Synthesis of heteroglycoclusters by using orthogonal chemoselective ligations

• Baptiste Thomas,
• Michele Fiore,
• Isabelle Bossu,
• Pascal Dumy and
• Olivier Renaudet

Beilstein J. Org. Chem. 2012, 8, 421–427, doi:10.3762/bjoc.8.47

• : chemoselective ligation; click chemistry; cyclopeptide; heteroglycocluster; oxime; Introduction Multivalent interactions between carbohydrates and proteins play key roles in diverse biological events, including fertilization, cell–cell communication, host–pathogen interactions, immune response and cancer

• heteroglycoclusters by using a protocol based on orthogonal chemoselective ligations. Two series of compounds containing different combinations of two different sugars have been designed (Figure 1). In one series (heteroglycocluster 2:2), two αMan, αFuc and/or βLac are conjugated at alternate positions into the

• methods, we decided to explore two chemoselective strategies to achieve this purpose. We first selected the oxime ligation since we have previously used this approach successfully for the preparation of sophisticated molecular systems, such as synthetic vaccines [27][28], immunomodulators [29], lectin

Dioxane dibromide mediated bromination of substituted coumarins under solvent-free conditions

• Subrata Kumar Chaudhuri,
• Sanchita Roy and
• Sanjay Bhar

Beilstein J. Org. Chem. 2012, 8, 323–329, doi:10.3762/bjoc.8.35

• in 1e and 1f, vinylic bromination occurred regioselectively to furnish 2e and 2f in high yield without further bromination at C6 and C8, when a stoichiometric amount of DD was used (Table 1, entries 6 and 7). Interestingly, 7-(allyloxy)coumarin (1g) underwent chemoselective addition of bromine across

Recent advances in direct C–H arylation: Methodology, selectivity and mechanism in oxazole series

• Cécile Verrier,
• Pierrik Lassalas,
• Laure Théveau,
• Guy Quéguiner,
• François Trécourt,
• Francis Marsais and
• Christophe Hoarau

Beilstein J. Org. Chem. 2011, 7, 1584–1601, doi:10.3762/bjoc.7.187

• ]. Over the past decade, alternatives for more expeditive, practical and chemoselective arylating technics have arisen, thanks mainly to the great development of novel, stoichiometric and catalytic, direct arylation methodologies (Scheme 1). Thus novel classes of metallating agents resulting from various

• ], manganate ((Me3SiCH2)2Mn(TMP)Li·TMEDA) [3][8], cuprates (MeCu(TMP)(CN)Li2, (TMP)2CuLi) [9][10] and cadmium amides ((TMP)3CdLi) [11][12], for regio- and/or chemoselective deprotonative metalation of aromatics, producing arylmetal intermediates under smooth reaction conditions that are directly suitable for

Ratiometric fluorescent probe for enantioselective detection of D-cysteine in aqueous solution

• Xiao-bo Zhou,
• Wing-Hong Chan,
• Albert W. M. Lee and
• Chi-Chung Yeung

Beilstein J. Org. Chem. 2011, 7, 1508–1515, doi:10.3762/bjoc.7.176

• Cd2+–ACAQ. As cadmium is well-known for its strong affinity to sulfur-containing compounds, we envisioned that the Cd2+-bound ACAQ complex would demonstrate chemoselective binding toward amino acids. Among 22 amino acids, a tripeptide, cysteine derivative and β-mercaptopropionic acid (MPA), only Cys

Access to pyrrolo-pyridines by gold-catalyzed hydroarylation of pyrroles tethered to terminal alkynes

• Elena Borsini,
• Gianluigi Broggini,
• Andrea Fasana,
• Chiara Baldassarri,
• Angelo M. Manzo and
• Alcide D. Perboni

Beilstein J. Org. Chem. 2011, 7, 1468–1474, doi:10.3762/bjoc.7.170

• chemists. Gold catalysis has recently emerged as a suitable way to achieve such a goal, mainly thanks to the chemoselective alkynophilic properties of this attractive metal in different types of reactions [6][7][8][9][10][11][12][13][14][15]. Among the hydroarylation reactions, various kinds of heteroaryl

Functionalization of heterocyclic compounds using polyfunctional magnesium and zinc reagents

• Paul Knochel,
• Matthias A. Schade,
• Sebastian Bernhardt,
• Georg Manolikakes,
• Albrecht Metzger,
• Fabian M. Piller,
• Christoph J. Rohbogner and
• Marc Mosrin

Beilstein J. Org. Chem. 2011, 7, 1261–1277, doi:10.3762/bjoc.7.147

• report two protocols recently developed in our laboratories: A chemoselective Negishi cross-coupling protocol tolerating acidic hydrogen atoms. A chemoselective Kumada cross-coupling based on a new radical mechanism. 3.1 Chemoselective Negishi cross-coupling using substrates bearing acidic hydrogen atoms

• -group (Scheme 22) [53][54]. Remarkably, this reaction protocol was extended to substrates bearing an α-aminoester moiety, such as 152 providing the cross-coupling product 153 in 85% yield (Scheme 23 and Supporting Information File 1, Procedure 9) [54]. 3.2 Radical catalyzed Kumada chemoselective cross

• Information File 1. Preparation of polyfunctional heteroarylzinc reagents. LiCl-mediated insertion of zinc dust to aryl and heteroaryl iodides. Selective insertions of Zn in the presence of LiCl. Chemoselective insertion of zinc in the presence of LiCl. Preparation and reactions of benzylic zinc reagents. Ni

Gold(I)-catalyzed synthesis of γ-vinylbutyrolactones by intramolecular oxaallylic alkylation with alcohols

• Michel Chiarucci,
• Mirko Locritani,
• Gianpiero Cera and
• Marco Bandini

Beilstein J. Org. Chem. 2011, 7, 1198–1204, doi:10.3762/bjoc.7.139

• complexes allowed the preparation of a range of functionalized malonyl esters by direct activation of the allylic alcohol by gold. The methodology appears highly chemoselective toward the allylic lactonization, with the possibility to extend the protocol also to acetate derivatives. Working hypothesis for

Evaluation of a commercial packed bed flow hydrogenator for reaction screening, optimization, and synthesis

• Marian C. Bryan,
• David Wernick,
• Christopher D. Hein,
• James V. Petersen,
• John W. Eschelbach and
• Elizabeth M. Doherty

Beilstein J. Org. Chem. 2011, 7, 1141–1149, doi:10.3762/bjoc.7.132

• conditions [14]. One of the most dramatic results we observed was the complete loss of selectivity in the reduction of an azido group in the presence of an aromatic nitrile (Scheme 1). Initially, the chemoselective reduction of azido nitrile 1 was successfully performed with a 30 mm 10% Pt/C CatCart® to

Recent developments in gold-catalyzed cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2011, 7, 1075–1094, doi:10.3762/bjoc.7.124

• and reductive eliminations). Therefore, platinum(II) and particularly gold(I) or (III) complexes tend to activate alkynes, alkenes or allenes in a highly chemoselective manner; activation that opens interesting reaction pathways that usually involve carbocationic intermediates. Also very important is

• a 3C-atom component in the annulation. A precise explanation for this dichotomy has not been specifically addressed. Cycloadditions initiated by gold-activation of allenes Several gold catalysts can activate allenes in a very chemoselective way, triggering different types of cycloaddition processes

A novel high-yield synthesis of aminoacyl p-nitroanilines and aminoacyl 7-amino-4-methylcoumarins: Important synthons for the synthesis of chromogenic/fluorogenic protease substrates

• Xinghua Wu,
• Yu Chen,
• Herve Aloysius and
• Longqin Hu

Beilstein J. Org. Chem. 2011, 7, 1030–1035, doi:10.3762/bjoc.7.117

• was highly chemoselective, mild, and free of racemization in the coupling step [20]; was compatible with common protecting groups used in peptide chemistry including Fmoc, Boc, Cbz, and Trt; and more importantly, worked very efficiently for electron-deficient aromatic azides substituted with an

Triazole–Au(I) complex as chemoselective catalyst in promoting propargyl ester rearrangements

• Dawei Wang,
• Yanwei Zhang,
• Rong Cai and
• Xiaodong Shi

Beilstein J. Org. Chem. 2011, 7, 1014–1020, doi:10.3762/bjoc.7.115

• also influenced the allene reactivity, probably through gold catalyzed allene activation. The fact that TA–Au gave the dominant (E)-isomers strongly suggests that these complexes may be applied as the chemoselective catalyst in alkyne activation over allene. The reactions of propargyl ester 1a with TA

• -withdrawing groups were suitable for the reaction. Again, no indene by-products were observed in any of the tested cases, even with the electron-enriched p-OMe substituted alkyne 1d. These results highlighted the excellent chemoselective nature of the TA–Au catalyst. The terminal alkyne 1i did not give any

• propargyl ester, carbonate and carbamate 3,3-rearrangement for the synthesis of the corresponding substituted allene derivatives. The chemoselective nature of the TA–Au catalysts was clearly demonstrated, which makes them an interesting class of new catalysts for promoting organic transformations. The

A comparative study of the Au-catalyzed cyclization of hydroxy-substituted allylic alcohols and ethers

• Berenger Biannic,
• Thomas Ghebreghiorgis and
• Aaron Aponick

Beilstein J. Org. Chem. 2011, 7, 802–807, doi:10.3762/bjoc.7.91

• sensitive functional groups. While cyclization reactions of highly elaborated substrates are desirable, mild chemoselective methods are necessary for this endeavor. Homogeneous gold-catalyzed reactions have emerged as a powerful new methodology for the construction of a diverse array of molecular

• architectures; for recent reviews on Au-catalysis, see [2][3][4][5][6][7][8][9][10]. Generally, only mild conditions are necessary and these processes are highly chemoselective. While the typical substrates employed in these reactions effect transformations on alkyne, allene, and alkene moieties, recent reports

• such as benzoyl (16) were unsuitable. This may provide a basis for chemoselective transformations, as allyl esters are readily ionized by Pd0 complexes and the resulting π-allylpalladium species are alkylated by a variety of nucleophiles [27][28]. Finally, 1° allylic and 2° allylic ether substrates

A racemic formal total synthesis of clavukerin A using gold(I)-catalyzed cycloisomerization of 3-methoxy-1,6-enynes as the key strategy

• Jae Youp Cheong and
• Young Ho Rhee

Beilstein J. Org. Chem. 2011, 7, 740–743, doi:10.3762/bjoc.7.84

• , extensive attempts at the chemoselective hydrogenation of the trisubstituted olefin 2 gave only compound 1 with poor selectivity. For example, various metal (Pd or Rh)-catalyzed hydrogenations resulted in a mixture of 1 and 3. This problem was also noted in another work on the synthesis of clavukerin A [13

When cyclopropenes meet gold catalysts

• Frédéric Miege,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2011, 7, 717–734, doi:10.3762/bjoc.7.82

• chemoselective activation of the cyclopropene, in preference to the alkene, which allows the generation of a gold carbene intermediate. The relative reactivity of cyclopropenes compared to alkynes is an interesting issue that has been addressed by Wang et al. during their studies on the gold-catalyzed

• %). The hydroxyl group did not exert a particular role in this process since 1,2-diphenyl-3-propargylcyclopropene was rearranged to 1,2-diphenylbenzene (97%) under the same conditions [26]. The formation of phenols (and their derivatives) 77–81 could be explained by an initial chemoselective activation of

Gold-catalyzed naphthalene functionalization

• Pedro J. Pérez,
• M. Mar Díaz-Requejo and
• Iván Rivilla

Beilstein J. Org. Chem. 2011, 7, 653–657, doi:10.3762/bjoc.7.77

• are formed quantitatively. The use of the gold analogue also induces the formation of such fused cyclopropanes in addition to the products derived from the formal insertion of the carbene units into the C–H bonds of naphthalene. The system is completely chemoselective with regards to arene

Gold-catalyzed heterocyclizations in alkynyl- and allenyl-β-lactams

• Benito Alcaide and
• Pedro Almendros

Beilstein J. Org. Chem. 2011, 7, 622–630, doi:10.3762/bjoc.7.73

• products (Scheme 6). These transformations may involve a chemoselective (5-endo-trig versus 7-endo-trig) allenol oxycyclization with concomitant MOM ether deprotection. Taking into account the above results, it was decided to see whether the metal-catalyzed preparation of bicycles 9 can be directly

Synthesis of glycoconjugate fragments of mycobacterial phosphatidylinositol mannosides and lipomannan

• Benjamin Cao,
• Jonathan M. White and
• Spencer J. Williams

Beilstein J. Org. Chem. 2011, 7, 369–377, doi:10.3762/bjoc.7.47

• remaining hydroxyl groups afforded the glycoside 13, which was desilylated with HF·pyridine complex to yield 14. This chemoselective transformation uses conditions that are similar to those reported by Tam et al. [23], and result in desilylation in a significantly shorter period than that previously

The allylic chalcogen effect in olefin metathesis

• Yuya A. Lin and
• Benjamin G. Davis

Beilstein J. Org. Chem. 2010, 6, 1219–1228, doi:10.3762/bjoc.6.140

• . Plausible explanation for chemoselective CM of diene 16 [25]. a) Efficient cross-metathesis of S-allylcysteine [17]. b) Comparison of relative reactivity between allylic heteroatom derivatives. a) Macrocycle synthesis by carbonyl-relayed RCM. b) Putative complex in carbonyl-relayed RCM [33]. a) Sulfur

Total synthesis of (±)-coerulescine and (±)-horsfiline

• Mukund G. Kulkarni,
• Attrimuni P. Dhondge,
• Sanjay W. Chavhan,
• Ajit S. Borhade,
• Yunnus B. Shaikh,
• Deekshaputra R. Birhade,
• Mayur P. Desai and
• Nagorao R. Dhatrak

Beilstein J. Org. Chem. 2010, 6, 876–879, doi:10.3762/bjoc.6.103

• 14. Finally, chemoselective reduction of amide 14 with n-BuLi and LAH (under the conditions reported in [27]) gave coerulescine. Compound 1, on treatment with N-bromosuccinimide, gave the 5-bromo derivative, which upon heating with sodium methoxide in the presence of cuprous iodide gave horsfiline in

Systematic investigations on the reduction of 4-aryl-4-oxoesters to 1-aryl-1,4-butanediols with methanolic sodium borohydride

• Subrata Kumar Chaudhuri,
• Manabendra Saha,
• Amit Saha and
• Sanjay Bhar

Beilstein J. Org. Chem. 2010, 6, 748–755, doi:10.3762/bjoc.6.94

• the keto moiety. Results of a detailed and systematic investigation of the reaction are described. Keywords: diols; esters; lactones; reduction; Introduction Chemoselective reductions of aldehydes, ketones and imines are generally accomplished using NaBH4 in methanol where other reducible functional

• chemoselective reduction of the oxo-group, occasionally with subsequent transesterification and the formation of the alkoxy-modified β-hydroxyesters. γ-Oxoesters react chemoselectively with sodium borohydride to produce the corresponding γ-hydroxyesters [1][2][17][23][24][25][26][27] (sometimes in the form of γ

• ][22][23][24][25][26][27] for the chemoselective reduction of the keto group of all types of γ-oxoesters. Mechanistic rationale for diol formation during the reduction of a γ-aryl-α,β-unsaturated-γ-ketoester with methanolic NaBH4. Facile reduction of γ-aryl-γ-ketoesters to the corresponding diols with

Synthesis of lipophilic 1-deoxygalactonojirimycin derivatives as D-galactosidase inhibitors

• Georg Schitter,
• Elisabeth Scheucher,
• Andreas J. Steiner,
• Arnold E. Stütz,
• Martin Thonhofer,
• Chris A. Tarling,
• Stephen G. Withers,
• Jacqueline Wicki,
• Katrin Fantur,
• Eduard Paschke,
• Don J. Mahuran,
• Brigitte A. Rigat,
• Michael Tropak and
• Tanja M. Wrodnigg

Beilstein J. Org. Chem. 2010, 6, No. 21, doi:10.3762/bjoc.6.21

• desired free amine 15 [25], the key building block for further modifications (Scheme 2). The chemoselective acylation of the free amine 15 was conducted with three different benzoic acid derivatives in order to investigate the influence of the potential basicity of an additional nitrogen at the aromatic

• )-1-deoxygalactonojirimycin (15) from 12 via 14. Synthesis of lipophilic 1-deoxy-D-galactonojirimycin derivatives 16–18 by chemoselective acylation of 15. Synthesis of compounds 19 as well as 20 from primary amine 15. Synthesis of compound 22. Inhibitory activities of compounds 16–20 and 22 with β

Prediction of reduction potentials from calculated electron affinities for metal-salen compounds

• Sarah B. Bateni,
• Kellie R. England,
• Anthony T. Galatti,
• Handeep Kaur,
• Victor A. Mendiola,
• Alexander R. Mitchell,
• Michael H. Vu,
• Benjamin F. Gherman and
• James A. Miranda

Beilstein J. Org. Chem. 2009, 5, No. 82, doi:10.3762/bjoc.5.82

• advantage of this variant of the ERC reaction was the ability to effect the reaction at a more positive potential than the unmediated ERC reaction, resulting in a more chemoselective reaction [5]. The postulated mechanism of the reaction operated via a Ni(II)-salen radical anion as the active catalyst and

2-Phenyl- tetrahydropyrimidine- 4(1H)-ones – cyclic benzaldehyde aminals as precursors for functionalised β²-amino acids

• Markus Nahrwold,
• Arvydas Stončius,
• Anna Penner,
• Beate Neumann,
• Hans-Georg Stammler and
• Norbert Sewald

Beilstein J. Org. Chem. 2009, 5, No. 43, doi:10.3762/bjoc.5.43

• serve as universal precursors for the asymmetric synthesis of functionalised β2-amino acids containing acid-labile protected side chains. Diastereoselective alkylation of the tetrahydropyrimidinone is followed by a chemoselective two step degradation of the heterocycle to release the free β2-amino acid

• . Chemoselective reduction of 10 was carried out by reaction with sodium borohydride in the presence of Ni(OAc)2. The “nickel boride” formed as black precipitate serves as a highly active hydrogenation catalyst, whereas an excess of NaBH4 serves as hydrogen source [45][46]. The reaction reaches completion within

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

• insertion The laboratory of G.A. Sulikowski proposed a synthesis of 1,2-aziridinomitosenes [106][107] using as key transformations a Buchwald–Hartwig cross-coupling [108][109][110] and a chemoselective intramolecular carbon-hydrogen metal-carbenoid insertion reaction (Scheme 39). The chiral pyrolidine 136

N-acylation of ethanolamine using lipase: a chemoselective catalyst

• Mazaahir Kidwai,
• Roona Poddar and
• Poonam Mothsra

Beilstein J. Org. Chem. 2009, 5, No. 10, doi:10.3762/bjoc.5.10

• microwave irradiation. Keywords: chemoselective; lipase; microwave irradiation; zein number; Introduction Microwave assisted enzyme catalysis is a popular developing methodology in the field of green chemistry [1]. Enzymes have gained pivotal importance in the production of fine chemicals, pharmaceuticals