RDKit Descriptor Calculator

Hi,

In RDKit Descriptor Calculator, I have seen that the descriptor ‘NumUnspecifiedStereoCenter’ which calculates the number of unspecified atomic stereocenters in a molecule. Actually what does the unspecified indicate here? Does it deal with the particular configuration of stereocenters (ANDn, ORn, ABSn)? Can you please explain what it actually counts?

An unspecified stereocenter, by the RDKit definition, is an atomic stereocenter that could have tetrahedral chirality specified but that does not.

The RDKit does not currently support extended stereochemistry like AND, OR, and ABS.

-greg