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Search for "stereocontrol" in Full Text gives 124 result(s) in Beilstein Journal of Organic Chemistry.

Fluorination of some highly functionalized cycloalkanes: chemoselectivity and substrate dependence

  • Attila Márió Remete,
  • Melinda Nonn,
  • Santos Fustero,
  • Matti Haukka,
  • Ferenc Fülöp and
  • Loránd Kiss

Beilstein J. Org. Chem. 2017, 13, 2364–2371, doi:10.3762/bjoc.13.233

Graphical Abstract
  • fluorination based on hydroxy–fluorine interconversion seems to be an eloquent, simple and efficient procedure for the creation of a certain fluorinated organic molecule, regio- and stereoselectivity, stereocontrol and substrate influence remain a challenge in the case of highly functionalized frameworks
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Published 06 Nov 2017

Homologated amino acids with three vicinal fluorines positioned along the backbone: development of a stereoselective synthesis

  • Raju Cheerlavancha,
  • Ahmed Ahmed,
  • Yun Cheuk Leung,
  • Aggie Lawer,
  • Qing-Quan Liu,
  • Marina Cagnes,
  • Hee-Chan Jang,
  • Xiang-Guo Hu and
  • Luke Hunter

Beilstein J. Org. Chem. 2017, 13, 2316–2325, doi:10.3762/bjoc.13.228

Graphical Abstract
  • amino acid unit in a natural peptide without changing the overall length of the peptide [16]. The presence of three vicinal fluorine atoms on the amino acid backbone of 6 gives rise to eight possible stereoisomeric forms, which presents a synthetic challenge of stereocontrol. As an initial contribution
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Published 01 Nov 2017

Intramolecular glycosylation

  • Xiao G. Jia and
  • Alexei V. Demchenko

Beilstein J. Org. Chem. 2017, 13, 2028–2048, doi:10.3762/bjoc.13.201

Graphical Abstract
  • for elaborate protecting and leaving group manipulations, functionalization, tedious purification, and sophisticated characterization. Achieving high stereocontrol in glycosylation reactions is arguably the major hurdle that chemists experience. This review article overviews methods for intramolecular
  • very first experiments performed by Arthur Michael and Emil Fischer in the late 1800’s, the glycosylation reaction remains challenging to chemists. Enzymatic glycosylation reactions are highly stereoselective [33]. However, the stereocontrol of chemical glycosylation reactions remains cumbersome
  • as a flattened oxacarbenium intermediate (Scheme 1a). Early attempts to achieve some stereocontrol of glycosylations were mainly dedicated to the development of participating groups and optimization of the reaction conditions. More recently, the research emphasis is switching towards understanding of
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Published 29 Sep 2017

The chemistry and biology of mycolactones

  • Matthias Gehringer and
  • Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159

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Published 11 Aug 2017

A speedy route to sterically encumbered, benzene-fused derivatives of privileged, naturally occurring hexahydropyrrolo[1,2-b]isoquinoline

  • Olga Bakulina,
  • Alexander Ivanov,
  • Vitalii Suslonov,
  • Dmitry Dar’in and
  • Mikhail Krasavin

Beilstein J. Org. Chem. 2017, 13, 1413–1424, doi:10.3762/bjoc.13.138

Graphical Abstract
  • -diastereoselectivity of the CCR is well documented in the literature [33] and is, therefore, unsurprising. However, the stereocontrol achieved in this reaction over 3 stereocenters present in 10l (obtained in 81% yield as a single diastereomer) is certainly quite noteworthy and was confirmed by X-ray analysis (Figure
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Published 18 Jul 2017

Polyketide stereocontrol: a study in chemical biology

  • Kira J. Weissman

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

Graphical Abstract
  • biosynthesis of reduced polyketides in bacteria by modular polyketide synthases (PKSs) proceeds with exquisite stereocontrol. As the stereochemistry is intimately linked to the strong bioactivity of these molecules, the origins of stereochemical control are of significant interest in attempts to create
  • this approach to provide answers to fundamental biological questions. Keywords: chemical biology; polyketide synthases; reduced polyketides; stereocontrol; Introduction Reduced polyketides and their derivatives form the basis for a number of medicines in current clinical usage, notably anti
  • so in principle, 1024 (210) different stereoisomers are possible. Yet, nature reliably assembles only one stereoisomer (at least at detectable levels), at once revealing the strict stereocontrol underpinning the pathway and the importance of synthesizing this particular version. Indeed, the crystal
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Published 24 Feb 2017

Silyl-protective groups influencing the reactivity and selectivity in glycosylations

  • Mikael Bols and
  • Christian Marcus Pedersen

Beilstein J. Org. Chem. 2017, 13, 93–105, doi:10.3762/bjoc.13.12

Graphical Abstract
  • the reaction intermediate is a radical that prefers to be axial. On the other hand, with acetate protective groups, the addition of deuterium occurred predominantly from the β-side [45][46]. The principle of conformational stereocontrol was also used for the stereoselective addition of carbon radicals
  • C-glycosides it has been possible to obtain conformationally derived stereocontrol so that persilylated donors adopting a 1C4 conformation give the β-products. However, for O-glycosylation, this type of selectivity has been difficult to achieve. Some very useful stereoselectivities are obtained with
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Published 16 Jan 2017

Strategies in asymmetric catalysis

  • Tehshik P. Yoon

Beilstein J. Org. Chem. 2017, 13, 63–64, doi:10.3762/bjoc.13.8

Graphical Abstract
  • synthetic problems. The articles collected in this Thematic Series for the Beilstein Journal of Organic Chemistry provide a snapshot of both types of efforts. Several of these papers report new catalyst designs or relatively new concepts in catalytic stereocontrol. Others document the application of
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Editorial
Published 10 Jan 2017

Diastereoselective anodic hetero- and homo-coupling of menthol-, 8-methylmenthol- and 8-phenylmenthol-2-alkylmalonates

  • Matthias C. Letzel,
  • Hans J. Schäfer and
  • Roland Fröhlich

Beilstein J. Org. Chem. 2017, 13, 33–42, doi:10.3762/bjoc.13.5

Graphical Abstract
  • coupling in high yield with good stereocontrol [38][39][40]. With the auxiliary controlled alkylation of enolates products being analogous to radical hetero-coupling can be synthesized [41][42]. However, both methods require costlier reaction conditions as inert gas, dry solvents and LDA as reagent, and
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Published 05 Jan 2017

Useful access to enantiomerically pure protected inositols from carbohydrates: the aldohexos-5-uloses route

  • Felicia D’Andrea,
  • Giorgio Catelani,
  • Lorenzo Guazzelli and
  • Venerando Pistarà

Beilstein J. Org. Chem. 2016, 12, 2343–2350, doi:10.3762/bjoc.12.227

Graphical Abstract
  • derivatives of the D-xylo and L-ribo series, respectively C-4 and C-2 epimers of the L-arabino series. Based on these aldol condensations together with the work previously performed on the L-arabino [33] and L-lyxo [34] series, a working mechanism is presented to explain the complete stereocontrol over the
  • formation of the two new stereogenic centres (red in Scheme 1). Furthermore, the stereochemical outcome of the intermediate inososes reduction by using different reagents, namely the stereocontrol over a third stereogenic centre (green in Scheme 1), is also reported. Results and Discussion The aldol
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Published 08 Nov 2016

Chiral ammonium betaine-catalyzed asymmetric Mannich-type reaction of oxindoles

  • Masahiro Torii,
  • Kohsuke Kato,
  • Daisuke Uraguchi and
  • Takashi Ooi

Beilstein J. Org. Chem. 2016, 12, 2099–2103, doi:10.3762/bjoc.12.199

Graphical Abstract
  • efficiently converted into 4ga and 4ha with rigorous relative and absolute stereocontrol (Table 2, entries 15 and 16). The absolute configuration of 4ca was unequivocally determined by X-ray crystallographic analysis (Figure 2), and the stereochemistry of the remaining examples was assumed to be analogous
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Published 28 Sep 2016

Enantioconvergent catalysis

  • Justin T. Mohr,
  • Jared T. Moore and
  • Brian M. Stoltz

Beilstein J. Org. Chem. 2016, 12, 2038–2045, doi:10.3762/bjoc.12.192

Graphical Abstract
  • . The resulting intermediate undergoes proton transfer and elimination of the phosphonium moiety, resulting in product 30 and regeneration of the catalyst. This exceptional demonstration of stereocontrol requires that the catalysts precisely organize both the electrophilic and nucleophilic reactants to
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Published 16 Sep 2016

Stereo- and regioselectivity of the hetero-Diels–Alder reaction of nitroso derivatives with conjugated dienes

  • Lucie Brulíková,
  • Aidan Harrison,
  • Marvin J. Miller and
  • Jan Hlaváč

Beilstein J. Org. Chem. 2016, 12, 1949–1980, doi:10.3762/bjoc.12.184

Graphical Abstract
  • and natural products as well as for the mild functionalization and derivatization of diene-containing natural products [1][2][3][4][5][6][7][8][9][10]. The reversibility of this reaction plays a considerable role in both the observed regio- and stereocontrol of the nitroso Diels–Alder reaction
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Published 01 Sep 2016

Experimental and theoretical insights in the alkene–arene intramolecular π-stacking interaction

  • Valeria Corne,
  • Ariel M. Sarotti,
  • Carmen Ramirez de Arellano,
  • Rolando A. Spanevello and
  • Alejandra G. Suárez

Beilstein J. Org. Chem. 2016, 12, 1616–1623, doi:10.3762/bjoc.12.158

Graphical Abstract
  • an element of stereocontrol in highly selective chemical transformations has been widely explored [9]. In this context, as part of our continuous interest in the development of new tools for asymmetric synthesis using levoglucosenone (a biomass-derived chiral enone) [10][11][12][13][14][15], we
  • aromatic rings. This can be useful in several fields, such as supramolecular chemistry, biology and material science and, in particular, in the area of asymmetric synthesis for the rational design of new elements of stereocontrol. Intramolecular aryl–vinyl π-stacking interaction of a levoglucosenone
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Published 28 Jul 2016

Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides

  • Franziska Hemmerling and
  • Frank Hahn

Beilstein J. Org. Chem. 2016, 12, 1512–1550, doi:10.3762/bjoc.12.148

Graphical Abstract
  • stereocontrol, while Tyr157 and Lys161 participate in pre-orienting NADPH for transfer of its pro-S proton [27][32]. The resulting secondary alcohol 43 is processed similar to its enantiomer 39 in actinorhodin biosynthesis to give (R)-DNPA (46) and finally graniticin (36) after tailoring. It has been proposed
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Published 20 Jul 2016

Automated glycan assembly of a S. pneumoniae serotype 3 CPS antigen

  • Markus W. Weishaupt,
  • Stefan Matthies,
  • Mattan Hurevich,
  • Claney L. Pereira,
  • Heung Sik Hahm and
  • Peter H. Seeberger

Beilstein J. Org. Chem. 2016, 12, 1440–1446, doi:10.3762/bjoc.12.139

Graphical Abstract
  • block 1 was designed (Figure 2). A levulinoyl (Lev) ester was chosen as temporary protecting group (TPG) since the Fmoc (fluorenylmethoxycarbonyl) group led to a loss of stereocontrol during glycosylations with this glucuronic acid (GlcA) building block (data not shown). Glucose building blocks 2 and 3
  • glucose building block. This monomer did not suffer from a loss of stereocontrol as was observed in the case of the similarly protected GlcA building block. The desired trisaccharide 5 was observed as the main product from the automated synthesis by HPLC analysis (Figure 5). The Lev protecting group had
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Published 12 Jul 2016

Towards the total synthesis of keramaphidin B

  • Pavol Jakubec,
  • Alistair J. M. Farley and
  • Darren J. Dixon

Beilstein J. Org. Chem. 2016, 12, 1096–1100, doi:10.3762/bjoc.12.104

Graphical Abstract
  • -controlled Michael reaction remained present. Accordingly, we chose to probe reactivity and establish relative stereocontrol using a close model system comprising pronucleophile 8 and furanyl nitroolefin 11 (Scheme 1). The δ-valerolactone pronucleophile 8 was synthesised by the enolate acylation of δ
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Published 30 May 2016

Bifunctional catalysis

  • Darren J. Dixon

Beilstein J. Org. Chem. 2016, 12, 1079–1080, doi:10.3762/bjoc.12.102

Graphical Abstract
  • effect of the two complementary functional groups can lead to new reactivity and stereocontrol in reactions that were previously challenging or unprecedented. With multiple points of diversity in the two functional groups and the chiral scaffold, these catalysts can be readily tuned to optimise
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Editorial
Published 25 May 2016

1H-Imidazol-4(5H)-ones and thiazol-4(5H)-ones as emerging pronucleophiles in asymmetric catalysis

  • Antonia Mielgo and
  • Claudio Palomo

Beilstein J. Org. Chem. 2016, 12, 918–936, doi:10.3762/bjoc.12.90

Graphical Abstract
  • catalysts were not efficient in terms of stereoselectivity. However, good results regarding both, yield and stereocontrol, were observed when the Rawal catalyst C1 [60][61] was employed (Scheme 2). Under the optimized conditions the reaction, as shown in Scheme 2, worked equally well regardless of the
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Published 09 May 2016

Synthesis and in vitro cytotoxicity of acetylated 3-fluoro, 4-fluoro and 3,4-difluoro analogs of D-glucosamine and D-galactosamine

  • Štěpán Horník,
  • Lucie Červenková Šťastná,
  • Petra Cuřínová,
  • Jan Sýkora,
  • Kateřina Káňová,
  • Roman Hrstka,
  • Ivana Císařová,
  • Martin Dračínský and
  • Jindřich Karban

Beilstein J. Org. Chem. 2016, 12, 750–759, doi:10.3762/bjoc.12.75

Graphical Abstract
  • enabled a high degree of regio- and stereocontrol necessary for the introduction of heteroatomic substituents at C-2, C-3, and C-4. The synthesis of the analogs 6–8 has not yet been reported to our knowledge, while the synthesis of 1, 4 and 5 represents an alternative to the published procedures [2][20
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Published 20 Apr 2016

A selective and mild glycosylation method of natural phenolic alcohols

  • Mária Mastihubová and
  • Monika Poláková

Beilstein J. Org. Chem. 2016, 12, 524–530, doi:10.3762/bjoc.12.51

Graphical Abstract
  • acetylated salidroside 22 from moderate (ZnO–ZnCl2, 49%) to good yields (DDQ–I2, 61% and ZnO–I2, 63%) with strict β-stereocontrol. On the other side, the glucosylation of p-O-acetylated coniferyl alcohol 12 with bromide 13 failed under these conditions. Coniferyl aldehyde 24 was detected and isolated as a
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Published 15 Mar 2016

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

  • Giorgos Koutoulogenis,
  • Nikolaos Kaplaneris and
  • Christoforos G. Kokotos

Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48

Graphical Abstract
  • , respectively, in excellent yields and stereoselectivities (Scheme 13) [24]. Computational studies were employed, in order to support the mechanistic pathway and the origins of stereocontrol. Secondary amino-thioureas as organocatalysts promoting asymmetric transformations that lead to a six-membered ring In
  • , Enders and co-workers described the three-component domino Michael–Michael aldol reaction between β-ketoesters 153, nitroalkenes 77 and α,β-unsaturated aldehydes 154, producing heavily substituted cyclohexanes 155 containing six contiguous stereocenters with excellent stereocontrol (Scheme 49) [70]. In
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Published 10 Mar 2016

Application of 7-azaisatins in enantioselective Morita–Baylis–Hillman reaction

  • Qing He,
  • Gu Zhan,
  • Wei Du and
  • Ying-Chun Chen

Beilstein J. Org. Chem. 2016, 12, 309–313, doi:10.3762/bjoc.12.33

Graphical Abstract
  • stereocontrol [6][7][8][9][10][11][12]. Maleimides are also good nucleophilic precursors in the MBH reactions and in 2013, Chimni developed an asymmetric MBH reaction of isatins and maleimides with excellent enantioselectivity [13]. Later, the same group expanded this strategy to isatin-derived ketimines under
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Published 18 Feb 2016

Diastereoselective Ugi reaction of chiral 1,3-aminoalcohols derived from an organocatalytic Mannich reaction

  • Samantha Caputo,
  • Andrea Basso,
  • Lisa Moni,
  • Renata Riva,
  • Valeria Rocca and
  • Luca Banfi

Beilstein J. Org. Chem. 2016, 12, 139–143, doi:10.3762/bjoc.12.15

Graphical Abstract
  • the diastereoselectivity. We had anticipated that the binding of the Lewis acid to the free alcohol, followed by intramolecular activation of the aldehyde, would establish a cyclic transition state, thereby enabling better stereocontrol. It is indeed well-known that the Ugi reaction does not proceed
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Published 26 Jan 2016

Recent advances in copper-catalyzed asymmetric coupling reactions

  • Fengtao Zhou and
  • Qian Cai

Beilstein J. Org. Chem. 2015, 11, 2600–2615, doi:10.3762/bjoc.11.280

Graphical Abstract
  • advantage of a chiral (R)-BINOL-bridge to link the two aromatic acids and obtained the coupling product with excellent stereocontrol (up to 100% de) (Scheme 1) [16][17][18][19]. In 1998, Martin et al. [20] applied this strategy to the asymmetric intramolecular biaryl coupling of sugar derivatives carrying 2
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Published 15 Dec 2015
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