More Recent Approaches

An attempt has been made to define a single critical value, like for brittle fracture, from these curves (5). However, the amount of crack growth which is used to define this critical value is inevitably rather arbitrary. A more recent approach (6) is to fit a power law curve of the form... 

The steric constant Es and related quantities do not constitute the only approach to the study of steric effects on reactivity. Steric strain energy calculations and topological indices are more recent approaches. Qualitative concepts have been... 

One of the more recent approaches for designing xc functionals is based on inverting eq. (6.7). An accurate electron density may be calculated by advanced wave... 

We then turn to a more recent approach to the determination of i by Point [51, 52] in Sect. 3.7 explaining how it differs from that of Lauritzen and Hoffman (LH). Section 3.8 covers other proposed nucleation models and we conclude with an overview of nucleation theories and their successes and most notable shortcomings. 

With only few exceptions, most log P programs refer to the octanol-water system. Based on Rekker s fragmental constant approach, a log P calculation for aliphatic hydrocarbon-water partitioning has been reported [96]. Another more recent approach to alkane-water log P and log D is based on the program VolSurf [97]. It is believed that these values may offer a better predictor for uptake in the brain. 

There are two main scopes for the use of microbiocides in PVC and other polymers. The classical approach is the protection of susceptible plastic material whereas a more recent approach is the achievement of biocidal surfaces. 

A more recent approach, which also profits from the synthetic versatility of stabilized thionium ions, has been elaborated by Berard and Piras [22]. These authors observed that the cyclobutane thionium ions 1-76 obtained from the cyclopropyl phenyl sulfides 1-75 by treatment with pTsOH under anhydrous conditions can be trapped by an adjacent electron-rich aromatic ring to give the chromane derivatives 1-77 in good to excellent yields (Scheme 1.20). As expected, 1-77 were obtained as single diastereoisomers with a ds-orientation of the methyl and the phenylthio group as a consequence of steric constraints. 

In a more recent approach, the same group synthesized macrocycles using a Passerini reaction followed by a ring-closing metathesis [23], but the final cycliza-tion gave only low yields. 

A more recent approach is the reductive 1,4-dechlorination of l,2-bis(chloromethyl)-... 

More recent approaches to the effects of the ligands on the redox activity of metal complexes are based upon the assumption that the electrode potential of a redox change involving a metal complex is determined by the additivity of the electronic contribution of all the ligands linked to the metal centre, or to the overall balance between the c-donor and the 7r-acceptor capability of each ligand.3 In particular two ligand electrochemical parameters have gained popularity ... 

A more recent approach to the epoxidation of allylic alcohols makes use of a vanadium polyoxometallate, together with a sterically demanding chiral tartrate (or TADDOL) -derived hydroperoxide, to give a highly chemoselective, regiose-lective and enantioselective outcome (Figure 11.2). ... 

Space limitations unfortunately preclude a full discussion of two more recent approaches to permanently immobilized Ru catalysts, see (a) Monolithic Materials New High-Performance Supports for Permanently Immobilized Metathesis Catalysts, M. Mayr, B. Mayr, M.R. Buchmeiser, Angew. Chem. 2001, 113, 3957-3960 Angew. Chem. Int. Ed. 2001,... 

More recent approaches have used resin extractions, initially the nonionic resin XAD2 and XAD7. These resins are effective where the pH was kept at 10 while mixing the plasma and resin. The supernatant is discarded and the bile... 

Besides eight syntheses, which started from L-phenylalanine or a derivative, two approaches towards (+)-preussin employed L-serine or L-aspartic acid. In one of the more recent approaches towards preussin Craig and coworkers [63] used l-serine (103) as starting material (Scheme 27). 

The preparatively useful and simple N-alkylation procedure that utilizes a combination of carboxylic acid and sodium borohydride has been applied to carbazole giving an efficient 9-ethylation. Also of preparative importance is the use of thallous ethoxide as base in dimethylformamide-ether 9-methyl-, 9-ethyl-, n-propyl-, n-butyl-, benzyl-, and n-allylcarbazoles were efficiently produced, as well as 9,9 -dicarbazolylalkanes using C3, C4, and Cg dihalides. 2-Acetyl- and 2-vinylcarbazole were also efficiently 9-ethylated by this route. Another more recent approach to N-alkylation of carbazole utilizes potassium terf-butoxide in the presence of a catalytic quantity of 18-crown-6 9-methylcarbazole was prepared in high yield. ... 

The structures of the compounds were elucidated by a combination of NMR techniques (lH-, 13C-, and 13C-DEPT NMR) and chemical transformation, enzymatic degradation, and as well as mass spectrometry, which gives information on the saccharide sequence. A more recent approach consists of an extensive use of high-resolution 2D NMR techniques, such as homonuclear and heteronuclear correlated spectroscopy (DQF-COSY, HOHAHA, HSQC, HMBC) and NOE spectroscopy (NOESY, ROESY), which now play the most important role in the structural elucidation of intact glycosides. These techniques are very sensitive and non destructive and allow easy recovery of the intact compounds for subsequent biological testing. 

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