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

Azo-dimethylaminopyridine-functionalized Ni(II)-porphyrin as a photoswitchable nucleophilic catalyst

• Jannis Ludwig,
• Julian Helberg,
• Hendrik Zipse and
• Rainer Herges

Beilstein J. Org. Chem. 2020, 16, 2119–2126, doi:10.3762/bjoc.16.179

• , spiropyranes, and stilbenes [2]. Diarylethenes were reported in the context of photoswitchable catalysis as inhibitors of the Karstedt´s catalyst [3] and for pKa modulation in acid–base-controlled processes [4]. Molecular motors for stereodivergent anion binding catalysis [5], azopeptides for the acetylation

• -porphyrin. The DMAP-catalyzed acetylation of alcohols should not suffer from this drawback because the reactive intermediate (acylpyridinium cation) is positively charged and does not coordinate to the Ni2+ ion [33]. Another promising approach towards coordination-based, photoswitchable catalysts are

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

Synthesis, docking study and biological evaluation of ᴅ-fructofuranosyl and ᴅ-tagatofuranosyl sulfones as potential inhibitors of the mycobacterial galactan synthesis targeting the galactofuranosyltransferase GlfT2

• Marek Baráth,
• Jana Jakubčinová,
• Zuzana Konyariková,
• Stanislav Kozmon,
• Katarína Mikušová and
• Maroš Bella

Beilstein J. Org. Chem. 2020, 16, 1853–1862, doi:10.3762/bjoc.16.152

• diacetate 18 under acetolysis conditions (Ac2O/BF3∙OEt2) [22]. However, besides the expected diacetate 18, 1,2,6-tri-O-acetate 19 was observed and isolated as a byproduct (Scheme 4). The cleavage of the O-benzyl ethers followed by acetylation of the liberated hydroxy groups under acidic conditions was

Tuneable access to indole, indolone, and cinnoline derivatives from a common 1,4-diketone Michael acceptor

• Dalel El-Marrouki,
• Sabrina Touchet,
• Abderrahmen Abdelli,
• Hédi M’Rabet,
• Mohamed Lotfi Efrit and
• Philippe C. Gros

Beilstein J. Org. Chem. 2020, 16, 1722–1731, doi:10.3762/bjoc.16.144

• -catalyzed acetylation of these alcohols, which gave the corresponding acetates 2a–d [59]. The nitrenones 3a–d were finally obtained in an acceptable yield by reacting the acetate derivatives with the appropriate nitroalkanes [60]. The next step was the transformation of the nitro group of 3a–d via the Nef

Synthesis of the tetrasaccharide repeating unit of the O-specific polysaccharide of Azospirillum doebereinerae type strain GSF71^T using linear and one-pot iterative glycosylations

• Arin Gucchait,
• Pradip Shit and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2020, 16, 1700–1705, doi:10.3762/bjoc.16.141

• treatment with HClO4-SiO2 [34]; (c) selective acetylation of the primary hydroxy group, and (d) removal of the benzyl groups by catalytic transfer hydrogenation [35] using triethylsilane in the presence of Pearlman’s catalyst [36] to furnish the desired tetrasaccharide 1 in 50% overall yield with the two O

Synthesis of Streptococcus pneumoniae serotype 9V oligosaccharide antigens

• Sharavathi G. Parameswarappa,
• Claney L. Pereira and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2020, 16, 1693–1699, doi:10.3762/bjoc.16.140

• vaccines. The serotype 9V is part of the currently marketed conjugate vaccine and contains an acetate modification. To better understand the importance of glycan modifications in general and acetylation in particular, defined oligosaccharide antigens are needed for serological and immunological studies

• escape the host immune response [1][7]. These polysaccharides of SP consist of repeating units (RU) that range from di- to heptasaccharides that may be branched and/or charged [8]. Modifications such as O-acetylation, phosphorylation, and sulfation further increase CPS complexity. Many bacterial

• polysaccharides are O-acetylated [9][10]. Especially SP serotypes, such as 9 (A, V) and 18C differ in O-acetylation. Two O-acetylated serotypes (9V and 18C) are part of the commercial vaccine Prevnar® 13. The traditional CPS isolation approach produces varying length CPS with different degrees of acetylation. An

Azidophosphonium salt-directed chemoselective synthesis of (E)/(Z)-cinnamyl-1H-triazoles and regiospecific access to bromomethylcoumarins from Morita–Baylis–Hillman adducts

• Soundararajan Karthikeyan,
• Radha Krishnan Shobana,
• Kamarajapurathu Raju Subimol,
• J. Helen Ratna Monica and
• Ayyanoth Karthik Krishna Kumar

Beilstein J. Org. Chem. 2020, 16, 1579–1587, doi:10.3762/bjoc.16.130

• ) acetylation, (ii) azidation, and (iii) cycloaddition to produce IV–VIII. In spite of the broad scope and synthetic utility, it is evident that the multistep synthetic methodology is the only existing module for cycloaddition reactions. Our research group is focused on developing one-pot synthetic

Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

Efficient synthesis of piperazinyl amides of 18β-glycyrrhetinic acid

• Dong Cai,
• ZhiHua Zhang,
• Yufan Meng,
• KaiLi Zhu,
• LiYi Chen,
• ChangXiang Yu,
• ChangWei Yu,
• ZiYi Fu,
• DianShen Yang and
• YiXia Gong

Beilstein J. Org. Chem. 2020, 16, 798–808, doi:10.3762/bjoc.16.73

• described in Scheme 1 and Table 1 led us to consider a new approach for preparing the piperazinyl amide 4 (Scheme 2). Two general procedures for the synthesis of compound 8 are documented. One method involves acetylation of 18β-glycyrrhetinic acid, followed by amidation of the resulting ester 2 to give

Combining enyne metathesis with long-established organic transformations: a powerful strategy for the sustainable synthesis of bioactive molecules

• Valerian Dragutan,
• Ileana Dragutan,
• Albert Demonceau and
• Lionel Delaude

Beilstein J. Org. Chem. 2020, 16, 738–755, doi:10.3762/bjoc.16.68

• affording a protected tetracyclic kempane derivative. The latter was further converted into (+)-kempene-2 (14a) in 91% yield by deprotection and acetylation (Scheme 17). A reduction of the intermediate ketone with lithium aluminum hydride followed by an acetylation finally led to (+)-kempene-1 (14b) and

Design and synthesis of diazine-based panobinostat analogues for HDAC8 inhibition

• Sivaraman Balasubramaniam,
• Sajith Vijayan,
• Liam V. Goldman,
• Xavier A. May,
• Kyra Dodson,
• Sweta Adhikari,
• Fatima Rivas,
• Davita L. Watkins and
• Shana V. Stoddard

Beilstein J. Org. Chem. 2020, 16, 628–637, doi:10.3762/bjoc.16.59

• involve acetylation/deacetylation of histone proteins by histone deacetylases (HDACs) [1]. HDACs belong to an important family of enzymes consisting of 18 isozymes. They control protein acetylation, which is a change that occurs after translation. In addition, they regulate gene transcription, cell

• differentiation, cell cycle progression and apoptosis by targeting both histone and non-histone proteins. The balance between acetylation and deacetylation is pivotal for typical cell function. Abnormal or increased HDAC expression has been reported in several human tumors and cancer cell lines [2]. As such, the

Convenient synthesis of the pentasaccharide repeating unit corresponding to the cell wall O-antigen of Escherichia albertii O4

• Tapasi Manna,
• Arin Gucchait and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2020, 16, 106–110, doi:10.3762/bjoc.16.12

• -iodosuccinimide (NIS) and perchloric acid supported over silica (HClO4/SiO2) [28][29] furnished disaccharide derivative 8 in 79% yield, which on de-O-acetylation using sodium methoxide [30] gave the disaccharide acceptor 9 in 95% yield. NMR spectral analysis of compound 9 confirmed its formation with appropriate

• -1C), 5.50 (s, PhCH), 4.79 (d, J = 7.5 Hz, H-1B) in 1H NMR and at δ 103.3 (C-1B), 100.8 (PhCH), 99.0 (C-1A), 97.1 (C-1C) in 13C NMR spectra]. Compound 12 was subjected to a set of reactions consisting of a one-pot [32] de-O-acetylation and benzylation using benzyl bromide and sodium hydroxide in the

• subjected to a sequence of reactions consisting of (i) reductive transformation of the azido group into an acetamido group by the treatment with thioacetic acid [34]; (ii) transformation of the N-phthalimido group into acetamido group using hydrazine hydrate followed by selective N-acetylation [35]; (iii

Starazo triple switches – synthesis of unsymmetrical 1,3,5-tris(arylazo)benzenes

• Andreas H. Heindl and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2020, 16, 22–31, doi:10.3762/bjoc.16.4

• . The azobenzene building block 8, with an unsubstituted phenyl ring and two orthogonal nitrogen substituents in the 3- and 5-position (Scheme 3), was prepared. The synthesis commenced with the acetylation of 3,5-dinitroaniline (4) in 95% yield, followed by the selective reduction of one nitro group

SnCl₄-catalyzed solvent-free acetolysis of 2,7-anhydrosialic acid derivatives

• Kesatebrhan Haile Asressu and
• Cheng-Chung Wang

Beilstein J. Org. Chem. 2019, 15, 2990–2999, doi:10.3762/bjoc.15.295

• -protected hydroxymethyl group-substituted compound 11 in order to increase its reactivity by reducing the steric hinderance and destabilizing effect of the electron-withdrawing carboxy group at the anomeric center (Scheme 2) [35]. This included a LiBH4 reduction in MeOH and THF, followed by acetylation of

• as catalyst under neat conditions, which provided the expected β-ring-opened product 12 in a moderate yield (Table 1, entry 5). This acetolysis reaction resulted in regioselective acetylation of positions O-7 and O-2 in line with the principles of green chemistry. It is known that anomeric acetates

Chemical synthesis of the pentasaccharide repeating unit of the O-specific polysaccharide from Escherichia coli O132 in the form of its 2-aminoethyl glycoside

• Debasish Pal and
• Balaram Mukhopadhyay

Beilstein J. Org. Chem. 2019, 15, 2563–2568, doi:10.3762/bjoc.15.249

• rhamnosyl donor 3 ensured the formation of the desired 1,2-trans glycoside. Peaks at 4.52 ppm (s, 1H, H-1′) in the 1H NMR and at 98.1 (C-1′) in the 13C NMR spectra confirmed the stereochemistry of the newly formed glycosidic linkage. Further, Zemplén de-O-acetylation [14] gave the disaccharide acceptor 5 in

• the target molecule. First, the phthalimido group was removed using ethylenediamine [26] followed by acetylation with Ac2O in the presence of pyridine [27] to furnish the desired acetamido functionality. Next, the benzylidene group was hydrolyzed using 80% AcOH at 80 ºC [28]. Further, Zemplén de-O

• -acetylation using NaOMe in MeOH followed by hydrogenolysis in a ThalesNano continuous flow hydrogenation assembly using a 10% Pd-C cartridge [29]. After three cycles of hydrogenation, formation of the target pentasaccharide 1 was evident from the mass spectrum (Scheme 4). Conclusion In conclusion, the

Synthesis of novel sulfide-based cyclic peptidomimetic analogues to solonamides

• José Brango-Vanegas,
• Luan A. Martinho,
• Lucinda J. Bessa,
• Andreanne G. Vasconcelos,
• Alexandra Plácido,
• Alex L. Pereira,
• José R. S. A. Leite and
• Angelo H. L. Machado

Beilstein J. Org. Chem. 2019, 15, 2544–2551, doi:10.3762/bjoc.15.247

• anhydride to yield 7. Despite the good results for the acetylation of peptides 6 with R = Me at room temperature, the reaction of the ones with R = n-hexyl needed to be conducted under heat conditions (50 °C). Acidic treatment of the acetates 7 with trifluoroacetic acid: triisopropylsilane decoupling

Indium-mediated C-allylation of melibiose

• Christian Denner,
• Manuel Gintner,
• Hanspeter Kählig and
• Walther Schmid

Beilstein J. Org. Chem. 2019, 15, 2458–2464, doi:10.3762/bjoc.15.238

• unprotected elongated disaccharides in the equilibrium of the pyranoid as well as furanoid isomers in both anomeric forms, respectively. Per-O-acetylation has been performed to facilitate separation of the isomeric mixture for structural identification. The main product revealed to adopt a β-pyranoid form of

• rate. Additionally, intense stirring of the reaction mixture thereby preventing indium powder cluster formation (Table 1, entry 7) turned out to be of advantage for the progress of the reaction. After the allylation subsequent per-O-acetylation gave a mixture of respective epimeric products at position

• -acetylation was conducted leading to a mixture of all four species, indicated by NMR analysis (Scheme 3). In the case of 2-syn the β-pyranose species 5-syn-β was obtained as the main product, besides α-pyranose (5-syn-α) as well as both anomers of the furanoid form (Scheme 4). The overall yield obtained over

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

• . The same methodology was applied in the preparation of (2S,3S)-148. β-Amino acids: (+)-Isoserine ((R)-152) was synthesized from the aziridine ester (2R,1'R)-5b in three simple steps (Scheme 39) [92]. Treatment of (2R,1'R)-5b with acetyl chloride led to N-acetylation with concomitant opening of the

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

• ][60]. They have been employed for a number of organic reactions viz., hydrosilylation of aldehydes and ketones, acetylation reactions, redox reactions, oxidative esterification, etc. [61][62][63]. Thus, in concern with increasing demand for sustainable development, a growing number of catalytic