Menadione: a platform and a target to valuable compounds synthesis

• Acácio S. de Souza,
• Ruan Carlos B. Ribeiro,
• Dora C. S. Costa,
• Fernanda P. Pauli,
• David R. Pinho,
• Matheus G. de Moraes,
• Fernando de C. da Silva,
• Luana da S. M. Forezi and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43

Natural dolomitic limestone-catalyzed synthesis of benzimidazoles, dihydropyrimidinones, and highly substituted pyridines under ultrasound irradiation

• Kumar Godugu,
• Venkata Divya Sri Yadala,
• Mohammad Khaja Mohinuddin Pinjari,
• Trivikram Reddy Gundala,
• Lakshmi Reddy Sanapareddy and
• Chinna Gangi Reddy Nallagondu

Beilstein J. Org. Chem. 2020, 16, 1881–1900, doi:10.3762/bjoc.16.156

• –proline, trimethylsilyl chloride (TMSCl), Amberlite® IR-120, indion 190, trifluoroethanol, YCl3, HClO4–SiO2, MMZY zeolite, Er(OTf)3, etc. [22][23][24][25][26][27][28][29][30]. Developments in already established multicomponent reactions (MCRs) are interesting topics in organic synthesis. For instance, the

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

• glycosylations followed by in situ removal of the PMB group in one pot. The stereochemical outcome of the newly formed glycosidic linkages was excellent using thioglycoside derivatives as glycosyl donors and a combination of N-iodosuccinimide (NIS) and perchloric acid supported on silica (HClO4-SiO2) as the

• glycosyl activator. Keywords: Azospirillum doebereinerae; glycosylation; HClO4-SiO2; O-polysaccharide; tetrasaccharide; Introduction The development of plant-growth-promoting agents has become an attractive area of research in the agricultural sciences to reduce the need for chemical fertilizers, which

• on silica (HClO4-SiO2) [31][32]. HClO4-SiO2 was used as a noncorrosive solid acid in the glycosylation reactions. The selection of functional groups and their post-glycosylation modifications led to the formation of partially O-acetylated tetrasaccharide 1, as found in the naturally isolated

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

• corresponding to the cell wall O-antigen of the Escherichia albertii O4 strain in very good yield with the desired configuration at the glycosidic linkages using thioglycosides and trichloroacetimidate derivatives as glycosyl donors and perchloric acid supported over silica (HClO4/SiO2) as a solid supported

• protic acid glycosyl activator. The expected configuration at the glycosidic linkages was achieved using a reasonable selection of protecting groups in the manosaccharide intermediates. Keywords: Escherichia albertii O4; glycosylation; HClO4/SiO2; O-antigen; pentasaccharide; Introduction Diarrheal

• -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

Robust perfluorophenylboronic acid-catalyzed stereoselective synthesis of 2,3-unsaturated O-, C-, N- and S-linked glycosides

• Madhu Babu Tatina,
• Xia Mengxin,
• Rao Peilin and
• Zaher M. A. Judeh

Beilstein J. Org. Chem. 2019, 15, 1275–1280, doi:10.3762/bjoc.15.125

• yields and selectivities are similar to those reported using HClO4·SiO2 [33]. Based on the excellent results obtained with the reactions of glucals 1a and 4a with O-, C-, N-, S-nucleophiles, we further extended the scope of this reaction to 3,4-di-O-acetyl-L-rhamnal (6a, Figure 3). As a demonstration

Mannich base-connected syntheses mediated by ortho-quinone methides

• Petra Barta,
• Ferenc Fülöp and
• István Szatmári

Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43

• ], silica-supported perchloric acid (HClO4-SiO2) [34][35][36] and sulfuric acid [35], chlorosulfonic acid [38], sodium hydrogen sulfate (NaHSO4·H2O) [39], ferric(III) hydrogen sulfate [Fe(HSO4)3; 40], strontium(II) triflate, Sr(OTf)2; [41], copper-exchanged heteropoly acids, Cu1·5PMo12O40 (CuPMo) and Cu1

Selective and eco-friendly procedures for the synthesis of benzimidazole derivatives. The role of the Er(OTf)₃ catalyst in the reaction selectivity

• Natividad Herrera Cano,
• Jorge G. Uranga,
• Mónica Nardi,
• Antonio Procopio,
• Daniel A. Wunderlin and
• Ana N. Santiago

Beilstein J. Org. Chem. 2016, 12, 2410–2419, doi:10.3762/bjoc.12.235

• hexafluorophosphate ion (PHP) [15], perchloric acid adsorbed on silica gel (HClO4–SiO2) [16], polystyrene sulfonic acid [34], HSO3Cl in 2-propanol [35], trimethylsilyl chloride (TMSCl) [36], or Amberlite (IR-120) [37]. It is worth mentioning that these previously reported catalysts required longer reaction times than

Synthesis of the pentasaccharide repeating unit of the O-antigen of E. coli O117:K98:H4

• Pintu Kumar Mandal

Beilstein J. Org. Chem. 2014, 10, 2724–2728, doi:10.3762/bjoc.10.287

• acid on silica (HClO4/SiO2) [28][29] afforded 3-azidopropyl (2,3-di-O-benzyl-β-D-glucopyranosyl)-(1→4)-2,3,6-tri-O-benzyl-β-D-galactopyranoside (9) in 85% yield. Selective 6-O-benzoylation of compound 9 was accomplished with benzoyl cyanide [30] to furnish disaccharide acceptor 10 in 80% yield

• . Reagents: (a) N-iodosuccinimide (NIS), TMSOTf, CH2Cl2, MS 4 Å, −30 °C, 1 h, 72%; (b) HClO4/SiO2, CH3CN, rt, 20 min, 85%; (c) benzoyl cyanide, DCM/pyridine, rt, 2 h, 80%; (d) N-iodosuccinimide (NIS), TfOH, CH2Cl2, MS 4 Å, −30 °C, 1 h, then 0 °C, 1 h, 77%; (e) NOBF4, Et2O/CH2Cl2 (3:1), −15 °C, 1 h, 75%; (f

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

• , which include (a) stereoselective [2 + 2] block glycosylation; (b) application of general glycosylation reactions by using thioglycosides as glycosyl donors and a combination of N-iodosuccinimide (NIS) and perchloric acid supported over silica (HClO4–SiO2) [17][18] as glycosyl activator; (c

• -benzylidene acetal with triethylsilane and iodine [22] furnished compound 6 in 82% yield. Stereoselective glycosylation of compound 6 with thioglycoside derivative 3 in the presence of a combination of N-iodosuccinimide (NIS) and HClO4–SiO2 [17] gave disaccharide derivative 7 in a 77% yield. Formation of

• -dimethoxypropane and p-toluenesulfonic acid [23] furnished disaccharide derivative 8 in 74% yield (Scheme 1). In a separate experiment, stereoselective glycosylation of thioglycoside derivative 4 with the thioglycoside acceptor 5 in the presence of a combination of NIS and HClO4–SiO2 [17] in dichloromethane

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

• conversion of O-acetyl group to O-benzyl group [22], (iv) activation of glycosyl trichloroacetimidate and thioglycoside donors by perchloric acid supported on silica (HClO4–SiO2) [23][24][25][26], and late stage TEMPO mediated selective oxidation [27][28][29] of the primary hydroxy group to the carboxylic

• silica (HClO4–SiO2) [23][24] as glycosylation activator to give ethyl (3,4,6-tri-O-acetyl-2-azido-2-deoxy-α-D-glucopyranosyl)-(1→3)-2,4-di-O-benzyl-1-thio-α-L-rhamnopyranoside (6) in 81% yield. Stereoselective formation of compound 6 was confirmed from its spectral analysis (presence of signals at δ 5.35

• disaccharide acceptor 2 in the presence of a combination of N-iodosuccinimide (NIS) and HClO4–SiO2 [25][26] furnished tetrasaccharide derivative 8 in 82% yield. Stereoselective formation of new α-glycosyl linkage in compound 8 was confirmed from the 1D and 2D NMR spectral analysis (presence of signals at δ