gistfile1.txt

    SELECT ?smiles
    WHERE {
      SERVICE wikibase:mwapi {
        bd:serviceParam wikibase:endpoint "www.wikidata.org";
          wikibase:api "Search";
          mwapi:srsearch "haswbstatement:P235 -haswbstatement:P274";
          mwapi:srlimit "max".
        ?cmp wikibase:apiOutputItem mwapi:title.
      }
      OPTIONAL { ?cmp wdt:P2017 ?isoSmi }
      OPTIONAL { ?cmp wdt:P233 ?canSmi }
      BIND (COALESCE(?isoSmi, ?canSmi) AS ?smiles)
      FILTER (BOUND(?smiles))
      MINUS { ?cmp wdt:P31/wdt:P279* wd:Q25276 }
    }