Fragment, creation

Fragment creation using retrosynthetically motivated shredding rules (may be altered by the user). 

The basic function of the JME Editor is to allow the creation and modification of molecules and reactions directly within a web page. The editor has all the standard chemical drawing and editing capabilities, mduding a rich set of keyboard shortcuts for adding common structural fragments easily (Figure 2-130). 

Up to this point we have addressed primarily the flaw structure and energy concepts in stress-wave loaded solids governing the creation of new fracture surface area (or the mean fragment size) in catastrophic fragmentation events. It remains to consider a concept which is frequently the end concern in impulsive fracture applications, namely, the distribution in sizes of the particles produced in the dynamic fragmentation event. 

When all available spectral information is processed the task involves creation of the most probable structure. If there are some facts indicating one or another structure a priori, one should try to draw theoretical possible pathways of its fragmentation and compare the result with the experimental spectrum. 

Fig. 6. The basic diagrams of the transport equation for p,0). (a) The diagonal fragment, (b) The destruction fragment, (c) The creation fragment.

The first part of this program is readily achieved. Indeed, let us consider for example the three diagrams of Fig. 6c (p. 175) for the creation fragment, which we respectively denote by A, B, and C. We have... 

The mass spectrometer can be regarded as a kind of chemistry laboratory, especially designed to study ions in the gas phase. [1,2] In addition to the task it is usually employed for - creation of mass spectra for a generally analytical purpose - it allows for the examination of fragmentation pathways of selected ions, for the study of ion-neutral reactions and more. Understanding these fundamentals is prerequisite for the proper application of mass spectrometry with all technical facets available, and for the successful interpretation of mass spectra because Analytical chemistry is the application of physical chemistry to the real world. [3]... 

Note that aldol condensations I, II and III concern the creation of a relative configuration 2,3-syn, which can be easily achieved starting from the (Z)-enolates 74a-74c. Scheme 9.27 summarises the synthesis of 93 and 95, which are equivalent to fragments B and A, respectively. Compound 88 is the abovementioned Prelog-Djerassi lactonic acid 42 which is obtained in optically pure from (>98% ee). On the other hand, for the stereochemical control of the aldol condensation IV a different methodology is necessary whih involves the coupling of two structurally predefined reactants and which will not be discussed here (Scheme 9.28). An important feature of this reaction is that the coordination of Li" " with the oxygen atom at the P-position of the aldehyde 95 is mainly responsible for the observed stereoselection [22e]. 

In creating synthetic routes for the development of drug molecules, the synthetic chemist wants to create a molecular entity in which functional groups (carbonyls, amines, etc.) are correctly positioned in three-dimensional space this will enable the creation of functional biophoric fragments such as the pharmacophore. The synthetic chemist has ten general classes of reactions available for such synthetic tasks ... 

In the following sections, we will describe in detail efforts to build fragment collections and the processes involved in their creation. Two such efforts were performed at a major pharmaceutical company (Pfizer) while a third took place at a biotech company (Vernalis). 

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