Total synthesis of leopolic acid A, a natural 2,3-pyrrolidinedione with antimicrobial activity

• Atul A. Dhavan,
• Rahul D. Kaduskar,
• Loana Musso,
• Leonardo Scaglioni,
• Piera Anna Martino and
• Sabrina Dallavalle

Beilstein J. Org. Chem. 2016, 12, 1624–1628, doi:10.3762/bjoc.12.159

• -nonyltriphenylphosphonium bromide and n-BuLi at −78 °C (11). Deprotection and treatment with triphosgene and phenylalanine benzyl ester at rt allowed the formation of compound 13. Finally, catalytic hydrogenation afforded the desired leopolic acid A (1), whose spectroscopic data completely matched with those reported in

• before, we decided to incorporate the structural features found in leopolic acid into this novel heterocyclic system. Accordingly, Wittig olefination of 14, followed by coupling with L-phenylalanine benzyl ester, and subsequent catalytic hydrogenation in EtOAc of 16 afforded the analogue of leopolic acid

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

• using a mixture of lithium hydroxide and hydrogen peroxide to avoid elimination reactions which are common for uronic acid methyl esters under strongly basic conditions [30][32]. In the next step, the remaining esters were removed employing sodium hydroxide in methanol. Finally, catalytic hydrogenation

Conjugate addition–enantioselective protonation reactions

• James P. Phelan and
• Jonathan A. Ellman

Beilstein J. Org. Chem. 2016, 12, 1203–1228, doi:10.3762/bjoc.12.116

• the enantioselective reduction of α-substituted conjugate addition acceptors, including catalytic hydrogenation, multiple reviews have already appeared on this topic, and therefore asymmetric catalytic reduction will not be covered here [11][12][13]. Conjugate addition followed by terminal

Muraymycin nucleoside-peptide antibiotics: uridine-derived natural products as lead structures for the development of novel antibacterial agents

• Daniel Wiegmann,
• Stefan Koppermann,
• Marius Wirth,
• Giuliana Niro,
• Kristin Leyerer and
• Christian Ducho

Beilstein J. Org. Chem. 2016, 12, 769–795, doi:10.3762/bjoc.12.77

• )-selective Wittig–Horner reaction with phosphonate 66 [111] in order to obtain the didehydro amino acid 67. The next important step of this route was an asymmetric catalytic hydrogenation [112][113] with the chiral Rh(I)–DuPHOS catalyst 68 to prepare the (6'S)-configured product 69 [109][110]. Subsequent

Opportunities and challenges for direct C–H functionalization of piperazines

• Zhishi Ye,
• Kristen E. Gettys and
• Mingji Dai

Beilstein J. Org. Chem. 2016, 12, 702–715, doi:10.3762/bjoc.12.70

• α-methylbenzyl group is bulky enough to prevent the aforementioned side reactions and the resulting diastereomeric α-functionalized piperazines could then afford good separation. Furthermore, this “chiral auxiliary” can be removed upon catalytic hydrogenation. As shown in Figure 10, a variety of

Diastereoselective synthesis of new O-alkylated and C-branched inositols and their corresponding fluoro analogues

• Charlotte Collet,
• Françoise Chrétien,
• Yves Chapleur and
• Sandrine Lamandé-Langle

Beilstein J. Org. Chem. 2016, 12, 353–361, doi:10.3762/bjoc.12.39

• , after hydroboration using BH3 in THF at 0 °C followed by conventional oxidation using H2O2/NaOH, in 70–80% yield. Subsequent catalytic hydrogenation under pressure with Pd(OH)2 as the catalyst [45] allowed to obtaining quantitatively the fully hydroxylated inositols myo-3, scyllo-3, myo-4 and scyllo-4

Enabling technologies and green processes in cyclodextrin chemistry

• Giancarlo Cravotto,
• Marina Caporaso,
• Laszlo Jicsinszky and
• Katia Martina

Beilstein J. Org. Chem. 2016, 12, 278–294, doi:10.3762/bjoc.12.30

• . The catalytic hydrogenation of 6I-azido-6I-deoxy-β-CD using Pd/C was achieved under US irradiation in MeOH/H2O in 20 min (20.4 kHz, 80 W, yield: 88%); hydrogen was supplied at 1 bar pressure [15]. Sonochemical metals depassivation in organometallic reactions is well established [17]. A typical example

• monosubstituted CDs under conventional condition or under US irradiation. The data show that reaction time were dramatically reduced and the yield was generally slightly increased. Under US irradiation, the 6I-amino-β-CD was obtained by catalytic hydrogenation, while under conventional conditions the reduction of

• (yield range 52–69%) [52]. Analogously catalytic hydrogenation in a pressure-resistant MW reactor, gave heptakis(6-amino-6-deoxy)-β-CD from a solution of heptakis(6-azido-6-deoxy)-β-CD in methanol/H2O [53]. The desired product was obtained in 90% yield after 3 h of irradiation at 70 °C. Reaction with

Synthesis and reactivity of aliphatic sulfur pentafluorides from substituted (pentafluorosulfanyl)benzenes

• Norbert Vida,
• Jiří Václavík and
• Petr Beier

Beilstein J. Org. Chem. 2016, 12, 110–116, doi:10.3762/bjoc.12.12

• . 19F NMR yields are given. Synthesis of para-benzoquinone 12 and oxidation to maleic acid 4. 19F NMR yields are shown, in parentheses isolated yields. Catalytic hydrogenation and Diels–Alder reaction of benzoquinone 12. Decomposition of 3 in water. Formation of acids 5, 18 and 19 from lactone 3

Exploring architectures displaying multimeric presentations of a trihydroxypiperidine iminosugar

• Camilla Matassini,
• Stefania Mirabella,
• Andrea Goti,
• Inmaculada Robina,
• Antonio J. Moreno-Vargas and
• Francesca Cardona

Beilstein J. Org. Chem. 2015, 11, 2631–2640, doi:10.3762/bjoc.11.282

• [24][33]. The versatility of our synthetic methodology allows access to differently substituted N-alkylated trihydroxypiperidines by simply using the same aldehyde and different amines as the nitrogen source in a double reductive amination strategy [24][25]. In particular, catalytic hydrogenation with

Cross-metathesis reaction of α- and β-vinyl C-glycosides with alkenes

• Ivan Šnajdr,
• Kamil Parkan,
• Filip Hessler and
• Martin Kotora

Beilstein J. Org. Chem. 2015, 11, 1392–1397, doi:10.3762/bjoc.11.150

• -deoxyribosides on hand, the feasibility of catalytic hydrogenation was also briefly explored. Compounds possessing the heptenyl side chain (β-4b), tridecafluorononenyl side chain (β-4c), and the styryl side chain (β-4d) were chosen as substrates. In all cases the hydrogenation by using Pd/C under low pressure of

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

• subjected to the RCM with G-I (12) as a catalyst in CH2Cl2. Later, catalytic hydrogenation followed by deacetylation gave compound 141 (48%). Similarly, alkyne metathesis of compound 142 was carried out in the presence of Mo(CO)6 and 2-fluorophenol in chlorobenzene and heated under reflux to yield the

• °C in dimethyl propylene urea (DMPU) gave dione 235 (72%). An RCM sequence of compound 235 in the presence of G-I (12) catalyst gave the RCM product 236. A subsequent catalytic hydrogenation generated the saturated dione 237. Finally, the pyridine ring has been introduced by reacting dione 237 with

The chemical behavior of terminally tert-butylated polyolefins

• Dagmar Klein,
• Henning Hopf,
• Peter G. Jones,
• Ina Dix and
• Ralf Hänel

Beilstein J. Org. Chem. 2015, 11, 1246–1258, doi:10.3762/bjoc.11.139

• Lebensmittelsicherheit (BVL), Messeweg 11/12, D-38104 Braunschweig, Germany 10.3762/bjoc.11.139 Abstract The chemical behavior of various oligoenes 2 has been studied. The catalytic hydrogenation of diene 3 yielded monoene 4. Triene 7 was hydrogenated to diene 8, monoene 9 and saturated hydrocarbon 10. Bromine addition

• of the hydrocarbons 2. Results and Discussion Catalytic hydrogenation We started our studies on the reactive behavior of polyolefins 2 with one of the formally simplest alkene reactions: catalytic hydrogenation. When diene 3 was hydrogenated under relatively mild conditions (Pd/C, EtOH, room temp

• levels. The polyenes 2 stabilized by terminal tert-butyl substituents. The catalytic hydrogenation of diene 3. The catalytic hydrogenation of triene 7. Addition of bromine to model dienes. Bromine addition to diene 3 and triene 7. Bromine addition to the higher oligoenes 19–22. Epoxidation of triene 7

Cathodic hydrodimerization of nitroolefins

• Michael Weßling and
• Hans J. Schäfer

Beilstein J. Org. Chem. 2015, 11, 1163–1174, doi:10.3762/bjoc.11.131

• in [6][7][8]. There have been reports on the reductive dimerization of nitro alkenes prior to 1991. 1,4-Dinitro-2,3-diphenylbutane (3) has been obtained in less than 20% yield in the catalytic hydrogenation of β-nitrostyrene (4) [11]. Hydrodimerization of 4 was observed in enzymatic reduction [12

An intramolecular C–N cross-coupling of β-enaminones: a simple and efficient way to precursors of some alkaloids of Galipea officinalis

• Hana Doušová,
• Radim Horák,
• Zdeňka Růžičková and
• Petr Šimůnek

Beilstein J. Org. Chem. 2015, 11, 884–892, doi:10.3762/bjoc.11.99

• catalytic hydrogenation of the corresponding quinolones 2 (Scheme 2) with yields not greater than 43%. In the present work, we introduce a quite different approach to the exocyclic enaminones 1 based on an intramolecular C–N cross-coupling of enaminones 3 (Scheme 2). Results and Discussion The synthesis of

Hydrogenation of unactivated enamines to tertiary amines: rhodium complexes of fluorinated phosphines give marked improvements in catalytic activity

• Sergey Tin,
• Tamara Fanjul and
• Matthew L. Clarke

Beilstein J. Org. Chem. 2015, 11, 622–627, doi:10.3762/bjoc.11.70

• as purification step, particularly if catalysts could be recycled, although that is likely to be challenging in moisture sensitive catalytic hydrogenation chemistry. The ligand electronic effects seem counter intuitive at first glance, but they support the finding by DFT calculations that enamine

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