Synthesis of the C8’-epimeric thymine pyranosyl amino acid core of amipurimycin

• Pramod R. Markad,
• Navanath Kumbhar and
• Dilip D. Dhavale

Beilstein J. Org. Chem. 2016, 12, 1765–1771, doi:10.3762/bjoc.12.165

• ester 15. Acetylation of 15 with acetic anhydride in pyridine gave acetate derivative 16 in 95% yield. Having fully functionalized intermediate 16 in hand, we thought to incorporate the purine nucleobase using Vorbrüggen conditions. Thus, reaction of glycosyl donor 16 with bis(trimethylsilyl)-2-(N

Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides

• Franziska Hemmerling and
• Frank Hahn

Beilstein J. Org. Chem. 2016, 12, 1512–1550, doi:10.3762/bjoc.12.148

• agglomerin A (147) biosynthesis proceeds as a two-step process [143]. An initial acyl transferase Agg4-catalysed acetylation of the primary hydroxy group in 158 is followed by dehydratase Agg5-catalysed acetic acid elimination, leading to olefin 147 (Scheme 22). This mechanism was confirmed by gene knockout

• analogous acetylation–elimination process was experimentally confirmed for quartromicin D1 (151) biosynthesis (Scheme 22) [145]. VstJ has been identified as a probable candidate for the enzyme-catalysed [4 + 2] cycloaddition in versipelostatin A (153) biosynthesis by heterologous expression, gene knockout

Synthesis of 2-substituted tetraphenylenes via transition-metal-catalyzed derivatization of tetraphenylene

• Shulei Pan,
• Hang Jiang,
• Yanghui Zhang,
• Yu Zhang and
• Dushen Chen

Beilstein J. Org. Chem. 2016, 12, 1302–1308, doi:10.3762/bjoc.12.122

• substituted ones. Although direct bromination [22], nitration [22], and acetylation [45] of tetraphenylene via electrophilic aromatic substitution have been reported, it is still desirable to develop new methods for the derivatization of tetraphenylenes. Herein we report several synthetic protocols for the

Reactions of N,3-diarylpropiolamides with arenes under superelectrophilic activation: synthesis of 4,4-diaryl-3,4-dihydroquinolin-2(1H)-ones and their derivatives

• Larisa Yu. Gurskaya,
• Diana S. Belyanskaya,
• Dmitry S. Ryabukhin,
• Denis I. Nilov,
• Irina A. Boyarskaya and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2016, 12, 950–956, doi:10.3762/bjoc.12.93

• -acetylation reactions were carried out. Compounds 2a,d,e and h were N-formylated in the system POCl3–DMF–CHCl3 under the Vilsmeier–Haack reaction conditions with formation of compounds 5a–d (Scheme 2). Apart from that, dihydroquinolinones 2a,e–h were acetylated into derivatives 6a–e (Scheme 2). Then reactions

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

• . Acetylation of the thus formed primary alcohol resulted in compound 38. This was followed by benzyl and Cbz deprotection and the subsequent urea formation with the imidazolium salt 39 to furnish tripeptide 40. After Boc deprotection, the resultant amine was guanidinylated using isothiourea 41. The thus

Synthesis and in vitro cytotoxicity of acetylated 3-fluoro, 4-fluoro and 3,4-difluoro analogs of D-glucosamine and D-galactosamine

• Štěpán Horník,
• Lucie Červenková Šťastná,
• Petra Cuřínová,
• Jan Sýkora,
• Kateřina Káňová,
• Roman Hrstka,
• Ivana Císařová,
• Martin Dračínský and
• Jindřich Karban

Beilstein J. Org. Chem. 2016, 12, 750–759, doi:10.3762/bjoc.12.75

• in terms of product purity. Hydrogenolysis of 42 on palladium in ethanol/HCl followed by acetylation of the amino group furnished the target acetylated 3-fluoro-D-GlcNAc 5 as a chromatographically separable mixture of anomers (Table 1). Addition of HCl was found necessary to effect a clean

Elucidation of a masked repeating structure of the O-specific polysaccharide of the halotolerant soil bacteria Azospirillum halopraeferens Au4

• Elena N. Sigida,
• Yuliya P. Fedonenko,
• Alexander S. Shashkov,
• Nikolay P. Arbatsky,
• Evelina L. Zdorovenko,
• Svetlana A. Konnova,
• Vladimir V. Ignatov and
• Yuriy A. Knirel

Beilstein J. Org. Chem. 2016, 12, 636–642, doi:10.3762/bjoc.12.62

• -methylglucose, 2,4-di-O-methylrhamnose, 2,4-di-O-methylfucose, 2-O-methylfucose, and 3,4-di-O-methylxylose were identified by GLC–MS of partially methylated alditol acetates derived after methylation of the OPS with MeI followed by hydrolysis and acetylation [14]. Therefore, the OPS contains 3-substituted Rha

• afforded complementary oligosaccharides, which identification shed light on the nature of the OPS irregularity and, combined with chemical analysis and NMR spectroscopic analysis data, enabled the structure elucidation of the OPS. Chemical modifications of the OPS, such as O-methylation or O-acetylation

• -stoichiometric substituents in the OPS has been reported for phytopathogens Pseudomonas syringae [29] and Xanthomonas campestris [30] as well as for beneficial rhizobacteria, including free-living Azospirillum spp. [31][32][33][34][35] and root-nodulating Rhizobium spp. [24]. Moreover, the degree of acetylation

Regiodefined synthesis of brominated hydroxyanthraquinones related to proisocrinins

• Joyeeta Roy,
• Tanushree Mal,
• Supriti Jana and
• Dipakranjan Mal

Beilstein J. Org. Chem. 2016, 12, 531–536, doi:10.3762/bjoc.12.52

• lactol 34 with methylmagnesium bromide afforded diol 35 in 72% yield. Selective oxidation of the allylic alcohol group in 35 with MnO2, followed by acetylation of the secondary hydroxy group with acetyl chloride, triethylamine and DMAP furnished cyclohexenone 36 (Scheme 5). The Hauser annulation of

A selective and mild glycosylation method of natural phenolic alcohols

• Mária Mastihubová and
• Monika Poláková

Beilstein J. Org. Chem. 2016, 12, 524–530, doi:10.3762/bjoc.12.51

• commercial p-hydroxyphenylcarbaldehydes 4a–c which are less expensive than the corresponding p-hydroxybenzyl alcohols (Scheme 1). The conventional acetylation of 4a–c with acetic anhydride in pyridine gave p-acetoxyphenylcarbaldehydes 5a–c in more than 98% yields. Subsequently the aldehyde function was

• corresponding alcohols, tyrosol and coniferyl alcohol. Therefore p-O-acetylated tyrosol (9) and p-O-acetylated coniferyl alcohol (12) were prepared from acids 7 and 10 by a two-step sequence: acid-catalysed acetylation of the phenolic hydroxy group (isolated yields >94%) followed by the reduction of the

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

• rather contradictory concerning the acetylation of this tertiary alcohol using acetic anhydride [50][51]. With regard to a PET application, the protection of this hydroxy group is of paramount importance since the free hydroxy group could impair the incorporation of the radioactive fluorine. Therefor

• several methods of acetylation were carried out on myo-14, which was used as model. The best results for the acetylation of the tertiary alcohol in good yield was obtained with the transesterification method using isopropenyl acetate as acylating agent and p-toluenesulfonic acid as catalyst at 80 °C for 2

• stage. For this, compounds myo-20 and scyllo-20 were reacted with tosyl chloride in the presence of a catalytic amount of triethylamine at room temperature for 3 h to give tosylated myo-22 and scyllo-22 in 70 and 71% yield, respectively. Next, acetylation of the tertiary alcohol was performed before

Study on the synthesis of the cyclopenta[f]indole core of raputindole A

• Nils Marsch,
• Mario Kock and
• Thomas Lindel

Beilstein J. Org. Chem. 2016, 12, 334–342, doi:10.3762/bjoc.12.36

• propargylacetates 46 and 47 (Scheme 7), which were obtained by Sonogashira alkynylations of N-TIPS-6-iodoindoline (39), followed by acetylation (for experimental procedures, see Supporting Information File 1). Xuegong She and coworkers had obtained indanone derivatives from arylpropargylic esters in a Pt(II

Mycothiol synthesis by an anomerization reaction through endocyclic cleavage

• Shino Manabe and
• Yukishige Ito

Beilstein J. Org. Chem. 2016, 12, 328–333, doi:10.3762/bjoc.12.35

• -disaccharide 2 in 90% yield (Scheme 4). After removing the phthaloyl and acetyl groups by using ethylenediamine in dimethylformamide (DMF), a carbamate group was introduced using triphosgene in the presence of NaHCO3. Acetylation of both the hydroxy and carbamate groups was carried out using acetic anhydride

Supramolecular structures based on regioisomers of cinnamyl-α-cyclodextrins – new media for capillary separation techniques

• Gabor Benkovics,
• Ondrej Hodek,
• Martina Havlikova,
• Zuzana Bosakova,
• Pavel Coufal,
• Milo Malanga,
• Eva Fenyvesi,
• Andras Darcsi,
• Szabolcs Beni and
• Jindrich Jindrich

Beilstein J. Org. Chem. 2016, 12, 97–109, doi:10.3762/bjoc.12.11

• previously prepared and characterized by our research group, but our attempts to separate the single 2-O- and 3-O-regioisomers without further modification were unsuccessful [10]. In order to isolate the single regioisomers using this published method, exhaustive per-O-acetylation of the mixture of

• regioisomers, chromatographic separation of the per-O-acetylated derivatives and the de-O-acetylation of the separated per-O-acetylated regioisomers would be necessary. This three-step reaction procedure makes the large scale preparation of the single regioisomers expensive and time-consuming. For α-CD we were

Genicunolide A, B and C: three new triterpenoids from Euphorbia geniculata

• Alia Farozi,
• Javid A. Banday and
• Shakeel A. Shah

Beilstein J. Org. Chem. 2015, 11, 2707–2712, doi:10.3762/bjoc.11.291

• 2.03 (s, 3H), δC 170.2, 21.3], a trisubstituted double bond [νmax 1630, 1042, 880 cm−1, δ 5.56 (d, J = 5.2 Hz, 1H, H-15)] [36] and a secondary equatorial hydroxy group [νmax 3500 cm−1] whose carbinylic proton resonated at δ 3.16 (dd, J = 8.1 Hz, 1H, H-3). On acetylation with Ac2O–C5H5N, at room

• –1, δ 3.17 (dd, J = 11.1 Hz, 1H)]. Its presence was confirmed by acetylation of 2 to 2a [δ 2.05 (s, 9H), δC 170.1, 170.7 and 170.8] and oxidation to diacetoxy ketone 2b [νmax 1736, 1730, 1680 cm–1, δC 170.5, 170.6, 215.2 (C-21)]. The mass spectrum of compound 2 exhibited RDA fragment ions at m/z 416

• , H-3, 1H)]. On acetylation with Ac2O–C5H5N, at room temperature, it afforded monoacetate 3a [1735, δ 2.05 (s, 3H), δC 170.5] and on oxidation with CrO3–C5H5N, it yielded a ketone which gave a positive Zimmermann test for 3-keto group [37] confirming the presence of the C-3 equatorial secondary

Stereochemistry of ring-opening/cross metathesis reactions of exo- and endo-7-oxabicyclo[2.2.1]hept-5-ene-2-carbonitriles with allyl alcohol and allyl acetate

• Piotr Wałejko,
• Michał Dąbrowski,
• Lech Szczepaniak,
• Jacek W. Morzycki and
• Stanisław Witkowski

Beilstein J. Org. Chem. 2015, 11, 1893–1901, doi:10.3762/bjoc.11.204

• compounds 6E and 10E were deacetylated (MeOH/KCN) [24] to give 8E and 12E. The samples 7Z, 8Z, 8E, and 12Z were subjected to acetylation (Py/Ac2O) to give 5Z, 6Z, 6E and 10Z, respectively. The acetates were directly characterized by GC–MS. Based on retention indices and literature data (MS spectra identity

Towards inhibitors of glycosyltransferases: A novel approach to the synthesis of 3-acetamido-3-deoxy-D-psicofuranose derivatives

• Maroš Bella,
• Miroslav Koóš and
• Chun-Hung Lin

Beilstein J. Org. Chem. 2015, 11, 1547–1552, doi:10.3762/bjoc.11.170

• starting material was recovered. Next, the azide 3 (contaminated with some elimination products) was subjected to reduction with powdered Zn and NH4Cl as reducing agents [23] followed by acetylation to afford 3-acetamido-3-deoxy-1,2:4,5-di-O-isopropylidene-6-O-pivaloyl-D-altritol (4) in a good yield. It

• 63% yield. The β-anomer was detected in a negligible amount and could not be separated from the above-mentioned byproduct. Acetylation of the 4-hydroxy group in derivative 10 under standard conditions yielded fully protected 3-acetamido-4-O-acetyl-3-deoxy-1,2-O-isopropylidene-6-O-pivaloyl-α-D

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

• quantitatively the same mixture of epimeric 1-(D-galactopyranosyl)prop-2-enes that were dissolved in ethanol and treated with ether. This allowed the α-epimer to precipitate and it could afterwards be isolated as a pure crystalline product in 60% yield [42]. Its acetylation afforded 1-(tetra-O-acetyl-α-D

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

• oxalyl chloride in the presence of DMF generated the acid chloride, which on further reaction with p-xylylenediamine (306) in the presence of N,N’-diisopropylethylamine (DIPEA) in dichloromethane followed by de-O-acetylation gave the bisazide 307 (37%). The latter compound was reacted with the dialkyne

The synthesis of active pharmaceutical ingredients (APIs) using continuous flow chemistry

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2015, 11, 1194–1219, doi:10.3762/bjoc.11.134

• which although commercially available was expensive and could be generated from 1,3-cyclohexadione (104). The sequence consisted of O-acetylation, a Steglich rearrangement, oxidation and a final methylation reaction. As the use of flow chemistry had already improved the O-acetylation during scale-up

Gold-catalyzed formation of pyrrolo- and indolo-oxazin-1-one derivatives: The key structure of some marine natural products

• Sultan Taskaya,
• Nurettin Menges and
• Metin Balci

Beilstein J. Org. Chem. 2015, 11, 897–905, doi:10.3762/bjoc.11.101

• ]. Results and Discussion The starting compound 11 was synthesized via a slightly modified route by acetylation of pyrrole with trichloroacetyl chloride in 99% yield [42][43]. The propargyl ester 13 [44][45][46] was obtained in high yield from the reaction of 12 with propargyl bromide in the presence of NaH

DNA display of glycoconjugates to emulate oligomeric interactions of glycans

• Alexandre Novoa and
• Nicolas Winssinger

Beilstein J. Org. Chem. 2015, 11, 707–719, doi:10.3762/bjoc.11.81

• resulted in acetylation of the glycan thus blocking the glycan’s hydroxy groups. The generality of this method was illustrated with the synthesis of 16 different DNA conjugates containing one or two glycan units. Analysis of glycan-modified duplexes by CD spectroscopy indicated minimal perturbation of the

Synthesis of a hexasaccharide partial sequence of hyaluronan for click chemistry and more

• Marina Bantzi,
• Stephan Rigol and
• Athanassios Giannis

Beilstein J. Org. Chem. 2015, 11, 604–607, doi:10.3762/bjoc.11.67

• reducing conditions (Zn, AcOH) [28] and subsequently the liberated amino groups were acetylated to furnish compound 8. Eventually, the silyl group and all benzylidene moieties were removed by treatment with Olah's reagent to give, after acetylation, derivative 9. Finally, oxidation of the terminal olefinic

Chemoselective O-acylation of hydroxyamino acids and amino alcohols under acidic reaction conditions: History, scope and applications

• Tor E. Kristensen

Beilstein J. Org. Chem. 2015, 11, 446–468, doi:10.3762/bjoc.11.51

• therefore be an important theme throughout most of this text. However, this methodology is founded upon a few pioneering but more narrow-scoped precursor techniques. Early chemoselective O-acetylation of hydroxyamino acids In 1942, Sakami and Toennies reported a method for the preparation of the O-acetyl

• derivatives of naturally occurring hydroxyamino acids (Scheme 1), a method that was also patented [9][10]. Being mindful of the known accelerating effect of the presence of acids in acetylation reactions of alcohols with acetic anhydride as well as the inhibitory effect of strong acids on the acetylation of

• amines with acetic anhydride, Sakami and Toennies scrutinized this effect through use of perchloric acid (HClO4), at first during titration experiments involving the acetylation of certain amino acids. They then exploited this reactivity pattern to develop a preparatory method for the class of O

Synthesis and biological evaluation of a novel MUC1 glycopeptide conjugate vaccine candidate comprising a 4’-deoxy-4’-fluoro-Thomsen–Friedenreich epitope

• Manuel Johannes,
• Maximilian Reindl,
• Bastian Gerlitzki,
• Edgar Schmitt and
• Anja Hoffmann-Röder

Beilstein J. Org. Chem. 2015, 11, 155–161, doi:10.3762/bjoc.11.15

• ’-fluoro-TF SPPS building block 11 started by conversion of peracetylated D-glucose 1 into β-thio-glycoside 2 [45][46] under Lewis acid catalysis in 81% yield (Scheme 1). Subsequent Zemplén deacetylation [47], followed by 4,6-benzylidene acetal formation and acetylation provided fully protected precursor 3

• amino acids and the more reactive HATU/HOAt/NMM cocktail in NMP for attachment of building block 11 and a triethylene glycol spacer [52], the desired glycopeptide was assembled. Release from the resin using TFA/iPr3SiH/water (10:1:1) followed by careful de-O-acetylation with NaOMe/MeOH (pH 9.0) and

First chemoenzymatic stereodivergent synthesis of both enantiomers of promethazine and ethopropazine

• Paweł Borowiecki,
• Daniel Paprocki and
• Maciej Dranka

Beilstein J. Org. Chem. 2014, 10, 3038–3055, doi:10.3762/bjoc.10.322

• that generated ester (R)-(−)-6a was enantiomerically pure (>99% ee) regardless of the time and the conversion. In turn, the reaction rate was considerably improved in Novozym 435-catalyzed analytical scale acetylation. This revealed that Candida antarctica lipase B (CAL-B) immobilized on acrylic resin

• ≈ MTBE ≈ Et2O > toluene ≈ vinyl acetate, and the reaction enantioselectivity: toluene > vinyl acetate > n-hexane > MTBE ≈ Et2O > pentane. As it was observed, the acetylation reaction in toluene was mostly enantioselective (E = 180), thus transforming the racemic starting material (±)-3 into optically

• experiments, this extremely enantioselective lipase preparation afforded recovery of ester (R)-(−)-6a with perfect optical purity (>99% ee) at a conversion in the rage of 39–49% (Table 2, entries 4–7). On the other hand, since the Lipozyme TL IM-catalyzed acetylation tends to cease before achieving 50