Complexation of Polyethyleneglycol Containing Small Molecules with Magnesium Chloride as a Purification and Isolation Strategy

Polyethyleneglycol (PEG) containing compounds are often non-crystalline, gel-like oils, which pose great challenges for handling, purification, and isolation, particularly on large scales. To overcome these isolation challenges, a new procedure has been established, which is based on the discovery that complexation with magnesium chloride (MgCl2) can transform these oily intermediates into solid complexes. This method significantly improves the handling of PEG compounds and leads a more process-friendly isolation for larger scale handling. Often, the resulting PEG–MgCl2 complexes could be used directly in subsequent transformations, such as a peptide coupling. Alternately, the inorganic Mg salt used in these weakly bonded complexes can be readily dissociated and removed from the desired PEG derivatives.