Fernando Macedo

Design, syntheses and evaluation of benzoylthioureas as urease inhibitors of agricultural interest

Urea is one of the most used nitrogen fertilizers worldwide. However, occurrence of urea hydrolysis to ammonia and carbon dioxide on soil surface, catalyzed by soil ureases, considerably reduces nitrogen availability to crops. In this study, we describe the design, synthesis and screening of sixty five benzoylthioureas (BTUs) for their ability to inhibit purified jack bean and soil ureases. BTUs were readily obtained in one pot, two steps synthesis with no need of cumbersome procedures for product purification. In vitro assays revealed BTUs 11, 12, 14, 19–22 and 37 as the most active jack bean urease inhibitors. Such BTUs were found to be able to bind to both catalytic and allosteric sites of urease, acting therefore as mixed-type inhibitors. Out of 28 compounds that effectively inhibited soil ureases activity, BTUs 3, 6, 10, 12, 16, 19 and 22 were determined to be more potent than the reference inhibitor N-(butyl) thiophosphoric triamide (NBPT; 40%). The other 22 BTUs were as potent as NBPT on soil ureases. The temperature-tolerance of BTUs, along with their ability to inhibit soil ureases, makes of this class of compounds potential additive for urea-based fertilizers.

3-Benzoyl-1-[4-(methyl­sulfan­yl)phen­yl]thio­urea

The title compound, C15H14N2OS2, adopts a helix conformation. An intramolecular N—H⋯O hydrogen bond leads to a six-membered pseudo-ring [r.m.s. deviation = 0.0212 Å, maximum deviation = 0.033 (1) Å for the N atom bearing the benzoyl group] in the central unit. The benzene and (methylsulfanyl)benzene ring [r.m.s = 0.0028 Å and largest deviation of 0.067 (3) Å for the methylsulfanyl C atom] make dihedral angles of 31.76 (8) and 54.68 (6)°, respectively, with the pseudo-ring plane. The dihedral angle between the benzene rings is 85.71 (8)°. In the crystal, pairs of weak N—H⋯S interactions form inversion dimers and mediate a linear chain along [001].

Synthetic approach towards cuparene-type sesquiterpenes via highly regioselective epoxide opening under acid catalysis

Obtaining cuparene-type sesquiterpenes is a significant synthetic challenge mainly because of the construction of the sterically hindered quaternary centres. We report herein the successful construction of such quaternary moiety by a highly regioselective opening of (+/−)-2,5-dimethoxy-4-methyl-α-methylstyrene oxide by the acetone silyl enol ether catalysed by Lewis acid. Additionally, an efficient epoxidation of the highly activated 2,5-dimethoxy-4-methyl-α-styrene was accomplished by modifications on the dioxirane-promoted epoxidation protocol. Intensive optimisations for both key steps allowed the synthesis of the desired branched homo-aldol adduct, proposed as a key intermediate for a short synthetic alternative towards enokipodins.Graphical abstract

A review on the development of urease inhibitors as antimicrobial agents against pathogenic bacteria

Graphical abstract

Sínteses totais das enoquipodinas

Enokipodins comprises a family of sesquiterpenes isolated from the mushroom Flammulina velutipes. These substances are attractive synthetic targets due to either their biological potential or structural characteristics. Since their isolation, about a decade ago, a considerable number of successful total syntheses have been published. Both via a racemic or enantioselective approach, these studies describe original and creative synthetic routes, particularly concerning the methodology used for constructing the benzylic quaternary center of these natural products. In this brief review, we discuss the reported total synthesis of enokipodins, focusing on the strategy adopted for the quaternary stereogenic center.

rac-5-(1-Methyl­eth­yl)-2-sulfanylidene­imidazolidin-4-one

In the title compound, C6H10N2OS, the 2-sulfanylideneimidazolidin-4-one fragment is essentially planar (r.m.s. deviation = 0.0033 Å). In the crystal, one amino group is involved in N—H⋯O hydrogen bonding, which links pairs of molecules into inversion dimers, while the other amino group generates weak N—H⋯S hydrogen bonds, which link these dimers into chains in [10-1]. The chains are further aggregated into layers parallel to the ac plane through weak C—H⋯O interactions.