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ChemOffice.Com - CambridgeSoft

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Administrator<br />

The hit list will include the following:<br />

OH<br />

OH<br />

The dot indicates an atom shared between the two<br />

fragments. The hit list will not include this molecule<br />

if the overlap option is deselected.<br />

Full Structure Searching<br />

Selecting the Full Structure radio button in the<br />

Search Type Preferences finds structures that<br />

completely match the query. You may get more<br />

than one hit if there are duplicates in the database<br />

or if there are stereoisomers in the database and you<br />

did not specify a particular one to be matched. For<br />

more information, see “Stereochemistry” on page<br />

322.<br />

Stereochemistry<br />

You can specify whether or not you want a<br />

structure search to consider stereochemistry. Given<br />

a structure with one or more stereocenters, you can<br />

store four different possibilities:<br />

• A given absolute configuration. To specify this,<br />

centers must be drawn with stereo bonds, and<br />

the entire structure marked Abs (CHIRAL).<br />

• A racemic mixture of the drawn configuration<br />

and its mirror image. This is drawn as above,<br />

but without the Abs (CHIRAL) mark.<br />

• An unmarked structure, representing unknown<br />

stereochemistry, or a mixture of all possible<br />

stereoisomers.<br />

• A given relationship between centers. That is, a<br />

known orientation of the substituents with<br />

respect to each other, rather than a known<br />

absolute configuration. To specify this, centers<br />

are drawn, not with the standard hashed and<br />

wedged bonds, but with thick stereo bonds.<br />

If these options are checked in the Search tab of the<br />

Preferences dialog, then any stereochemistry<br />

indicated on the query must be matched by the<br />

target. For more information on changing<br />

searching preferences, see “Setting Search Details<br />

Preferences” on page 327.<br />

3D Properties<br />

3D queries are particularly useful in<br />

pharmacophore searching where you are looking<br />

for a particular 3D relationship among atoms and<br />

bonds, for example in a series of potential receptor<br />

ligands. You can create a 3D query in ChemDraw<br />

Pro by adding geometries (lines, planes, etc.) and<br />

constraints (specified as ranges) to a query<br />

structure. For example, you might specify that two<br />

atoms must be between 4Å and 5Å apart, or that<br />

two planes must be separated by 80-100°.<br />

ChemFinder can then use these properties to refine<br />

a search. See the ChemDraw User’s Manual for<br />

information on how to add 3D properties to<br />

structures.<br />

Reaction Searches<br />

You can search and store reactions. In a reaction,<br />

one or several compounds (reactants) are<br />

transformed into other compounds (products).<br />

Individual reactants (or products) are separated<br />

from each other with plus signs. The reactants are<br />

separated from the products with an arrow.<br />

Reactions may have multiple steps, for example<br />

(A) (B) (C) (D). Here, (A) is the<br />

reactant and (D) is the product. (B) and (C) are<br />

intermediates for the complete reaction.<br />

A multi-step reaction is actually a shorthand<br />

notation for many related reactions. In the example<br />

above, (B) is an intermediate for the complete<br />

reaction, but it is also a reactant relative to (C) or<br />

(D). It is also a product relative to (A). The<br />

322•Searching<br />

<strong>CambridgeSoft</strong><br />

Reaction Searches

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