As shown in the TCMGeneDIT web site, they have links to the STITCH database. I will need to contact them if this part of dataset is needed.
When you have the STITCH/PubchemIDs, you can also use them for mapping to DBpedia. You can retrieve the IDs from DBpedia like this:
SELECT *
WHERE {?dbpedia_uri <http://dbpedia.org/property/pubchem> ?pubchem_id}
Cheers,
Matthias
