I apologize in advance if I will be not enough precise in the question but I'm new in this field. I'm trying to perform a mapping between different compound identifiers by mean of PubChem database. I analyzed the compound identifiers such as PubChem CID, SID, InChI, SMILE and CAS number, moreover I understood that if a molecule has more isomers at each isomer will be assigned a diverse CAS number, but why at same CAS number id are there different CIDs?. I have not clear the reason of different molecular structure (different CIDs) but same CAS number. I suppose that the structural difference, shown by different CIDs, is not to attribute to the isomery but to something else, what? To explain me better, in PubChem the budesonide compound has several CID identifiers (3033890; 2462; 24867460; 46780910; 40000; 5702148; 122130640; 5281004; 63006) and two CAS number corresponding to isomers 51333-22-3 and 51372-29-3. I observed the compound structure of every CIDs and I noticed a slight difference in the chemical structure but how is this structure difference called?
Thanks in advance to everyone that will can help me!