Enhancing support loadings

This review has only lightly touched upon the topic of support stability under various reaction conditions. The main reason for this is that very little has been written on the subject. Many of those developing new supports have primarily done so for the fields of solid-phase peptide and/or oligonucleotide synthesis, areas which encompass a very narrow range of reaction conditions. As the field of combinatorial chemistry matures and new reaction types are attempted, an overall stability profile will gradually emerge. 

21 Bhaskar, N.K., King, B.W., Meyers, P. and Westlake, J.P., In Epton, R. (Ed.) Innovation and Perspectives in Solid Phase Synthesis, 3rd International Symposium, Mayflower Worldwide, Birmingham, U.K., 1994, p.451. 

24 Zalipsky, S., Albericio, F. and Barany, G., In Hruby, V.J., Deber, C.N. and Kopple, K.D. (Eds.) Peptides Structure and Function (Proceedings ofthe Ninth American Peptide Symposium), Pierce Chemical Co, Rockford, IL, U.S.A, 1985, pp. 257-260. 

33 Winther, L, Nielsen, C.S, Pedersen, W.B. and Berg, R.H, Peptides 1994, 23rd European Peptide Symposium, Braga, Portugal, September 4-10, 1994, poster no. 101. 

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Nevertheless, there are some problems correlated with the use of this support, such as its voluminous nature when swollen, its lack of physical stability im-der harsh handling conditions, and its incompatibility with a number of solvents (8). For this reason, several groups of researchers have investigated a number of alternative solid supports, for solid-phase chemistry, in order to improve resin properties, such as physical robustness, ease of handling, enhancement in loading,... 

Friedel-Crafts Alkylation. The Friedel-Crafts alkylation of arenes with benzyl alcohol as alkylating agent has been investigated with Hf(OTf)4 supported on MCM-41. The catalytic activity of Hf(OTf)4 was enhanced by loading onto MCM-41 due to increased dispersion and gave the benzylated product in high yield. The system was reusable without loss of activity. 

This information is supported by stress-strain behavior data collected in actual materials evaluations. With computers the finite element method (FEA) has greatly enhanced the capability of the structural analyst to calculate displacement, strain, and stress values in complicated plastic structures subjected to arbitrary loading conditions (Chapter 2). FEA techniques have made analyses much more precise, resulting in better and more optimum designs. 

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