In Compounds and Reagents libraries, uniqueness rules can be based on the chemical structure if the Include structure uniqueness checking option is enabled.
In the case of Reagents, when a CAS number is entered, it will be always used for uniqueness checking.
There are seven uniqueness rules for chemical structures:
1. Double Bond Stereo: Double bonds with E/Z geometric stereochemistry only match bonds with the same stereo configuration.
If this rule is enabled, the following structures are considered different compounds, since the first one has E stereochemistry and the second has Z stereochemistry:
To be considered duplicates, both structures must have the same stereo configuration.
2. Full: Matches must contain the query structure and contain no additional non-hydrogen atoms bonded to any of the atoms in the query structure. Additional non-bonded atoms are allowed.
If this rule is enabled, a full match is a structure that matches the structure that is being registered, except for additional hydrogen atoms. For example:
These are considered unique compounds because the second structure has a carbon atom bonded to an atom in the query structure.
3. Match Charge Carbon: An uncharged carbon only matches a similarly uncharged carbon.
If this rule is enabled, the structures below are considered different, as there is a charged carbon atom in the first molecule, but it is not charged in the second:
4. Match Charge Hetero: An uncharged heteroatom only matches a similarly uncharged heteroatom.
This rule applies to atoms like N, O, S, P, Cl, Br, etc. If this rule is enabled, the following structures will be considered different compounds, as the oxygen atom is charged in the first one and not charged in the second:
5. Identity: Matches must be chemically identical, including stereochemistry, charges, and isotopy. This setting supersedes all other individual settings.
Only molecules that are identical to the structure are going a match. If this rule is enabled, then the rest of uniqueness rules are ignored, as this rule supersedes the others.
If the Identity rule is enabled, an example of unique compounds would be:
Structures with different isotopes are considered different compounds.
6. Tautomer: All tautomeric forms are considered as matches (the Ful rule must be enabled for Tautomer check to work). This setting supersedes Match Charge Carbon and Match Charge Hetero.
If this rule is enabled, the following structures are considered duplicates:
Considerations for the Tautomer uniqueness rule:
- The Full uniqueness rule must be enabled in order for the Tautomer uniqueness rule to work.
- The Tautomer uniqueness check supersedes the Match Charge Carbon and Match Hetero uniqueness rules.
- The Tautomer uniqueness check considers all tautomeric forms to be a match.
- The Identity rule supersedes this rule. Tautomeric forms will not be considered a match if the Identity rule is on.
7. Tetrahedral Stereo: Stereogenic centers with explicitly defined stereo configuration match only those with the same stereo configuration, but do not match those with the opposite or unspecified stereo configuration, or those without tetrahedral stereochemistry.
This uniqueness rule is specific for stereo configuration and will provide a match only when the stereo configuration in the chiral carbons is the same.
If this rule is enabled, the following structures are considered different compounds:
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