Antonio Quesada

Cytotoxic halogenated metabolites from the Brazilian red alga Laurencia catarinensis.

Seven new (1-7) and seven previously reported (8-14) halogenated metabolites were isolated from the organic extract of the Brazilian red alga Laurencia catarinensis. The structure elucidation and the assignment of the relative configurations of the new natural products were based on detailed NMR and MS spectroscopic analyses, whereas the structure of metabolite 6 was confirmed by single-crystal X-ray diffraction analysis. The absolute configuration of metabolite 1 was determined using the modified Moshers method. The in vitro cytotoxicity of compounds 1-14 was evaluated against HT29, MCF7, and A431 cell lines.

Dolabellanes with antibacterial activity from the brown alga Dilophus spiralis.

Seventeen diterpenes featuring the dolabellane skeleton (1-17) were isolated from the organic extracts of the brown alga Dilophus spiralis. Seven compounds are new natural products (1, 3, 5, 6, 11, 14, 15) and eight are structurally revised (2, 4, 7-10, 12, 13), among which three are reported for the first time from a natural source (4, 9, 10). The structure elucidation and the assignment of the relative configurations of the isolated natural products were based on detailed analyses of their spectroscopic data. The structure of metabolite 10 was confirmed by single-crystal X-ray diffraction analysis, whereas the absolute configurations of compounds 2, 4-10, 12, and 13 were determined using the modified Moshers method on the semisynthetic product 18 and chemical interconversions. The antibacterial activities of compounds 1-18 were evaluated against six strains of Staphylococcus aureus, including multidrug- and methicillin-resistant variants.

Symmetrically 4,6-disubstituted 2-aminopyrimidines and 2-amino-5-nitrosopyrimidines: interplay of molecular, molecular-electronic and supramolecular structures.

The structures of six symmetrically 4,6-disubstituted 2-aminopyrimidines, four of them containing a 5-nitroso substituent, have been determined. The nitroso compounds, in particular, exhibit polarized molecular-electronic structures leading to extensive charge-assisted hydrogen bonding. The intermolecular interactions observed include hard hydrogen bonds of N-H...N and N-H...O types together with O-H...O and O-H...N types in 2-amino-4,6-bis(2-hydroxyethylamino)-5-nitrosopyrimidine; soft hydrogen bonds of the C-H...O type in both 2-amino-4,6-bis(morpholino)-5-nitrosopyrimidine (3) and 2-amino-4,6-bis(benzylamino)-5-nitrosopyrimidine (4), and of the C-H...pi(arene) type in both 2-amino-4,6-bis(piperidino)pyrimidine (1) and 2-amino-5-nitroso-4,6-bis(3-pyridylmethoxy)pyrimidine (5); and aromatic pi...pi stacking interactions in 2-amino-5-nitroso-4,6-bis(3-pyridylmethoxy)pyrimidine. The supramolecular structures formed by the hard hydrogen bonds are finite, zero-dimensional in (1), one-dimensional in 2-amino-4,6-bis(3-pyridylmethoxy)pyrimidine (2), two-dimensional in both (3) and (4), and three-dimensional in both (5) and 2-amino-4,6-bis(2-hydroxyethylamino)-5-nitrosopyrimidine.

Supramolecular structures of N4-substituted 2,4-diamino-6-benzyloxy-5-nitrosopyrimidines

The molecular and supramolecular structures of eight N(4)-substituted 2,4-diamino-6-benzyloxy-5-nitrosopyrimidines are discussed, along with one analogue containing no nitroso substituent. The nitroso derivatives all exhibit polarized molecular-electronic structures leading to extensive charge-assisted hydrogen bonding between the molecules. The intermolecular interactions include hard hydrogen bonds of N-H...O and N-H...N types, together with O-H...O and O-H...N types in the monohydrate of 2-amino-6-benzyloxy-4-piperidino-5-nitrosopyrimidine, soft hydrogen bonds of C-H...O, C-H...pi(arene) and N-H...pi(arene) types and aromatic pi...pi stacking interactions. The predominant supramolecular structure types take the form of chains and sheets, but no two of the structures determined here exhibit the same combination of hydrogen-bond types.

Potential for use of synthetic sex pheromone for mating disruption of the olive pyralid moth, Euzophera pinguis.

The potential for pheromone-based mating disruption of the olive pyralid moth (OPM), Euzophera pinguis, in olive groves was investigated during the second flight period in small-plot trials in 2002. The female of this species emits a blend of (9Z,12E)-tetradecadien-1-ol and (9Z,12E)-tetradecadienyl acetate, which were synthesized for field tests. Mating disruption efficacy in 0.8-ha trials was evaluated using two parameters: reduction of male capture in pheromone traps and reduction of infestation in infestation-prone sites. White rubber septa containing 10 mg of pheromone blend as disruptant were applied at a density of 50 septa/ha for each treatment. Mean catches of E. pinguis males in pheromone traps were greatly reduced (>95%) in pheromone-treated plots relative to similar traps placed in control plots. In addition, significant reductions were recorded (35–40%) in the oviposition and infestation levels during pheromone treatment. The total amount of pheromone blend released from disruption dispensers during the field trials was estimated to average 5.4 mg/ha/day, over 56 days.

Hydro­gen bonding in 2-amino-4-methoxy-6-methyl­pyrimidine, 2-benzyl­amino-4-benzyl­oxy-6-methyl­pyrimidine and 4-benzyl­amino-2,6-bis­(benzyl­oxy)­pyrimidine: π-stacked chains of fused R22(8) rings, and centrosymmetric R22(8) dimers

Molecules of 2-amino-4-methoxy-6-methylpyrimidine, C(6)H(9)N(3)O, (I), lie on mirror planes in space group Pnma and are linked by two N-H...N hydrogen bonds [H...N = 2.26 and 2.34 A, N...N = 3.136 (2) and 3.212 (2) A, and N-H...N = 175 and 172 degrees ] into chains of edge-fused R(2)(2)(8) rings, which themselves are linked into sheets by aromatic pi-pi-stacking interactions. In 2-benzylamino-4-benzyloxy-6-methylpyrimidine, C(19)H(19)N(3)O, (II), and 4-benzylamino-2,6-bis(benzyloxy)pyrimidine, C(25)H(23)N(3)O(2), (III), the molecules are linked by paired N-H.N hydrogen bonds [H...N = 2.16 A, N.N = 3.039 (2) A and N-H...N = 165 degrees in (II); H...N = 2.15 A, N...N = 2.980 (2) A and N-H...N = 176 degrees in (III)] into centrosymmetric R(2)(2)(8) dimers, with no direction-specific interactions between these dimeric units.

Parnapimarol and Nepetaparnone from Nepeta parnassica

Parnapimarol (1), a new pimarane diterpene, along with nepetaparnone (2) and nepetanudone (3), one new and one previously reported nepetalactone dimer, respectively, were isolated from the dichloromethane extract of the aerial parts of Nepeta parnassica, collected on Mt. Parnassos, Greece. The structures and relative configurations of 1-3 were determined on the basis of their spectroscopic characteristics (1D and 2D NMR, IR, MS). The structure of 2 was confirmed by single-crystal X-ray diffraction analysis. The insecticidal activity of 1-3 against ants and mosquito larvae was also evaluated.

Hydrogen bonding in 2-amino-4,6-dimethoxypyrimidine, 2-benzylamino-4,6-bis(benzyloxy)pyrimidine and 2-amino-4,6-bis(N-pyrrolidino)pyrimidine: chains of fused rings and a centrosymmetric dimer

Molecules of 2-amino-4,6-dimethoxypyrimidine, C(6)H(9)N(3)O(2), (I), are linked by two N-H.N hydrogen bonds [H.N 2.23 and 2.50 A, N.N 3.106 (2) and 3.261 (2) A, and N-H.N 171 and 145 degrees ] into a chain of fused rings, where alternate rings are generated by centres of inversion and twofold rotation axes. Adjacent chains are linked by aromatic pi-pi-stacking interactions to form a three-dimensional framework. In 2-benzylamino-4,6-bis(benzyloxy)pyrimidine, C(25)H(23)N(3)O(2), (II), the molecules are linked into centrosymmetric R(2)(2)(8) dimers by paired N-H.N hydrogen bonds [H.N 2.13 A, N.N 2.997 (2) A and N-H.N 170 degrees ]. Molecules of 2-amino-4,6-bis(N-pyrrolidino)pyrimidine, C(12)H(19)N(5), (III), are linked by two N-H.N hydrogen bonds [H.N 2.34 and 2.38 A, N.N 3.186 (2) and 3.254 (2) A, and N-H.N 163 and 170 degrees ] into a chain of fused rings similar to that in (I).

2-Amino-5-nitro-4,6-dipiperidinopyrimidinium hydrogen­sulfate monohydrate: hydrogen-bonded sheets containing highly distorted cations

In the title compound, C(14)H(23)N(6)O(2)(+) x HSO(4)(-) x H(2)O, the pyrimidinium ring of the cation adopts a twist-boat conformation, induced by steric clashes between adjacent ring substituents; the anions and the water molecules are linked by three O-H.O hydrogen bonds [H...O = 1.70-1.78 A, O...O = 2.548 (2)-2.761 (2) A and O-H...O = 161-168 degrees ] into chains of edge-fused R(4)(4)(12) rings, which are linked into sheets by the cations, via three N-H...O hydrogen bonds [H...O = 1.96-2.17 A, N...O = 2.820 (2)-2.935 (2) A and N-H...O = 145-173 degrees ].

2-Amino-4,6-di­methoxy-5-nitro­so­pyrimidine–water (4/3): seven independent molecular components are linked into a three-dimensional framework by six three-centre and eight two-centre hydrogen bonds

In the title compound, 4C(6)H(8)N(4)O(3).3H(2)O, the pyrimidine molecules all exhibit a polarized molecular electronic structure; the seven-component asymmetric unit can be selected as a closed cyclic aggregate and the linking of these aggregates can be analysed in terms of translational chain motifs running parallel to [110], [210] and [011], which combine to generate a single three-dimensional framework.