Chemoenzymatic synthesis and biological evaluation of enantiomerically enriched 1-(β-hydroxypropyl)imidazolium- and triazolium-based ionic liquids

• Paweł Borowiecki,
• Małgorzata Milner-Krawczyk and
• Jan Plenkiewicz

Beilstein J. Org. Chem. 2013, 9, 516–525, doi:10.3762/bjoc.9.56

• control the direction of an enzymatic reaction and its specificity in a nonaqueous environment has resulted in the development of so-called "solvent engineering". After testing several solvents for lipase-catalyzed acetylation of (±)-3a and (±)-3b with vinyl acetate, we determined the following order of

• turn, conversion exceeding 57% was beneficial for high optical purity of the remaining alcohol (+)-5a (Table 1, entries 6 and 7, >97% ee). In the lipase-catalyzed acetylation of alcohol (±)-3b the best results were achieved with native Pseudomonas fluorescens lipase (Amano AK) suspended in 2-methyl-2

• acetylation of (±)-3a, the highest reaction rates for (±)-3b were observed with Amano PS-IM in MTBE. As usual, the optical purities of the acetate, as well as of the remaining alcohol, were dependent on the enzyme used and the conversion rate. For example, with Amano AK the reaction reached 37% conversion

Efficient Cu-catalyzed base-free C–S coupling under conventional and microwave heating. A simple access to S-heterocycles and sulfides

• Silvia M. Soria-Castro and
• Alicia B. Peñéñory

Beilstein J. Org. Chem. 2013, 9, 467–475, doi:10.3762/bjoc.9.50

• and 2i (Table 3, entries 3 and 9). The reaction between 4-iodoaniline and 1 under CuI/1,10-phenanthroline catalysis afforded quantitatively the corresponding 4-iodoacetanilide as the only product. The acetylation of the amino group competes effectively with the cross-coupling reaction. A similar

• acetylation reaction was also observed with 2-iodophenol. In consequence, protected amino and hydroxy groups were required for the copper-mediated C–S bond formation to proceed properly (Table 3, entries 3, 4 and 9). This copper-catalyzed coupling reaction was also applied to heteroaromatic and other

Thermotropic and lyotropic behaviour of new liquid-crystalline materials with different hydrophilic groups: synthesis and mesomorphic properties

• Alexej Bubnov,
• Miroslav Kašpar,
• Věra Hamplová,
• Ute Dawin and
• Frank Giesselmann

Beilstein J. Org. Chem. 2013, 9, 425–436, doi:10.3762/bjoc.9.45

• acid, ethanol was evaporated, and the aqueous mixture was left to stand in the refrigerator overnight. The crude substance was separated on fritted glass and crystallized from ethanol. Purification of crude phenol 2 was performed after its acetylation: 3 hours boiling with acetanhydride followed by

De novo synthesis of D- and L-fucosamine containing disaccharides

• Daniele Leonori and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2013, 9, 332–341, doi:10.3762/bjoc.9.38

• strategic N-protecting group was evaluated. Direct glycosylation by using the building block D-8a was not possible. Hence, a direct N-Boc deprotection/N-acetylation sequence afforded D-10 in 84% yield (Scheme 6A). Direct glycosylation of D-10 by using glycosylating agent 11 [67] and BF3·Et2O as the

Synthesis and testing of the first azobenzene mannobioside as photoswitchable ligand for the bacterial lectin FimH

• Vijayanand Chandrasekaran,
• Katharina Kolbe,
• Femke Beiroth and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2013, 9, 223–233, doi:10.3762/bjoc.9.26

• , acetylation of the 4- and 6-hydroxy groups, and then acid-mediated regioselective ring opening of the 2,3-orthoester in the same pot to yield the free 3-OH azobenzene mannoside 10 in an overall yield of 43%. Thus, the required protecting group pattern was obtained in a highly efficient way, based on the

• regioselective opening of orthoacetates to yield a vicinal arrangement of equatorial OH and axial O-acetyl groups [21][22]. The acetylation pattern was clearly confirmed by 1H NMR spectroscopy showing the expected downfield shift for the H-3 signal resonating at 4.32 ppm (H-2: 5.30 ppm, H-4: 5.17 ppm). Next

• ). The crude orthoester-protected mannoside 9 (594 mg) was dissolved in pyridine (2.5 mL), and acetic anhydride (1.26 mL) was added for O-acetylation. The reaction mixture was stirred at rt for 3 h. Then, pyridine was removed under reduced pressure, and the residue was dissolved in ethyl acetate (20 mL

Synthesis of 5-(ethylsulfonyl)-2-methoxyaniline: An important pharmacological fragment of VEGFR2 and other inhibitors

• Miroslav Murár,
• Gabriela Addová and
• Andrej Boháč

Beilstein J. Org. Chem. 2013, 9, 173–179, doi:10.3762/bjoc.9.20

• three simple synthetic steps (N-acetylation, O-methylation, N-acetyl deprotection). Later on 2-amino-4-(ethylsulfonyl)phenol was discontinued from current commercial sources. Compound 5 is still available in small 1 g quantities but at a price that was unfavourable (e.g., as part of the AldrichCPR

A new synthetic access to 2-N-(glycosyl)thiosemicarbazides from 3-N-(glycosyl)oxadiazolinethiones and the regioselectivity of the glycosylation of their oxadiazolinethione precursors

• El Sayed H. El Ashry,
• El Sayed H. El Tamany,
• Mohy El Din Abdel Fattah,
• Mohamed R. E. Aly,
• Ahmed T. A. Boraei and
• Axel Duerkop

Beilstein J. Org. Chem. 2013, 9, 135–146, doi:10.3762/bjoc.9.16

• of the N-glycosides 8–10 (Scheme 3) mediated with ammonia in aqueous methanolic solution led to de-O-acetylation of the glycan moieties along with aminolysis of the oxadiazole ring affording 2-N-(glycosyl)thiosemicarbazides 11–13 instead of the corresponding nucleosides 14–16. The oxadiazole ring

• cleavage combined with de-O-acetylation of 8–10 is proven by three facts. First, the molecular weights derived from the mass spectra of the products 11–13 are higher by seventeen atomic mass units than would be those of the deacetylated products 14–16. Second, the IR spectra of 11–13 show new amide

• conditions remained unchanged compared to the cleavage of 8–10, derivatives 26 and 27 (Scheme 6) yielded different products under these conditions. Oxadiazole ring cleavage combined with de-O-acetylation converted 26 into the corresponding 2-N-(glycosyl)thiosemicarbazide 29 while the galactonucleoside 27 was

Glycosylation efficiencies on different solid supports using a hydrogenolysis-labile linker

• Mayeul Collot,
• Steffen Eller,
• Markus Weishaupt and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2013, 9, 97–105, doi:10.3762/bjoc.9.13

• avoid neutralization of the activator during glycosylation reactions, unreacted amino groups were capped by acetylation. Resin loadings with the amide-bound linkers 25–29 were determined by using variants including the ester insert for rapid cleavage (Table 1). Glycosylation with monosaccharide building

Thioester derivatives of the natural product psammaplin A as potent histone deacetylase inhibitors

• Matthias G. J. Baud,
• Thomas Leiser,
• Vanessa Petrucci,
• Mekala Gunaratnam,
• Stephen Neidle,
• Franz-Josef Meyer-Almes and
• Matthew J. Fuchter

Beilstein J. Org. Chem. 2013, 9, 81–88, doi:10.3762/bjoc.9.11

• epigenetic modifications, their biological outcomes, and how their misregulation is involved in diseases such as cancer [1][2]. The dynamic post-translational acetylation/deacetylation of histone proteins is one of the most commonly studied epigenetic events, and occurs at specific lysine residues on the N

• -terminal histone tails, which project out from the nucleosome (the fundamental repeating unit of chromatin). Acetylation/deacetylation of such lysine residues is achieved by the action of histone acetyltransferases (HATs) and histone deacetylases (HDACs), respectively. Histone deacetylation by HDACs causes

A bisazobenzene crosslinker that isomerizes with visible light

• Subhas Samanta,
• Harris I. Qureshi and
• G. Andrew Woolley

Beilstein J. Org. Chem. 2012, 8, 2184–2190, doi:10.3762/bjoc.8.246

• nitrite with HCl (Scheme 2). Compound 4 was prepared by hydrogenation with H2/Pd-C from sodium 2-acetamido-5-nitrobenzenesulfonate (5), which was obtained from commercially available sodium 2-amino-5-nitrobenzenesulfonate (6) by acetylation using acetic anhydride. 1,4-Diphenylpiperazine (7) was

S-Fluorenylmethyl protection of the cysteine side chain upon N^α-Fmoc deprotection

• Johannes W. Wehner and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2012, 8, 2149–2155, doi:10.3762/bjoc.8.242

• (TES) as cation scavenger [12] yields the O-acetylated glycoamino acid derivative 6 together with its respective disulfide (not shown in Scheme 2), and de-O-acetylation under Zemplén conditions [13] furnishes the unprotected compound 3-dimer after oxidation in air, as reported previously [3]. However

• glycoamino acid derivative 6 was not obtained. De-O-acetylation of 8 gave mannopyranoside 9 with maintained fluorenylmethyl protection at the sulfur atom. The structure of the S-Fm-protected glycoamino acid derivative 8 could be unequivocally confirmed by NMR analysis and MALDI–TOF mass spectrometry. The

Synthesis of a derivative of α-D-Glcp(1->2)-D-Galf suitable for further glycosylation and of α-D-Glcp(1->2)-D-Gal, a disaccharide fragment obtained from varianose

• Carla Marino,
• Carlos Lima,
• Karina Mariño and
• Rosa M. de Lederkremer

Beilstein J. Org. Chem. 2012, 8, 2142–2148, doi:10.3762/bjoc.8.241

• was treated with DSB, as previously reported for other glycosylaldonolactones [10][25][28]. Although lactol 6 was obtained, the reaction was slow and even after several days it was not complete (Scheme 1). Acetylation of the HO-3 of 5 did not improve the reduction step. Certainly, the presence of the

Chemical modification allows phallotoxins and amatoxins to be used as tools in cell biology

• Jan Anderl,
• Hartmut Echner and
• Heinz Faulstich

Beilstein J. Org. Chem. 2012, 8, 2072–2084, doi:10.3762/bjoc.8.233

• chloride (Table 2). In order to avoid concurrent acylation of the 6’-OH of tryptophan, the phenolic OH was methylated before acetylation. For coupling to polylysine the natural carboxy group of aspartic acid as present in β-amanitin was used, which after activation as N-hydroxysuccinimide ester reacted

Convergent synthesis of the tetrasaccharide repeating unit of the cell wall lipopolysaccharide of Escherichia coli O40

• Abhijit Sau and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2012, 8, 2053–2059, doi:10.3762/bjoc.8.230

• 101.6 (C-1B), 101.5 (PhCH), 100.8 (C-1C), 100.2 (C-1A), 97.3 (C-1D) in the 13C NMR spectrum]. Compound 10 was subjected to a sequence of reactions involving (a) removal of N-phthalimido group by using hydrazine hydrate [25]; (b) N-acetylation by using acetic anhydride and pyridine; (c) removal of

Modulating the activity of short arginine-tryptophan containing antibacterial peptides with N-terminal metallocenoyl groups

• H. Bauke Albada,
• Alina-Iulia Chiriac,
• Michaela Wenzel,
• Maya Penkova,
• Julia E. Bandow,
• Hans-Georg Sahl and
• Nils Metzler-Nolte

Beilstein J. Org. Chem. 2012, 8, 1753–1764, doi:10.3762/bjoc.8.200

• of the N-terminal arginine residue in non-toxic and non-hemolytic (RW)3 peptides can modulate the kinetics of the peptide’s antibacterial activity. Acetylation completely suppresses this activity. In comparison, replacement of the N-terminal arginine residue with the organometallic ferrocenoyl moiety

Antifreeze glycopeptide diastereomers

• Lilly Nagel,
• Carsten Budke,
• Axel Dreyer,
• Thomas Koop and
• Norbert Sewald

Beilstein J. Org. Chem. 2012, 8, 1657–1667, doi:10.3762/bjoc.8.190

• ×), 143.9, 144.0 (aryl), 156.7 (CO-Fmoc), 169.3, 169.9, 170.2, 170.5 (CO); MS (ESI) m/z: [M + Na]+ 733.2. General synthetic procedure for the simultaneous reduction and N-acetylation step (GP2) Fmoc-L-allo-Thr(α/β-Ac3GalN3)-Ot-Bu (2A) or Fmoc-D-Thr(α/β-Ac3GalN3)-Ot-Bu (2B) was dispensed in a mixture of

• vessel of the peptide synthesizer. Subsequently, HOAt (0.25 mmol, 2.25 equiv) dissolved in DMF (1 mL) and DIPEA (0.28 mmol, 2.75 equiv) were transferred manually. Unreacted amino groups were capped by an acetylation reaction after coupling of the glycosylated building block using acetic anhydride (0.5

The Amadori rearrangement as glycoconjugation method: Synthesis of non-natural C-glycosyl type glycoconjugates

• Katharina Gallas,
• Gerit Pototschnig,
• Florian Adanitsch,
• Arnold E. Stütz and
• Tanja M. Wrodnigg

Beilstein J. Org. Chem. 2012, 8, 1619–1629, doi:10.3762/bjoc.8.185

• pyridine, then triethylamine (0.08 equiv) and HCN (8 equiv) were added, and the reaction was kept in a sealed flask at room temperature for several days. For monitoring of the reaction by TLC, a small amount of the reaction mixture was subjected to a per-O-acetylation. After complete consumption of the

• aldose was indicated by TLC (per-O-acetylation of a sample of the reaction mixture was performed, EE/C (ethyl acetate/cyclohexane) 1:1 v/v) and 5 g of the crude heptononitriles 15a and 15b was obtained. This mixture of heptononitriles (2.5 g) was treated in water (50 mL) containing acetic acid (0.75 mL

• material was indicated by TLC (per-O-acetylation of a small sample, C/EE 1:1 v/v) and 3.5 g of the crude heptononitriles 21a and 21b were obtained. Heptononitriles 21a and 21b (3.5 g, 14.1 mmol) were treated as described in distd water (40 mL) employing acetic acid (1.23 mL, 1.5 equiv) and Pd/BaSO4 (2.1 g

Automated synthesis of sialylated oligosaccharides

• Davide Esposito,
• Mattan Hurevich,
• Bastien Castagner,
• Cheng-Chung Wang and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2012, 8, 1601–1609, doi:10.3762/bjoc.8.183

• (OAc)2 and catalytic amounts of BF3·Et2O [23] and gave disaccharides 12 and 13, respectively after acetylation (Scheme 1). Removal of the anomeric acetate mediated by hydrazine acetate provided the hemiacetals, which was followed by introduction of the anomeric N-phenyl trifluoroacetimidate to furnish

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

• by the enzyme CYP3A4 and designated chemically as (R)-5-[2(phenylsulfonyl)ethyl]-3-(N-methylpyrrolidin-2-ylmethyl)-1H-indole. Various procedures for the synthesis of eletriptan hydrobromide are known [6][7][8], but the one generally used is the synthesis shown in Scheme 1. Acetylation of (R)-5-bromo

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

• formal synthesis of a and a'. A mixture of a and b will be easily obtained from the protected hydroxy aldehyde 24 by the straight forward procedure outlined in Scheme 6. Reduction of the aldehyde function of 24 and acetylation of the resulting primary alcohol followed by cleavage of the silyl group will

Chemo-enzymatic modification of poly-N-acetyllactosamine (LacNAc) oligomers and N,N-diacetyllactosamine (LacDiNAc) based on galactose oxidase treatment

• Christiane E. Kupper,
• Ruben R. Rosencrantz,
• Birgit Henßen,
• Helena Pelantová,
• Stephan Thönes,
• Anna Drozdová,
• Vladimir Křen and
• Lothar Elling

Beilstein J. Org. Chem. 2012, 8, 712–725, doi:10.3762/bjoc.8.80

• experiment (bold printed in tables) and confirmed by the downfield glycosylation shift of the involved carbons (C-4 for Glc, C-3 for Gal). Chemical shifts of GlcNAc carbons C-2 agree with N-acetylation. Because of isomerism on the NH-C=S bond, signals of H-1A and CS were not detected. Chemical shifts of

• spin system –(CH2)4CHCH(N–)CH(N–)CH2– of biotin. The anomeric configuration (β) of all saccharide units was determined from the JH-1,H-2 coupling constants. Chemical shifts of GlcNAc carbons C-2 agree with N-acetylation. Because of isomerism on the NH–C=S bond, protons H-1A resonate as two broad

Synthesis and antiviral activities of spacer-linked 1-thioglucuronide analogues of glycyrrhizin

• Christian Stanetty,
• Andrea Wolkerstorfer,
• Hassan Amer,
• Andreas Hofinger,
• Ulrich Jordis,
• Dirk Claßen-Houben and
• Paul Kosma

Beilstein J. Org. Chem. 2012, 8, 705–711, doi:10.3762/bjoc.8.79

• (structure not shown). The secondary amino group in compound 8 was subjected to further derivatization by N-acetylation (triethylamine, acetic anhydride), which gave compound 9 in 96% yield. Deprotection of the ethyl 1-thio-glucuronide derivatives 8 and 9 was achieved by acid-catalyzed cleavage of the

Investigation of the network of preferred interactions in an artificial coiled-coil association using the peptide array technique

• Raheleh Rezaei Araghi,
• Carsten C. Mahrenholz,
• Rudolf Volkmer and
• Beate Koksch

Beilstein J. Org. Chem. 2012, 8, 640–649, doi:10.3762/bjoc.8.71

• . In the second coupling step, the anchor position Fmoc-β-alanine-OPfp in dimethylsulfoxide (DMSO) was used. Residual amino functions between the spots were capped by acetylation. The Fmoc group was cleaved by using 20% piperidine in dimethylformamide (DMF). The cellulose-bound peptide arrays were

Synthesis of fluorinated maltose derivatives for monitoring protein interaction by ¹⁹F NMR

• Michaela Braitsch,
• Hanspeter Kählig,
• Georg Kontaxis,
• Michael Fischer,
• Toshinari Kawada,
• Robert Konrat and
• Walther Schmid

Beilstein J. Org. Chem. 2012, 8, 448–455, doi:10.3762/bjoc.8.51

• The synthesis of the 2-F-maltose reporter system was performed following a modified protocol developed by Dax et al. [23][24]. Starting from maltose (1), disaccharide α-bromide 3 was obtained in excellent yield by a standard acetylation procedure and subsequent treatment with hydrobromic acid in

Ion-exchange-resin-catalyzed adamantylation of phenol derivatives with adamantanols: Developing a clean process for synthesis of 2-(1-adamantyl)-4-bromophenol, a key intermediate of adapalene

• Nan Wang,
• Ronghua Wang,
• Xia Shi and
• Gang Zou

Beilstein J. Org. Chem. 2012, 8, 227–233, doi:10.3762/bjoc.8.23

• conditions. Moreover, no unacetylated product was detected during the monitoring of the reaction progress, implying that acetylation of carbinol proceeded faster than the adamantylation under these acidic conditions. Conclusion In summary, we have developed a clean process for the synthesis of 2