DMSO is used as a reaction medium in selected steroid-intermediate processes. A documented spironolactone route uses it during conversion of a protected steroid ketone into an epoxide.
A step before the finished API
In this route, a sulfonium reagent and base generate a sulfur ylide, which reacts with the steroid 17-ketone. DMSO provides the medium for this carbonyl-to-epoxide conversion. Further transformations build the lactone and introduce the acetylthio group of spironolactone.
These are separate operations. The solvent used for one stage need not be used throughout the synthesis. Our spironolactone application article explains this particular DMSO-containing step in more detail.
Selecting DMSO for the intermediate
The relevant quality requirements come from the reaction mixture: the steroid substrate, sulfonium reagent, base and any additional solvent. Water and other impurities should be controlled against the established process.
Compare conversion, intermediate impurities and isolation when evaluating a different DMSO supply. Base-containing mixtures also need compatibility and thermal assessment. Downstream solvent removal is part of the API process, separate from incoming solvent testing.
For a steroid-intermediate enquiry, tell YUJI which step uses DMSO and provide the required specification.