DMSO is used in a published ganciclovir route during protected-guanine coupling and in a later crystallization operation. These are two separate applications within the disclosed process.
Reaction medium for coupling
The coupling step builds the required nucleoside-related structure from the protected starting components. DMSO provides the reaction medium. Protecting groups, electrophile and reaction conditions determine conversion and the pattern of related impurities.
Evaluate selectivity and the quality of the isolated intermediate when comparing solvent supplies. A favorable result on one guanine derivative cannot be assumed for every nucleobase or antiviral.
A later crystallization use
The same disclosure uses DMSO with another solvent during ganciclovir crystallization. Here dissolution, solvent composition and the resulting solid are the practical concerns.
Assess impurity removal, filtration, washing and residual solvent as part of this operation. Requirements for a crystallization mixture may differ from those for the earlier reaction solvent.
Set water and impurity limits separately for each step. Base-containing reaction mixtures need their own compatibility review, including the documented hazards of sodium hydride/DMSO combinations.
For sourcing, tell YUJI whether your DMSO is intended for coupling or crystallization and provide the corresponding specification.