Navegando por Autor "Maltha, Célia Regina Álvares"

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Síntese de novos herbicidas derivados do 1, 2a, 4a, 5- tetrametil- 8- oxabiciclo[ 3. 2. 1] oct- 6- en- 3- ona
(Química Nova, 2004-03) Barbosa, Luiz Cláudio de Almeida; Maltha, Célia Regina Álvares; Demuner, Antônio Jacinto; Filomeno, Claudinei Andrade; Silva, Antônio Alberto da
In this paper we report the synthesis of biologically active compounds through a [3+4] cycloaddition reaction to produce the main frame structure, followed by several conventional transformations. The 1,2a,4a,5-tetramethyl-8-oxabicyclo[3.2.1]oct-6-en-3-one (11) obtained from a [3+4] cycloaddition reaction was converted into 1,2a,4a,5-tetramethyl-6,7-exo-isopropylidenedioxi-8 -oxabicyclo[3.2.1]octan-3-one (13) in 46% yield. This was further converted into the alcohols 1,2a,4a,5-tetramethyl-6,7-exo-isopropylidenedioxi-8-oxabicyclo[3.2.1]octan-3 a-ol (14), 1,2a,4a,5-tetramethyl-6,7-exo-isopropylidenedioxi-8 -oxabicyclo[3.2.1]octan-3b-ol (15), 1,2a,4a,5-tetramethyl-3-butyl-6,7-exo-isopropylidenedioxi-8-oxabicyclo[3.2.1]octan-3 a-ol (17), 1,2a,4a,5-tetramethyl-3-hexyl-6,7-exo-isopropylidenedioxi-8-oxabicyclo[3.2.1]octan-3 a-ol (18) and 1,2a,4a,5-tetramethyl-3-decyl-6,7-exo-isopropylidenedioxi-8-oxabicyclo[3.2.1]octan-3 a-ol (19). Dehydration of 17, 18 and 19 with thionyl chloride in pyridine resulted in the alkenes 20, 21 and 22 in ca. 82% - 89% yields from starting alcohols. The herbicidal activity of the compounds synthesized was evaluated at a concentration of 100 µg g-1. The most active compound was 21 causing 42,7% inhibition against Cucumis sativus L.
Síntese e avaliação da atividade fitotóxica de lactonas derivadas do 2, 4- dimetil- 8- oxabiciclo[ 3. 2. 1]- oct- 6- en- 3- ona
(Química Nova, 2002-04) Barbosa, Luiz Cláudio de Almeida; Maltha, Célia Regina Álvares; Borges, Eduardo Euclides Lima
The alkene 2,4-dimethyl-8-oxabicyclo[3.2.1]-oct-6-en-3-one (3) was converted to 1,3,10-trimethyl-8-oxabicyclo[5.3.0]-dec-3-ene-2,9-dione (7) and 1,3-dimethyl-8-oxabicyclo[5.3.0]-dec-3-ene-2,9-dione (8) with a 55% overall yield in both cases. Lactones (7) and (8) were converted in two steps to 1,3,4-trimethyl-13-methylene-6-oxatricyclo[8.3.0.0 3,7]-trideca-2,5,12-trione (12) (63%) and 1,3-dimethyl-13-methylene-6-oxatricycle[8.3.0.0 3,7]-trideca-2,5,12-trione (13) (45% from 8). The effect of lactones (7), (8), (12), (13) and the intermediates (5) and (6), at the concentration of 250 mg mL-1, on the growth of Cucumis sativus L. and Sorghum bicolor L. was evaluated. The best results were observed for lactone (13) that caused 100% inhibition on the root growth of C. sativus and lactone (12) that inhibited 90% of the root growth for S. bicolor.
Síntese e avaliação da atividade fitotóxica de novos análogos oxigenados do ácido helmintospórico
(Química Nova, 2003-09) Barbosa, Luiz Cláudio de Almeida; Demuner, Antônio Jacinto; Maltha, Célia Regina Álvares; Silva, Patrícia Silvana da; Silva, Antônio Alberto da
Several compounds related to helminthosporic acid (3) were synthesized via the [3+4] cycloaddition. The reaction of 3-hydroxymethyl-2-methylfuran (12) with 1,1,3,3-tetrabromo-4-methylpentan-2-one (13) resulted in 7-hydroxymethyl-4a-isopropyl-1a-methyl-8-oxabicyclo[3.2.1]oct-6-en-3-one (8) (37%) and 7-hydroxymethyl-2a-isopropyl-1a-methyl-8-oxabicyclo[3.2.1]oct-6-en-3-one (14) (12%), which were converted into 7-formyl-4a-isopropyl-1a-methyl-8-oxabicyclo[3.2.1]oct-6-en-3-one (16) (32% from 8) and 7-formyl-2a-isopropyl-1a-methyl-8-oxabicyclo[3.2.1]oct-6-en-3-one (18) (40% from 14), respectively. Reduction of (8) resulted in 7-hydroxymethyl-4a-isopropyl-1a-methyl-8-oxabicyclo[3.2.1]oct-6 -en-3a-ol (11) (63% from 8) and 7-hydroxymethyl-4a-isopropyl-1a-methyl-8-oxabicyclo[3.2.1]oct-6-en-3 b-ol (15) (30% from 8). The 4a-isopropyl-1a-methyl-3-oxo-8-oxabicyclo[3.2.1]oct-6-en-7-oic acid (19) was obtained by oxidation of (16) (78%). The results of biological tests are described in details. The best result was observed for compound (15) that caused 76% inhibition on the root growth of D. tortuosum.