Modifications creative

The structure of cationic lipids and polymers is readily amenable to chemical modification [35, 36] allowing the exploration of a virtually unlimited number of combinations and strategies at the mercy of chemists creative abilities. Various reviews have been focused on cationic lipids, dendrimers and polymers in terms of their chemical structures and their transfection properties [36—41], in an attempt to shed some light on the chemical requirements necessary to mediate gene delivery. The focus of this chapter will be to explore these carriers from a synthetic perspective, with a description of the chemical strategies used for the preparation via synthetic organic chemistry (excluding polymer synthesis) of cationic lipids and dendrimers. 

In order to utilize this approach the firm must develop systems that result in a compliant organization without restricting the required creativity or flexibility needed for method development, therefore, all of the quality elements listed in Table 1 must be implemented in the analytical research laboratory. Table 9 lists the modifications required to utilize developmental data. 

The first series of modifications featured in this chapter were all motivated by Good Intentions. In spite of creative ideas and considerable effort, these modifications failed because no one took the time to examine and expose their weaknesses. These undetected weaknesses caused undesired side effects. 

Although perfumers will sometimes try to produce as exact a duplication of a perfume as possible, and much can be learned by doing so, the most common application of the GC/MS-plus-perfumer analyses has been for the rapid development of approximate matches. The formulations of these matches are then used for the creative development of modifications, adaptations for different media, and so on, or even as the inspiration for genuinely original creations. 

We hope that the creativity of chemists dealing with synthesis of cyclophanes as well as synthesis of other classes of compounds will be stimulated to try new, creative syntheses of sophisticated, strained molecules. Thus, in view of successful fourfold-pyrolyses and the availability of the modification for sulfones of low volatility [18], sixfold-pyrolyses of sulfones promise some potential. This synthetic method will be undispensable for the synthesis of large, complex, and sophisticated molecules. 

Unique new enzymes are now readily accessible in quantity with properties that are amenable to modification on demand. It is my firm belief that such fascinating possibilities not only open new playgrounds for creative minds but will also assist each practising scientist with effective tools for tackling the future challenges in Organic Synthesis, and it is my hope that this volume will actively support this goal. 

Acknowledgments. We wish to acknowledge and thank Dr. F.L. Weitl, who has ably and creatively synthesized the macrochelating agents described here, and Dr. P. W. Durbin and her coworker S. Jones, whose evaluation of these compounds in mice has been essential in the modification and improvement of these materials. This research is supported by the Division of Nuclear Sciences, Office of Basic Energy Sciences, U.S. Department of Energy under Contract No. W-7405-Eng-48. 

The efficiency of the intramolecular Diels-Alder reactions of furan has been described in several reviews, including an excellent treatise by Lipshutz. Steric factors, rather than electronic or solvent effects, appear to have the greatest influence on the outcome of the cycloaddition [1,19,20]. Electronically-disfavored cycloadditions can be brought about by creative functional group modifications. Thus, an electron-deficient furan, such as one bearing an a-keto group, can be masked and induced to undergo cycloaddition, as shown in Eq.8 [21]. 

Those who would degrade the technique of molecular modification by reference to it as mere manipulation capable of achieving only me too products in the pharmaceutical industry, thus show not only a profound ignorance of the concretely demonstrable results of modem therapeutic research but also their ignorance of a profound method that is everywhere one of the most powerful creative resources in both man and nature. 

Thus, it is clear that Verhulst s logistic model exhibits the phenomenon of bifurcation. Nevertheless, it is a non-creative bifurcation. If the system is subject to a modification of the external parameters, the system can only shift fi-om one stable branch to another. 

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