Synthesis and physicochemical evaluation of fluorinated lipopeptide precursors of ligands for microbubble targeting

• Masayori Hagimori,
• Estefanía E. Mendoza-Ortega and
• Marie Pierre Krafft

Beilstein J. Org. Chem. 2021, 17, 511–518, doi:10.3762/bjoc.17.45

• the mixture of HBTU, HOBT, and DIPEA (3 equiv/3 equiv/6 equiv) in DMF were added to the resin and shaken for 30 min. The reaction was monitored using a Kaiser test based on the reaction of ninhydrin. After washing with DMF (3 × 2 mL) and DCM (3 × 2 mL), 25% of acetic anhydride in DCM (2 mL) was added

pH- and concentration-dependent supramolecular self-assembly of a naturally occurring octapeptide

• Goutam Ghosh and
• Gustavo Fernández

Beilstein J. Org. Chem. 2020, 16, 2017–2025, doi:10.3762/bjoc.16.168

• thoroughly washed with DMF. Subsequently, a Kaiser test [23] was performed to monitor the deprotection step. A few resin beads were placed in a small vial and washed with ethanol, and then, two drops of each of the three solutions were added and heated to 100 °C for 4–6 min. The color change of the initially

• procedure was confirmed by a Kaiser test. Several cycles of deprotection, coupling, and washing procedures were repeated until the desired peptide was obtained. The N-terminus of the peptide was acetylated by adding 10 mL of a mixture of acetic anhydride/pyridine/DMF 1:2:3 to the peptidyl resin at room

Synthesis and conformational preferences of short analogues of antifreeze glycopeptides (AFGP)

• Małgorzata Urbańczyk,
• Michał Jewgiński,
• Joanna Krzciuk-Gula,
• Jerzy Góra,
• Rafał Latajka and
• Norbert Sewald

Beilstein J. Org. Chem. 2019, 15, 1581–1591, doi:10.3762/bjoc.15.162

• the resin. After two minutes the diisopropyl azodicarboxylate (DIAD) solution was added dropwise to the reaction mixture. Once the reaction was complete, the o-NBS protecting group was removed by using 2-mercaptoethanol and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). The Kaiser test did not reveal any

Novel solid-phase strategy for the synthesis of ligand-targeted fluorescent-labelled chelating peptide conjugates as a theranostic tool for cancer

• Sagnik Sengupta,
• Mena Asha Krishnan,
• Premansh Dudhe,
• Ramesh B. Reddy,
• Bishnubasu Giri,
• Sudeshna Chattopadhyay and
• Venkatesh Chelvam

Beilstein J. Org. Chem. 2018, 14, 2665–2679, doi:10.3762/bjoc.14.244

• residue. This is unequivocally confirmed by performing the Kaiser test on polypeptide chain 15 which does not turn dark blue after the cleavage of the N10-(trifluoroacetyl) group from the pteroate entity (Scheme 4). The secondary amine of the pteroate core generated in 15 after the cleavage of the N10

• -(trifluoroacetyl) group does not give positive Kaiser test (see Experimental section). Using 2 M aqueous piperidine we successfully cleaved the Tfa protecting group from the side chain of 15 to give a polypeptide chain 16 that is still intact with the resin. The successful cleavage of the Tfa group from the lysine

• side chain is confirmed by performing the Kaiser test on resin beads containing polypeptide chain 16 which turned dark blue. The free ε-amino group thus liberated was covalently attached to the fluorescent tag such as tetraethylrhodamine B by standard peptide bond formation chemistry. Protecting groups

Design and biological characterization of novel cell-penetrating peptides preferentially targeting cell nuclei and subnuclear regions

• Anja Gronewold,
• Mareike Horn and
• Ines Neundorf

Beilstein J. Org. Chem. 2018, 14, 1378–1388, doi:10.3762/bjoc.14.116

• rt as described previously [20]. CF-polymers were cleaved by treatment with 20% piperidine for 45 min. The successful coupling was verified by a Kaiser test [43]. To cleave the peptides from the resin, a mixture of triisopropylsilane (TIS), H2O and concentrated trifluoroacetic acid (TFA) (1:1:38 v/v

Synthesis of nanodiamond derivatives carrying amino functions and quantification by a modified Kaiser test

• Gerald Jarre,
• Steffen Heyer,
• Elisabeth Memmel,
• Thomas Meinhardt and
• Anke Krueger

Beilstein J. Org. Chem. 2014, 10, 2729–2737, doi:10.3762/bjoc.10.288

• ]pyrimidine derivatives. For the quantification of primary amino groups a modified photometric assay based on the Kaiser test has been developed and validated for different types of aminated nanodiamond. The results correspond well to values obtained by thermogravimetry. The method represents an alternative

• wet-chemical quantification method in cases where other techniques like elemental analysis fail due to unfavourable combustion behaviour of the analyte or other impediments. Keywords: amino groups; carbon nanomaterials; Diels–Alder reaction; Kaiser test; nanodiamond; pyrazine; Introduction Surface

• (0.60 mmol g−1) is corroborated by the value obtained in the modified Kaiser test (see below). The reduction of the nitrile groups has an important influence on the colloidal stability of the ND conjugate. Whereas the nitrile derivate 4 is soluble in rather nonpolar organic solvents, the amino derivate

Multivalent display of the antimicrobial peptides BP100 and BP143

• Imma Güell,
• Rafael Ferre,
• Kasper K. Sørensen,
• Esther Badosa,
• Iteng Ng-Choi,
• Emilio Montesinos,
• Eduard Bardají,
• Lidia Feliu,
• Knud J. Jensen and
• Marta Planas

Beilstein J. Org. Chem. 2012, 8, 2106–2117, doi:10.3762/bjoc.8.237

• (Oxyma) (4 equiv), N,N′-diisopropylcarbodiimide (DIPCDI) (4 equiv) in DMF at room temperature for 1 h. The completion of the reactions was monitored by the Kaiser test. Fmoc group removal was achieved with piperidine/DMF (3:7, 1 × 2 min + 1 × 10 min). After each coupling and deprotection step, the resin

Investigation of the network of preferred interactions in an artificial coiled-coil association using the peptide array technique

• Raheleh Rezaei Araghi,
• Carsten C. Mahrenholz,
• Rudolf Volkmer and
• Beate Koksch

Beilstein J. Org. Chem. 2012, 8, 640–649, doi:10.3762/bjoc.8.71

• -residues to twofold for the first and onefold for the second coupling. The completion of these couplings was indicated by a negative Kaiser test. Prior to each deprotection step, capping of the possibly nonacylated N-termini was carried out by treatment with 10% acetic anhydride and 10% DIEA in DMF (3 × 10

A practical synthesis of the ¹³C/¹⁵N- labelled tripeptide N-formyl- Met-Leu-Phe, useful as a reference in solid- state NMR spectroscopy

• Sven T. Breitung,
• Jakob J. Lopez,
• Gerd Dürner,
• Clemens Glaubitz,
• Michael W. Göbel and
• Marcel Suhartono

Beilstein J. Org. Chem. 2008, 4, No. 35, doi:10.3762/bjoc.4.35

• ]. Quantitative conversion in each reaction was monitored by the Kaiser test [16][17]. The resulting tripeptide 4 was formylated under mild conditions with 13C-labelled ethyl formate to obtain 5 [18]. The main advantage of using ethyl formate is the possibility of re-isolation of the expensive 13C-labelled

• /15N-labelled Fmoc-Leu-OH (250 mg, 0.69 mmol), HOBt*H2O (145 mg, 0.945 mmol) and DIC (145 µL, 0.945 mmol) in NMP (2.5 mL) was aspirated into the syringe for the next coupling step. After 3 h the resin was washed with NMP (5 ×) and a few beads were tested for quantitative conversion by the Kaiser test

• mmol) and DIC (145 µL, 0.945 mmol) in NMP (2.5 mL). In case of quantitative coupling (Kaiser test), the Fmoc-protecting group was removed and the resin was washed with DMF (5 ×) and CH2Cl2 (5 ×). The beads were dried in the syringe under reduced pressure. Formylation of the N-terminus: For the