Development and mechanistic studies of calcium–BINOL phosphate-catalyzed hydrocyanation of hydrazones

• Carola Tortora,
• Christian A. Fischer,
• Sascha Kohlbauer,
• Alexandru Zamfir,
• Gerd M. Ballmann,
• Jürgen Pahl,
• Sjoerd Harder and
• Svetlana B. Tsogoeva

Beilstein J. Org. Chem. 2025, 21, 755–765, doi:10.3762/bjoc.21.59

• bioactive α-hydrazino acids [46][47][48]. This reaction has also been achieved by a lanthanide–PYBOX complex [49] and through asymmetric transfer hydrocyanation of aldimines with a boron compound [50]. Hence, we reasoned that the enantioselective hydrocyanation of hydrazones might be possible with a calcium

• subsequent step to yield hydrazino nitrile 2 (Table 2) from which α-hydrazino acids could be obtained by harsher hydrolysis conditions. It is important to note that compound 12 also exhibits geometric isomerism (Figure 2 depicts the lower-energy configuration), which arises from the newly formed CN double

• hydrocyanation reaction of hydrazones, towards precursors of α-hydrazino acids. Model achiral catalyst 4, pre-formed by reaction of Ca(OiPr)2 and biphenyl phosphate 3, led to racemic product 2 in nearly full conversion in different reaction times, depending on the amount of catalyst used. Biphenyl phosphate 3

Synthesis of extended fluorinated tripeptides based on the tetrahydropyridazine scaffold

• Thierry Milcent,
• Pascal Retailleau,
• Benoit Crousse and
• Sandrine Ongeri

Beilstein J. Org. Chem. 2024, 20, 3174–3181, doi:10.3762/bjoc.20.262

• synthesis of tripeptides incorporating new fluorinated heterocyclic hydrazino acids, based on the tetrahydropyridazine scaffold is described. Starting from simple fluorinated hydrazones, these non-proteinogenic cyclic β-amino acids were easily prepared by a zinc-catalyzed aza-Barbier reaction followed by an

• intramolecular Michael addition. Preliminary conformational studies on tripeptides including this scaffold in the central position show an extended conformation in solution (NMR) and in the solid state (X-ray). Keywords: fluoroalkyl groups; heterocycles; hydrazino acids; peptides; tetrahydropyridazines

• strategy, the control of the stereoselectivity of the intramolecular aza-Michael addition could be envisaged with various chiral catalysts in further studies. These heterocyclic hydrazino acids, when incorporated into the peptidic structure, appear to confer an extended conformation. These interesting

Synthesis of acylhydrazino-peptomers, a new class of peptidomimetics, by consecutive Ugi and hydrazino-Ugi reactions

• Angélica de Fátima S. Barreto,
• Veronica Alves dos Santos and
• Carlos Kleber Z. Andrade

Beilstein J. Org. Chem. 2016, 12, 2865–2872, doi:10.3762/bjoc.12.285

• -hydrazino acid moiety, e.g., the vitamin B6 antagonist linatine and the antibiotic negamycin (Figure 3). In the early 1970s, the first attempts to peptide modifications by hydrazino acids generated bioactive pseudopeptides [39]. Analogously to azapeptides, these compounds possess a conformational constraint

Approaches towards the synthesis of 5-aminopyrazoles

• Ranjana Aggarwal,
• Vinod Kumar,
• Rajiv Kumar and
• Shiv P. Singh

Beilstein J. Org. Chem. 2011, 7, 179–197, doi:10.3762/bjoc.7.25

• and sodium nitrite in water at 0–5 °C to provide an intermediate diazonium salt. The latter underwent cycloaddition with an isocyanate in a one-pot reaction to give compound 43 (Scheme 10) [41]. 5-Aminopyrazoles 45 have recently been prepared by Boc deprotection of the α-hydrazino acids 44 with TFA in