Sugar-derived oxazolone pseudotetrapeptide as γ-turn inducer and anion-selective transporter

• Sachin S. Burade,
• Sushil V. Pawar,
• Tanmoy Saha,
• Navanath Kumbhar,
• Amol S. Kotmale,
• Manzoor Ahmad,
• Pinaki Talukdar and
• Dilip D. Dhavale

Beilstein J. Org. Chem. 2019, 15, 2419–2427, doi:10.3762/bjoc.15.234

• converted to C-3-tetrasubstituted furanoid sugar azido ester 3 as per our reported protocol [12]. Hydrolysis of the ester functionality in 3 with LiOH at room temperature afforded azido acid 4a in 92% yield, while hydrogenation of 3 using 10% Pd/C in MeOH at room temperature for 3 h afforded the amino ester

• 4b in 86% yield (Scheme 1). The coupling of 4a and 4b using 2-chloro-1-N-methylpyridinium iodide (CMPI), as a coupling reagent, in the presence of Et3N in dichloromethane at 40 °C for 12 h gave azido ester dipeptide 5 in 75% yield. Hydrogenation of 5 using 10% Pd/C in methanol gave amino ester

Small anion-assisted electrochemical potential splitting in a new series of bistriarylamine derivatives: organic mixed valency across a urea bridge and zwitterionization

• Keishiro Tahara,
• Tetsufumi Nakakita,
• Alyona A. Starikova,
• Takashi Ikeda,
• Masaaki Abe and
• Jun-ichi Kikuchi

Beilstein J. Org. Chem. 2019, 15, 2277–2286, doi:10.3762/bjoc.15.220

• /C (0.0145 g) was refluxed in dry ethanol (10 mL) for 1 h. After dropwise addition of hydrazine monohydrate (0.30 mL), the reaction mixture was refluxed overnight. After filtration of Pd/C and concentrating the filtrate to dryness, the resulting white solid (0.320 g) was identified as 4-amino-4’,4

• mmol) and Pd/C (0.0145 g) in dry ethanol (10 mL) was refluxed for 1 h. After dropwise addition of hydrazine monohydrate (0.30 mL), the reaction mixture was refluxed overnight. After filtration and concentrating the filtrate to dryness, the resulting white solid (0.320 g) was identified as 4-amino-4’,4

• JNM-ECP400 spectrometer with tetramethylsilane (TMS) as internal standard (0 ppm). EIMS measurements were performed using a JEOL JMS-700 MStation spectrometer. Synthesis and characterization of compounds Synthesis of 1a The mixture of 4,4’-dimethoxy-4’’-nitrotriphenylamine (0.351 g, 1.00 mmol) and Pd

A review of the total syntheses of triptolide

• Xiang Zhang,
• Zaozao Xiao and
• Hongtao Xu

Beilstein J. Org. Chem. 2019, 15, 1984–1995, doi:10.3762/bjoc.15.194

• was isomerized in the presence of base and dehydrated to give diene 45. Reduction of 45 with 10% Pd/C afforded 8 in good yield (60%) after recrystallization. Benzylic oxidation of 8 (CrO3/HOAc, 45%), followed by C-14 ether cleavage (BBr3) and subsequent sodium borohydride reduction afforded 46 with

• mixture of 51 and 52, subsequent Pd/C-catalyzed hydrogenation and tetrabutylammonium fluoride (TBAF)-mediated desilylation yielding the desired tricyclic 54 (83% yield, 98% ee). Overall, the known intermediate 7-oxotriptophenlide 59 was obtained in an efficient, elegant and scalable way in 10 steps with

• corresponding carboxylic acid followed by hydrogenolysis with H2/Pd-C led in spontaneous lactonization to give the key butenolide 66. Oxidation of 66 with CrO3/AcOH–H2O, followed by saponification and reduction afforded known benzyl alcohol 46 (19% from 66). Then, phenol 46 was converted to the corresponding

Design, synthesis and biological evaluation of immunostimulating mannosylated desmuramyl peptides

• Rosana Ribić,
• Ranko Stojković,
• Lidija Milković,
• Mariastefania Antica,
• Marko Cigler and
• Srđanka Tomić

Beilstein J. Org. Chem. 2019, 15, 1805–1814, doi:10.3762/bjoc.15.174

• %. Synthesis of C-modified desmuramyl peptides. Reagents and conditions: a) H2, 10% Pd/C, MeOH, 38 psi, rt, 24 h, 96%; b) adamant-1-ylamine hydrochloride, EDC·HCl, HOBt·H2O, Et3N, DCM/dioxane 1:1, 0 °C → rt, 48 h, 60%; c) TFA/DCM 1:2, rt, 1 h, quantitative. Synthesis of the mannose precursor. Reagents and

• % Pd/C, 48 h, rt, 83–92%. Synthesis of mannosylated peptides with glycolyl linker. Reagents and conditions: a) EDC·HCl, HOBt·H2O, Et3N, DCM/DMF 1:1, 0 °C → rt, 72 h, 26–67%; b) NaOMe/MeOH, rt, 1 h, 59–89%. Supporting Information Supporting Information File 520: Experimental and characterization data

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

Design and synthesis of multivalent α-1,2-trimannose-linked bioerodible microparticles for applications in immune response studies of Leishmania major infection

• Chelsea L. Rintelmann,
• Tara Grinnage-Pulley,
• Kathleen Ross,
• Daniel E. K. Kabotso,
• Angela Toepp,
• Anne Cowell,
• Christine Petersen,
• Balaji Narasimhan and
• Nicola Pohl

Beilstein J. Org. Chem. 2019, 15, 623–632, doi:10.3762/bjoc.15.58

• , hydrogenolysis of the benzyl ethers under continuous flow (0.3–1 mL/min) and H2 pressure (30–60 bar) using an H-cube apparatus was found to be effective at removing the benzyl ethers, but arduously slow (>48 h) from the limited surface-mediated interactions with the Pd/C cartridge. By comparison, batch

A chemoenzymatic synthesis of ceramide trafficking inhibitor HPA-12

• Seema V. Kanojia,
• Sucheta Chatterjee,
• Subrata Chattopadhyay and
• Dibakar Goswami

Beilstein J. Org. Chem. 2019, 15, 490–496, doi:10.3762/bjoc.15.42

• the amine using LiAlH4 with concomitant debenzoylation, followed by the acylation of the amine with lauric acid to afford 9a, and finally, ii) reductive cleavage by hydrogenolysis using Pd–C/H2 leading to debenzylation (Scheme 3). However, during hydrogenolysis, the elimination of the -OBn group led

• from 9. Conditions: (i) (a) LiAlH4 (1 M in THF)/THF/25 °C/3 h, (b) DCC/DMAP/lauric acid, CH2Cl2/25 °C/18 h; (ii) (a) H2/10% Pd–C/EtOH/25 °C or (b) DDQ/CH2Cl2–H2O 4:1/3 h. Actual synthesis of 2 from 9. Conditions: (i) DDQ/CH2Cl2–H2O 4:1/3 h; (ii) a) LiAlH4/THF/25 °C/3 h, b) DCC/DMAP/lauric acid, CH2Cl2

Sigmatropic rearrangements of cyclopropenylcarbinol derivatives. Access to diversely substituted alkylidenecyclopropanes

• Guillaume Ernouf,
• Jean-Louis Brayer,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2019, 15, 333–350, doi:10.3762/bjoc.15.29

• achieved in the presence of Pd/C as a catalyst. Concomitant hydrogenolysis of two carbon–chlorine bonds also took place under these conditions and a 71:29 diastereomeric mixture of the monochloracetamides 19f/19’f was obtained (41%). The rather small difference of steric hindrance between the methyl and

• -acylamino)cyclopropanes] possessing a single substituent at C2, it is possible to rely either on the steric hindrance or on the coordinating ability of the amide group. Thus, the hydrogenation of trifluoroacetamide 51 catalyzed by Pd/C afforded N-trifluoroacetylaminocyclopropane 55 as the major diastereomer

• by Rh/C occurred on the less hindered face of the alkene and gave rise to cyclopropyl α-alkoxy ester 72 as a single detectable diastereomer. When Pd/C was used as the catalyst, cleavage of the PMB group took place concomitantly and the α-hydroxy ester 73 arising from addition of hydrogen on the less

Synthesis of nonracemic hydroxyglutamic acids

• Dorota G. Piotrowska,
• Iwona E. Głowacka,
• Andrzej E. Wróblewski and
• Liwia Lubowiecka

Beilstein J. Org. Chem. 2019, 15, 236–255, doi:10.3762/bjoc.15.22

• , dioxane/water; d) NaIO4, then NaOCl2, H2NSO3H; e) MeI, K2CO3, acetone; f) AcOH, H2O; g) NaOH, MeOH; h) PDC, DMF; i) CF3COOH, CH2Cl2; j) H2, 5% Pd/C, MeOH, H2O. Two-carbon homologation of the protected L-serine. Reagents and conditions: a) Fmoc-succinimide, Na2CO3, dioxane, H2O; b) (3-hydroxymethyl)-3

• O-benzyl-L-serine. Reagents and conditions: a) (CF3CH2O)2P(O)CH2COOMe, KHMDS, 18-crown-6; b) I2, MeCN; c) Bu3SnH, AIBN, benzene, reflux; d) H2, 10% Pd/C, ethanol; e) CrO3, acetone, then CH2N2, ether; f) 3 M HCl, 80 °C. Synthesis of (2S,3R)-2 employing a one-pot cis-olefination–conjugate addition

• . Reagents and conditions: a) NaClO2, 30% H2O2, NaH2PO4, MeCN; b) ClCOOEt, NEt3, then CH2N2, ether; c) MeOH, PhCOOAg, NEt3; d) LiOH, THF/H2O; e) ClCOOBn, NEt3, DMAP; f) TFA, H2O; g) NaIO4, acetone/water; h) NaHCO3, THF/H2O; i) H2C=CHCH2Br, NaHCO3, DMF; j) H2, 10% Pd/C, MeOH/HCl. Synthesis of (4S)-4-hydroxy-L

Novel solid-phase strategy for the synthesis of ligand-targeted fluorescent-labelled chelating peptide conjugates as a theranostic tool for cancer

• Sagnik Sengupta,
• Mena Asha Krishnan,
• Premansh Dudhe,
• Ramesh B. Reddy,
• Bishnubasu Giri,
• Sudeshna Chattopadhyay and
• Venkatesh Chelvam

Beilstein J. Org. Chem. 2018, 14, 2665–2679, doi:10.3762/bjoc.14.244

• (tert-butoxy) protected DUPA precursor 3 (0.250 g, 0.434 mmol) in dichloromethane (10 mL), 10 mol % Pd/C (40 mg) was added. The reaction mixture was hydrogenated under an atmosphere of H2 gas (1 atm) for 24 h at room temperature. After completion of the reaction, Pd/C was filtered off through a celite

• tris(tert-butoxy) protected DUPA ligand 4. Reagents and conditions: (a) Triphosgene, triethylamine, dichloromethane (DCM), −50 °C to rt; (b) L-glutamic acid γ-benzyl-α-tert-butylester hydrochloride, triethylamine, DCM, rt, overnight; (c) H2, Pd/C, CH2Cl2, 24 h, rt. Attempted synthesis of PSMA targeted

Synthesis of a leopolic acid-inspired tetramic acid with antimicrobial activity against multidrug-resistant bacteria

• Luce Mattio,
• Loana Musso,
• Leonardo Scaglioni,
• Andrea Pinto,
• Piera Anna Martino and
• Sabrina Dallavalle

Beilstein J. Org. Chem. 2018, 14, 2482–2487, doi:10.3762/bjoc.14.224

• ) triphosgene, DIEA, DCM, rt, 3 h, 50%; d) trifluoroacetic acid, DCM, rt, 3 h, 95%; e) pentafluorophenol, DCC, EtOAc, 0 °C, 1h, then rt, 3 h, 60%. Synthesis of compound 1. Reagents and conditions: a) n-BuLi, THF, −60 °C, 220 min, 60%; b) H2, Pd/C 10%, AcOEt, rt, 100 min, 72%. Supporting Information Supporting

Synergistic approach to polycycles through Suzuki–Miyaura cross coupling and metathesis as key steps

• Sambasivarao Kotha,
• Milind Meshram and
• Chandravathi Chakkapalli

Beilstein J. Org. Chem. 2018, 14, 2468–2481, doi:10.3762/bjoc.14.223

• %). Next, exposure of the diallyl derivative 73a to G-II catalyst 2 yielded the cyclized product 74 (72%). Eventually, hydrogenation of the RCM product 74 was achieved with H2, Pd/C conditions to give the saturated 2,3,4,5-tetrahydro-1-benzazepine 75 in 81% yield (Scheme 11). Naphthoxepine derivatives play

• %). Subsequently, hydrogenation of compounds 126 and 125 was accomplished with H2 under Pd/C catalysis conditions to afford the respective saturated macrocyclic products 127 (80%) and 128 (90%). Since the small ring cyclophane is highly strained, compound 125 was formed as a minor product (Scheme 19). Recently, Li

A novel and practical asymmetric synthesis of eptazocine hydrobromide

• Ruipeng Li,
• Zhenren Liu,
• Liang Chen,
• Jing Pan,
• Kuaile Lin and
• Weicheng Zhou

Beilstein J. Org. Chem. 2018, 14, 2340–2347, doi:10.3762/bjoc.14.209

• replaced with HOAc/H2O (2:1) or Pd/C was selected as a catalyst, the reaction gave a similar result as with Raney-Ni as catalyst in NH3/CH3OH. It seems that compound 5 easily reacted with the carbonyl group to form the five-membered ring. Since the carbonyl group is necessary for the following Mannich

• improved the reaction yield (Table 3, entries 4 and 5). The reductive methylation of 14 under Eschweiler–Clarke conditions (HCOOH/formalin/reflux) furnished 15 in quantitative yield. The latter was reduced by NaBH4 in methanol at room temperature, and then dehydration and hydrogenation with H2/Pd/C in

Semi-synthesis and insecticidal activity of spinetoram J and its D-forosamine replacement analogues

• Kai Zhang,
• Jiarong Li,
• Honglin Liu,
• Haiyou Wang and
• Lamusi A

Beilstein J. Org. Chem. 2018, 14, 2321–2330, doi:10.3762/bjoc.14.207

• , and then 10% Pd/C (0.36 g, 0.33 mmol) was added. The mixture was stirred under hydrogen at room temperature for 48 h. The mixture was then filtered. The filtrate was evaporated under reduced pressure, and the residue was purified by column chromatography on silica gel (200–300 mesh) to afford pure 1

Diazirine-functionalized mannosides for photoaffinity labeling: trouble with FimH

• Femke Beiroth,
• Tomas Koudelka,
• Thorsten Overath,
• Stefan D. Knight,
• Andreas Tholey and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2018, 14, 1890–1900, doi:10.3762/bjoc.14.163

• efficiency. Synthesis of photolabile α-D-mannosides 3 and 4. a) H2, Pd-C, methanol, rt, 6 h, 94%; b) HATU, DIPEA, dry DMF, N2, rt, overnight, quant.; c) 1. 50% TFA in water, rt, 3 h; 2. HATU, 8, DIPEA, dry DMF, N2, rt, 14 h, 19% (over 2 steps); d) dry methanol, rt, 16 h, 59%; e) Et3N, dry methanol, rt, 15 h

Water-soluble SNS cationic palladium(II) complexes and their Suzuki–Miyaura cross-coupling reactions in aqueous medium

• Alphonse Fiebor,
• Richard Tia,
• Banothile C. E. Makhubela and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1859–1870, doi:10.3762/bjoc.14.160

• relatively low energy barrier indicates that the reaction proceeds at a fast rate in getting to the intermediate (IM1), thus it is kinetically favoured. The reaction then proceeds via transition state TS2, leading to the cleavage of the C(sp2)–Br bond and the formation of a new Pd–C(sp2) bond, to form a cis

• intermediate of energy −93.0 kcal/mol. The new Pd–C(sp2) bond distance of 2.00 Å falls within the reported Pd–C(sp2) bond distances [47][48]. Since the bromo ligand is larger in atomic radius than the chloro ligands the more stable form of the oxidative addition product is the trans form. As such, the cis

• product can isomerise to a more stable trans intermediate of energy −93.6 kcal/mol having a Pd–C(sp2) bond length of 1.99 Å. Next, under the optimal conditions with 17d as a catalyst (since it provided the highest yield in the presence of TBAB, Table 2, entry 26), we examined the substrate scope with

Cobalt–metalloid alloys for electrochemical oxidation of 5-hydroxymethylfurfural as an alternative anode reaction in lieu of oxygen evolution during water splitting

• Jonas Weidner,
• Stefan Barwe,
• Kirill Sliozberg,
• Stefan Piontek,
• Justus Masa,
• Ulf-Peter Apfel and
• Wolfgang Schuhmann

Beilstein J. Org. Chem. 2018, 14, 1436–1445, doi:10.3762/bjoc.14.121

• oxidation of HMF on carbon black supported monometallic Pd/C and Au/C, and bimetallic Pd-Au/C catalysts [27]. Their studies revealed that the reaction pathway was influenced by the type of catalyst and the applied potential [27]. Furthermore, Choi and Cha found that the overpotential required to initiate

Spectroelectrochemical studies on the effect of cations in the alkaline glycerol oxidation reaction over carbon nanotube-supported Pd nanoparticles

• Dennis Hiltrop,
• Steffen Cychy,
• Karina Elumeeva,
• Wolfgang Schuhmann and
• Martin Muhler

Beilstein J. Org. Chem. 2018, 14, 1428–1435, doi:10.3762/bjoc.14.120

• structural similarity of the possible oxidation products makes the assignment of occurring IR bands to certain species challenging. Glycerol oxidation was studied over different catalytically active metals, such as Au [15], AuAg/C [16], Pt [17][18], Au/C [19][20], Pt/C [20][21], Pd/C [20], PdAu/C [22], PdNi

Enantioselective phase-transfer catalyzed alkylation of 1-methyl-7-methoxy-2-tetralone: an effective route to dezocine

• Ruipeng Li,
• Zhenren Liu,
• Liang Chen,
• Jing Pan and
• Weicheng Zhou

Beilstein J. Org. Chem. 2018, 14, 1421–1427, doi:10.3762/bjoc.14.119

• with allyl or propargyl bromide to obtain C12 and C13. In another way, cinchonidine was reduced by H2/Pd/C to yield dihydrocinchonidine, and then reacted with 4-trifluoromethylbenzyl bromide to obtained C14. C15 was prepared from cinchonidine via bromination, debromination and condensation with 4

A selective removal of the secondary hydroxy group from ortho-dithioacetal-substituted diarylmethanols

• Anna Czarnecka,
• Emilia Kowalska,
• Agnieszka Bodzioch,
• Joanna Skalik,
• Marek Koprowski,
• Krzysztof Owsianik and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2018, 14, 1229–1237, doi:10.3762/bjoc.14.105

• –CF3COOH, TMSCl/NaI failed to reduce secondary OH groups in diheteroaromatic systems and the reduction with H2/Pd/C-ZnBr2 was very slow [32]. On the other hand, some rigid diarylmethanols were successfully reduced to benzo[b]indeno[2,1-d]thiophenes using the Et3SiH–CF3COOH system which was reported in the

• tried to remove the OH group using the Pd-catalytic hydrogenolysis (Scheme 3). In case of 6b (X = S), no reaction occurred and only the substrate was recovered, most probably due to poisoning of the catalyst by the 1,3-dithianyl sulfur atoms. However, the successful catalytic hydrogenolysis (5% Pd/C) of

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

Synthetic avenues towards a tetrasaccharide related to Streptococcus pneumonia of serotype 6A

• Aritra Chaudhury,
• Mana Mohan Mukherjee and
• Rina Ghosh

Beilstein J. Org. Chem. 2018, 14, 1095–1102, doi:10.3762/bjoc.14.95

• conditions [41], followed by hydrogenation with H2/Pd-C in EtOH/EtOAc/AcOH solvent to give the deprotected tetrasaccharide 23 in 85% yield over two steps. 1H NMR in D2O of the target tetrasaccharide 23 showed the anomeric protons of the galactose, glucose, and rhamnose residues from the non-reducing end

• , 45 min; c) NaOMe, MeOH, rt; d) H2, Pd/C, EtOH/EtOAc/AcOH, rt. Optimization of protocol for the synthesis of disaccharide 3. Supporting Information Supporting Information File 145: Experimental details for the preparation of compounds 1, 3a, 4, 5, 6a, 6b, 7, 12a, 19, 20, 21, and 23 and the

The first Pd-catalyzed Buchwald–Hartwig aminations at C-2 or C-4 in the estrone series

• Ildikó Bacsa,
• Dávid Szemerédi,
• János Wölfling,
• Gyula Schneider,
• Lilla Fekete and
• Erzsébet Mernyák

Beilstein J. Org. Chem. 2018, 14, 998–1003, doi:10.3762/bjoc.14.85

• -13α-estrone (13). The efficient C(sp2)–N coupling method elaborated above proved to be suitable for the reaction of 2-bromo-3-benzyl ether 2 and benzophenone imine as an amine precursor (Scheme 2). The deprotection was achieved by hydrogenolysis using a Pd/C catalyst. The resulting newly-synthesized 2

A stereoselective and flexible synthesis to access both enantiomers of N-acetylgalactosamine and peracetylated N-acetylidosamine

• Bettina Riedl and
• Walther Schmid

Beilstein J. Org. Chem. 2018, 14, 856–860, doi:10.3762/bjoc.14.71

• peracetylated to yield compounds 8a and 8b. The azide function was reduced with H2 and Pd/C in acetic anhydride to gain the fully acetylated amino sugars 2a and 2b. In the final step, the compounds were deprotected using a mixture of MeOH/H2O/Et3N to yield D-GalNAc (1a) and L-GalNAc (1b). As proof of concept

• ) triethyl phosphonoacetate, NaH, DCM; b) TMSN3, Pd(PPh3)4, EtOH; c) i) DOWEX H+, MeOH; ii) O3, dimethyl sulfide, DCM/MeOH; iii) Ac2O, DMAP, pyridine; d) H2, Pd/C, Ac2O; e) MeOH/H2O/Et3N (10:10:1). Proposed mechanism of the Pd-catalyzed azide substitution of 6a in protic solvent. Approach towards

• peracetylated D-IdoNAc 2c, reactions and conditions: a) Ti(OiPr)4, t-BuOOH, D-DET, DCM; b) i) (COCl)2, DMSO, Et3N, DCM, ii) triethyl phosphonoacetate, NaH, DCM; c) TMSN3, Pd(PPh3)4, EtOH; d) i) DOWEX H+, MeOH; ii) O3, dimethyl sulfide, DCM/MeOH; iii) Ac2O, DMAP, pyridine; e) H2, Pd/C, Ac2O. Supporting

An alternative to hydrogenation processes. Electrocatalytic hydrogenation of benzophenone

• Cristina Mozo Mulero,
• Alfonso Sáez,
• Jesús Iniesta and
• Vicente Montiel

Beilstein J. Org. Chem. 2018, 14, 537–546, doi:10.3762/bjoc.14.40

• a polymer electrolyte membrane electrochemical reactor (PEMER). Palladium (Pd) nanoparticles were synthesised and supported on a carbonaceous matrix (Pd/C) with a 28 wt % of Pd with respect to carbon material. Pd/C was characterised by transmission electron microscopy (TEM), and thermogravimetric

• important to note that, formation of “active hydrogen” is the main step in this process and hydrogen-active powder electrocatalysts such as Pd/C, Pt/C or Raney-nickel have been demonstrated as the optimal choice [16][17]. Moreover, the organic molecule adsorption rate must be faster than that one associated

• water-in-oil (w/o) microemulsion (water/Brij@30/n-heptane). This methodology has been previously used in our laboratory [27][28]. We first explored the morphology, size and dispersion of Pd nanoparticles supported on Vulcan XC72R carbonaceous material (Pd/C electrocatalysts) using TEM micrographs. As