Phase target product

We have suggested that separation strategies be planned with the following goal in mind the target product(s) in a final reaction mixture should partition into a phase that is different from all the other components of the mixture.181 When this goal is met, reactions can be purified simply by workup, which involves simple phase separation techniques such as evaporation, extraction, and filtration. 

The major side reaction associated with the use of mixed anhydrides is aminolysis at the carbonyl of the carbonate moiety (Figure 7.4, path B). The product is a urethane that resembles the desired protected peptide in properties, except that the amino-terminal substituent is not cleaved by the usual deprotecting reagents. Hence, its removal from the target product is not straightforward. The problem is serious when the residues activated are hindered (Val, lie, MeXaa), where the amounts can be as high as 10%. Other residues generate much less, but the reaction cannot be avoided completely, with the possible exception of activated proline (see Section 7.22). This is one reason why mixed anhydrides are not employed for solid-phase synthesis. 

The use of reactive polymer supports to selectively remove target products from a solution-phase mixture... 

Solid-phase target-oriented total synthesis of natural products ... 

Solid-phase Target-Oriented Total Synthesis of Natural Products... 

The paradigm shift from critical activities from later drug development to earlier discovery phases some years ago has effectively led to a change in lead optimization and added a new dimension of complexity, while it is envisioned that from a multidimensional, data-driven process more suitable candidates in accord with the therapeutic target product profiles may emerge for the treatment of currently unmet medical needs. 

For a preparahve applicahon, focus is on recovering the targeted products while ophmizing produchon costs. The object of the separation is to reach the purity and recovery yield required for one or more specific components of the feed mixture. To maximize produchon, injechons are made as often as possible. The amount of stahonary phase used is set in order to minimize the costs of the product, equipment, and eluent consumption. Figure 12.2 presents the preparahve chromatogram of the same compounds as in Figure 12.1, where the injected amount is maximized in order to ophmize the process [5]. 

The liquid phase is poured into receptacle 8. Then, to wash dihydroxydiphenylsilane, the reactor is filled with a necessary amount of water, the mixture is agitated and after settling the acid waters are poured into collector 8. The target product is sampled to determine its solubility in acetone. If the solubility is complete, reactor 7 is filled with water again, the aqueous solution of the product is poured into centrifuge 9, which is a vertical suspended three-tower self-installing machine. 

These equations are supplemented by the equilibrium relationship between the solid and local liquid phase concentrations. Langmuir isotherm was chosen for the adsorption isotherm of a target product or by product ... 

When the relative volumes are known and the diffusion coefficients in the capsule core and capsule membrane can be estimated a priori in single component adsorption, the parameter to work with is the effective diffusivity in the adsorbent pore (Dn). Then, with the above estimated parameter values, the parameters of competitive adsorption are the maximum concentration at the solid phase of the adsorbent (CsmT), and the equilibrium constants of the target product (KS1) and byproduct (KS2)-... 

In the case of heterophasic copolymers, the polymer from the gas-phase reactor is transferred into another, smaller gas-phase reactor where the rubbery copolymer is made. After this step, hydrocarbon residuals are removed, and the powder is transferred to the extrusion section. Polymerization conditions in each reactor can be independently controlled, enabling production of both standard uni-modal and broad molecular weight multimodal grades. The production rate ratios between the reactors can be adjusted to meet the targeted product properties. 

Le et al. (2006) employed "amorphous citrate" gel method to prepare single phase ceramic powders of LaNiOs with controlled grain size by thermal annealing. The target product was obtained at 650 °C with particle sizes from 30 to 65 ran at annealing temperatures from 650 to 750 °C, while the crystalline sized varied from 10 to 15 ran. Accordingly, a wide... 

In the capture phase the objectives are to isolate, concentrate and stabilise the target product. 

In the capture phase the objectives are to isolate, concentrate and stabilise the target product. The product should be concentrated and transferred to an environment which will conserve potency/activity. At best, significant removal of other critical contaminants can also be achieved. 

The solute is the product of the pre-purification steps. It contains the target product and the impurities. Although the solute is a part of the chromatographic system it is not a free parameter like the eluent or the adsorbent. Subsequent to previous crude separations the composition of the feedstock is fixed and the chromatographic system is completed by the choice of mobile phase and adsorbent. 

In addition, more product can be loaded on a silica gel than on reversed phase materials. Furthermore the separated products are readily recovered by simple evaporation procedures, while the isolation of products from an RP separation process often require additional work-up steps. These steps include the removal of salts or other aqueous phase additives and extraction of the target product after evaporation of the organic phase (Section 4.3.3.5). 

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