Extensibility Wang method

In a more extensive study, 33 substituted carboxylic acids were coupled to chlorinated Wang resin employing an identical reaction protocol (Scheme 7.8b). In the majority of cases, the microwave-mediated conversion reached at least 85% after 3-15 min at 200 °C. These microwave conditions represented a significant rate enhancement with respect to the conventional protocol, which required 24-48 h. The microwave protocol has additional benefits in comparison to the conventional method, as the amounts of acid and base equivalents can be reduced and potassium iodide is no longer needed as an additive [28]. While no attempt was made to opti-... 

The photochemiluminiscence (PCL) assay was initially used by Popov and others (1987). Popov and Lewin (1994 1996) have extensively studied this technique to determine water-soluble and lipid-soluble antioxidants. The PCL assay measures the antioxidant capacity, toward the 02 radical, in lipidic and water phase. This method allows the quantification of both the antioxidant capacity of hydrophilic and/or lipophilic substances, either as pure compounds or complex matrices from different origin synthetic, vegetable, animal, human, etc. The PCL method is based on an approximately 1,000-fold acceleration of the oxidative reactions in vitro by the presence of an appropriate photosensitizer. The PCL is a very quick and sensitive method. Chua and others (2008) used this assay to determine the antioxidant potential of Cin-namomum osmophloeum, whereas Kaneh and Wang and others (2006) determined the antioxidant capacity of marigold flowers. The antioxidant activity of tree nut oil extracts was also assessed by this method (Miraliakbari and Shahidi 2008). 

Standard solid-phase peptide synthesis requires the first (C-terminal) amino acid to be esterified with a polymeric alcohol. Partial racemization can occur during the esterification of N-protected amino acids with Wang resin or hydroxymethyl polystyrene [200,201]. /V-Fmoc amino acids are particularly problematic because the bases required to catalyze the acylation of alcohols can also lead to deprotection. A comparative study of various esterification methods for the attachment of Fmoc amino acids to Wang resin [202] showed that the highest loadings with minimal racemization can be achieved under Mitsunobu conditions or by activation with 2,6-dichloroben-zoyl chloride (Experimental Procedure 13.5). iV-Fmoc amino acid fluorides in the presence of DMAP also proved suitable for the racemization-free esterification of Wang resin (Entry 1, Table 13.13). The most extensive racemization was observed when DMF or THF was used as solvent, whereas little or no racemization occurred in toluene or DCM [203]. 

A solid-phase extension of the UDC strategy for the preparation of highly pure and diverse arrays of l,4-benzodiazepine-2,5-diones has been reported. The method employed Wang resin-bound a-amino adds [75]. Another interesting solid-phase synthesis of l,4-benzodiazepine-2,5-diones was reported by Chen et al. [18b] that employed the Rink-isocyanide resin as the convertible isocyanide. 

Booksh, K.S., Lin, Z., Wang, Z., and Kowalski, B.R., Extension of trilinear decomposition method with an application to the flow probe sensor, Anal. Chem., 66, 2561-2569, 1994. 

Welch et al. evaluated analytical procedures and environmental issues. They investigated methods for the extraction and detection of cocaine, some of its metabolites, morphine, and codeine from hair. They concluded from a round-robin study that extractions with 0.1 ATHCL are as efficient to remove the target compounds from hair as enzymatic digestion that dissolve the hair. GC/MS with either El or Cl provides accurate determinations of the targeted compounds. External contamination by powdered or vapor-deposited cocaine was incompletely removed by all approaches tested, making it difficult to differentiate incorporated drug from external contamination. This was also proved in extensive laboratory experiments by Wang and Cone. ... 

Heteronuclear-correlation (HETCOR) MQMAS NMR is a very useful method for studying the connectivity between spin-1/2 and quadrupolar nuclei under high-resolution conditions. It was first demonstrated for a spin-3/2 nucleus by Wang et al. with a spectrum of NajPjOg correlating the Na and P (1=1/2) isotropic resonances [69]. Several schemes have been proposed to obtain similar spectra for spin-5/2 nuclei [92-94]. However, we have recently demonstrated that these schemes result in distorted spectra and that an extension of the original scheme proposed by Wang et al. should be used instead[95]. 

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