Substructure screening

Elemental composition Determination of substructures Screening for unknowns ... 

Adamson GW, Cowell J, Lynch MF, McLure AHW, Town WG, Yapp AM. Strategic considerations in the design of screening systems for substructure searches of chemical structure files. J Chem Docum 1973 13 153-7. 

The synthesis of small, focused arrays based on some of the hits may help define a series if the desired compounds are not available through substructure or similarity searching. The purpose of this type of array is not to optimize a hit but to help prioritize a series for further synthetic work. Inclusion of the original hit in the array is useful for confirmation of activity, particularly when supplies are limited or the screening sample was of low purity. 

Why evolution only made use of these elements cannot be answered. The fact that the Periodic Table holds the possibility of allowing something as wonderful as life to come into existence is and remains a mystery. But not only that at the end of the development, a being appears on the screen that is able to discover these very elements and to find out about their substructures. And the fact that we can ponder over this is even more mysterious. 

Creation of the retron or substructure. The user "draws" the retron on the computer screen with the mouse. Different menus allow the introduction of the necessary heteroatoms and atomic groups. 

You can then choose what bond order you want for the selected bond. You can select several bond orders at the same time. Click "Double," leaving the orders single and double both marked. Click "OK". The dialog box will disappear. Observe, however, that the bond remains selected. Click anywhere in the window for defining substructures and the rectangle round the selected bond will vanish. The screen will now look like the following figure ... 

When we have this dialog box on screen, we say we are in disconnection mode. On both right and left you can see the substructure previously introduced. The left-hand box remains to show the user how the retron looks like. It is not possible to alter the content of this box. The user can process the figure on the right to lead to the disconnection of the retron (i.e. elaboration of the synthon). These procedures are basically for ... 

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