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

Convergent synthesis of the tetrasaccharide repeating unit of the O-antigen of Shigella boydii type 9

• Abhishek Santra and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2011, 7, 1182–1188, doi:10.3762/bjoc.7.137

• recently developed environmentally benign reaction conditions for protecting group manipulations and glycosylations such as, (i) O-acetylation using sulfamic acid [20], (ii) regioselective ring opening of the benzylidene acetal using a combination of triethylsilane and iodine [21], (iii) direct one-pot

• acetylation using acetic anhydride in the presence of sulfamic acid [20] followed by regioselective reductive ring opening of the benzylidene acetal using a combination of triethylsilane and iodine [21] to furnish 4-methoxyphenyl (2,3-di-O-acetyl-6-O-benzyl-α-D-glucopyranosyl)-(1→4)-2,3,6-tri-O-acetyl-β-D

• cleavage of ethers and reduction of the azido group to an amine by hydrogenation over 20% Pd(OH)2/C followed by N-acetylation to furnish target tetrasaccharide 1 as its sodium salt and 4-methoxyphenyl glycoside in 64% yield (Scheme 3). Spectroscopic analysis of compound 1 confirmed its formation (presence

Synthesis, reactivity and biological activity of 5-alkoxymethyluracil analogues

• Lucie Brulikova and
• Jan Hlavac

Beilstein J. Org. Chem. 2011, 7, 678–698, doi:10.3762/bjoc.7.80

• containing trimethylsilyl chloride and the silylated acetyluracil coupled with 2-chlorotetrahydrofuran (114) to afford 5-acetyl-1-(tetrahydrofuran-2-yl)uracil (115). Subsequent reduction of the keto group with sodium borohydride gave 5-(1-hydroxyethyl)-1-(tetrahydrofuran-2-yl)uracil (116). Final acetylation

• of 3',5'-dihydroxyl groups with the TBDMS group followed by a Pd-catalyzed coupling reaction with vinyl acetate to give the protected 5-vinyluridine 129 in 68% yield. Oxidation with OsO4 with subsequent acetylation with acetic anhydride in pyridine gave nucleoside 131. The target phosphoramidite 134

• '-deoxyuridine 128 was subjected to a Stille coupling reaction with tributyl(vinyl)tin using Pd(MeCN)2Cl2 as a catalyst (Scheme 23, reaction conditions 2). This coupling reaction was followed by the oxidation of the vinyl group of nucleoside 129 by OsO4 and acetylation of vicinal diol 130. After deprotection of

Novel carbazole–pyridine copolymers by an economical method: synthesis, spectroscopic and thermochemical studies

• Aamer Saeed,
• Madiha Irfan and
• Shahid Ameen Samra

Beilstein J. Org. Chem. 2011, 7, 638–647, doi:10.3762/bjoc.7.75

• of tetrabutylammonium bromide (TBAB) as a phase-transfer catalyst [23][24][25]. The N-alkylcarbazoles were subsequently subjected to Friedel–Crafts acetylation at the active positions of carbazole, viz. 3 and 6, with anhydrous aluminum chloride in dry chloroform [26]. The monomers were purified by

Unusual behavior in the reactivity of 5-substituted-1H-tetrazoles in a resistively heated microreactor

• Bernhard Gutmann,
• Toma N. Glasnov,
• Tahseen Razzaq,
• Walter Goessler,
• Dominique M. Roberge and
• C. Oliver Kappe

Beilstein J. Org. Chem. 2011, 7, 503–517, doi:10.3762/bjoc.7.59

• (3). We have identified virtually all the peaks in the HPLC chromatograms and therefore have a rather complete picture of the complex degradation processes (Scheme 2, Figure S1 in Supporting Information File 1). The main degradation path starts with the N-acetylation of the tetrazole nucleus at

An overview of the key routes to the best selling 5-membered ring heterocyclic pharmaceuticals

• Marcus Baumann,
• Ian R. Baxendale,
• Steven V. Ley and
• Nikzad Nikbin

Beilstein J. Org. Chem. 2011, 7, 442–495, doi:10.3762/bjoc.7.57

• consequently slowing down the irreversible acetylation of a serine residue by aspirin itself. This finding is relevant as aspirin is clinically used in combination with celecoxib to attenuate its cardiovascular side effects. Based on this in vitro study, it is suggested that the cardioprotective effects of low

Regioselective ester cleavage during the preparation of bisphosphonate methacrylate monomers

• Kamel Chougrani,
• Gilles Niel,
• Bernard Boutevin and
• Ghislain David

Beilstein J. Org. Chem. 2011, 7, 364–368, doi:10.3762/bjoc.7.46

• of the reaction mixture probably due to the higher acidity of the medium and are in agreement with the previously described deprotections using water as solvent [31]. We prepared two model compounds 24 and 25 derived from acetylation of HEMA (22) and (hydroxybutyl)methacrylic acid (HBMA, 23

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

• GlcNAc, mannose and N-acetylamine, which could serve as effective mimics of post-translational protein modifications (glycosylation, lysine acetylation). Conclusion Since the early work by Hoye on secondary allylic alcohols [19] and later the studies on allyl sulfides by our group [17], the allyl

Achiral bis-imine in combination with CoCl₂: A remarkable effect on enantioselectivity of lipase-mediated acetylation of racemic secondary alcohol

• K. Arunkumar,
• M. Appi Reddy,
• T. Sravan Kumar,
• B. Vijaya Kumar,
• K. B. Chandrasekhar,
• P. Rajender Kumar and
• Manojit Pal

Beilstein J. Org. Chem. 2010, 6, 1174–1179, doi:10.3762/bjoc.6.134

• acetylation of the (R)-isomer of a racemic benzylic secondary alcohol with 91% ees. The methodology was used for the preparation of the known drug rivastigmine. Keywords: acetylation; bis-imine; cobalt chloride; enantioselectivity; lipase; Introduction The development and use of newer synthetic methods for

• enhancing their economic viability [10][11]. Recently, we have observed that achiral bis-imines in combination with CoCl2 improved the enantioselectivity substantially in CAL-B (Candida antarctica lipase B) [12][13] mediated acetylation of a racemic secondary alcohol with vinyl acetate. Here we report our

• -imines in combination with CoCl2 [16] in the lipase-mediated acetylation of a benzylic secondary alcohols. Accordingly, a number of achiral bis-imines were prepared and used to generate the desired complex. While a number of methods have been reported to prepare Schiff bases by reacting an amine with a

Carbasugar analogues of galactofuranosides: α-O-linked derivatives

• Jens Frigell and
• Ian Cumpstey

Beilstein J. Org. Chem. 2010, 6, 1127–1131, doi:10.3762/bjoc.6.129

• acetylation of the free alcohols. The major product 8 gave a C2 acetate 9, as shown by the downfield shift of H2 in the 1H NMR spectrum, indicating nucleophilic attack at C1 during the epoxide-opening step to give an α-talo configured product. The minor product gave a C1 acetate on acetylation, indicating

• the third benzyl ether protecting group had been lost. The mass spectrum showed a peak at m/z 363, consistent with a bicyclic system. Acetylation with acetic anhydride and pyridine gave a monoacetate 14 according to NMR spectroscopy and mass spectrometry (m/z 405). We deduced the structure of the

Preparation of aminoethyl glycosides for glycoconjugation

• Robert Šardzík,
• Gavin T. Noble,
• Martin J. Weissenborn,
• Andrew Martin,
• Simon J. Webb and
• Sabine L. Flitsch

Beilstein J. Org. Chem. 2010, 6, 699–703, doi:10.3762/bjoc.6.81

• encountered with purification, the glycosylation with Hg(CN)2 was further optimised by increasing both the temperature and the amount of acceptor. The problem of separation of the alcohol from the product was solved by acetylation of the crude reaction mixture to lower the polarity of the free alcohol

Synthesis of 6-PEtN-α-D-GalpNAc-(1–>6)-β-D-Galp-(1–>4)-β-D-GlcpNAc-(1–>3)-β-D-Galp-(1–>4)-β-D-Glcp, a Haemophilus influenzae lipopolysacharide structure, and biotin and protein conjugates thereof

• Andreas Sundgren,
• Martina Lahmann and
• Stefan Oscarson

Beilstein J. Org. Chem. 2010, 6, 704–708, doi:10.3762/bjoc.6.80

• cleavage of the formed imidate and afforded the desired pentasaccharide in the above noted yield. Reduction of the azido group in 17 and subsequent acetylation afforded compound 18 (91%). Removal of the TBDMS group, again using TBAF, gave derivative 19 (85%), ready for the introduction of the

Synthesis of glycosylated β³-homo-threonine conjugates for mucin-like glycopeptide antigen analogues

• Florian Karch and
• Anja Hoffmann-Röder

Beilstein J. Org. Chem. 2010, 6, No. 47, doi:10.3762/bjoc.6.47

• reduction and acetylation led to the formation of conjugate 2a in 56% yield. During biosynthesis TN antigen acts as an immediate precursor of the TF antigen. As a consequence, a biomimetic approach towards larger TACA structures via stepwise assembly of the glycan chain has been pursued in various antigen

• chain protective groups was achieved upon treatment with a mixture of TFA, triisopropylsilane and water. The resulting partially deblocked glycopeptide 7 was isolated after purification by semi-preparative RP-HPLC in a yield of 36%, based on the loaded resin 5. The final de-O-acetylation of the glycan

A thermally-induced, tandem [3,3]-sigmatropic rearrangement/[2 + 2] cycloaddition approach to carbocyclic spirooxindoles

• Kay M. Brummond and
• Joshua M. Osbourn

Beilstein J. Org. Chem. 2010, 6, No. 33, doi:10.3762/bjoc.6.33

• 5 could be obtained by way of a thermal [3,3]-sigmatropic rearrangement of the propargylic acetate 6 to give compound 5 where R2 = OAc (Figure 2) [27]. Preparation of propargylic acetate 9a was accomplished by the addition of the lithium acetylide of 8 to N-methyl isatin (7) followed by acetylation