requiring a chromatographic separation of the product mixture. The

Influence of intramolecular hydrogen bonds on the binding potential of methylated β-cyclodextrin derivatives

• Gerhard Wenz

Beilstein J. Org. Chem. 2012, 8, 1890–1895, doi:10.3762/bjoc.8.218

• ]. The host–guest complexes, so-called cyclodextrin inclusion compounds, find many applications such as solubilization of pharmaceutical drugs, dispersion of cosmetics, catalysis, or chromatographic separation of enantiomers [2][7][8]. Application of β-CD 1 is hampered by its low solubility of 18.8 g L−1

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

Reactions of nitroxides XIII: Synthesis of the Morita–Baylis–Hillman adducts bearing a nitroxyl moiety using 4-acryloyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl as a starting compound, and DABCO and quinuclidine as catalysts

• Jerzy Zakrzewski

Beilstein J. Org. Chem. 2012, 8, 1515–1522, doi:10.3762/bjoc.8.171

• EIMS and IR spectra of the synthesized compounds 5a–o, 1H and 13C NMR of 5d with phenylhydrazine, and the chromatographic separation of 5l. Supporting Information File 276: Detailed spectrographic data. Acknowledgments The work was supported by the Polish Ministry of Science and Higher Education, 429

Stereoselective synthesis of trans-fused iridoid lactones and their identification in the parasitoid wasp Alloxysta victrix, Part I: Dihydronepetalactones

• Nicole Zimmermann,
• Robert Hilgraf,
• Lutz Lehmann,
• Daniel Ibarra and
• Wittko Francke

Beilstein J. Org. Chem. 2012, 8, 1246–1255, doi:10.3762/bjoc.8.140

• the Favorskii-rearrangement step [22], again requiring a difficult chromatographic separation. Furthermore, this multistep route has several major disadvantages: The formation of mixtures of epimers entails to separations at several stages which have proven to be problematic. Moreover, several

Synthesis and in silico screening of a library of β-carboline-containing compounds

• Kay M. Brummond,
• John R. Goodell,
• Matthew G. LaPorte,
• Lirong Wang and
• Xiang-Qun Xie

Beilstein J. Org. Chem. 2012, 8, 1048–1058, doi:10.3762/bjoc.8.117

• tosylated derivatives exhibited improved stability as evidenced by 1H NMR (Table 1, entries 1–7, and Supporting Information File 1, S76–S81). Incorporation of the tosyl group also eased the chromatographic separation of the syn- and anti-isomers for entries 2–7, thus compounds 7{2–7} were obtained as single

Stereoselective, nitro-Mannich/lactamisation cascades for the direct synthesis of heavily decorated 5-nitropiperidin-2-ones and related heterocycles

• Pavol Jakubec,
• Dane M. Cockfield,
• Madeleine Helliwell,
• James Raftery and
• Darren J. Dixon

Beilstein J. Org. Chem. 2012, 8, 567–578, doi:10.3762/bjoc.8.64

• ’’, under slightly modified conditions (water was used instead of MeOH as the solvent). Pleasingly the reaction proceeded smoothly and only two, 2a and 2a’’, of the possible eight diastereoisomeric tetracyclic compounds were obtained in good combined yield (70%, Scheme 4). Chromatographic separation

Scalable synthesis of (1-cyclopropyl)cyclopropylamine hydrochloride

• Sergei I. Kozhushkov,
• Alexander F. Khlebnikov,
• Rafael R. Kostikov,
• Dmitrii S. Yufit and
• Armin de Meijere

Beilstein J. Org. Chem. 2011, 7, 1003–1006, doi:10.3762/bjoc.7.113

• laboratory required chromatographic separation of the intermediately prepared N-Boc derivative, which involved the rather costly di-tert-butyl pyrocarbonate and made that an overall three-step procedure. Experimental 1H and 13C NMR spectra were recorded at 300 MHz [1H] and 62.9 MHz [13C, additional DEPT

Single enantiomer synthesis of α-(trifluoromethyl)-β-lactam

• Václav Jurčík,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2011, 7, 759–766, doi:10.3762/bjoc.7.86

• end, X-ray crystallography of the major diastereoisomers of 5a and 5b was attempted after chromatographic separation. Despite considerable effort however we could not obtain crystals of single isomers of 5a or 5b suitable for X-ray structure analysis. Thus, a preparation of 5c was carried out as

Synthesis and crystal structures of multifunctional tosylates as basis for star-shaped poly(2-ethyl-2-oxazoline)s

• Richard Hoogenboom,
• Martin W. M. Fijten,
• Guido Kickelbick and
• Ulrich S. Schubert

Beilstein J. Org. Chem. 2010, 6, 773–783, doi:10.3762/bjoc.6.96

• recently reported a post-modification route for the synthesis of star-shaped poly(2-ethyl-2-oxazoline) by coupling of an acetylene-functionalized poly(2-ethyl-2-oxazoline) to a heptakis-azido functionalized β-cyclodextrin [18]. However, this method required chromatographic separation of the star-shaped

Kinetic studies and predictions on the hydrolysis and aminolysis of esters of 2-S-phosphorylacetates

• Milena Trmčić and
• David R. W. Hodgson

Beilstein J. Org. Chem. 2010, 6, 732–741, doi:10.3762/bjoc.6.87

• with ~30% of the “carboxylate” arising through competing hydrolysis processes. Chromatographic separation proved time consuming and resolution of the products was poor, further illustrating the need to improve selectivity and avoid purification steps. Furthermore, the preparation of bromoacetyl-N

Polar tagging in the synthesis of monodisperse oligo(p-phenyleneethynylene)s and an update on the synthesis of oligoPPEs

• Dhananjaya Sahoo,
• Susanne Thiele,
• Miriam Schulte,
• Navid Ramezanian and
• Adelheid Godt

Beilstein J. Org. Chem. 2010, 6, No. 57, doi:10.3762/bjoc.6.57

• alkyne protecting groups triisopropylsilyl and hydroxymethyl (HOM) and on the polar tagging with the hydroxymethyl moiety for an easy chromatographic separation of the products. This paper provides an update of this synthetic route. For the deprotection of HOM protected alkynes, γ-MnO2 proved to be

• as polar tags for the chromatographic separation. Polar tagging with HOM [47][48][49] or HOP [34][42][45][50][51][52][53][54][55][56][57] has been the key to the successful syntheses of a variety of aryleneethynylene building blocks and oligomers [42][45][47][48][49][50][51][52] and of oligoeneynes

• amount of the carbometalation product 5a from 2–16% to 1–5%. Nevertheless, large scale preparative chromatographic separation on silica gel is tedious. Carbometalation product 5a and monomer 1a1 have very similar Rf-values and, unfortunately, the byproduct is eluted first. Luckily, contamination of

Novel banana-discotic hybrid architectures

• Hari Krishna Bisoyi,
• H. T. Srinivasa and
• Sandeep Kumar

Beilstein J. Org. Chem. 2009, 5, No. 52, doi:10.3762/bjoc.5.52

• . Experimental All the reagents and solvents were used as received without any further purification except CH2Cl2 which was dried and distilled before the reactions. Column chromatographic separation was performed on silica gel (100–200 mesh). 1H NMR spectra were recorded in CDCl3 on a 400 MHz (Bruker AMX 400