A simple and efficient method for the preparation of 5-hydroxy-3-acyltetramic acids

• Johanna Trenner and
• Evgeny V. Prusov

Beilstein J. Org. Chem. 2015, 11, 323–327, doi:10.3762/bjoc.11.37

• attempts to remove the benzyl group under various catalytic hydrogenation conditions failed entirely. Cleavage of the DMB group with TFA [16] was also tried, but brought no success and extensive formation of polymerization products of the corresponding iminium ion was observed. Oxidative cleavage of the

Synthesis of divalent ligands of β-thio- and β-N-galactopyranosides and related lactosides and their evaluation as substrates and inhibitors of Trypanosoma cruzi trans-sialidase

• María Emilia Cano,
• Rosalía Agusti,
• Alejandro J. Cagnoni,
• María Florencia Tesoriero,
• José Kovensky,
• María Laura Uhrig and
• Rosa M. de Lederkremer

Beilstein J. Org. Chem. 2014, 10, 3073–3086, doi:10.3762/bjoc.10.324

• trans-sialidase. Taking into consideration that mainly ester but also glycosidic linkages are labile in biological fluids, we choose amide and thioglycosidic bonds to attach the sugar residues to the platforms. 2,3,4,6-Tetra-O-acetyl-β-D-galactosylamine (1) was obtained by catalytic hydrogenation of 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

• (DCPM) ester of N-Fmoc-protected Ile 37, was condensed with N-Z-protected (βMe)Phe-OH 39. After removal of the Z group from the N-terminus of the resulting dipeptide 42 by catalytic hydrogenation, the product was coupled with N-Fmoc-protected (2R,1'R,2'R)-[3-(mono-, di- or tri-)fluoromethylcyclopropyl

A versatile δ-aminolevulinic acid (ΑLA)-cyclodextrin bimodal conjugate-prodrug for PDT applications with the help of intracellular chemistry

• Chrysie Aggelidou,
• Theodossis A. Theodossiou,
• Antonio Ricardo Gonçalves,
• Mariza Lampropoulou and
• Konstantina Yannakopoulou

Beilstein J. Org. Chem. 2014, 10, 2414–2420, doi:10.3762/bjoc.10.251

• stretching vibrations of the azido group (2104 cm−1, (Supporting Information File 1, Figure S5). The so obtained conjugate 9 was subsequently reduced under strongly acidic catalytic hydrogenation conditions to 2 in nearly quantitative yield. Crucial to the spectroscopic characterization of the product was

Derivatives of the triaminoguanidinium ion, 3. Multiple N-functionalization of the triaminoguanidinium ion with isocyanates and isothiocyanates

• Jan Szabo,
• Kerstin Karger,
• Nicolas Bucher and
• Gerhard Maas

Beilstein J. Org. Chem. 2014, 10, 2255–2262, doi:10.3762/bjoc.10.234

• was combined with benzaldehyde and hydratropic aldehyde to furnish the corresponding tris(imines), which were converted into 1,2,3-tris(benzylamino)guanidinium salts by catalytic hydrogenation in the former, and by borane reduction in the latter case. The resulting alkyl-substituted

• halides, tosylates and triflates. In our hands, solvent-free heterogenous mixtures of the solid guanidinium salt and a liquid alkylating reagent did not react as desired. Therefore, we developed a two-step alkylation procedure, by which the catalytic hydrogenation of 1,2,3-tris(benzyliminyl)guanidinium

• %) under sonication of the reaction mixture with ultrasound. Concerning the conversion of salt 4 into a 1,2,3-tris(2-phenylpropylamino)guanidinium salt 5, all attempts to reduce 4 by catalytic hydrogenation failed, and classical reducing agents such as sodium borohydride and lithium aluminum hydride showed

Five-membered ring annelation in [2.2]paracyclophanes by aldol condensation

• Henning Hopf,
• Swaminathan Vijay Narayanan and
• Peter G. Jones

Beilstein J. Org. Chem. 2014, 10, 2021–2026, doi:10.3762/bjoc.10.210

• compounds 2 we previously prepared precursors such as 5 (easily available by Wittig–Horner reaction of the appropriate bis-formyl cyclophanes) and subjected them to catalytic hydrogenation followed by a double Friedel–Crafts cyclization. However, it appeared to us that a more direct route to these useful

Postsynthetic functionalization of glycodendrons at the focal point

• Thisbe K. Lindhorst and
• Katharina Elsner

Beilstein J. Org. Chem. 2014, 10, 1482–1487, doi:10.3762/bjoc.10.152

• cross coupling products 16 and 17 in 77% and 43% respective yields. Again, only the trans-metathesis products were obtained. The cross-coupled alkenes 14 and 16 were carried on in catalytic hydrogenation reactions for reduction of the double bond, followed by deprotection of the sugar isopropylidene

Stereoselective synthesis of carbocyclic analogues of the nucleoside Q precursor (PreQ₀)

• Sabin Llona-Minguez and
• Simon P. Mackay

Beilstein J. Org. Chem. 2014, 10, 1333–1338, doi:10.3762/bjoc.10.135

• trans-isomers. After column chromatography the isolated diol 12 showed a diastereomeric purity of >99% by 1H NMR. The dibenzoate 13 was obtained in good yield following standard acylation conditions [31]. Final removal of the two benzyl groups was accomplished in excellent yield using catalytic

• hydrogenation [30], using EtOAc as a co-solvent to improve the substrate solubility. Amine 14 was coupled with 9 and the pivalamide and benzoate groups were cleaved in the one-pot procedure previously described to afford 15, the (1RS,2SR,3RS)-3-aminocyclopentane-1,2-diol derivative of PreQ0. Adapting a protocol

Amino acid motifs in natural products: synthesis of O-acylated derivatives of (2S,3S)-3-hydroxyleucine

• Oliver Ries,
• Martin Büschleb,
• Markus Granitzka,
• Dietmar Stalke and
• Christian Ducho

Beilstein J. Org. Chem. 2014, 10, 1135–1142, doi:10.3762/bjoc.10.113

• of the benzyl ester by catalytic hydrogenation, 6-methylheptanoic acid (26) could be obtained in 92% yield for the final step (Scheme 5). With respect to the (2S,3S)-3-hydroxyleucine motif occurring in several different peptidic natural products (vide supra), we also investigated the synthesis of N

Visible light mediated intermolecular [3 + 2] annulation of cyclopropylanilines with alkynes

• Theresa H. Nguyen,
• Soumitra Maity and
• Nan Zheng

Beilstein J. Org. Chem. 2014, 10, 975–980, doi:10.3762/bjoc.10.96

• 21 in 52% yield. The fused indoline motif was formed via an intramolecular Heck reaction under Fu’s conditions [41] to provide a mixture of two olefinic regioisomers 22, which were converted to saturated fused indoline 23 under standard catalytic hydrogenation conditions in a combined yield of 40

Group-assisted purification (GAP) chemistry for the synthesis of Velcade via asymmetric borylation of N-phosphinylimines

• Jian-bo Xie,
• Jian Luo,
• Timothy R. Winn,
• David B. Cordes and
• Guigen Li

Beilstein J. Org. Chem. 2014, 10, 746–751, doi:10.3762/bjoc.10.69

• -catalyzed borylation of the imine anchored with chiral auxiliaries [16][17]; (3) to conduct asymmetric catalytic hydrogenation as the key step to control the chiral center of boronic aicd [18]. As anticipated, the above known syntheses required traditional purification methods using column chromatography or

A novel family of (1-aminoalkyl)(trifluoromethyl)- and -(difluoromethyl)phosphinic acids – analogues of α-amino acids

• Natalia V. Pavlenko,
• Tatiana I. Oos,
• Yurii L. Yagupolskii,
• Igor I. Gerus,
• Uwe Doeller and
• Lothar Willms

Beilstein J. Org. Chem. 2014, 10, 722–731, doi:10.3762/bjoc.10.66

• did not form hydrochlorides under this procedure consistent with the strongly acidic nature of the CF3 phosphinic acid group. Catalytic hydrogenation of intermediates 13a,b with Pd/C removed the benzyl groups and produced the corresponding acids 14a,b in high yields. The hydrophosphinylation of

• catalytic hydrogenation conditions (II). To a solution of compounds, containing N-Bn fragment (5 mmol) in ethanol (10 mL) 10% Pd/C (0.05 g) was added, and the mixture was hydrogenated at room temperature and normal pressure. After ~3 h the precipitation commenced, and water (5 mL) was added to dissolve this

Synthesis of (2S,3R)-3-amino-2-hydroxydecanoic acid and its enantiomer: a non-proteinogenic amino acid segment of the linear pentapeptide microginin

• Rajendra S. Rohokale and
• Dilip D. Dhavale

Beilstein J. Org. Chem. 2014, 10, 667–671, doi:10.3762/bjoc.10.59

• ]. While targeting the synthesis of 2a, the Wittig olefination of 3a with n-hexyltriphenylphosphonium bromide and t-BuOK gave olefin 4a as a diasteromeric mixture of Z and E-isomers in the ratio 9.5:0.5 as shown by 1H NMR of the crude product. The catalytic hydrogenation of alkene 4a with 10% Pd/C in

From porphyrin benzylphosphoramidate conjugates to the catalytic hydrogenation of 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin

• Marcos C. de Souza,
• Leandro F. Pedrosa,
• Géssica S. Cazagrande,
• Vitor F. Ferreira,
• Maria G. P. M. S. Neves and
• José A. S. Cavaleiro

Beilstein J. Org. Chem. 2014, 10, 628–633, doi:10.3762/bjoc.10.54

• of the catalytic hydrogenation to TPPF20 with 10% Pd/C was then studied with a variety of solvents. The results showed that ethanol/DMF is the solvent of choice to produce chlorin TPCF20 and an ethanol/DMF/NEt3 mixture is more adequate to produce isobacteriochlorin (TPIF20). Keywords: catalytic

• with 10% Pd/C and NEt3 the benzyl groups could not be selectively removed without affecting the phosphoramidate moiety and the porphyrin core. Catalytic hydrogenation of TPPF20 with H2/10% Pd/C There are many methods for performing the reduction of porphyrins (or metalloporphyrins) leading to different

• levels of hydrogenation on the β-pyrrolic double bonds [12][13]. Most of these methods employ chemicals other than H2 as hydrogen donors to reduce porphyrins into chlorins [14][15][16][17][18]. In our case, we decided to investigate the extent of the direct catalytic hydrogenation with H2 over TPPF20 in

New syntheses of 5,6- and 7,8-diaminoquinolines

• Maroš Bella and
• Viktor Milata

Beilstein J. Org. Chem. 2013, 9, 2669–2674, doi:10.3762/bjoc.9.302

• method, the Skraup reaction of 3-chloroaniline led to 7-chloroquinoline which, after nitration, replacement of the chlorine atom by the amino group and catalytic hydrogenation on 5% palladium on charcoal, yielded 7,8-diaminoquinoline [10]. The preparation of 5,6-diaminoquinoline is more effective because

• recrystallisation from toluene (Scheme 1). The temperature of the chlorination (90 °C) was found to be crucial, since heating of the reaction mixture under reflux led to a rapid decomposition. The catalytic hydrogenation of 6-chloroderivative 2 using 10% palladium on charcoal or Raney nickel did not afford 7,8

• -chloroderivative 2 was performed in two successive steps. First, the reductive deselenation with SnCl2·2H2O in concentrated hydrochloric acid afforded 4-chlorodiaminoquinoline 4 in 89% yield. The subsequent catalytic hydrogenation on 10% palladium on charcoal in the absence of base, after filtration of 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

• excellent yield [7]. This bicyclic adduct was converted by ozonolysis followed by LAH reduction into the all-cis-derivative 15, whose benzyl ether protection group was finally removed by catalytic hydrogenation over palladium on carbon [7][8]. The full experimental details and the complete set of the

Synthesis of the calcilytic ligand NPS 2143

• Henrik Johansson,
• Thomas Cailly,
• Alex Rojas Bie Thomsen,
• Hans Bräuner-Osborne and
• Daniel Sejer Pedersen

Beilstein J. Org. Chem. 2013, 9, 1383–1387, doi:10.3762/bjoc.9.154

• ethanol under reflux. Subsequently, the crude pyridinium salt 10 was exposed to the sodium salt of 2-nitropropane (11) to give nitro compound 12. Reduction of the nitro group in 12 by catalytic hydrogenation at atmospheric pressure to produce amine 6 has previously been described by Kamal and Chouhan [17

Simple and rapid hydrogenation of p-nitrophenol with aqueous formic acid in catalytic flow reactors

• Rahat Javaid,
• Shin-ichiro Kawasaki,
• Akira Suzuki and
• Toshishige M. Suzuki

Beilstein J. Org. Chem. 2013, 9, 1156–1163, doi:10.3762/bjoc.9.129

• produced in the syntheses of various chemicals including dyes, pharmaceuticals, and anticorrosive lubricants [14][15][16]. The catalytic hydrogenation of aromatic nitro compounds with H2 has been studied extensively in the presence of Pd, Pt, Ni, and Rh metals [14][16][17][18][19][20][21][22]. In the light

• catalytic hydrogenation of p-nitrophenol. Influence of temperature on the conversion of 0.01 M p-nitrophenol with 0.1 M formic acid at 30 °C and 40 °C. Tubular reactors coated with Pd, PdO, Pd–Ag, porous Pd or porous PdO were applied for demonstration of the catalytic activity. All experiments were

Amyloid-β probes: Review of structure–activity and brain-kinetics relationships

• Todd J. Eckroat,
• Abdelrahman S. Mayhoub and
• Sylvie Garneau-Tsodikova

Beilstein J. Org. Chem. 2013, 9, 1012–1044, doi:10.3762/bjoc.9.116

• ). Boric acid catalyzed condensation of 4-nitro-2-aminophenol (103) and 4-dimethylaminobenzoic acid (101) gave the nitro intermediate 104. Catalytic hydrogenation as above gave the amine intermediate, and subsequent reaction with 4-iodobenzoyl chloride (105) and installation of the radiolabel gave the

• to decrease molecular weight and increase lipophilicity and afforded [125I]IBOX (94) [70]. Compound 94 was prepared via boric acid catalyzed condensation of 5-nitro-2-aminophenol (100) and 4-dimethylaminobenzoic acid (101) to give the nitro intermediate 102, which was reduced through catalytic

• hydrogenation to the amine (Scheme 8A). Subsequent conversion to the diazonium ion and displacement with iodide ion gave IBOX, which was radiolabeled to give 94. Compound 94 showed similar affinity for Aβ1-40 aggregates when compared to 58a, and it was able to label Aβ plaques in postmortem AD brain sections

Simple synthesis of pyrrolo[3,2-e]indole-1-carbonitriles

• Adam Trawczyński,
• Robert Bujok,
• Zbigniew Wróbel and
• Krzysztof Wojciechowski

Beilstein J. Org. Chem. 2013, 9, 934–941, doi:10.3762/bjoc.9.107

• ketone 5d upon reduction with SnCl2 cyclized to pyrrolo[3,2-f]quinoline-9-carbonitrile 7 [17]. The removal of the benzyloxymethyl group from 1-(benzyloxymethyl)pyrrolo[3,2-e]indoles by catalytic hydrogenation has been described by Macor [6]. The hydroxy group from the N-hydroxypyrrole fragment can be

Synthesis and stability study of a new major metabolite of γ-hydroxybutyric acid

• Ida Nymann Petersen,
• Jesper Langgaard Kristensen,
• Christian Tortzen,
• Torben Breindahl and
• Daniel Sejer Pedersen

Beilstein J. Org. Chem. 2013, 9, 641–646, doi:10.3762/bjoc.9.72

• group to provide the desired alcohol 11 proved difficult and complex mixtures were obtained on using both TBAF in THF and HF in pyridine. Fortunately, glucuronidation also proceeded with acceptor 7 to give 4, and in this case the benzyl group was easily removed by catalytic hydrogenation to provide

Design and synthesis of a photoswitchable guanidine catalyst

• Philipp Viehmann and
• Stefan Hecht

Beilstein J. Org. Chem. 2012, 8, 1825–1830, doi:10.3762/bjoc.8.209

• was converted by known procedures into its corresponding nitroso derivative 7 [19], followed by a Mills coupling with 4-aminoacetophenone (8) to give azobenzene 9 in 93% yield over two steps. Nitroazobenzene 9 was transformed into its amino derivative 10 by catalytic hydrogenation. Note that under the

Synthesis of compounds related to the anti-migraine drug eletriptan hydrobromide

• Suri Babu Madasu,
• Nagaji Ambabhai Vekariya,
• M. N. V. D. Hari Kiran,
• Badarinadh Gupta,
• Aminul Islam,
• Paul S. Douglas and
• Korupolu Raghu Babu

Beilstein J. Org. Chem. 2012, 8, 1400–1405, doi:10.3762/bjoc.8.162

• pyrrolidine 10 is converted to bromoindolyl pyrrolidine 9. Further, 9 will convert into 6 due to debromination during the hydrogenation reaction of 13 and it can carry forward up to eletriptan hydrobromide (1). Indolyl pyrrolidine 6 was prepared by catalytic hydrogenation of bromoindolyl pyrrolidine (9) with

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

• Robert Hilgraf,
• Nicole Zimmermann,
• Lutz Lehmann,
• Armin Tröger and
• Wittko Francke

Beilstein J. Org. Chem. 2012, 8, 1256–1264, doi:10.3762/bjoc.8.141

• -protected diol 11. Using Jones reagent, the free hydroxy group of 11 was oxidized to the carboxylic acid 12, and the benzyl ether was cleaved upon catalytic hydrogenation over Pd/C to produce the hydroxy acid 5. The latter served as the immediate precursor for the formation of either of the two

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

• – which would later reflect the trans,trans relationship between substituents at C7-C7a and at C7a-C4a of the dihydronepetalactones a and b – a formal “anti”-addition of hydrogen to the cyclopentene 16 had to be carried out (Scheme 3). Usually, both homogeneous and heterogeneous catalytic hydrogenation

• aldehyde 23. We expected that catalytic hydrogenation of the trisubstituted cylopentene 23 with a heterogeneous catalyst would preferentially take place from the sterically less hindered side of the molecule. This would lead to an all-cis configured hydrogenation product which would endure considerable

• steric strain. Due to the CH-acidity at the α-position of the formyl group, epimerization of the all-trans product 24 under acidic or basic conditions could be expected. Lange et al. reported the catalytic hydrogenation of a structurally close analogue, (5R)-1-formyl-2-methyl-5-isopropylcyclopent-1-ene