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Item Síntese e atividade fitotóxica de 2- fenil- 6, 7- exo- isopropilidenodioxi- 8- oxabiciclo [ 3. 2. 1] oct- 2- eno(Química Nova, 2000-07) Barbosa, Luiz Cláudio A.; Demuner, Antônio J.; Costa, Adilson V.; Borges, Eduardo E. L.; Mann, JohnSynthesis and phytotoxic activity of 2-Phenyl-6,7-exo isopropylidenedioxi-8-oxabicyclo[3.2.1]oct-2-ene.The [3+4] cycloaddition between furan and the oxyallyl cation generated from 1-bromo-1-phenylpropan-2-one (4), resulted in the formation of 2-phenyl-8-oxabicyclo[3.2.1]oct-6-en-3-one (5) in 30% yield. This compound was further converted into 2-phenyl-6,7-exo-isopropylidenedioxi-8-oxabicyclo[3.2.1]oct-2-ene (13) in 35.4% yield. The selective effect of compound (13) and its isomer 3-phenyl-6,7-exo-isopropylidenedioxi-8-oxabicyclo[3.2.1]oct -2-ene (1a) on the radicle growth of Sorghum bicolor L. (sorghum) and Cucumis sativus L. (cucumber) were evaluated. For both plants, compound 13 showed to be more potent than its isomer 1a.Item 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 daIn 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.Item Síntese de novas fitotoxinas derivadas do 8- oxabiciclo[ 3. 2. 1] oct- 6- en- 3- ona(Química Nova, 2005-05) Barbosa, Luiz C. A.; Maltha, Célia R. A.; Demuner, Antônio J.; Ganen, Flávia R.; Silva, Antônio A. daThe [4+3] cycloaddition was utilized in order to prepare 8-oxabicyclo[3.2.1]oct-6-en-3-one (1) derivatives. The correspondent acetonide 6 was converted into several alcohols (11-16). Addition of aryllithium reagents to 6 resulted in 3-(2-fluorophenyl)-6,7-exo-isopropylidenedioxy -8-oxabicyclo[3.2.1]octan-3a-ol (11, 72%) and 3-(2,4-dimethoxyphenyl)-6,7-exo-isopropylidenedioxy-8-oxabicyclo[3.2.1]octan -3a-ol (16, 20%). The 3-butyl-6,7-exo-isopropylidenedioxy-8-oxabicyclo[3.2.1]octan-3 a-ol (15, 56%) was obtained through a Grignard reaction. Reduction of 6 resulted in 6,7-exo-isopropylidenedioxy-8-oxabicyclo[3.2.1]octan-3 b-ol (7, 62%) and 6,7-exo-isopropylidenedioxy-8-oxabicyclo[3.2.1]octan-3 a-ol (8, 20%). The alcohols were treated with thionyl chloride in pyridine, and the corresponding alkenes were obtained with 31-80% yield. The effect of these compounds on the development of radicle and aerial parts of Sorghum bicolor was evaluated.Item Preparation and phytotoxicity of sorgoleone analogues(Química Nova, 2001-11) Barbosa, Luiz Cláudio de Almeida; Ferreira, Maria Lúcia; Demuner, Antonio Jacinto; Silva, Antonio Alberto da; Pereira, Rita de Cássia3,5-Dimethoxybenzylic alcohol was converted into the 2-acetoxy-5-methoxy-3-(pent-1-yl)-1,4-benzoquinone (12), in seven steps, with an overall yield of 14.6%. The natural quinone sorgoleone (1) was isolated from Sorghum bicolor and converted into the corresponding quinone (13) having a saturated side chain. The selective effects of these compounds (1, 12 and 13), at the dose of 5.6 mg of a.i./ g of substrate, on the growth of Cucumis sativus, Lactuca sativa, Desmodium tortuosum, Hyptis suaveolens and Euphorbia heterophylla were evaluated. All three compounds caused some inhibition on the root growth of the test plants (0.0-69.19%) with the aerial parts less affected. The results showed that the triene unit of the sorgoleone side chain is not essential for the phytotoxicity and also the synthetic quinone was as active as the natural product.Item 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 daSeveral 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.Item 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 LimaThe 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.Item Synthesis of new aliphatic and aromatic phytotoxic derivatives of 2α, 4α-dimethyl-8-oxabicyclo[3.2.1]oct-6-en-3-one(Pest Management Science, 2003-06-11) Barbosa, Luiz C de A; Alvarenga, Elson S de; Demuner, Antônio J; Figueiredo, Remilson; Silva, Antônio A daSeveral new compounds with potential herbicidal activity were synthesized from 2α,4α-dimethyl-6,7-exo-isopropylidenedioxy-8-oxabicyclo[3.2.1]octan-3-one (4). Seven aromatic alcohols were prepared by reaction of (4) with aryllithium reagents, where the aryl groups were 4-ethoxyphenyl (5, 70% yield), 4-ethylphenyl (6, 82% yield), 4-butylphenyl (7, 78% yield), 4-tert-butylphenyl (8, 81% yield), 2,4-dimethoxyphenyl (9, 75% yield), 2-ethylphenyl (10, 12% yield) and para-(4-bromophenoxy)phenyl (11, 24% yield). Reaction of the acetonide (4) with Grignard reagents formed also four aliphatic alcohols where the alkyl groups are ethyl (13, 78%), butyl (14, 85%), hexyl (15, 81%) and octyl (25, 92%). The alcohols (5), (6), (7), (8), (13), (14), (15) and (25) were reacted with thionyl chloride in pyridine, forming their respective alkenes (17, 76%), (18, 74%), (19, 83%), (20, 73%), (22, 78%), (26, 62%), (23, 77%) and (24, 66%). The effect of these compounds, at the concentration of 5.5 µg g−1, on the development of radicle and aerial parts of Sorghum bicolor (L) Moench, Euphorbia heterophylla L, Brachiaria decumbens and Desmodium tortuosum DC was evaluated.