Towards Novel Products

The main focus on modem biopharmaceuticals should be directed towards novel products which will be either monoclonal antibodies, recombinant proteins, cell and gene therapeutics, or viral products. Apart from product classes, new approaches to manufacture are also advancing, with transgenic animals and plants complementing existing cell culture-based expression (see Part IV, Chapters 5-11). (For a recent review, see Ref [8].)... 

V. Synthetic Studies toward Novel Heterocyclic Compounds and Natural Products... 

New synthetic methods are the lifeblood of organic chemistry. Synthetic efforts toward natural products often provide the impetus for the development of novel methodology. Reactive synthons derived from 1,3-dioxanes have proven to be valuable intermediates for both syn- and anfz-1,3-diols found in many complex natural products. Coupling reactions at the 4-position of 1,3-dioxanes exploit anomeric effects to generate syu-1,3-diols (cyanohydrin acetonides), autz-1,3-diols (4-acetoxy-1,3-dioxanes), and either syn- or azztz-1,3-diols (4-lithio-1,3-dioxanes). In the future, as biologically active polyol-containing natural products continue to be discovered, the methods described above should see much use. 

Structural characterization of NRPSs has yielded significant insight into the enzymology of these complex biosynthetic machines and has provided a framework for engineering these systems toward novel function. As summarized in this section, X-ray crystal and NMR structures have been determined for both individual NRPS domains and multidomain constructs. Overall, these studies support a monomeric structure for NRPS assembly line units where significant domain motion is necessary to allow participation of the various active sites in the chemistry leading to peptide products. 

Selection-coupled analysis/phase segregation. One strategy for simplifying the analytical challenge is to use phase segregation. Three subclasses are possible. In the first of these, a phase transition is part of the selection process. This includes not only the familiar crystallization-induced enantiomeric enrichment discussed above but also the experiments (primarily employed in experiments directed toward the production of novel materials) such as those described by Lehn and coworkers in 2005. In this study, an acylhydrazone library was created from guanosine hydrazide and a mixture of aldehydes (Fig. 1.22) in the presence of metal ions, formation of G-quartet structures led to the production of a gel. 

A novel method for production of paraffinic hydrocarbons, suitable as diesel fuel, from renewable resources was illustrated. The fatty acid ethyl ester, ethyl stearate, was successfully converted with high catalyst activity and high selectivity towards formation of the desired product, heptadecane. Investigation of the impact of catalyst reduction showed that the reduction pretreatment had a beneficial effect on the formation of desired diesel compound. The non-pretreated catalyst dehydrogenated ethyl stearate to ethyl oleate. The experiments at different reaction temperatures, depicted that conversion of ethyl stearate was strongly dependent on reaction temperature with Eact=69 kj/mole, while product selectivities were almost constant. Complete conversion of ethyl stearate and very high selectivity towards desired product (95%) were achieved at 360°C. 

The last example cited involves the microwave-assisted route towards novel 5-substituted-2,3-dihydroimidazo [1,2-c] thieno [3,2-e] pyrimidines described by Rao and co-workers. Employing microwave heating and an easy work-up procedure, the products were obtained in improved yields over the conventional methods (Scheme 3.53)83. 

Another concept towards novel MCRs was established in 1993 by us the union of MCRs [23], Our objective was to find reactions with maximal numbers of participating starting materials. Thus we considered combining several MCRs, since a single MCR already contains a high number of educts. Two MCRs can be combined if the product or an advanced intermediate of the first MCR is a intermediate or starting material of the second MCR. The starting materials should ideally not have the possibility for irreversible side reactions under the reaction conditions used. Scheme 3.16 illustrates this approach. 

The alteration of fermentation conditions, such as pH, drastically affects product concentrations. Research with C. ljungdahlii has shown that at high pH values (5.5-6), acetate was the dominant product, while at a lower pH (4-4.5), there was a drastic shift towards the production of ethanol. " Inhibition by end products or intermediates is the principal factor that limits metabolic rates and final product concentrations in many fermentation processes. Product inhibition can greatly affect the economics of commercialization. With regards to ethanol inhibition, growth of B. methylotrophicum was inhibited at alcohol concentrations of 5g/L. " However, a recently isolated clostridial strain was shown to tolerate ethanol concentrations up to 78g/L. Efforts have been made to eliminate the drawbacks of inhibition by improvement of bacterial strains to tolerate higher product concentrations and/or by use of novel separation coupled fermentation processes such as pervaporation, extraction, and membrane separation. 

However, in the 21st century, the ethical pharmaceutical industry has been fully geared towards the production of relatively safer, less toxic, more effective, higher therapeutic index, novel, innovative medicaments that will evidently help the mankind to afford a disease-free society besides, the elder ones with a glaring hope to live a still longer life span. 

Oksman-Caldentey, K.M. (2007) Tropane and nicotine alkaloid biosynthesis-novel approaches towards biotechnological production of plant-derived pharmaceuticals. Curr. Pharm. 

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