22321-84-2Relevant articles and documents
Spectroscopic and biocatalytic properties of a chlorophyll-containing extract in silica gel
Lipke, Agnieszka,Trytek, Mariusz,Fiedurek, Jan,Majdan, Marek,Janik, Ewa
, p. 158 - 164 (2013/10/08)
UV-Vis absorption and fluorescence spectra of chlorophyll a (in the form of spinach extract) in acetone solution and in silica gel showed a predominance of pigment dimers in its overall concentration and an evident transformation of chlorophyll a to pheophytin with time. The dimerization constant of chlorophyll a in acetone was log Kdim = 2.14, whereas the constants for chlorophyll a and pheophytin a in alcogel were log Kdim = 4.70 and log Kdim = 5.22, respectively. Biocatalytic experiments indicated the possibility of using the pigment embedded in silica gel, i.e. mainly its dimeric form, for biotransformation of α-pinene to pinocarveyl hydroperoxide, trans-pinocarveol, pinocarvone and myrtenal. The advantage of a heterogeneous biocatalytic system (composed of a solvent and silica gel) over a homogeneous system (single phase of chloroform) is the possibility of reusing the biocatalyst with about 10% preservation of its activity.
Mechanism of the aerobic oxidation of α-Pinene
Neuenschwander, Ulrich,Guignard, Florian,Hermans, Ive
experimental part, p. 75 - 84 (2011/02/21)
A combined experimental and theoretical approach is used to study the thermal autoxidation of α-pinene. Four different types of peroxyl radicals are generated; the verbenyl peroxyl radical being the most abundant one. The peroxyl radicals propagate a long
Photooxygenation in polystyrene beads with covalently and non-covalently bound tetraarylporphyrin sensitizers
Griesbeck, Axel G.,El-Idreesy, Tamer T.,Bartoschek, Anna
, p. 245 - 251 (2007/10/03)
Two reaction protocols are described which involve the use of polymer supports as reaction media for photooxygenation processes: 1) The use of polystyrene beads (PS) loaded with tetraphenyl- (TPP) or tetratolylporphyrin (TTP), swollen with the substrate in an appropriate organic solvent and subsequent irradiation under air. Products were isolated simply by dissolution in alcoholic solvents and filtration. 2) Covalently linked tetrastyrylporphyrin in polystyrene-divinylbenzene beads were synthesized by emulsifier-free emulsion polymerization and directly used for the photooxygenation protocol described above. The latter alternative allows also the use of less polar solvents for the extraction of the oxygenation products from the polymer beads. From the sensitizer loading degree, an optimal substrate/sensitizer molar ratio of 1,000-2,000 was determined and recyclization is possible for at least five times resulting in a minimum turnover number (with respect to the sensitizer TTP) of 5 × 104 (after five cycles). Both approaches were applied to the ene reaction of singlet oxygen with citronellol (1), the regioisomeric pinenes 3 and 5, and the allylic alcohols 9a - c, respectively, as well as to the [4 + 2]-cycloadditions of singlet oxygen to sorbinol (7) and the chiral diene 11.
