Catechol-functionalized Initiator

Figure 10.6 Schematic representation of polymer preparation using catechol-modified and polymerizable monomers (A) and using a polymer-bound initiator to form a block copotymer (B). In the presence of bi-functional crosslinkers, potymerization forms a three-dimensional pol3mier network containing catechol (C). R represents the side chain of the monomers used to copotymerize with the catechol-functionalized monomers.

Waldmann et al. used tyrosinase which is obtained from Agaricus bisporus for the oxidation of phenols to give ortho-quinones via the corresponding catechols in the presence of oxygen (scheme 33).1881 A combination of this enzymatic-initiated domino process with a Diels-Alder reaction yields the functionalized bicyclic components 164 and 165 as a 33 1 mixture starting from simple p-methyl-phenol 160 in the presence of ethyl vinyl ether 163 as an electron rich dienophile via the intermediates 161 and 162 in an overall yield of 77%. 

Table 2 The reactivity of complexes [M(triphos)(catecholate)J+ (M=Co, Rh, Ir) with molecular oxygen as a function of the catecholate/ semiquinone oxidation potential. I=no reactivity 11= the oxygenated complex regenerates the initial complex in the quinone form by release of superoxide ion III = the oxygenated complex regenerates the initial complex in the quinone form by release of molecular oxygen...

Novel carbonylative carbocyclizations of 1,6-diynes promoted by Ru3(CO)i2/P(hex-c)3 in the presence of HSiMc2Bu-Z give bicyclic o-catechol derivatives by incorporating two carbon monoxide molecules as the 1,2-dioxyethenyl moiety (equations 148 and 149)346. This reaction is tolerant of functional groups such as ester, ketone, ether and amide. The disilylated product 366 is formed through dehydrogenative silylation of the initially formed mono-silyl product 365 under the reaction conditions. 

Determine the total protein in triplicate by the Bradford method using bovine serum albumin as standard solution [2], Determine the enzymatic activity of jack fruit crude extract in triplicate by measuring the absorbance at 410 nm of o-quinone produced by the reaction between 2.8 mL of 0.05 mol L 1 catechol solution and 0.2 mL of supernatant solution in 0.1 mol L 1 phosphate buffer solution (pH 7.0) at 25°C. The initial rate of enzyme-catalyzed reaction is a linear function of time for 1.5-2.0min. One activity unit is defined as a quantity of enzyme that causes the increase of 0.001 absorbance per minute under conditions described above [1]. 

Figure 2.22. Initial velocity of oxygen consumption as a function of the substrate (catechol) concentration in the presence of 0.074mg (7.11 x 1(T9M) tyrosinase (A), 2.0mg (2.8 x 1(T4M with a corresponding concentration of the mineral active sites, [M5]1.71xl(r6) of 8-Mn02 (B) and 10.0 mg (1.40 x 10 3M with a corresponding concentration of the mineral active sites, [M ]8.54 x 10-6) of S-Mn02 (C). Reprinted from Naidja, A., Liu, C., and Huang, P. M. (2002). Formation of protein-birnessite complex XRD, FTIR, and AFM analysis. J. Coll. Interface Sci. 251,46-56, with permission from Elsevier.

Fig. 8-15. Changes in the degree of the darkening of catechol solution at the initial pH of 6.0 as influenced by various oxides as a function of time (Shindo and Huang, 1984b).

Figure 10.4 Diversity of chemistiy structures utilized to create biomimetic adhesive polymers. Catechol side chain (A) modification alters its interfacial binding strength and reactivity. Substitution can be achieved by replacing -H at the para position with chloro-(B), nitro- (C) and hydrojyl (D) groups or a hydro)yl group at the meta position (E). The benzene ring can be substituted with a pyridine group (F). Linking the catechol with a polymer can be achieved via reaction of the amino acid (G), acid (H), or amine (I) groups. Catechol modified with a bromide propionamide Initiator to initiate polymerization (J) or functionalized with polymerizable methacrylamide (K), vinyl (L), and M-carboxyanhydride (NCA, M) groups.

Figure 10.7 Schematic representation of initiator-modified catechol to prepare pol miers end-functionalized with eateehol. R represents the side ehain of the monomers used during polymerization.

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