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ChemOffice.Com - CambridgeSoft

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The “A” label denotes that the atom may match any<br />

atom except hydrogen. The indicator near the bond<br />

indicates that the bond has been defined; in this<br />

case, in the Bond Properties dialog of ChemDraw,<br />

you specified that the bond type may be single or<br />

double, S/D. Finally, by entering “S,Se,Te”<br />

enclosed in brackets, you specified that one of these<br />

elements must match in the target molecules.<br />

Searching Link Nodes and Multivalent<br />

Rs (MVRs)<br />

ChemFinder versions 8 and later contain a new<br />

atom type, the link node. A link node is a<br />

placeholder for zero or more unspecified atoms. It<br />

is especially useful when searching for targets with<br />

any of several ring sizes, or chains substituted in<br />

particular ways at either end. While link nodes are<br />

traditionally divalent, ChemFinder places no<br />

constraints on the upper limit of the range. Multivalent<br />

R (and A) atoms are functionally similar to<br />

link nodes. They may be thought of as “higher<br />

valent” link nodes.<br />

O<br />

(CH 2 ) 1-2<br />

Br<br />

(CH 2 ) 0-200<br />

Br<br />

Searching Fullerenes<br />

A search of fullerenes can illustrate the restrictions<br />

you can place on a formula search. Suppose you<br />

want to find all fullerenes containing 20 to 80<br />

carbon atoms, but you also do not want to include<br />

large organic molecules.<br />

The formula query could be:<br />

C20-80 H0<br />

By designating zero hydrogen atoms, you exclude<br />

hydrocarbons from the hit list. By clearly<br />

capitalizing the elements and spacing the query, you<br />

avoid searching ambiguities, although there were no<br />

ambiguities in this example.<br />

Hits cyclopropanones,<br />

cyclobutanones, and<br />

ß-lactams<br />

Cl Ph<br />

A<br />

A multivalent “A” query<br />

Hits alpha, omegadibromides<br />

and<br />

bromine<br />

Cl Ph<br />

(LN) 1-999<br />

The traditional representation of a link node is CH2,<br />

but this is misleading because any atom type can<br />

substitute for the link node. For this reason,<br />

ChemFinder represents link nodes as LN.<br />

NOTE: ChemDraw recognizes link nodes, but does not<br />

support an “LN” atom type. Use (R) instead of (LN) when<br />

drawing the query in ChemDraw or with the ChemDraw<br />

ActiveX control.<br />

Although any atom type of a target atom matches a<br />

link node, you can impose two restrictions the on<br />

the link node:<br />

• Unsaturation<br />

• Ring topology.<br />

ChemFinder<br />

<strong>ChemOffice</strong> 2005/ChemFinder Searching • 339<br />

Search Examples

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