Raffaele Tabacchi

In the title compound, C₁₇H₂₇NO₂, the piperidine ring has a chair conformation and is positioned normal to the benzene ring. In the crystal, molecules are linked by C—H...O hydrogen bonds, forming chains propagating along the c-axis direction.

The essential oil extracted from Piper betle L. leaf using pilot plant steam distillation was tested against the adult housefly, Musca domestica, for insecticidal activity. LC₅₀ values at the end of 24 and 48 h exposure periods were 10.3 and 8.7 mg/dm³, respectively. Ceylon citronella oil (Cymbopogon nardus) used as a standard showed LC₅₀s of 26.5 and 24.2 mg/dm³ for the same exposure periods. Bioassay‐guided fractionation of P. betle leaf oil revealed safrole and eugenol as the active principles against M. domestica, safrole showing LC₅₀ values of 4.8 and 4.7 mg/dm³, and eugenol 7.3 and 6.2 mg/dm³ for the 24 and 48 h exposure periods, respectively, while citronellal (synthetic standard) showed equal LC₅₀ values of 14.3 mg/dm³ for the same exposure periods. Using safrole as the starting compound, eight analogues were prepared to study structure–activity relationships. Among the eight analogues, dihydrosafrole gave almost equal mortality at LC₅₀ 4.7 mg/dm³ as that of the parent compound safrole after 24 and 48 h exposure, but isosafrole was twice as active as safrole, showing LC₅₀ values of 2.3 and 2.2 mg/dm³ for the 24 and 48 h exposure periods. Our GC–MS studies on Sri Lankan P. betle leaf oil show that it contains safrole (52.7%), allylpyrocatechol diacetate (15.4%), eugenol (6.4%) and eugenyl acetate (5.8%) as the major components. Here we also present the GC–MS profile of fractions of Sri Lankan P. betle leaf oil. Copyright © 2006 John Wiley & Sons, Ltd.

The pure tannin extracts from grape berries of Gamay and Gamaret varieties contain a mixture of proanthocyanidins and proanthocyanidin gallates. A sensitive LC-MS method has been developed for the qualitative analysis of the oligomers and polymeric fractions. The potential of ESI-IT or MALDI-TOF mass spectrometry permit us to characterize these tannins. Polymers were fractionated according to the mean degree of polymerization (mDP), using either a divinylbenzene phase or a glass powder. The mDP is obtained by thiolysis reaction and the fractions are analyzed by MS. Polymeric proanthocyanidins (PPRA) were purified from grape berries at full bloom, pea size, bunch closure, véraison and harvest, their mDP calculated and their inhibitory capacity on B. cinerea stilbene oxidase tested at 3.5 to 70 nmoles for 3 ml of enzymatic reaction volume. ED50 of PPRA concentrations was measured for each developmental stage and for both grape varieties Gamay (sensitive to grey mould) and Gamaret (resistant). The higher the mDP of PPRA fraction, the more effective is the inhibitory activity. From grape berry pea size, mDP of PPRA of Gamaret (9.53 to 11.77) were always higher than those of Gamay (7.46 to 8.74) and ED50 of Gamaret PPrA were under 5 nmoles 3ml?1 while ED50 of Gamay PPRA were at 6.5 to 7.25 nmoles 3 ml?1.

The survival of plants is of fundamental importance to guarantee the biodiversity in natural areas and a sustainable agriculture. The National Centre of Competence in Research 'Plant Survival in Natural and Agricultural Ecosystems' devotes its research efforts to the understanding of mechanisms of plant survival. The mechanisms that plants employ to adapt to their biotic and abiotic environment and to cope with important stress factors are investigated. This is achieved by interdisciplinary interaction of disciplines within the NCCR. The particular role played by natural products and analytical chemistry in seven different projects is summarized.

Polymeric tannins, extracted from grape berries (Gamay variety), were fractionated according to their mean degree of polymerisation (mDP) on a styrene–divinylbenzene phase eluted with a gradient of methanol:chloroform. Increasing the percentage of methanol led to the solubilisation of higher molecular weight tannins. The mean mDP of each collected fraction was determined by acid‐catalysed degradation in the presence of a nucleophilic reagent. The fractionation method produced a linear gradient of mDP varying between 1.84 and 19.34. The fractions were partially characterised by matrix assisted laser desorption/ionisation time‐of‐flight mass spectrometry (MALDI‐TOF/MS). The spectra showed a complex mixture of proanthocyanidins and galloylated proanthocyanidins up to 4000 amu. Copyright © 2003 John Wiley & Sons, Ltd.

A short and efficient protocol for the asymmetric synthesis of cis‐ and trans‐3,4‐dihydro‐2,4,8‐trihydroxynaphthalen‐1(2H)‐one (1 and 2, resp.) is described, with a phthalide annulation as the key step. Introduction of a OH substituent at position 2 was performed by Sharpless dihydroxylation of a silyl enol ether or by means of an N‐sulfonyloxaziridine. The absolute configuration of each isomer was determined via Mosher‐ester derivatives. By comparison with previously recorded CD spectra of our natural sample, we established that the natural trans‐ and cis‐isomers from Ceratocystis fimbriata sp. platani were the (−)‐(2S,4S)‐isomer (−)‐2 and the (+)‐(2S,4R)‐isomer (+)‐1, respectively.