Efficiency of the Synthesis

If all operations are executed manually in the synthesis, one coupling step with each of the 20 amino acids can be easily realized every day. As a consequence, in 2, 3, 4, 5 or 6 days, 400, 8,000, 160,000, 3,200,000 or 64 million peptides, respectively, can be made. Or, to put it in another way, a chemist, working with the method, can produce, in a single week, more compounds than 

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The template effects of potassium and lithium ions are responsible for the efficiency of the synthesis of macrocyclic ligands in 18-CROWN-6 and2,2.7,7,12,12,17,l 7-OCTAMETHYL-21,22,23,24-TETRAOXAPER-HYDROQUATERENE. 

The choice of experimental conditions exerts a major influence on the course of Nenitzescu procedure and thereby determines the structure of the major product. The mechanism demonstrated to be operative for the method can be employed to understand the genesis of certain anomalous products and suggests ways to avoid them, thus increasing the efficiency of the synthesis of 5-hydroxyindoles. 

Macromonomers generally exhibit low molecular weights (up to 20,000) which allows accurate control of functionalization yield. Careful sample characterization and polydispersity control are necessary to check the efficiency of the synthesis. 

A one-pot technique, combining two or more glycosylation steps based on activation of one donor over another, have also been developed [182,189-191]. This one-pot technique is virtually a variation of a simple stepwise selective activation strategy, which allows further improvement in the efficiency of the synthesis by avoiding the necessity for isolation (and purification) of the intermediates. 

From this it can be concluded that the curvature of IDMS calibration curves can be described very accurately by means of higher order polynomials. The ability to check different models allows one to adapt the same calculation procedure regardless of the actual analytical situation. This is especially important in cases where, due to low efficiency of the synthesis, a large amount of unlabeled or partially labeled material is present in the IS. The setup of analyses with an IS of low mass increment is also facilitated (Jonckheere et al., 1982). In contrast to other calibration methods, no initial estimates of the amount of unlabeled product and/or influence of naturally... 

The Stoddart group has used the principles employed in their catenane studies to synthesise both a molecular trifoil knot and its isomeric large ring in very low yield. These isomers were separated by HPLC and characterised by liquid secondary ion mass spectrometry. The synthetic procedure, which is illustrated schematically in Figure 5.26, was based on the formation of a double-stranded supramolecular complex between an acyclic 7C-electron-rich, 1,5-dioxynaphthalene-based polyether and an acyclic 7i-electron-deficient bipyridinium-based tetracation. The extremely low efficiency of the synthesis in this case appears to reflect an unfavourable solution geometry of the intermediate host-guest complex - the latter... 

The conversion efficiency of the synthesis gas-to-methanol step is about 85%, and it is usually assumed that improved catalytic gasification techniques are required to raise the overall conversion efficiency above the 51% mentioned above (Faaij and Hamelinck, 2002). The total efficiency will become lower if all life-cycle contributions involving energy inputs, e.g. for collecting and transporting biomass, are included (EC, 1994). 

Synthesis. The synthesis of these new compounds are shown in Schemes 4-8. Condensation of -chloropivaloy1 chloride with tri-methylsilyl chloride-treated benzylhydroxylamine in methylene chloride in the presence of pyridine gave a hydroxamic acid derivative 9 in good yield. It is important to block the hydroxyl group of the hydroxylamine to ensure the desired N-acylation otherwise, a stable mixture of 40 60 N- and O-acylated products (9, 10) will be obtained. This isomeric mixture is not only difficult to separate but also reduces the efficiency of the synthesis. 

The synthesis of organic molecules by means of carbon ions can be considered. A relatively long series of essentially bimolecular reactions are suggested, as listed below. Energetics and rate constants for the species and processes listed are available (Le Teuff et al., 2000). Listed below are some of the reactions in the chain leading to the formation of ( -31 hi where n = 1 and 2. The efficiency of the synthesis depends on the ease of production of C+ in the dense molecular clouds. The slow radiative association rate of C " with H2 starts the chain of reactions ... 

The cleaned synthesis gas can enter the synthesis gas compressor (10), where it is compressed to synthesis pressure. Within the syngas compressor, the gas is dried by the ejector driven Casale liquid ammonia wash (11) to remove saturation water and possible traces of COj. This proprietary technology further increases the efficiency of the synthesis... 

The side chain is formally the assembly of an oxalate derivative, A-benzoylpiperazine and the azaindole (Figure 7). In exploring alternate options, we sought to explore both stepwise and convergent approaches—modifying the synthetic location of the side-chain installation and seeking an approach that offered the greatest impact to the overall efficiency of the synthesis. 

Even the shape of the specimen holder inside the oven can affect the synthesis. According to Liu et al., A semi-closed container retains the gas precursor for more time improving the efficiency of the synthesis [78]. 

In 2010, Li, Guan, and co-workers began a series of studies based on helical polymers. The first investigation addressed the efficiency of the synthesis of helical polymers. The monomer that was used in this study was a methoxy-substituted 2-amino benzoic acid (13). In a first test, the polymer was synthesized in AT-methyl pyrrolidone (NMP)/pyridine in the presence of LiCl (to avoid intramolecular hydrogen-bond formation) however. 

The efficiency of the synthesis could in fact be improved by a modification of the starting material, utilizing a more crowded chiral reagent with two centers of asymmetry ... 

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