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

• 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

• , the tetrahydropyridazines, six-atom nitrogenous heterocycles, are found in various bioactive molecules such as influenza virus neuraminidase inhibitors, GABA type A receptor modulators, and regulators of progesterone receptor or cannabinoid CB1 receptor antagonists (Figure 1) [6][7][8][9]. This

• electronic and structural properties of the fluorinated groups (CF3 or CF2H) and the geometric constraints due to its partially unsaturated cycle, which could help in the design of peptidomimetics. To our knowledge, only a few publications report the synthesis of tetrahydropyridazines with a carboxylic acid

Hydrazides in the reaction with hydroxypyrrolines: less nucleophilicity – more diversity

• Dmitrii A. Shabalin,
• Evgeniya E. Ivanova,
• Igor A. Ushakov,
• Elena Yu. Schmidt and
• Boris A. Trofimov

Beilstein J. Org. Chem. 2021, 17, 319–324, doi:10.3762/bjoc.17.29

• synthesis of three types of highly functionalized azaheterocyclic scaffolds (dihydropyridazines, tetrahydropyridazines, and partially saturated tricyclic systems) from readily available hydroxypyrrolines and hydrazides are described. The directions of the transformation of a common initial intermediate

• , namely a Brønsted acid-activated hydroxypyrroline, depend on the reaction conditions and the structure of the hydrazides. Keywords: hydrazides; pyridazines; pyrrolines; recyclization; ring expansion; Introduction Di- and tetrahydropyridazines are valuable heterocyclic motifs which are utilized as key

• followed by the introduction of 140 mol % of TFA and additional reflux for 3 h (Table 1, entry 11). Next, the substrate scope and functional group tolerance of the protocols aimed to the chemoselective synthesis of di- and tetrahydropyridazines were investigated. Several features of the developed methods