Search results for "urea"

Organocatalytic Enantioselective Synthesis of α-Hydroxyketones through a Friedel−Crafts Reaction of Naphthols and Activated Phenols with Aryl- and Al…

2016

[EN] An efficient organocatalytic asymmetric synthesis of alpha-hydroxyketones has been developed. Quinine-derived thiourea catalyzed the enantioselective Friedel Crafts alkylation of naphthols and activated phenols with aryl- and alkylglyoxal hydrates, providing the corresponding chiral alpha-hydroxyketones with high yields (up to 97%) and excellent enantioselectivities (up to 99% ee).

Organocatalytic Enantioselective Synthesis of Pyrazoles Bearing a Quaternary Stereocenter

2016

An efficient one-pot asymmetric synthesis of pyrazoles bearing a chiral quaternary stereocenter has been developed. Quinine-derived thiourea catalyzed the enantioselective addition of pyrazolones to isatin-derived ketimines, providing the corresponding acetylated pyrazoles after in situ treatment with Ac2O/Et3N. The corresponding pyrazoles were afforded in high yields and excellent enantioselectivities.

Acute pancreatitis in children. An Italian multicentre study

2002

Abstract Aim . To evaluate the clinical, morphological and aetiological aspects of acute pancreatitis in children in Italy. Patients . The hospital records of 50 consecutive patients with acute pancreatitis observed in 5 Italian Pediatric Departments were reviewed. Results . A total of 25 males and 25 females (median age 10.5 years, range 2–17) were studied. Of these patients, 48 (96%) had abdominal pain. The pancreatitis was associated with biliary disease in 10 patients (20%); it was due to viral infection in 6 patients (12%), pancreatic duct abnormalities in 4 (8%), familial chronic pancreatitis in 3 (6%), trauma in 5 (10%) and other causes in 5 (10%); the pancreatitis was of unknown ori…

Università degli studi di Palermo: caratteristiche del profilo post-laurea

2008

Prima, durante e dopo: il percorso degli studenti dall’immatricolazione fino a cinque anni dopo la laurea

Modeling of an annular photocatalytic reactor for water purification: oxidation of pesticides.

2004

Photocatalytic oxidation (PCO) over titanium dioxide (TiO2) is a “green” sustainable process for the treatment and purification of water and wastewater. However, the application of PCO for wastewater treatment on an industrial scale is currently hindered by a lack of simple mathematical models that can be readily applied to reactor design. Current models are either too simplistic or too rigorous to be useful in photocatalytic reactor design, scale-up, and optimization. In this paper a simple mathematical model is presented for slurry, annular, photocatalytic reactors that still retains the essential elements of a rigorous approach while providing simple solutions. The model extends the appl…

Clinical efficacy of a bleaching enzyme-based toothpaste. A double-blind controlled clinical trial.

2015

Abstract Objectives To assess the efficacy of a bleaching enzyme-based toothpaste. Material and methods A randomized clinical trial was carried out, comprising 48 participants with teeth exhibiting color A3 or higher according to the Vita Classical guide. One-half of the sample received the bleaching enzyme-based toothpaste (White Kin ® ), while the other received placebo toothpaste. Both products were supplied in identical containers and had the same composition except for the active components. The teeth color was measured with a spectrophotometer. The patients were instructed to brush their teeth three times a day during 3 min with the assigned product, during 12 weeks. The color measure…

Effect of 15% carbamide peroxide bleaching gel on color stability of giomer and microfilled composite resin: an in vitro comparison

2011

Objectives: The effect of 15% carbamide peroxide bleaching gel on color stability and surface topography of a giomer and a microfilled composite resin was evaluated in the present in vitro study. Study design: Forty discs measuring 10 mm in diameter and 1 mm in thickness were prepared from a giomer and a microfilled composite resin. Each material yielded 20 discs with completely smooth surfaces. Then a spectrophotometer was used to measure L* (lightness), a* (redness, greenness) and b* (blueness, yellowness) color coordinates of all the discs. Subsequently, the specimens were subjected to 15% carbamide peroxide bleaching gel. After measuring the color coordinates once again, color changes (…

Sesquiterpene lactones and lignans from Centaurea species

1992

Abstract The aerial parts of Centaurea calcitrapa yielded cnicin, cnicin 4′-acetate, melitensin, a related elemanolide, the two new germacranolides 11α,13- and 11β,13-dihydrosalonitenolide, and the lignans arctigenin, pinoresinol and 7′( S )-hydroxyarctigenin. The latter compound is described for the first time as a natural product. The aerial parts of Centaurea pabotii yielded 11,13-dihydrodeacylcynaropicrin, aguerin A and a new guaianolide related to cynaropicrin.

Sesquiterpenes from Centaurea aspera

2005

Abstract The aerial parts of two subspecies of Centaurea aspera L. (Asteraceae) yielded the germacranolides 1a – h , 2 , 3 , 4 and 5 , the elemane derivatives 6d and 6f , the lignan matairesinol, the degraded terpene loliolide, and the onopordopicrin–valine dimeric adduct 7 . From these, compounds 1e , 3 and 6d are natural products. The chemical composition of the two subspecies is very similar, a circumstance which does not support a taxonomic subdivision of the species.