ChemInform Abstract: Synthesis Based on Cyclohexadienes. Part 16. Synthesis of Methyl 2,7-Dimethyltricyclo (5.2.2.01,5)undec-5-ene-6-carboxylates

Synthesis of methyl 2, 7-dimethyltricyclo{5.2.2.0(1,5}undec-5-en-6-carboxylates, the tricyclic skeleton present in (+)-allo-cedrol (1) is described using the Diels-Alder strategy. Thus, Birch reduction of the aromatic acid 8 gives 5, the methyl ester of which is isomerised with DBU to a 1:1 mixture of the dienes 6 and 4. Cycloaddition of this mixture with 2-chloroacrylonitrile followed by hydrolysis yields the ketone 60 having the tricyclo{5.2.2.0(1.5)}undec-5-ene framework. Similar reaction with methyl vinyl ketone affords the regioisomeric adducts 61 and 62.

Effect of ester chemical structure and peptide bond conformation in fragmentation pathways of differently metal cationized cyclodepsipeptides

Fragmentation behavior of two classes of cyclodepsipeptides, isariins and isaridins, obtained from the fungus Isaria, was investigated in the presence of different metal ions using multistage tandem mass spectrometry (MS(n)) with collision induced dissociation (CID) and validated by NMR spectroscopy. During MS(n) process, both protonated and metal-cationized isariins generated product ions belonging to the identical `b-ion' series, exhibiting initial backbone cleavage explicitly at the beta-ester bond. Fragmentation behavior for the protonated and metal-cationized acyclic methyl ester derivative of isariins was very similar. On the contrary, isaridins during fragmentation produced ions belonging to the `b' or/and the `y' ion series depending on the nature of interacting metal ions, due to initial backbone cleavages at the beta-ester linkage or/and at a specific amide linkage. Interestingly, independent of the nature of the interacting metal ions, the product ions formed from the acyclic methyl ester derivative of isaridins belonged only to the `y-type'. Complementary NMR data showed that, while all metal ions were located around the beta-ester group of isariins, the metal ion interacting sites varied across the backbone for isaridins. Combined MS and NMR data suggest that the different behavior in sequence specific charge-driven fragmentation of isariins and isaridins is predetermined because of the constituent beta-hydroxy acid residue in isariins and the cis peptide bond in isaridins.

具有环氧化酶-2选择性抑制活性的多取代蒽醌的合成

1-甲基-2-甲氧羰基-3, 6, 8-三羟基-7-甲氧基蒽醌是从唐菖蒲干球茎中分离到的具有环氧化酶-2选择性抑制活性的多取代蒽醌类化合物。本文试图合成该化合物，实现了其类似物的合成，同时发现了几个未见报道的反应。 1．通过Diels-Alder 反应合成了关键中间体——3-甲基-5-羟基-1, 2, 4-苯三甲酸三甲酯，1-COOMe选择性水解产物与1, 2, 3-三甲氧基苯进行分子间Friedel-Crafts反应的产物再进行分子内Friedel-Crafts反应得到了目标产物的类似物1-甲基-2-甲氧羰基-3-羟基-6，7，8-三甲氧基蒽醌（路线1）。目标产物及其它类似物的合成正在进行中。 2．以乙酰乙酸甲酯和巴豆醛为原料，经过Michael加成、分子内的Aldol反应、芳香化、选择性甲酰化和还原反应，得到关键中间体2-甲基-3-羟甲基-6-甲氧基苯甲酸甲酯及其衍生物。通过该化合物与3，4，5-三甲氧基苯甲酸甲酯进行Friedel-Crafts烷基化反应得到了多取代的二苯基甲烷衍生物，拟进一步关环合成目标化合物（路线2）。 3．发现邻甲氧基苯甲酸甲酯中酯甲基可以被正丁基锂和仲丁基锂中烷基交换生成相应的酯，反应的机理不明确。当使用叔丁基锂时，得到的是邻甲氧基苯基叔丁酮，这个方法可以用来合成芳基叔丁酮类化合物。 4．以2-苄氧基-6-甲基苯甲酸甲酯为原料进行氯甲基化反应时，以苯和二氯乙烷作溶剂，发生了苄基的迁移和芳环的偶联，分别得到2，2'-二甲基-3，3'-二甲氧羰基-4，4'-二羟基联苯和2，2'-二甲基-3，3'-二甲氧羰基-4，4'-二羟基-5，5'-二苄基联苯。这是对称联苯合成的新方法。 5．水杨酸羟基邻对位的选择性甲酰化可以分别通过水杨酸和水杨酸甲酯用HMTA/CF3COOH来实现。 6．Lewis酸催化3，4，5-三甲氧基苄醇环化成1, 2, 3, 6, 7, 8, 11, 12, 13-nonamethoxyl-10,15-dihydro-5H-trbibenzo [a, d, g] cyclononene (NDTC)，产率(54%)高于已有方法（12%）。 Methyl 3,6,8-trihydroxy-7-methoxy-1-methylanthraquinone-2-carboxylate is a new COX-2 selective inhibitor isolated from Gladiolus gandavensis. Two strategies were investigated to synthesis this compound, in which some important reactions were discovered. 1. The key intermediate 5-hydroxy-3-methylbenzene-1,2,4-tricarboxylic acid 2,4-dimethyl ester was prepared via Diels-Alder reaction followed by selective hydrolysis of 1-COOMe. This compound was coupled with 1,2,3-trimethoxybenzene and the product undergo intramolecular Friedel-Crafts reaction to give methyl 3-hydroxy-5,6,7-trimethoxy-1-methylanthraquinone-2-carboxylate (1st route). The target compound and other analogues are being prepared with the same procedure. 2. The key intermediates methyl 3-hydroxymethyl-6-methoxy-2-methylbenzoate and its derivatives were prepared starting from crotonaldehyde and methyl acetoacetate via Michael addition, intramolecular aldol reaction, aromatization, formylation and reduction. The intermediates were coupled respectively with derivatives of gallic acid to give polysubstituted diphenylmethane. However, attempts to cyclize these compounds to the target compounds and analogues were not successful (2nd route). 3. In the process for ortho-lithiation of methyl 2-methoxybenzoate, the substrate converted respectively to n-butyl 2-methoxybenzoate and sec-butyl 2-methoxybenzoate when n-BuLi and sec-BuLi were used. However, tert-BuLi reacted with methyl 2-methoxybenzoate afford 2-methoxyphenyl tert-butyl ketone, which could be used to synthesize aryl tert-butyl ketones. 4. The transformtion of methyl 2-benzoxy-6-methylbenzoate to dimethyl 4,4'-dihydroxy-2,2'-dimethylbiphenyl-3,3'-dicarboxylate in benzene, and dimethyl 5,5'-dibenzyl-4,4'-dihydroxy-2,2'-dimethylbiphenyl-3,3'-dicarboxylate in 1,2-dichloroethane in the presence of ZnCl2 provides a new method for the synthesis of symmetric biphenyl. 5. The formylation of salicylic acid at C-5 and methyl 2-hydroxybenzoate at C-3 could be regioselectively realized by using HMTA/CF3COOH. 6. Racemic 1, 2, 3, 6, 7, 8, 11, 12, 13-nonamethoxyl-10, 15-dihydro-5H-trbibenzo [a, d, g] cyclononene was prepared via Lewis acids catalyzed trimerization of 3, 4, 5-trimethoxylbenzyl alcohol with yield (54%) higher than the reported procesure (12%).

五枫藤、小驳骨和川西茶藨的化学成分研究

八月瓜属植物五枫藤(Holboellia latifolia Wall.)和驳骨草属植物小驳骨(Gendarussa vulgaris Nees)均为药用植物, 前者化学成分研究不深入, 后者的化学成分未见报道。川西茶藨(Ribes takare D. Don)为茶藨子属植物, 没有化学成分的报道。本论文对三个植物的化学成分和活性成分进行了研究, 主要通过色谱方法分离得到了48 个化合物, 采用波谱分析或与已知标准品对照等手段鉴定了它们的结构, 其中有1 个新的原小檗碱类化合物和3 个新的联苯类化合物,发现了具有细胞毒活性和α-葡萄糖苷酶抑制活性的化合物。1、从五枫藤地上部分的95%乙醇提取物中分离得到了12 个化合物: 五加苷K (1)、hederagenin 3-O- α-L-rhamnopyranosyl-(1→2)- α-L-arabinopyranoside (2)、β-萘乙酸(3) 、3-O-α-L-rhamnopyranosyl-(1→2)-[β-D-glucopyranosyl-(1→3)]-α-L-arabinopyranosyl oleanolic acid 28-O-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl ester (4) 、3-O- α-L-rhamnopyranosyl-(1→2)-O- β- D-glucopyranosyl-(1→2)- α-L-arabinopyranosyl oleanolic acid (5) 、3-O-( β-D-glucopyranosiduronic acid)-oleanolic acid 28-O- β-D-glucopyranoside (6)、lup-20(29)-en-3-one (7)、lupeol (8)、β-谷甾醇(9)、齐墩果酸(10)、乌苏酸(11)、β-胡萝卜苷(12)。化合物1 对Lu-06、N-04 和Bre-04 癌细胞株的GI50 分别是0.77µg/mL、1.26 µg/mL 和1.55 µg/mL, 化合物2 对N-04 癌细胞株的GI50 为2.44 µg/mL。2、从小驳骨地上部分的95%乙醇提取物中分离得到了1 个原小檗碱类新化合物13-hydroxyl gusanlung A (25), β-谷甾醇(9)、齐敦果酸(10)、β-胡萝卜苷(12)、棕榈酸(1-)甘油酯(13)、棕榈酸(14)、阿苯哒唑(15)、阿苯哒唑砜(16)、阿苯哒唑亚砜(17)、aurantiamide acetate (18)、华良姜素(19)、芫花素(20)、(-)-丁香树酯醇(21)、gusanlung B (22) 、eupteleasaponinsⅤ acetate (23)、gusanlungA (24)、刺五加苷E (26)、岩白菜素(27)、咖啡酸(28)。化合物25 对肝癌细胞株(HepG2) 的GI50 为2.08 µg/mL。3、从川西茶藨地上部分的95%乙醇提取物中分离鉴定了22 个化合物: β-谷甾醇(9) 、β- 胡萝卜苷(12) 、O-acetyloleanolic aldehyde (29),4,7,8-trimethoxy-2,3-methylenedioxydibenzofuran (30) 、3', 5-dimethoxy-3, 4-methylenedioxybiphenyl (31) 、桦木醇(32) 、6,7-dimethoxy-1-methyl-3,4-dihydroquinolin-2-one (33)、3'-hydroxy-5-methoxy-3,4-methylenedioxybiphenyl (34) 、7-hydroxy-4,8-dimethoxy-2,3-methylenedioxydibenzofuran (35)、桦木醛(36)、没食子酸(37) 、6β- 羟基-4- 烯-3- 酮- 豆甾醇(38) 、5α, 8α-epidioxy-(22E,24R)-ergosta-6, 22-dien-3β-ol (39)、verrucofortine (40)、6-methoxycalpogoniumisoflavone A (41)、2-羟基二苯甲酮(42)、桦木酸(43), 3, 5-二甲氧基苯甲酸-4-O-β-D-吡喃葡萄糖苷(44)、洋芹素(45)、刺槐素(46)、水杨酸(47)、洋芹素-5-O- β-D-葡萄糖苷(48), 化合物30、31 和35 为新的联苯化合物。化合物30的α-葡萄糖苷酶抑制率为10.2% (1.00 mg/mL); 化合物35 的抑制率为17.2% (1.00mg/mL)。4、综述了1960 年以来原小檗碱类化合物药理活性研究进展。 Plants Holboellia latifolia Wall and Gendarussa vulgaris Nees, are used as folkmedicine. Ribes takare D. Don belongs to the genus Ribes. The three plants have notbeen chemically studied in detail. Chemical and bioactive study of three plants led tothe isolation of 48 compounds by chromatography. Their structures were elucidatedon the basis of spectroscopic evidence or comparison with authentic samples. Amongthe 48 componds isolated one protoberberine alkaloid and three biphenyls are newones. Cytotoxic and α-glucosidase inhibitory compounds had been found.1. Twelve compounds were isolated from the 95% ethanol extract of the aerial partof H. latifolia Wall. They were characterized as fellow: eleutheroside K (1),hederagenin-3-O- α-L-rhamnopyranosyl-(1→2)- α-L-arabinopyranoside (2),2-naphthyl acetic acid (3),3-O-α-L-rhamnopyranosyl-(1→2)-[β-D-glucopyranosyl-(1→3)]-α-L-arabinopyranosyl oleanolic acid 28-O-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl ester (4), 3-O- α-L-rhamnopyranosyl-(1→2)-O- β- D-glucopyranosyl-(1→2)- α-L-arabinopyranosyl oleanolic acid (5),3-O-( β-D-glucopyranosiduronic acid)-oleanolic acid-28-O- β-D-glucopyranoside (6),lup-20(29)-en-3-one (7), lupeol (8), β-sitosterol (9), oleanolic acid (10), ursolicacid (11), and β-daucosterol (12). Compound 1 showed moderate cytotoxicity againstLu-06 (GI50, 0.77 µg/mL), N-04 (GI50, 1.26 µg/mL) and Bre0-4 (GI50=1.55 µg/mL)and compound 2 showed moderate cytotoxicity against N-04 (GI50=2.44 µg/mL).2. A new protoberberine alkaloid, 13-hydroxyl gusanlung A (25), was isolated fromthe aerial part of Gendarussa vulgaris Nees, together with β-sitosterol (9), oleanolicacid (10), β-daucosterol (12), glycerol monopalmitate (13), palmific acid (14),albendazole (15), albendazole sulphone (16), albendazole sufloxide (17), aurantiamideacetate (18), kumatakenin (19), genkwanin (20), (-)-syringaresinol (21), gusanlung B(22), eupteleasaponinsⅤ acetate (23), gusanlung A (24), eleutheroside E (26),bergenin (27) and caffeic acid (28). Compound 25 showed cytotoxicity against HepG2 cells (GI50, 2.08 µg/mL).3. Phytochemical study of the Ribes takare D. Don led to the isolation of three newbiphenyls, 4,7,8-trimethoxy-2,3-methylenedioxydibenzofuran (30), 3', 5-dimethoxy-3,4-methylenedioxybiphenyl (31) and 7-hydroxy-4,8-dimethoxy-2,3-methylenedioxydibenzofuran (35), along with nineteenknown compounds, β-sitosterol (9), β-daucosterol (12), O-acetyloleanolic aldehyde(29), betulin (32), 6,7-dimethoxy-1-methyl-3,4-dihydroquinolin-2-one (33),3'-hydroxy-5-methoxy-3, 4-methylenedioxybiphenyl (34), betulinic aldehyde (36),gallic acid (37), stigmast-4-en-6β-ol-3-one (38), 5α, 8α-epidioxy-(22E, 24R)-ergosta-6,22-dien-3β-ol (39), verrucofortine (40), 6-methoxycalpogonium isoflavone A (41),2-hydroxybenzophenone (42), betulinic acid (43), 3,5-dimethoxygallic acid-4-O- β-D-glucopryranoside (44), apigenin (45), acacetin (46), salicylic acid (47) andapigenin-5-O- β-D-glucopryranoside (48). α-Glucosidase inhibitory rates ofcompound 30 and 35 were respectively 10.2% and 17.2% at a concentration of 1.00 mg/mL).4. Pharmacological activities of protoberberines were summarized.

Aliphatic Poly(ester-carbonate)s Bearing Amino Groups and Its RGD Peptide Grafting

This article deals with (1) synthesis of novel cyclic carbonate monomer (2-oxo [1,3]dioxan-5-yl)carbamic acid benzyl ester (CAB) containing protected amino groups; (2) ring-opening copolymerization of the cyclic monomer with L-lactide (LA) to provide novel degradable poly(ester-carbonate)s with functional groups; (3) removal of the protective benzyloxycarbonyl (Cbz) groups by catalytic hydrogenation to afford the corresponding poly(ester-co-carbonate)s with free amino groups; (4) grafting of oligopeptide Gly-Arg-Gly-Asp-Ser-Tyr (GRGDSY, abbreviated as RGD) onto the copolymer pendant amino groups in the presence of 1,1'-carbonyldiimidazole (CDI).

Liquid nitrogen and salicylic/lactic acid paint in the treatment of cutaneous warts in general practice

Patients with common hand warts and simple plantar warts attending a general practice wart clinic in Northern Ireland were assigned to one of three treatment groups - liquid nitrogen applied weekly, daily application of wart paint (lactic acid one part, salicylic acid one part, collodion four parts), or a combination of the two. Combination therapy cured 87% of common hand warts over a six week period, and was significantly more effective than either agent used separately (P

Phenolic compounds from forest industrial by-products

Em Portugal, as indústrias corticeira e de pasta de papel constituem um importante sector económico, contudo, gerando elevadas quantidades de subprodutos. Estes subprodutos poderiam ser explorados em aplicações de alto valor acrescentado, como fonte de compostos fenólicos, por exemplo, em vez de serem apenas queimados para produção de energia. Estes compostos são conhecidos pelas suas inúmeras propriedades, entre as quais, antioxidante, anti-inflamatória e anti-trombótica. Neste estudo as frações fenólicas da maior parte dos subprodutos gerados nas indústrias corticeira e de pasta de papel foram caracterizados em detalhe, com vista à sua valorização. A fração fenólica das cascas de Eucalyptus globulus, E. grandis, E. urograndis e E. maidenii, bem como da cortiça de Quercus suber e resíduos provenientes da sua exploração, nomeadamente, o pó de cortiça e os condensados negros, foi obtida por processos convencionais de extração sólido-líquido. No caso da casca de E. globulus, foi ainda avaliado o potencial de metodologias “verdes” no processo de extração de compostos fenólicos, usando extração com CO2 supercrítico. Esta técnica foi otimizada com recurso a metodologias de superfície de resposta. Na identificação e quantificação dos compostos fenólicos foi usada cromatografia líquida de alta resolução aliada a técnicas de espectrometria de massa. O teor de fenólicos totais foi ainda determinado pelo método de Folin- Ciocalteu, essencialmente para efeitos comparativos. A caracterização da fração fenólica de cada extrato foi ainda complementada com a análise da atividade antioxidante, usando o radical 2,2-difenil-1-picrilhidrazilo (DPPH). Foram identificados trinta compostos fenólicos na casca de E. globulus, 17 deles referenciados pela primeira vez como seus constituintes, nomeadamente os ácidos quínico, di-hidroxifenilacétic, cafeico e metil-elágico, bis-hexahidroxidifenoil( HHDP)-glucose, galoil- bis-HHDP-glucose, galoil-HHDPglucose, isoramnetina—hexosídeo, quercetina-hexosídeo, ácido metil-elágicopentosídeo, miricetina-ramnosídeo, isoramnetina-ramnosídeo, mearnsetina, floridzina, mearnsetina-hexosídeo, luteolina e uma proantocianidina B. Neste trabalho, foi estudada pela primeira vez a composição fenólica das cascas de E. grandis, E. urograndis e E. maidenii. Treze, doze e vinte e quatro compostos fenólicos foram identificados nas cascas de E. grandis, E. urograndis e E. maidenii, respetivamente. Entre estes compostos encontram-se os ácidos quínico, gálico, metilgálico, protocatequínico, clorogénico e elágico, catequina, galoil-bis-HHDP-glucose, digaloilglucose, epicatequina, quercetina-glucoronídeo, di-hidroxiisopropilcromona- hexosídeo, isoramnetina-hexosídeo, ácido elágicoramnosídeo, taxifolina, quercetina-hexosídeo, di-hidroxi- (metilpropil)isopropilcromona-hexosídeo, ácido metil-elágico-pentosídeo, miricetina-ramnosídeo, isoramnetina-ramnosídeo, aromadendrina-ramnosídeo, mearnsetina, mearnsetina-hexosídeo, eriodictiol, quercetina, isoramnetina e naringenina. A análise da fração fenólica da cortiça permitiu identificar vinte e dois compostos fenólicos, dez deles referenciados pela primeira vez como seus constituintes, nomeadamente, os ácidos quínico, salicílico, p-hidroxifenillático e metilgálico, ácido carboxílico da brevifolina, eriodictiol, naringenina, um éster isoprenílico do ácido cafeico, isoramnetina-ramnosídeo e isoramnetina. No pó de cortiça industrial foram identificados dezasseis compostos fenólicos, nomeadamente os ácidos quínico, gálico, protocatequínico, cafeico, ferúlico, elágico e metilgálico, esculetina, ácido carboxílico da brevifolina, coniferaldeído, um éster isoprenílico do ácido cafeico, uma dilactona do ácido valoneico, ácido elágico-pentosídeo, ácido elágico-ramnosídeo, isoramnetinaramnosídeo e isoramnetina. Destes, apenas o ácido elágico foi previamente referenciado como componente do pó de cortiça. Do mesmo modo, treze compostos fenólicos foram identificados no condensado negro, doze deles referenciados pela primeira vez como seus constituintes. São eles os ácidos quínico, gálico, p-hidroxifenil-láctico, protocatequínico, p-coumarico, cafeico e elágico, vanilina, esculetina, coniferaldeído, um éster isoprenílico do ácido cafeico e o eriodictiol. A extração supercrítica de compostos fenólicos da casca de eucalipto permitiu não só verificar os parâmetros que afetam a qualidade e quantidade finais dos extratos, como também obter os valores ótimos para estes parâmetros. Esta extração mostrou ainda ser bastante seletiva para determinados grupos de compostos fenólicos, como as flavanonas eriodictiol e naringenina e para o flavonol O-metilado isoramnetina. Este é também o primeiro estudo envolvendo a determinação da atividade antioxidante de extratos da cortiça e dos resíduos da sua exploração, bem como da casca de E. grandis, E. urograndis e E. maidenii. A vasta gama de compostos fenólicos identificados em cada extrato analisado, assim como as prominentes atividades antioxidantes, todas na mesma gama de valores do bem conhecido antioxidante comercial, ácido ascórbico, são claramente um grande contributo para a valorização destes subprodutos industriais.

3-O-Demethylation of thebaine and the synthesis of a flacourtia aglycone from benzoic acid.

Two synthetic projects were embarked upon, both fraught with protecting group nuance and reaction selectivity. Transformations of the opiate skeleton remain a valuable tool for the development of new medicines. Thebaine, a biosynthetic intermediate in the expression of morphine, was converted in three steps to oripavine through two parallel modes. Through the use of protecting group manipulations, two irreversible scaffold rearrangements were avoided during aryl methyl ether bond cleavage. This chemistry constitutes a new path in manipulations of the morphinan scaffold through protective groups. A new compound family, the flacourtosides, contains an unusual cyclohexenone fragment. The newly described compounds show in preliminary tests antiviral activity against dengue and chikungunya. This aglycone was approached on three pathways, all beginning with the chemoenzymatic dihydroxylation of benzoic acid. A first attempt from a known vinyl epoxide failed to epimerize and cooperate under deprotective conditions. A second and third attempt made use of a diastereoselective dihydroxylation reaction, which was critical in reaching the correct stereochemistry and oxidation state. The methyl ester of the aglycone was prepared, constituting the first synthesis of the non-trivial natural product framework.

Synthèse totale du méthyl ester de la zincophorine et étude DFT du transfert d’hydrogène diastéréosélectif impliquant des intermédiaires radicalaires vicinaux à un ester

Cet ouvrage traite d’une méthodologie pour l’induction de centres stéréogènes au sein des motifs propionates par la chimie des radicaux et de son application à la synthèse totale du méthyl ester de la zincophorine. Cet ionophore, aux propriétés biologiques intéressantes, présente plusieurs défis synthétiques dont une séquence de type polypropionate anti, anti, anti, anti difficilement accessible ainsi qu’un tétrahydropyrane trans trisubstitué. Récemment, l’intérêt renouvelé pour ces composés polyéthers, en tant qu’agents anticancéreux, accentue l’importance de stratégies versatiles permettant l’accès à ces structures ainsi qu’à leurs analogues. Depuis quelques années, notre groupe s’intéresse à la synthèse d’unités propionates acycliques par une séquence réactionnelle contrôlée uniquement par le substrat. La première étape découle d’une aldolisation de Mukaiyama entre un aldéhyde alpha-chiral et un énoxysilane tétrasubstitué portant une liaison carbone-halogène, et où l’issue stéréochimique dépend de la nature monodentate ou bidentate de l’acide de Lewis employé. La seconde réaction-clé implique la formation d’un radical tertiaire, vicinal à un ester, pouvant être réduit diastéréosélectivement en présence d’hydrure d’étain. La première section décrit l’élaboration de motifs tétrahydropyranes trisubstitués et l’induction des centres stéréogènes vicinaux par une réduction radicalaire. Nous avons révélé que l’issue diastéréosélective de la réaction de cyclisation par une iodoéthérification était dictée par le groupement gamma-méthyle des esters alpha,beta-insaturés de départ. Nous avons ensuite démontré que les produits de la réaction radicalaire anti et syn pouvaient être obtenus sélectivement à partir d’un intermédiaire commun, respectivement en prenant appui sur l’effet exocyclique ou endocyclique lors de la réduction. Par une stratégie complémentaire, nous avons révélé que le précurseur radicalaire pouvait également être obtenu par une réaction de cycloéthérification en présence d’un énoxysilane tétrasubstitué. Une étude systématique des substituants du cycle a révélé que certaines relations stéréochimiques conduisaient à une perte de sélectivité au détriment du produit anti. La seconde section concerne l’étude DFT au niveau BHandHLYP/TZVP des intermédiaires radicalaires impliqués lors du transfert d’hydrogène. Par une étude de décomposition de l’énergie d’activation, nous avons été en mesure de rationaliser l’issue diastéréosélective de la réaction sur la base des énergies de distorsion (∆Ed‡) et d’interaction (∆Eint‡) requises pour accéder à la paire d’états de transition pro-anti et pro-syn. De plus, nous avons démontré qu’une analyse NBO permettait de relativiser l’impact des interactions stéréoélectroniques. Par la suite, l’évaluation des intermédiaires radicalaires borinates et aluminates nous a permis de révéler que l’encombrement stérique de la chaîne propionate était la cause principale de la formation sélective des produits anti ou syn lors d’une réduction en présence d’un acide de Lewis. La dernière section décrit l’élaboration de la séquence polypropionate de la zincophorine, et de ses isomères, à partir du fragment tétrahydropyrane substitué. Au cours de notre étude, nous avons identifié que le nombre de sites de chélation potentiels devait être limité à trois lors de l’aldolisation en condition Cram-chélate. De plus, nous avons démontré que les différents motifs acétates sont accessibles sélectivement par l’utilisation d’un énoxysilane encombré. Par ailleurs, nous avons révélé qu’une même séquence réactionnelle pouvait être employée pour la synthèse du fragment C17–C25 de son analogue naturel CP-78,545, et avons complété la plus récente synthèse totale du méthyl ester de la zincophorine.

Ozonolysis of methyl oleate monolayers at the air–water interface: oxidation kinetics, reaction products and atmospheric implications

Ozonolysis of methyl oleate monolayers at the air–water interface results in surprisingly rapid loss of material through cleavage of the C[double bond, length as m-dash]C bond and evaporation/dissolution of reaction products. We determine using neutron reflectometry a rate coefficient of (5.7 ± 0.9) × 10−10 cm2 molecule−1 s−1 and an uptake coefficient of [similar]3 × 10−5 for the oxidation of a methyl ester monolayer: the atmospheric lifetime is [similar]10 min. We obtained direct experimental evidence that <2% of organic material remains at the surface on atmospheric timescales. Therefore known long atmospheric residence times of unsaturated fatty acids suggest that these molecules cannot be present at the interface throughout their ageing cycle, i.e. the reported atmospheric longevity is likely to be attributed to presence in the bulk and viscosity-limited reactive loss. Possible reaction products were characterized by ellipsometry and uncertainties in the atmospheric fate of organic surfactants such as oleic acid and its methyl ester are discussed. Our results suggest that a minor change to the structure of the molecule (fatty acid vs. its methyl ester) considerably impacts on reactivity and fate of the organic film.

Sequestration of prenylated benzoic acid and chromenes by Naupactus bipes (Coleoptera: Curculionidae) feeding on Piper gaudichaudianum (Piperaceae)

The curculionid beetle Naupactus bipes (Germar, 1824) (Coleoptera: Curculionidae: Brachycerinae) has shown feeding preference for leaves of Piper gaudichaudianum, demonstrating an unexpected specificity for an insect considered to be a generalist. The leaves of P. gaudichaudianum contain the prenylated chromenes gaudichaudianic acid (4, major compound) and its methyl ester (5) in addition to a chromene (3) lacking one prenyl residue. In addition to 4, roots contain the chromone methyl ester (1) and methyl taboganate (2, major compound). Feeding on roots, larvae of N. bipes sequester exclusively the root-specific compounds 1 and 2. Adult beetles sequester the leaf-specific chromenes 3 and 4, but were found to also contain compounds 1 and 2 that are absent in leaves. Therefore, it is suggested that 1 and 2 are sequestered by larvae and can be found in the body of adult insects after long-term storage. In addition, 3 and 4, the major compounds in leaves were found to be associated with the eggs.

The semi-synthetic kaurane ent-16 alpha-methoxykauran-19-oic acid induces vascular relaxation and hypotension in rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Development and characterization of biocompatible isotropic and anisotropic oil-in-water colloidal dispersions as a new delivery system for methyl dihydrojasmonate antitumor drug

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Hormesis method for increasing oat straw with a view to viability of direct-seeding systems

In conservation agriculture, mainly under direct seeding, maintaining the vegetation ground cover is essential, since this serves as a reservoir of nutrients which are slowly released to plants by microorganisms. Some authors have sought to study increases in the amount of straw in the soil, in addition to slowing down the process of decomposition, with hormesis being one of the techniques used. This technique states that all chemical substances are both poisonous and nonpoisonous, with only the dosage determining whether they are lethal or not. This study aimed to evaluate the dry weight and agronomic characteristics of a crop of black oat subjected to hormesis. The experimental design was of randomised blocks, with 12 treatments and 4 replications, giving a total of 48 experimental lots. The treatments were: Haloxyfop-R Methyl Ester at dosages of 0.625, 1.25 and 2.50 g ha(-1); Glyphosate at dosages of 12.50, 25.00 and 50.00 g ha-1; 2,4-D dimethylamine salt at dosages of 100.00, 200.00 and 300.00 g ha(-1); Alterbane at a dosage of 500.00 g ha(-1); Salicylic acid at a dose of 100 g ha(-1); and a control. It was concluded that for the subdosages under test, the herbicides 2,4-D at medium dosage and Verdict at low dosage were shown to be the best treatments for conserving straw as ground cover under direct seeding.

Inhibition of gastric acid secretion by stress: A protective reflex mediated by cerebral nitric oxide

Moderate somatic stress inhibits gastric acid secretion. We have investigated the role of endogenously released NO in this phenomenon. Elevation of body temperature by 3°C or a reduction of 35 mmHg (1 mmHg = 133 Pa) in blood pressure for 10 min produced a rapid and long-lasting reduction of distension-stimulated acid secretion in the rat perfused stomach in vivo. A similar inhibitory effect on acid secretion was produced by the intracisternal (i.c.) administration of oxytocin, a peptide known to be released during stress. Intracisternal administration of the NO-synthase inhibitor, NG-nitro-l-arginine methyl ester (l-NAME) reversed the antisecretory effect induced by all these stimuli, an action prevented by intracisternal coadministration of the NO precursor, l-arginine. Furthermore, microinjection of l-NAME into the dorsal motor nucleus of the vagus nerve reversed the acid inhibitory effects of mild hyperthermia, i.v. endotoxin, or i.c. oxytocin, an action prevented by prior microinjection of l-arginine. By contrast, microinjection of l-NAME into the nucleus tractus solitarius failed to affect the inhibitory effects of hyperthermia, i.v. endotoxin, or i.c. oxytocin. Immunohistochemical techniques demonstrated that following hyperthermia there was a significant increase in immunoreactivity to neuronal NO synthase in different areas of the brain, including the dorsal motor nucleus of the vagus. Thus, our results suggest that the inhibition of gastric acid secretion, a defense mechanism during stress, is mediated by a nervous reflex involving a neuronal pathway that includes NO synthesis in the brain, specifically in the dorsal motor nucleus of the vagus.