Molecule Widget (Labs) node gives errors for molecule containing R-groups when the format is set ...

Hello everybody,

Since a while I’m using the Molecule Widget (Labs) node to input molecules on WebPortal’s workflows. In general this node works great and it’s very valuable for KNIME cheminformaticians community. Nevertheless I discovered that it has problems in specific cases. When I set the format to SMARTS and I draw a molecules structure containing R groups the following error is triggered:

Error: Convert error! SMILES saver: Unknown atom attribute 6

I’m using KNIME AP 5.1 and Molecule Widget (Labs) node corresponds to Ketcher v2.7.2.

Does anyone know why this happens and if it can be fixed? Workarounds are also welcome.

An example workflow is attached below.

molecule_widget_lab_r-groups_smarts_problem.knwf