A combination of different spectroscopic techniques to monitor the "in situ" solid-phase synthesis of organic molecules

The efficacy, limitations and scope of different spectroscopic techniques to monitor solid-phase syntheses are discussed. The total solid-phase synthesis of a natural product derivative, 3,17-di-O-acetyllamellarin U, has been monitored by gel-phase NMR and HR-MAS NMR as appropriate. FT-IR and colorimetric tests also proved to be valuable tools for monitoring the progress of reactions. While the data obtained by FT-IR provided valuable information on some functional groups, the NMR data provided more specific structural information that allowed the progress of reactions to be monitored. After several reaction steps the "aging" of the resin only allowed the product covalently anchored to the resin to be investigated using an HR-MAS probe, a situation that severely limited the depth of analysis available.