Revising a query

if you retrieved no records or too few records (Substructure Search):

Check that your search domain is set to the entire database.

Change the structural constraints in your query.  Add query features to allow a more general search of your class of compound

For example:

remove any neutral fragments which are not near the chiral centers

remove any explicit bonds or atoms that are not required

change bond types to increase bond variation

use the atom query features List and add the feature Q (any hetero atoms), or the feature A (any atoms) to increase atom variation

remove stereochemical requirements.

Try a 'multiple-fragment' query.

If you retrieved  too many records:

Refine the structural constraints in your query, and then search the same list.

For example:

limit substitution at specific positions with explicit hydrogens

change bond types to force the retrieval of solely rings or solely chains

restrict atom or bond variation with explicit atoms or bonds

Save a list of the records retrieved, refine your query, and then search the saved list.

Save a list of the records retrieved, conduct an additional search for compounds that you want to exclude (and save them), and then subtract the two lists