Papers by Giancarlo Cravotto
The Chemistry of Coumarin Derivatives. Part 3. Synthesis of 3Alkyl4- hydroxycoumarins by Reductive Fragmentation of 3,3′-Alkylidene-4,4′- dihydroxybis(coumarins)
Cheminform, 1992
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
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The chemistry of coumarin derivatives. Part 3. Synthesis of 3-alkyl-4-hydroxycoumarins by reductive fragmentation of 3,3?-alkyiidene-4,4?-dihydroxybis[coumarins]
Helvetica Chimica Acta, 1991
Treatment of 3,3′-alkylidene-4,4′-dihydroxybis[coumarins] 1 with NaBH3CN in refluxing MeOH afford... more Treatment of 3,3′-alkylidene-4,4′-dihydroxybis[coumarins] 1 with NaBH3CN in refluxing MeOH affords 3-alkyl-4-hydroxycoumarins 2 and 4-hydroxycoumarin (3; Scheme 1). The reaction might take place via hydride trapping of alkylidenechromandiones C formed from 1 in a retro-Michael reaction. Such a retro-Michael reaction of 1 might be biologically relevant. The presence of C during the reductive fragmentation 1 2 is suggested by Diels-Alder and nucleophilic trapping of the alkylidenechromandiones C as well as from cross-over experiments with coumarins other than 3 (see Scheme 2). The reductive fragmentation of 1 allows the chemo- and regioselective synthesis of a variety of 3-alkyl-4-hydroxycoumarins 2 (see Table).
Journal of Separation Science, 2003
The thermodynamic parameters involved in the enantiomer separation of two homologous series of γ-... more The thermodynamic parameters involved in the enantiomer separation of two homologous series of γ-lactones (C6–C8 and C10–C12) and a group of structurally related monoterpenoids with a p-menthane skeleton (menthol, i-menthol, neo-menthol, neo-i-menthol, menthone, i-menthone, and 3-oxo-1,8-cineole) are determined to investigate how inverted substitution in positions 2 and 3 of the cyclodextrin ring with methyl and acetyl groups influences the enantioselectivity of 2-O-methyl-3-O-acetyl-6-O-t-hexyldimethylsilyl-γ-cyclodextrin and 2-O-acetyl-3-O-methyl-6-O-t-hexyl-dimethylsilyl-γ-cyclodextrin. The thermodynamic results show that the methyl and acyl groups, in positions 2 and 3 respectively, act complementarily to increase enantioselectivity and that the relative configuration of the stereogenic centres in the selectands influences enantiomer separation.
Journal of Separation Science, 2003
Molecular Mechanics and Molecular Dynamics calculations were performed to simulate the 1 : 1 comp... more Molecular Mechanics and Molecular Dynamics calculations were performed to simulate the 1 : 1 complex formation of 2-O-acetyl-3-O-methyl- and 2-O-methyl-3-O-acetyl-6-O-t-hexyldimethylsilyl-γ-cyclodextrins with a group of monoterpenoids having the p-menthane skeleton (menthol, i-menthol, neo-menthol, neo-i-menthol, menthone, i-menthone, and 3-oxo-1,8-cineole) using nitrogen as simulated gas carrier. 1 : 1 complexes of the terpenoids studied are stable and non-bonded van der Waals interactions are mainly responsible for complexation. The results suggest that the nature of the substituent (hydroxyl or oxo groups) at C3 on the cyclohexane ring, and its configuration for hydroxylated racemates, are responsible for the differences in complexation energies between the two investigated CD derivatives. This is in agreement with considerations of the difference in the experimental values of thermodynamic parameters, reported elsewhere, and may explain the difference in the enantioselectivity of the two CD derivatives for the terpenoids investigated. The substituents in position 1 are less involved in the chiral recognition process.
Chemical & Pharmaceutical Bulletin, 2004
Hydroxyacetophenones. -Positive effects are observed for products bearing a plain alkyl group or ... more Hydroxyacetophenones. -Positive effects are observed for products bearing a plain alkyl group or an ω-epoxy-farnesyl moiety. -(CRAVOTTO*, G.; BALLIANO, G.; TAGLIAPIETRA, S.; OLIARO-BOSSO, S.; NANO, G. M.; Chem.
Food Chemistry, 2009
A new method for the extraction and purification of ascorbic acid from two tropical fruits (acero... more A new method for the extraction and purification of ascorbic acid from two tropical fruits (acerola and camu-camu) is presented. 13C nuclear magnetic resonance and isotopic ratio mass spectroscopy (13C/12C) were used to recognize ascorbic acid coming from either natural or industrial sources. A quantitative 13C NMR procedure was optimized to calculate isotopic relative abundances on each molecular site; data
Journal of Food Engineering, 2010
Polyphenols, the well known naturally occurring antioxidants, are the most abundant secondary met... more Polyphenols, the well known naturally occurring antioxidants, are the most abundant secondary metabolites in grape wastes. Herein we investigate several non-conventional extraction methods vs classic solid–liquid extraction (SLE) to obtain phenolic compounds from grape seeds and skins. We compared SLE, ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE) and high pressure and temperature extraction (HPTE) in term of extraction yield and antioxidant
Tetrahedron-asymmetry, 2006
The absolute configuration of (+)-convolutamydine A 1 isolated from Amathia convoluta has been un... more The absolute configuration of (+)-convolutamydine A 1 isolated from Amathia convoluta has been unambiguously established as (R) by enantioselective synthesis, based on chiral auxiliary-directed π-face discrimination in an allyl metal addition to (1R,2S,5R)-8-phenylmenthyl ester 7. For an independent and unequivocal proof, the absolute stereochemistry of synthetic precursor 11 en route to 1 was determined by X-ray crystallography.
Phytochemistry, 1989
The aerial parts of Pallenis spinosa gave a new germacrane alcohol, whose structure and conformat... more The aerial parts of Pallenis spinosa gave a new germacrane alcohol, whose structure and conformation were established by spectral data, including 2D NMR.
Ultrasonics …, Apr 30, 2008
The mineralisation of 2,4-dichlorophenoxyacetic acid (2,4-D) in the presence of zero-valent iron ... more The mineralisation of 2,4-dichlorophenoxyacetic acid (2,4-D) in the presence of zero-valent iron and hydrogen peroxide (the advanced Fenton process -AFP) whilst being subjected to acoustic or hydrodynamic cavitation is reported. If the reaction is merely stirred then there is 57% removal of TOC whilst on irradiation the figure is 64% although the latter reaction is more rapid. Use of ultrasound alone results in only 11% TOC removal in 60 min of treatment time. Addition of iron powder marginally enhances the extent of degradation but an appreciable increase is observed in the presence of hydrogen peroxide which acts as a source for hydroxyl radicals by Fenton chemistry as well as by dissociation in the presence of ultrasound. The use of hydrodynamic cavitation in conjunction with the advanced Fenton process has also been found to be a useful tool for continuous remediation of water contaminated with 2,4-D. After 20 min of treatment the residual TOC is reduced to 30% and this probably represents the remaining highly recalcitrant small organic molecules.
MechanochemistryMeasuring the force of sound
Nature Chemistry, 2012
... polymers; b, cleavage of MCC (R 2 = 0.958) and MCT (R 2 = 0.961) polymers; c, cleavage of DCT... more ... polymers; b, cleavage of MCC (R 2 = 0.958) and MCT (R 2 = 0.961) polymers; c, cleavage of DCT, MCT and NCT polymers; d, cleavage of DCC, MCC (solid ... Pedro Cintas is in the Department of Organic and Inorganic Chemistry, University of Extremadura, 06006 Badajoz, Spain. ...
Steroids, 2007
Degradation of halobetasol propionate was observed in the presence of bases. A single cyclization... more Degradation of halobetasol propionate was observed in the presence of bases. A single cyclization product was isolated and fully characterized by MS, NMR and X-ray crystallography.
Chemosphere, 2007
The effect on halogenated aromatics of solid, non-toxic oxidants such as sodium percarbonate and ... more The effect on halogenated aromatics of solid, non-toxic oxidants such as sodium percarbonate and the urea/hydrogen peroxide complex (Fenton-like reagents) was investigated. A microwaves-assisted, solvent-free method for soil decontamination is presented. It marks a considerable advance in the search of more efficient, environment-friendly procedures for the degradative oxidation of persistent organic pollutants. Residual pollutants in treated soil samples were determined by GC/MS analysis after solvent extraction or direct thermal desorption. Results showed that 4-chloronaphthol, 2,4-dichlorophenoxyacetic acid and p-nonylphenol had been degraded completely, 2,4-dibromophenol to a large extent.
Bioorganic & medicinal chemistry letters, Jan 19, 2004
A few naturally occurring prenyl- and prenyloxycoumarins and several new related synthetic deriva... more A few naturally occurring prenyl- and prenyloxycoumarins and several new related synthetic derivatives were evaluated as inhibitors of squalene-hopene cyclase (SHC), a useful model enzyme, to predict their interactions with oxidosqualene cyclase (OSC). Umbelliprenin-10',11'-monoepoxide (IC(50) 2.5 microM) and the corresponding 6',7'-10',11' diepoxide (IC(50) 1.5 microM) were the most active enzyme inhibitors.
Beilstein journal of organic chemistry, 2014
We herein describe an environmentally friendly microwave-assisted oxidative esterification of alco... more We herein describe an environmentally friendly microwave-assisted oxidative esterification of alcohols and aldehydes in the presence of molecular oxygen and a heterogeneous catalysis (Pd/C, 5 mol %). This efficient and ligandless conversion procedure does not require the addition of an organic hydrogen acceptor. The reaction rate is strongly enhanced by mild dielectric heating. Furthermore, it is a versatile green procedure which generally enables the isolation of esters to be carried out by simple filtration in almost quantitative yields.
Efficient mechanochemical complexation of various steroid compounds with α-, β- and γ-cyclodextrin
Steroids, 2015
Mechanochemical technology enables solvent-free micronized solid dispersions and efficient molecu... more Mechanochemical technology enables solvent-free micronized solid dispersions and efficient molecular host-guest inclusion complexes to be formed in matrices which contain cyclodextrins (CDs). This type of complexation has been studied using α-, β- and γ-cyclodextrin with the dual aims of improving overall solubility and enhancing the bioavailability of common steroid compounds, such as cholic acids and β-sitosterols or lowering cholesterol content in products of animal origin. Several parameters have been studied and optimized: CD/compound molar ratio (1:1, 1:2, 2:1 and 3:1) in function of the cavity sizes of the three different CDs, milling time (from 5 to 40min) and rotation speed (from 100 to 300rpm). DSC (differential scanning calorimetry) analyses have revealed that inclusion complexes were efficiently formed after 40min milling (200rpm) for β-CD/cholesterol and β-CD/ugrsodeoxycholic acid (encapsulation efficiency 96% and 77% respectively). Besides steroid encapsulation/vehiculation, the mechanochemical technique may pave the way for new ideas in solventless steroid extraction from vegetal matrices with CDs.
Journal of Separation Science, 2002
Cyclodextrin derivatives in GC separation of racemates with different volatilities. Part XIX: The... more Cyclodextrin derivatives in GC separation of racemates with different volatilities. Part XIX: Thermodynamic aspects of enantioselective GC separation of some volatiles with c-cyclodextrins 2,3-substituted with methyl and acetyl groups
ChemInform Abstract: The Synthesis and Application of Polyamino Polycarboxylic Bifunctional Chelating Agents
ChemInform, 2011
Catalysis Science & Technology, 2011
Alkynylation. -A new green solid catalyst system consisting of Pd 2+ and Cu + nanoparticles suppo... more Alkynylation. -A new green solid catalyst system consisting of Pd 2+ and Cu + nanoparticles supported on β-cyclodextrin is developed and screened in Sonogashira coupling reactions of phenylacetylene and p-iodoanisole in water or glycerol giving the desired products with excellent GC yields. The catalyst is easily prepared via in situ reticulation with hexamethylene diisocyanate and triphenylphosphine under sonochemical conditions and can be easily recovered and reused three times without a significant loss of catalytic activity. -(CINTAS, P.; CRAVOTTO*, G.; GAUDINO, E. C.; ORIO, L.; BOFFA, L.; Catal. Sci. Technol. 2 (2012) 1, 85-87, http://dx.doi.org/10.1039/c1cy00378j ; Dip. Sci. Tecnol. Farm, Univ. Torino, I-10125 Torino, Italy; Eng.) -S. Adam
Highly efficient Synthesis of per-substituted amino-cyclodextrins under Microwave Irradiation in a closed Cavity
MRS Proceedings, 2013
ABSTRACT Synthetic chemists are paying ever more attention to enabling technologies as a means to... more ABSTRACT Synthetic chemists are paying ever more attention to enabling technologies as a means to opening the paths towards the double goal of achieving high efficiency and meeting green criteria. Non-conventional techniques that create unique environments which promote selective modification have been investigated by many as part of the search for more highly efficient synthetic derivatization of cyclodextrins (CD). A few optimized microwave-assisted protocols have so far been developed for the preparation of selective per-alkylated aminocyclodextrin. In this work, a series of β-CD derivatives, whose primary hydroxyls were all replaced by amino groups, has efficiently been synthesized from per-(6-iodo-6-deoxy)-β-CD via nucleophilic substitution with amines under microwave irradiation in closed vessel (N2 pressure). The reduction of per-(6-azido-6-deoxy)-β-CD to per-(6-amino-6-deoxy)-β-CD via catalytic hydrogenation has also been successfully carried out under dielectric heating.
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Papers by Giancarlo Cravotto