First, second and third generation

Explain the difference between the first-, second-, and third-generation cephalosporins. 

DISPLAY 8-1 Examples of First-, Second-, and Third-Generation Cephalosporins... 

Fig. 3.28 ROMP initiators, first, second and third generation Grubbs catalysts (complexes 71, 72, and 73, respectively) 74a-c 3-phenyl-indenylidene replaces the benzylidene carbene...

In all three of the above-mentioned chiral transformations, stoichiometric amounts of enantiomerically pure compounds are required. An important development in recent years has been the introduction of more sophisticated methods that combine the elements of the first-, second-, and third-generation methods and involve the reaction of a chiral substrate with a chiral reagent. The method is particularly valuable in reactions in which two new stereogenic units are formed stereoselectively in one step (Fig. 1-30, 4). 

The first part of this review deals with the synthesis and characterization of dendritic aliphatic polyesters based on 2,2-bis(dimethylol)propionic acid (bis-MPA) and 1,1,1 -tris(hydroxyphenyl)ethane (THPE), as core molecule. The convergent growth approach described earlier was applied. We also present H NMR self-diffusion studies of dendrimers of first, second, and third generation. 

Table 2. SEC Measurements of Dendritic Polyesters of First, Second, and Third Generation (D1, D2, and D3)...

The self-diffusion coefficients were calculated, and the effective radii of the dendrimers were estimated from the diffusion coefficients by assuming a spherical geometiy for all dendrimers. The so-obtained radii were 7.8,10.3, and 12.6 A for the first, second, and third generation dendrimer, respectively. 

First, second, and third generation dendrimers based on THPE (core) and bis-MPA (repeating unit) have been synthesized and characterized. SEC and NMR analyses verified that the dendrimers were monodisperse. Diffusion NMR was used to determine the dendrimers hydrodynamic radii in deuterated chloroform. First, second, and third generation dendrimers were found to be 7.8, 10.3, and 12.6 A, respectively. These were in agreement with sizes as determined from molecular models (Biichi). 

Calculate the packing factor for the first, second, and third generation of the fractal in Figure 2.12. 

Figure 28 Plot of ln(///0) versus (in arbitrary units) for the first, second, and third generation ferrocene dendrimers based on A. The largest compound shows the smallest slope a D. (Reprinted with permission from D. Valentini, M. Pregosin, P. S. Ruegger, H (2000) Organometallics 19 2551. 2000 American Chemical Society)...

Cojocel C, Goettsche U., Toelle K-L., Baumann, K. Nephrotoxic potential of first-, second-, and third-generation cephalosporins. Arch Toxicol 1988 62 458-464. 

Fig. 6.18. The structure of CB[7] and the first, second and third generation ferrocene-dendrimers (FCl, FC2 and FC3, respectively) and a schematic representation of their complexes along with their diffusion coefficients at different pH [44a]. (Adapted with permission from ref. [44a]. Copyright 2005 Royal Society of Chemistry.)...

Modulators and inhibitors of multidrug efflux transporters, such as Pgp, are used to reduce or inhibit MDR, which leads to a failure of the chemotherapy of, for example, cancers, epilepsy, bacterial, parasitic, and fungal diseases. Binding and transport of first-, second-, and third-generation modulators and inhibitors of Pgp take into account the properties of the drug (H-bonding potential, dimensions, and pK values) as well as the properties of the membrane. 

Penicillins Ampicillin Carbenicillin Ticarcillin Cephalosporins First, second, and third generation Mezlocillin Piperacillin Imipenem/cilastatin Aztreonam... 

Oncolytic Adenoviruses. A class of AdVs has been developed to specifically kill cancer cells, an approach that has been termed virotherapy [56]. Contrary to the approach pursuedi with first-, second-, and third-generation adenovirus vectors, these oncolytic or conditionally replicating adenoviruses (CRAds) are engineered in such a way that they retain the ability to replicate. This replication however, is tumor selective—the virus will only infect and proli-ferate in malignant cells with mutations in specific tumor suppressor genes [2, 19, 56]. Thus, a transgene is actually not required for the therapeutic effect to take place. 

Stewart P A, McLean W P (2005). Public Opinion Toward the First, Second and Third Generations of Plant Biotechnology. In Vitro Cell Developmen. Biol.—Plant 41(6) 718-724. 

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