A compound has sulfate ester when it has any of the groups below. A parent group is never matched itself, and its count of a compound is the number of occurrences of all of them together.

Parent groups under it: sulfate monoester (acid or anion).

Groups directly under it

Through the parent groups above, also: sulfate monoester (acid), sulfate monoester (anion).

In the ATB

• 200 annotated compounds have it;
• 1 of them have experimental reference data;
• 8 are monofunctional: this is their only group, once (rings count as groups, so a phenol is not).

The annotated compounds are those with experimental reference data plus small, neutral organic compounds (up to 12 heavy atoms), not every ATB molecule. Through the API: GET /api/v1/molecules?functional_group=sulfate.

Annotation scheme 2.