Aziridination of alkenes promoted by iron or ruthenium complexes

Molecules containing an aziridine functional group are a versatile class of organic synthons due to the presence of a strained three member, which can be easily involved in ring-opening reactions and the aziridine functionality often show interesting pharmaceutical and/or biological behaviours. For these reasons, the scientific community is constantly interested in developing efficient procedures to introduce an aziridine moiety into organic skeletons and the one-pot reaction of an alkene double bond with a nitrene [NR] source is a powerful synthetic strategy.Herein we describe the catalytic activity of iron or ruthenium complexes in promoting the reaction stated above by stressing the potential and limits of each synthetic protocol

Expression of genes associated with anthocyanin synthesis in red-purplish, pink, pinkish-green and green grape berries from mutated 'Sangiovese' biotypes: A case study

Using normal red-purplish grape bunches and pink, pink-green and green berry colour-mutated biotypes of cv. Sangiovese (V. vinifera L.), we investigated their anthocyanin metabolism via biochemical and molecular assays. The number and composition of the different types of anthocyanins were analysed by spectrophotometry and chromatography. The expression of six structural genes of the biosynthetic pathway (chalcone synthase [CHS], chalcone isomerase [CHI], flavanon-3-hydroxylase [F3H], dihydroflavonol 4-reductase [DFR], leucoanthocyanidin dioxygenase [LDOX] and UDP-glucose 3-O-flavonoid:glucosyltransferase [UFGT]) was determined over the four weeks subsequent to veraison via Northen blot and Real Time PCR.The grapes from the non-mutated biotype showed a prevailing accumulation of monoglycoside anthocyanin fractions, with only traces of acetyl and p-coumaroyl derivatives. The berries of the mutated biotypes showed a gradual berry pigment loss associated with a reduction in total anthocyanin content, although anthocyanin composition was the same of the non-mutant biotype. Indeed, the Northern blot assay data, as confirmed by the quantitative Real Time PCR tests, showed a differential expression in the berries of the non mutated and mutated biotypes for the UFGT gene, proving normal in the red-purplish, lower in the biotypes with pink and pink-green berries and wholly lacking in the green one. Thus, the UFGT gene in berry skin of colour-mutated 'Sangiovese' biotypes is controlled independently of the other structural genes encoding enzymes in the anthocyanin biosynthetic pathway and its capacity of expression is a critical factor in the synthesis and storage of these compounds.

Row orientation effects on whole-canopy gas exchange of potted and field-grown grapevines

The effects of canopy orientation (North-South vs. East-West) on total canopy assimilation (TCA) and transpiration (TCE) were evaluated on potted grapevines mounted on wheeled platforms for full swivel relation. Eight vines were assembled in pairs to form four canopy walls 2 m long, 1.1 m tall and 0.25-0.30 m wide. TCA and TCE readings were also taken in the field on four NS-oriented, hedgerow cordon-trained grapevines. Diurnal trends of TCA recorded on potted vines showed little variability when related to row orientation. The TCE pattern for EW followed essentially that of light intensity, whereas a NS orientation induced a marked decrease in TCE at midday before recovering in mid-afternoon. As a result, water use efficiency (WUE) in NS rows was higher during the midday hours. Total canopy water loss in NS was linearly correlated with estimates of intercepted light, suggesting that water use was a function of both, light intensity and canopy geometry (i.e. more light lost to the ground at noon, hence less transpiration). The results for the NS-oriented field-grown canopies differed to some extent from those of the pot experiments. TCA showed a more marked afternoon decline and TCE flattened at noon, though with no apparent decrease. WUE efficiency was lowest at the highest evaporative demand. The daily water loss of field vines could not be predicted by total light interception estimates only, indicating a more complex regulation of canopy transpiration than recorded on potted plants

Gas-exchange response of grapevine leaves under fluctuating light

Gas exchange responses to lightflecks of different frequency and duration were studied in mature grapevine leaves. Light-response curves under intermittent light showed lower carbon exchange rate (CER) than continuous light at non-saturating PFD levels (10-500 µ molm-2 s-1). White-dark and white-green alternating light of equal bright and shade periods at 0.33-5.33 Hz systematically resulted in improved light utilization as compared to high continuous light. Transpiration (T) was slightly more limited than the CER under intermittent light, resulting in higher water use efficiency. No differences in carboxylation efficiency were found by comparing the high continuous light treatment to white-dark lightflecks at 0.33 and 2.67 Hz. Our results show that, under short-term alternating light, CER of the grapevine leaf fully responds to the mean PFD level resulting from light oscillations

Porphyrin-based homogeneous catalysts for the CO 2 cycloaddition to epoxides and aziridines

The direct insertion of carbon dioxide (CO2) into three-membered rings, such as epoxides and aziridines, represents a relevant strategy to obtain cyclic carbonates and oxazolidinones, which are two useful classes of fine chemicals. The synthesis of these compounds can be efficiently catalyzed by a combination of metal porphyrin complexes and various co-catalysts in homogeneous systems. The catalytic efficiency of these systems is discussed herein by taking into account both the characteristics of the metals and the nature of the co-catalysts, either when used as two-component systems or when combined in bifunctional catalysts. Moreover, mechanistic proposals of the CO2 cycloaddition processes are reported to provide a rationale of catalytic cycles in order to pave the way for designing more active and efficient catalytic procedures

Effects of canopy manipulations on whole-vine photosynthesis: Results from pot and field experiments

A two-year study was conducted with potted and field-grown grapevines to examine the effects of canopy restriction and leaf removal on total vine assimilation (TVA). TVA was measured using a flow-through gas exchange system equipped with flexible plastic chambers enclosing the entire canopy. Canopy restriction was applied to potted bush-shaped (BS) and field-grown spur-pruned cordon (SPC) vines on trellises to force the foliage into the smallest canopy volume. Leaf removal was performed on free cordon (FC) and SPC-trained vines at different dates to eliminate internal leaves shaded to varying extent. Canopy restriction reduced TVA more severely in the BS canopies than in the trellised SPC vines. Leaf removal elicited varying responses depending upon canopy shape, initial canopy density and leaf/fruit ratio. The FC vine showed no decrease in TVA after 27 % of its total leaf area had been removed, suggesting the occurrence of active photosynthetic compensation. TVA decreased with defoliation in the SPC vine, although the effect was mostly due to the leaf removal applied earlier in the season. In the FC vine a regression of total leaf area versus TVA showed maximum TVA at 6.0-6.5 m(2) of leaf area per meter of canopy. In SPC vines this relationship indicated a linear increase of TVA with leaf area and the lack of a saturation threshold under our experimental conditions. Sugar accumulation in the grapes of SPC vines correlated closely to the ratios leaf area/fruit and TVA/yield

Preliminary results on the use of a modified point quadrat method for estimating canopy structure of grapevine training systems

The reliability of a modified point quadrat method designed to describe the structure and seasonal canopy dynamics of the training systems simple curtain (SC) and traditional spur-pruned cordon (SPC) was tested in a two-year study. The method relies upon an unbiased sampling procedure as each canopy insertion is first identified within a ground-projected area by a random number generation routine (RND). From each insertion, the height of each contact with either leaves or clusters is then recorded along the vertical axis. Although the method suffered from a somewhat low percentage of effective insertions early in the season, the total leaf area-to-surface area ratio and the leaf layer number calculated for both canopy types are in accordance with those reported by others for high vigour canopies. Canopy dynamics showed an asymmetric growth in the SC starting at bloom. Both trellises resulted in similar canopy density indices and a high correlation was found between total leaf area and total number of leaf contacts

Molecular characterization of officially registered Sangiovese clones and of other Sangiovese-like biotypes in Tuscany, Corsica and Emilia-Romagna

The present study was designed (1) to identify and determine the origin of the genetic variability via SSR and AFLP within a group of 39 Sangiovese clones officially listed in the National Grapevine Registry, (2) to pinpoint varietal differences and potential family relations among 34 Sangiovese-like biotypes, via the SSR markers. Most biotypes are regarded as Sangiovese but sometimes are known under different names. In both studies the reference standard was the registered Sangiovese clone SG 12T.No polymorphism was found among the officially listed 39 clones analysed at 6 microsatellite loci. This enabled us to confirm their origin from a single mother plant, thereby supporting the view that any morphological or qualitative differences may be the result of propagation-related mutagenic events. A subsequent AFLP analysis of 26 of the 39 clones showed polymorphic bands in three of them (two identical) that may correspond to a mutagenic event. Assays with SSR markers on 34 Sangiovese-like biotypes collected in Tuscany, Corsica and Emilia-Romagna showed that 28 are identical with the reference Sangiovese clone SG 12T, while the remaining 6 (Sangiovese 1, Sangiovese 6, Morellino, Poverina, Sangiovese forte and Brunellone) are genetically different from SG 12T and among one another so that no direct family relations could be established

Diversity assessment of seedlings from self-pollinated Sangiovese grapevines by ampelography and microsatellite DNA analysis

A population of Vitis vinifera L. seedlings deriving from a single self-pollinated Sangiovese vine were assayed for diversity by ampelographic and genetic techniques. After field-transplantation in 1987, the seedlings were initially screened in 1995. Twenty-four seedlings were of standard Vigour and grape production. Woody cuttings from the 24 seedlings and the mother plant were self-rooted in 1995, and each Vine was morphologically analysed and compared in 1997 using 31 descriptors of the ampelographic data sheet (OIV 1983) which are also recommended by UPOV for varietal identification - three for young shoots, 7 for shoots at bloom, 17 for adult leaves, one for flowers and 3 for berries. - In 1996 DNA was extracted from young apical leaves of the mother plant and the 24 seedlings. Ten molecular microsatellites, VVS1, VVS2, VVS5, VVS16, VVS29, VVMD5, VVMD6, VVMD7, VVMD17 and VVMD28, were used for progeny and mother plant comparison. The descriptor-based analysis showed that 12 of the 24 seedlings were morphologically similar amongst themselves and not different fr-om the mother; the remaining 12 differing from each other and from the parent. The microsatellite analysis differentiated all 24 seedlings from the mother plant. Only two seedlings showed the same allele patterns at the 10 tested loci, although they differed morphologically. The results of both analyses indicate that self-pollination can generate phenotypically similar individuals that are difficult to distinguish morphologically, while their genetic polymorphism can easily be detected by microsatellite analysis. Thus it is possible, as suggested by RIVES (1961), that certain ancient cultivars comprise a number of clones that derive via vegetative propagation from closely related mother plants. Corroboration of the polyclonal origin in such cases can be performed by techniques combining morphological and molecular approaches

A custom-built simple system for conditioning and measurement of in situ whole-cluster transpiration

A custom-built, low-cost gas exchange system designed for conditioning of the cluster microclimate and for fully automated measurements of in situ whole-cluster transpiration is presented. Measurements were carried out on potted Sangiovese grapevines at the onset of veraison, To increase the range of variability in cluster transpiration, air streams of different vapor pressure deficits (VPD) were created by conditioning the temperature of the incoming flow. Heating was created and maintained for 10 d (26 June - 5 July) by air flow through a metal segment equipped with three 75 W (warm) or 100 W (hot) light bulbs, The cluster transpiration rates recorded for the unheated (control) clusters throughout the conditioning period varied from 0.18 to 0.28 mmol m-2 s-1. While the daily transpiration rates of clusters supplied with warm air were similar to those of the control, water loss began to decrease significantly in clusters treated with hot air from day 4 onward and stayed lower throughout the remaining conditioning period. The gas exchange system presented here proved sensitive enough to detect the typically low transpiration rates of berries during ripening; effects due to air heating could be separated from fluctuations caused by daily variation of weather.