186,189 research outputs found
Synyhesis of a renewable hydroperoxide from (+)-norcamphor:implications of steric modification of the bicyclic framework on asymmetric sulfoxidation
No full textA renewable tertiary hydroperoxide has been efficiently synthesized in 83% overall yield starting from commercially available (+)-endo-2-norborneol. This oxygen donor, derived from (+)-norcamphor, when employed in Ti(O i-Pr)(4)-catalyzed sulfoxidations, proved to be considerably more reactive when compared to a previously reported camphor-derived hydroperoxide. Reduced steric hindrance of the new oxidant lowered the level of asymmetric induction achieved in the oxidation, but stereo-convergent kinetic resolution has been exploited to improve enantioselectivity. Excellent recovery (95%) of the tertiary alcohol at the end of the sulfoxidation provides a highly advantageous chiral resource saving protocol
Catalytic asymmetric epoxidation of allylic alcohols using a renewable hydroperoxide
No full textSharpless modified asymmetric epoxidation of allylic alcohols can be successfully performed using an easily accessible and renewable tertiary furyl hydroperoxide in the presence 20 mol% of the chiral Ti(O-i-Pr)(4)/L-DIPT/MS 4 Angstrom system
Synthesis of easily accessible enantiopure tertiary furyl hydroperoxide and use in asymmetric sulfoxidation
No full text
Renewable enantiopure camphor-derived hydroperoxides: synthesis and use in asymmetric oxidations
No full textCharacterization of high purity lycopene from tomato wastes using a new pressurized extraction approach
No full textIn this paper, a method for the extraction of high purity lycopene from tomato wastes is presented. The method is based on a pressurized extraction that uses the Extractor Naviglio, and it is performed in the 0.7-0.9 MPa range. Tomato skin, the byproduct deriving from manufacturing of tomato, in a water dispersion, are used as starting material. Lycopene is transferred, for the effect of the high pressure used, in the form of molecular aggregates into the water as a dispersion, while apolar compounds remain in the matrix. The aggregates are easily purified in a single subsequent step by using methanol, thus, obtaining lycopene at 98% chromatographic purity or higher. A new stationary phase, phenyl-hexyl silicone, and a simple water/acetonitrile gradient were used for HPLC analysis of lycopene. The extract was characterized by UV-Vis spectrophotometry, H-1 NMR, C-13 NMR, and electrospray ionization mass spectrometry. An average recovery of 2.8 mg lycopene/kg tomato waste can be obtained after 4 hours of extraction and using tap water as the extracting liquid. The recovery percentage was of about 10%. The exhausted tomato byproduct can be easily dried and used in agriculture or as feeding for animals
Characterization of High Purity Lycopene from Tomato Wastes Using a New Pressurized Extraction Approach
No full textIn this paper, a method for the extraction of high purity lycopene from tomato wastes is presented. The method is based on a pressurized extraction that uses the Extractor Naviglio, and it is performed in the 0.7-0.9 MPa range. Tomato skin, the byproduct deriving from manufacturing of tomato, in a water dispersion, are used as starting material. Lycopene is transferred, for the effect of the high pressure used, in the form of molecular aggregates into the water as a dispersion, while apolar compounds remain in the matrix. The aggregates are easily purified in a single subsequent step by using methanol, thus, obtaining lycopene at 98% chromatographic purity or higher. A new stationary phase, phenyl-hexyl silicone, and a simple water/acetonitrile gradient were used for HPLC analysis of lycopene. The extract was characterized by UV-Vis spectrophotometry, 1H NMR, 13C NMR, and electrospray ionization mass spectrometry. An average recovery of 2.8 mg lycopene/kg tomato waste can be obtained after 4 hours of extraction and using tap water as the extracting liquid. The recovery percentage was of about 10%. The exhausted tomato byproduct can be easily dried and used in agriculture or as feeding for animals
From naïve Drawing to Cartesian Representation
No full textThe results of a didactic experience with 7 year-old pupils are reported. A series of motory and drawing activities, together with guided discussions, leads children to gradually master the bidimensional representation of space-time relationship. Therefore, a possibility is devised to introduce, to utilize and to understand very early a quite sophisticated mathematical tool, like the Cartesian plane
Enantioselective epoxidation of chalcones and naphtoquinones by (+)norcamphor-derived hydroperoxide
No full text(+)-Norcamphor-derived hydroperoxide has been employed in the asymmetric epoxidation of electron poor alkenes such as trans-chalcones and naphthoquinones. Optimization of the reaction conditions required the employment of n-BuLi/THF at -20degreesC to achieve ees up to 58%. The epoxide of vitamin K-3 has now been obtained with the best up to now reported value of enantioselectivity (51% ee)
From naïve Drawing to Cartesian Representation
No full textThe results of a didactic experience with 7 year-old pupils are reported. A series of motory and drawing activities, together with guided discussions, leads children to gradually master the bidimensional representation of space-time relationship. Therefore, a possibility is devised to introduce, to utilize and to understand very early a quite sophisticated mathematical tool, like the Cartesian plane
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