Resin loading

Swali, V., Wells, N.J., Langley, G.J., and Bradley, M. (1997) Solid-phase dendrimer synthesis and the generation of super-high-loading resin beads for combinatorial chemistry. J. Org. Chem. 62, 4902-4903. 

After isolating the product of a solid phase synthesis, the support (resin + linker) is usually discarded as waste, although successful examples of its reuse in further synthetic cycles are known with trityl type linkers (Frechet and Haque 1975). To reduce both volume of operation and amount of waste, the loading of the resin (quantified as millimoles of functionality per gram) has to be increased. Besides theoretical limitations (for polystyrene this is reached when every phenyl ring is substituted by the linker), there may be practical boundaries for using highly loaded resins in solid-phase supported synthesis. This issue was studied... 

To study the effect of loading, the synthesis depicted in Scheme 1 was repeated using different resin loadings. The conditions during reactions on higher loaded resins (2b and 2c) as compared to the initially used 2a did not need any adjustments. The quality of the product was comparable and the ratio of product to solid support was increased (Table 1). 

Despite the success with gel-phase NMR spectroscopy the spectra obtained are of limited value because of the broad peaks, and indeed the NMR spectra of unlabelled samples need relatively long acquisition times (because of the low abundance of C) especially with lightly loaded resins such as TentaGel and Argo-Gel. NMR [206, 207] and NMR [208, 209] spectroscopy of gel beads have also been shown to be a convenient NMR technique for monitoring reactions of fluorine or phosphorous-containing molecules, respectively, attached to solvent-swollen polymer supports. 

Ly, X Xu, Y Ly, K Zhang, G. Photo-assisted degradation of anionic and cationic dyes over iron(lll)-loaded resin in the presence of hydrogen... 

The catalyst-loaded resin column was washed with methanol dichlo-romethane and diethyl ether and dried under high vacuum. (Adapted from Hafez et ah, 2001)... 

Becker ML, Liu JQ, Wooley KL. Functionahzed micellar assemblies prepared via block copolymers synthesized by hving free radical polymerization upon peptide-loaded resins. Biomacromolecules 2005 6 220-228. 

Special reference should be made to resin-liquid systems, where the phenomenon of swelling makes the case more complex. A resin s matrix is flexible and when immersed in a liquid, its volume expands, leading to an increase in its particle diameter and in turn, to a decrease in particle density (mass of diy resin per volume of swollen particle). Furthermore, the loading of the resin with ions results in further changes in its volume (Helfferich, 1995). Thus, in these cases, the particle density and diameter as well as the hydraulic density should be referred to for the swollen and loaded resin. In practice, a mean value is frequently used. 

Loaded resin Cleavage conditions Product, yield (purity) Ref. 

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