OPSIN (Open Parser for Systematic IUPAC Nomenclature) is an open source freely available program for converting chemical names, especially those that are systematic in nature, to chemical structures. The software is available as a Java library, command-line interface and as a web service (opsin.ch.cam.ac.uk). OPSIN accepts names that conform to either IUPAC or CAS nomenclature and can convert them to SMILES, InChI and CML (Chemical Markup Language).
OPSIN has grown from covering only simple general organic chemical nomenclature to the point of having competent coverage of all areas of organic chemical nomenclature. One of the most recent additions is comprehensive support for the nomenclature of carbohydrates. This brings support for dialdoses, diketoses, ketoaldoses, alditols, aldonic acids, uronic acids, aldaric acids, glycosides and oligosacchardides, in both the open chain and cyclic forms, named systematically or from trivial sugar stems with support for modification terms such as anhydro or deoxy.
OPSIN’s support for specialised and general organic nomenclature will be demonstrated through illustrative examples and accompanying performance metrics. We focus in particular on areas of nomenclature for which support was recently added and those that are complex to implement such as fused ring nomenclature.