Dear Sudipta, Use Phenix eLBOW. Give the input SMILES string and get the pdb and cif restraint files as output. Also you can use http://cactus.nci.nih.gov/translate/ to first get the pdb coordinate file from the SMILES string and then run Phenix eLBOW to get the cif restraints.
Best regards, Avinash Punekar
