Synthetic strategies toward 1,3-oxathiolane nucleoside analogues

• Umesh P. Aher,
• Dhananjai Srivastava,
• Girij P. Singh and
• Jayashree B. S

Beilstein J. Org. Chem. 2021, 17, 2680–2715, doi:10.3762/bjoc.17.182

• was prepared from ᴅ-mannose (3c) by protecting the primary alcohol with a tosyl group, followed by protection of the four hydroxy groups by acetylation. Further, bromo-substituted sugar compound 10 was obtained by a bromination reaction of the anomeric acetyl group. 1,6-Thioanhydro-β-mannose

• hydroxyoxathiolane 32. Further, acetylation of the hydroxyoxathiolane in the presence of methanesulfonic acid gave a 1:2 mixture of the trans-diastereomer 33 and the cis-diastereomer 34. The esterification using ʟ-menthol as a chiral auxiliary resulted in a diastereomeric mixture, which was successfully

• afforded the thiol compound 3nb. Further treatment of the thiol 3nb with methyl glyoxylate in dichloromethane solvent along with molecular sieves (4 Å), followed by in situ acetylation using Ac2O, pyridine, and catalytic 4-(N,N-dimethylamino)pyridine (DMAP) provided compound 37. The second route involves

Synthesis of new bile acid-fused tetrazoles using the Schmidt reaction

• Dušan Đ. Škorić,
• Olivera R. Klisurić,
• Dimitar S. Jakimov,
• Marija N. Sakač and
• János J. Csanádi

Beilstein J. Org. Chem. 2021, 17, 2611–2620, doi:10.3762/bjoc.17.174

• selective acetylation [43], followed by oxidation. Enones 4 and 8 were prepared by dehydrogenation of corresponding ketones with SeO2 in refluxing acetic acid [44]. Microwave-assisted heating of the reaction mixture in a closed vessel (150 °C) helped in decreasing the reaction time for dehydrogenation

Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds

• Sumana Mandal,
• Raju D. Chaudhari and
• Goutam Biswas

Beilstein J. Org. Chem. 2021, 17, 2348–2376, doi:10.3762/bjoc.17.153

• in the key step for the synthesis of (±)-thallusin (207, Scheme 62). A complex mixture of Hg(OTf)2 and N,N-dimethylaniline (DMA) (1.2 equiv) was initially used for olefin cyclization to produce a regio- and a stereoisomeric mixture of acetate 205 after reduction and acetylation of the crude product

Progress and challenges in the synthesis of sequence controlled polysaccharides

• Giulio Fittolani,
• Theodore Tyrikos-Ergas,
• Denisa Vargová,
• Manishkumar A. Chaube and
• Martina Delbianco

Beilstein J. Org. Chem. 2021, 17, 1981–2025, doi:10.3762/bjoc.17.129

• tuning of the DP and fraction of acetylation (FA). Chitooligosaccharides (COS: β(1–4)-linked oligomers of GlcNAc and/or GlcN) have gained popularity due to their exceptional antimicrobial, antitumor, and immune modulatory activities [29][213][214][215][216][217]. Methods to obtain well-defined COS with

• COS, which requires tedious purification steps. Furthermore, degradation of natural chitin often lacks proper control over the pattern of acetylation (PA). Acetolysis also often leads to heterogeneous mixtures [232][233][234][235]. A controlled acetolysis of chitin, followed by the one-pot trans-N

• were removed with hydrazine under reflux and the free amino groups were acetylated to obtain the fully N-acetylated COS [255]. Control over the pattern of N-acetylation was for the first time achieved using two monosaccharides bearing an azido (N3) and a N-Phth moieties as precursors of the free and N

Regioselective N-alkylation of the 1H-indazole scaffold; ring substituent and N-alkylating reagent effects on regioisomeric distribution

• Ryan M. Alam and
• John J. Keating

Beilstein J. Org. Chem. 2021, 17, 1939–1951, doi:10.3762/bjoc.17.127

• effect by Conrow et al. to give regioselective access to N-1 alkylindazoles on kilogram scale, albeit over two steps from the corresponding N-1 acylindazole via reductive acetylation–deacetoxylation [20]. Although electronic and steric factors can influence the regiochemical outcome of indazole N

Natural products in the predatory defence of the filamentous fungal pathogen Aspergillus fumigatus

• Jana M. Boysen,
• Nauman Saeed and
• Falk Hillmann

Beilstein J. Org. Chem. 2021, 17, 1814–1827, doi:10.3762/bjoc.17.124

• and the 3-keto group are crucial for its antibacterial activity whereas, acetylation of the C-6 hydroxy group reduces the activity of HA [169]. Previous studies have also shown the antitrypanosomal, antifungal and cilioinhibitory properties of HA [72][83][86][87][88]. For these properties and little

A systems-based framework to computationally describe putative transcription factors and signaling pathways regulating glycan biosynthesis

• Theodore Groth,
• Rudiyanto Gunawan and
• Sriram Neelamegham

Beilstein J. Org. Chem. 2021, 17, 1712–1724, doi:10.3762/bjoc.17.119

• acetylation, methylation, and phosphorylation, which alter TF access; and iii) methylation of CpG islands in promoter regions that inhibit gene expression [4][5]. There are currently several isolated studies of TF–glycogene interactions, but a systematic “systems-level analysis” is absent. Many of these

Chemical synthesis of C6-tetrazole ᴅ-mannose building blocks and access to a bioisostere of mannuronic acid 1-phosphate

• Eleni Dimitriou and
• Gavin J. Miller

Beilstein J. Org. Chem. 2021, 17, 1527–1532, doi:10.3762/bjoc.17.110

• is widely used as a gelling agent [1][2][3][4][5]. Detailed consideration of the alginate sub-structure indicates non-uniform proportions of M and G units (and their homo- or heteropolymeric block-groupings) which, alongside acetylation of M residues, presents a structurally heterogeneous

• constituent M and G residues and C2/C3 acetylation for one M residue. b) Introduction of bioisosteric carboxylate groups at C6 within a ᴅ-manno thioglycoside donor, P = appropriate protecting group. a) H2N(CH2)2CN, PyBOP, DIPEA, CH2Cl2, 0 °C, 40 min, 47% (+44% 3); b) TBSOTf, imidazole, DMAP, DMF, 24 h, 80%; c

Double-headed nucleosides: Synthesis and applications

• Vineet Verma,
• Jyotirmoy Maity,
• Vipin K. Maikhuri,
• Ritika Sharma,
• Himal K. Ganguly and
• Ashok K. Prasad

Beilstein J. Org. Chem. 2021, 17, 1392–1439, doi:10.3762/bjoc.17.98

• the nucleobases with propargyl bromide in the presence of K2CO3. Nucleoside 94 was synthesized from thymidine (93) which was first tritylated at the C-5′ primary hydroxy position followed by acetylation at the C-3′ secondary hydroxy group [61]. Next, detritylation and tosylation of the protected

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

• synthesis of coumarin (90) was also reported, which involved an intramolecular aldol-type condensation of the acetylated intermediate 89 derived from salicylaldehyde (88, Scheme 18) [125]. The initial O-acetylation step was telescoped directly into the next reactor; the two-step process gave an overall

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

• Joseane A. Mendes,
• Paulo R. R. Costa,
• Miguel Yus,
• Francisco Foubelo and
• Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

Synthesis of multiply fluorinated N-acetyl-D-glucosamine and D-galactosamine analogs via the corresponding deoxyfluorinated glucosazide and galactosazide phenyl thioglycosides

• Vojtěch Hamala,
• Lucie Červenková Šťastná,
• Martin Kurfiřt,
• Petra Cuřínová,
• Martin Dračínský and
• Jindřich Karban

Beilstein J. Org. Chem. 2021, 17, 1086–1095, doi:10.3762/bjoc.17.85

• thioglycosides was sluggish and incomplete. Protecting the primary hydroxy group at C6 by O-benzylation (Scheme 3, compounds 27–31) was essential before treatment with thioacetic acid; otherwise, an O6-acetylated byproduct was formed. Acetylation of the anomeric hydroxy group occurred only to a very limited

Simulating the enzymes of ganglioside biosynthesis with Glycologue

• Andrew G. McDonald and
• Gavin P. Davey

Beilstein J. Org. Chem. 2021, 17, 739–748, doi:10.3762/bjoc.17.64

• modification of monosaccharides, for example through sulfation, acetylation or phosphorylation, which follow the same pattern as decoration. Glycologue structure identifiers order branches by linkage position, writing the branch with the lowest linkage first, reading from right to left. Modifiers are written

• will also influence the kinetics [48][51]. Future extensions to this work will consider the effects of acetylation of sialic acid residues, since this modification reduces the negative charge of the carbohydrate, thus altering binding affinity, while an increased incidence of 9-O-acetylated GD3 is

Synthesis of dibenzosuberenone-based novel polycyclic π-conjugated dihydropyridazines, pyridazines and pyrroles

• Ramazan Koçak and
• Arif Daştan

Beilstein J. Org. Chem. 2021, 17, 719–729, doi:10.3762/bjoc.17.61

• literature procedures (2j was synthesized by acetylation of 2i, while 2b and 2g were purchased) [57][58][59][60][61][62][63]. When dibenzosuberenone (1) and s-tetrazines 2a–j (1.1 equiv) were dissolved in toluene in a sealed tube and stirred at 100–125 °C for 2–48 h, a sequence of a [4 + 2]-Diels–Alder

Stereoselective syntheses of 3-aminocyclooctanetriols and halocyclooctanetriols

• Emine Salamci and
• Yunus Zozik

Beilstein J. Org. Chem. 2021, 17, 705–710, doi:10.3762/bjoc.17.59

• are reported. Reduction of cyclooctene endoperoxide, obtained by photooxygenation of cis,cis-1,3-cyclooctadiene, with zinc yielded a cyclooctene diol followed by acetylation of the hydroxy group, which gave dioldiacetate by OsO4/NMO oxidation. The cyclooctane dioldiacetate prepared was converted to

• with sodium azide of the corresponding cyclic sulfate intermediate 9, which contains the only stereocentre. The cyclic sulfate 9 could be synthesized from diacetatediol 7 [33]. For this purpose, the reduction of the endoperoxide 5 with zinc followed by acetylation of the hydroxy group and OsO4/NMO

α,γ-Dioxygenated amides via tandem Brook rearrangement/radical oxygenation reactions and their application to syntheses of γ-lactams

• Mikhail K. Klychnikov,
• Radek Pohl,
• Ivana Císařová and
• Ullrich Jahn

Beilstein J. Org. Chem. 2021, 17, 688–704, doi:10.3762/bjoc.17.58

• simplified by further useful reaction steps. Results Tandem nucleophilic substitution/Brook rearrangement/radical α-oxygenation reactions The N-allylic α-(trimethylsilyl)acetamides 8a–m were efficiently prepared by a two-step sequence. First, N-allyl acetamides 11a–m were synthesized by N-acetylation of the

Synthesis of (Z)-3-[amino(phenyl)methylidene]-1,3-dihydro-2H-indol-2-ones using an Eschenmoser coupling reaction

• Lukáš Marek,
• Lukáš Kolman,
• Jiří Váňa,
• Jan Svoboda and
• Jiří Hanusek

Beilstein J. Org. Chem. 2021, 17, 527–539, doi:10.3762/bjoc.17.47

• derivative. Such nitrogen protection/deprotection (e.g., acetylation/deacetylation) is often used in the other synthetic strategies described in Scheme 1. Therefore, the starting isatin was acetylated first with acetic anhydride [47] in 95% yield and then reduced with various complex borohydrides (e.g

Unexpected rearrangements and a novel synthesis of 1,1-dichloro-1-alkenones from 1,1,1-trifluoroalkanones with aluminium trichloride

• Beatrice Lansbergen,
• Catherine S. Meister and
• Michael C. McLeod

Beilstein J. Org. Chem. 2021, 17, 404–409, doi:10.3762/bjoc.17.36

• step with PPh3 and CHCl3 [11], CCl4 [12], or with the phosphonate reagent LiCCl2-P(O)(OEt)2 [13][14] (Figure 2a). Alternatively, the aldehydes are converted to trichloromethyl carbinols 3 using various methodologies [15][16][17], followed by acetylation and elimination to provide the desired

Novel library synthesis of 3,4-disubstituted pyridin-2(1H)-ones via cleavage of pyridine-2-oxy-7-azabenzotriazole ethers under ionic hydrogenation conditions at room temperature

• Romain Pierre,
• Anne Brethon,
• Sylvain A. Jacques,
• Aurélie Blond,
• Sandrine Chambon,
• Sandrine Talano,
• Catherine Raffin,
• Branislav Musicki,
• Claire Bouix-Peter,
• Loic Tomas,
• Gilles Ouvry,
• Rémy Morgentin,
• Laurent F. Hennequin and
• Craig S. Harris

Beilstein J. Org. Chem. 2021, 17, 156–165, doi:10.3762/bjoc.17.16

• to hydrolyze than the Py–Cl bond (Table 1). Using conditions described in the literature (Table 3, entry 1), we obtained a 45% isolated yield of 16 with side products arising namely from acetylation of the product that were easily removed by preparative LC–MS. Using aqueous HCl led to severe

Progress in the total synthesis of inthomycins

• Bidyut Kumar Senapati

Beilstein J. Org. Chem. 2021, 17, 58–82, doi:10.3762/bjoc.17.7

• the corresponding primary amide, acetylation of acid 56a followed by acid chloride formation of acetate 56b and in situ ammonium hydroxide treatment was found to be fruitful to produce inthomycin B (+)-2 in reasonable yield (Scheme 4). This synthetic route introduced the chiral entry to any member of

• derivative (rac)-63 was subjected to undergo acetylation, acid chloride formation, and quenching with ammonium hydroxide to produce amide derivative (rac)-64 in 70% yield. Finally, saponification of acetate (rac)-64 using lithium hydroxide gave racemic inthomycin A ((rac)-1) in 14% overall yield (Scheme 5

• diastereoisomers. Then, the key aldol reaction of 123 with silyl enol ether 53 under optimized Mukaiyama–Kiyooka conditions, followed by TIPS deprotection, afforded adduct (3R)-(+)-11 in 63% yield and with 94% ee. Ester hydrolysis followed by acetylation of (3R)- (+)-11 produced acid derivative (+)-76 [50] in 87

Pentannulation of N-heterocycles by a tandem gold-catalyzed [3,3]-rearrangement/Nazarov reaction of propargyl ester derivatives: a computational study on the crucial role of the nitrogen atom

• Giovanna Zanella,
• Martina Petrović,
• Dina Scarpi,
• Ernesto G. Occhiato and
• Enrique Gómez-Bengoa

Beilstein J. Org. Chem. 2020, 16, 3059–3068, doi:10.3762/bjoc.16.255

• was prepared via the palladium-catalyzed reduction of the corresponding phosphate 17 [54]. Iodination and Sonogashira coupling, followed by acetylation led to the formation of the desired enynyl acetate 20. This compound was treated with 5 mol % Ph3PAuCl/AgSbF6 in DCM, and after 6 h, this afforded the

3-Acetoxy-fatty acid isoprenyl esters from androconia of the ithomiine butterfly Ithomia salapia

• Florian Mann,
• Daiane Szczerbowski,
• Lisa de Silva,
• Melanie McClure,
• Marianne Elias and
• Stefan Schulz

Beilstein J. Org. Chem. 2020, 16, 2776–2787, doi:10.3762/bjoc.16.228

• catalysis [33]. Final acetylation of the hydroxy esters delivered the target compound isoprenyl 3-acetoxyoctadecanoate (11). Comparison of mass spectra and retention index confirmed the identity of the naturally occurring compound and 11. An enantioselective synthesis of isoprenyl (Z)-3-acetoxyoctadec-13

• was obtained in good yield. The following stannoxane induced transesterification and the final acetylation procedure delivered 12. The two isomeric natural 3-acetoxyoctadecenyl esters had retention indices of 2678 and 2692, respectively, while synthetic 12 showed an I of 2688. Therefore, the second

Enzyme-instructed morphological transition of the supramolecular assemblies of branched peptides

• Dongsik Yang,
• Hongjian He and
• Bing Xu

Beilstein J. Org. Chem. 2020, 16, 2709–2718, doi:10.3762/bjoc.16.221

• assemblies of the peptides. The attachment of DEDDDLLI sequences to the ε-amine of the lysine residue of a tetrapeptide produces branched peptides that form micelles. Upon the proteolytic cleavage of the branch, catalyzed by proteinase K, the micelles turn into nanofibers. We also found that the acetylation

• cellular environment. Keywords: acetylation; branched peptides; enzyme; nanostructures; N-terminal; responsive; self-assembly; Introduction Peptides, being able to self-assemble to exhibit emergent properties and functions [1][2][3][4][5], have received considerable attentions recently. For example

• proteolysis to cleave the branch off 1, the micelles turn into nanofibers. Acetylation of the N-terminal of the branch forms 2, which exhibits an enhanced stability towards the proteolysis. In addition, the cleavage also occurs at other sites in the branch of 2, albeit less frequently, due to the acetylation

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

• using trifluoroacetyl nitrate which was in situ generated from conc. HNO3 and trifluoroacetic anhydride. On the other hand, formylation and acetylation were performed under microwave conditions at 130 °C using triflic anhydride and DMF or dimethylacetamide (DMA) to deliver the corresponding

Access to highly substituted oxazoles by the reaction of α-azidochalcone with potassium thiocyanate

• Mysore Bhyrappa Harisha,
• Pandi Dhanalakshmi,
• Rajendran Suresh,
• Raju Ranjith Kumar and
• Shanmugam Muthusubramanian

Beilstein J. Org. Chem. 2020, 16, 2108–2118, doi:10.3762/bjoc.16.178

• just at the start of the reaction and b is the photograph after the completion of the reaction. Further, the utility of the thiol group in 3 for the generation of a library of compounds was demonstrated by the simple acetylation and alkylation (Scheme 4 and Scheme 5). The acetylation of the thiol group

• in 3d proceeded smoothly with acetyl chloride in the presence of sodium hydride to afford 5 in good yield. The structure of the product and the site of acetylation was confirmed by X-ray crystallography of a single crystal of 5 [71] (Figure 3). The methylated and benzylated derivatives 6 and 7 were