Carbohydrate PEGylation, an approach to improve pharmacological potency

• M. Eugenia Giorgi,
• Rosalía Agusti and
• Rosa M. de Lederkremer

Beilstein J. Org. Chem. 2014, 10, 1433–1444, doi:10.3762/bjoc.10.147

• imine (Schiff base), which was subsequently reduced to PEG-g-chitosan with sodium cyanoborohydride [55], allowing retention of net charge. PEGylation can also be accomplished by condensation of the free amino groups with activated PEGs, such as PEG-NHS or PEG-p-nitrophenyl carbonate, converting the

Organobase-catalyzed three-component reactions for the synthesis of 4H-2-aminopyrans, condensed pyrans and polysubstituted benzenes

• Moustafa Sherief Moustafa,
• Saleh Mohammed Al-Mousawi,
• Maghraby Ali Selim,
• Ahmed Mohamed Mosallam and
• Mohamed Hilmy Elnagdi

Beilstein J. Org. Chem. 2014, 10, 141–149, doi:10.3762/bjoc.10.11

• then reacts with 7a to form the enamino ester 8a. Hydrolysis of 8a followed by cyclization affords 9 in 85% yield. The structure of 9 was unambiguously assigned by X-ray crystallographic methods (Figure 1). In contrast, we found that the p-nitrophenyl-substituted analogue 7b reacts with ethyl

Synthesis and testing of the first azobenzene mannobioside as photoswitchable ligand for the bacterial lectin FimH

• Vijayanand Chandrasekaran,
• Katharina Kolbe,
• Femke Beiroth and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2013, 9, 223–233, doi:10.3762/bjoc.9.26

• . The determined IC50 values were referenced to the inhibitory potency of methyl α-D-mannoside (MeMan) and p-nitrophenyl α-D-mannoside (pNPMan), respectively, each tested on the same plate. Thus, relative inhibitory potencies (RIP values) were obtained, which allow comparison of inhibitory potencies of

• p-nitrophenyl α-D-mannoside (pNPMan). This result can be rationalised by computer docking, showing that regardless of the configuration of the N=N double bond of the azobenzene moiety in 2, favourable interactions can be formed with the tyrosine gate of the FimH CRD. While the terminal mannoside

Facile synthesis of nitrophenyl 2-acetamido-2-deoxy-α-D-mannopyranosides from ManNAc-oxazoline

• Karel Křenek,
• Petr Šimon,
• Lenka Weignerová,
• Barbora Fliedrová,
• Marek Kuzma and
• Vladimír Křen

Beilstein J. Org. Chem. 2012, 8, 428–432, doi:10.3762/bjoc.8.48

• , Czech Republic 10.3762/bjoc.8.48 Abstract The synthetic procedures for a large-scale preparation of o- and p-nitrophenyl 2-acetamido-2-deoxy-α-D-mannopyranoside are described. The synthetic pathway employs the glycosylation of phenol with ManNAc oxazoline, followed by nitration of the aromatic moiety

• yielding a separable mixture of the o- and p-nitrophenyl derivative in a 2:3 ratio. Keywords: α-ManNAc; glycosidase; glycosylation; nitrophenyl; oxazoline; Introduction Hexosamines are fundamental structural elements and precursors of the peptidoglycan and membrane lipopolysaccharide layer as well as of

• synthesis of ManNAc-containing compounds, as well as the substrates for the hypothetical α-N-acetylmannopyranosidase, are required. This paper describes new robust and effective methods for the synthesis of both o-nitrophenyl 2-acetamido-2-deoxy-α-D-mannopyranoside (7) and p-nitrophenyl 2-acetamido-2-deoxy

A novel high-yield synthesis of aminoacyl p-nitroanilines and aminoacyl 7-amino-4-methylcoumarins: Important synthons for the synthesis of chromogenic/fluorogenic protease substrates

• Xinghua Wu,
• Yu Chen,
• Herve Aloysius and
• Longqin Hu

Beilstein J. Org. Chem. 2011, 7, 1030–1035, doi:10.3762/bjoc.7.117

• condense with p-nitrophenyl isocyanate to form the Nα-protected aminoacyl-pNAs [14]. However, commercially available p-nitrophenyl isocyanate often contains impurities due to degradation during storage; these impurities must be removed before use. In addition, a significant amount of hydantoin by-product

• electron-withdrawing group [18][19][20]. We postulated that the selenocarboxylate/azide amidation could be a good solution to the problem of synthesizing aminoacyl-pNAs and aminoacyl-AMCs. Instead of p-nitroaniline and 7-amino-4-methylcoumarin, p-nitrophenyl azide and 7-azido-4-methylcoumarin would be used

• Table 1 and Table 2, through the reaction of N-hydroxysuccinimide (HOSu)-activated esters or mixed anhydrides of Nα-protected amino acids with sodium hydrogen selenide to form their corresponding Nα-protected amino selenocarboxylate, followed by the coupling of the selenocarboxylate with p-nitrophenyl

En route to photoaffinity labeling of the bacterial lectin FimH

• Thisbe K. Lindhorst,
• Michaela Märten,
• Andreas Fuchs and
• Stefan D. Knight

Beilstein J. Org. Chem. 2010, 6, 810–822, doi:10.3762/bjoc.6.91

• the second case, a closed-gate conformation of FimH was used for the modeling [8]. This led to somewhat different predictions, as expected, however, the same trends were revealed for ligands 1–3 and 5 in comparison with the well-known standard ligands methyl α-D-mannoside (MeMan) and p-nitrophenyl α-D

Aromatic and heterocyclic perfluoroalkyl sulfides. Methods of preparation

• Vladimir N. Boiko

Beilstein J. Org. Chem. 2010, 6, 880–921, doi:10.3762/bjoc.6.88

Kinetic studies and predictions on the hydrolysis and aminolysis of esters of 2-S-phosphorylacetates

• Milena Trmčić and
• David R. W. Hodgson

Beilstein J. Org. Chem. 2010, 6, 732–741, doi:10.3762/bjoc.6.87

• shortfalls, 2-S-(5′-thiophosphoryluridine)acetic acid esters were prepared using p-nitrophenyl bromoacetate or m-nitrophenyl bromoacetate in combination with uridine-5′-monophosphorothioate. Kinetics of hydrolysis and aminolysis of the resulting p- and m-nitrophenyl 2-S-(5′-thiophosphoryluridine)acetates

• experimental measurements over a range of different buffer concentrations, to zero buffer concentration. The fact that little general base assistance was observed is in line with observations of reactions between p-nitrophenyl acetate and other relatively non-basic amines [3]. Surprisingly, no evidence for

• , where The pseudo first order rate coefficients, k0, for water-promoted hydrolyses of p-nitrophenyl ester 7 (R = pNP) and m-nitrophenyl ester 7 (R = mNP) were 1.8 × 10−3 min−1 and 1.1 × 10−3 min−1, respectively. The second order rate coefficients for hydroxide-promoted hydrolyses, kOH, for these species

Shelf-stable electrophilic trifluoromethylating reagents: A brief historical perspective

• Norio Shibata,
• Andrej Matsnev and
• Dominique Cahard

Beilstein J. Org. Chem. 2010, 6, No. 65, doi:10.3762/bjoc.6.65

• ). Interestingly, the method was developed for the synthesis of heteroaromatic diarylsulfonium salts. Thus, p-nitrophenyl trifluoromethyl sulfide was reacted first with xenon difluoride in the absence of solvent and then with boron trifluoride. The addition of an electron-rich heterocycle gave products 28 and 29

Chemical synthesis using enzymatically generated building units for construction of the human milk pentasaccharides sialyllacto-N-tetraose and sialyllacto-N-neotetraose epimer

• Dirk Schmidt and
• Joachim Thiem

Beilstein J. Org. Chem. 2010, 6, No. 18, doi:10.3762/bjoc.6.18

• p-nitrophenyl β-galactopyranoside and β-galactosidase (Bovin testes). The subsequent transsialylation was carried out with p-nitrophenyl sialoside (pNp-αNeu5Ac) and either sialidase from Salmonella typhimurium or from Newcastle disease virus [7]. Recently, a more effective higher yielding transfer

• a down field shifted doublet for H-4′ at δ 5.37 (J3′4′ = 2.9 Hz). A similar approach was employed for the synthesis of the protected epimer of sialyllacto-N-neotetraose 14. β-Galactosylation of 2-azidothioglucoside with p-nitrophenyl β-galactopyranoside and β-galactosidase (Bacillus circulans) gave

The Elbs and Boyland- Sims peroxydisulfate oxidations

• E. J. Behrman

Beilstein J. Org. Chem. 2006, 2, No. 22, doi:10.1186/1860-5397-2-22

• , although they obtained evidence for a peroxide, isolated only phenol (in substantial yield). Heller and Weiler [18] investigated a more stable analog, namely p-nitrophenyl hydroperoxide formed by ipso displacement of a nitro group from p-dinitrobenzene by the hydrogen peroxide anion.p-Nitrophenyl

Asymmetric aza-Diels- Alder reaction of Danishefsky's diene with imines in a chiral reaction medium

• Bruce Pégot,
• Olivier Nguyen Van Buu,
• Didier Gori and
• Giang Vo-Thanh

Beilstein J. Org. Chem. 2006, 2, No. 18, doi:10.1186/1860-5397-2-18

• was observed in the case of p-nitrophenyl (Table 3, entry 4, R = p-NO2C6H4,). This is due to hydrogen bond formation between the OH group of the chiral ionic liquid and the NO2 function of the substrate. A similar decrease in asymmetric induction was observed by our group in the mechanistically