Hydroxymethylphenoxy resin

The linker moves the point of substrate attachment away from the surface of the bead. This has the effect of reducing steric hindrance, thereby making reaction easier. The choice of linker will depend on the nature of the reactions used in the proposed synthetic pathway (Figure 6.5). For example, an acid labile linker, such as HMP (hydroxymethylphenoxy resin), would not be suitable if the reaction pathway contained reactions that were conducted under strongly acidic conditions. Consideration must also be given to the ease of detaching the product from the linker at the end of the synthesis. The method employed must not damage the required product but must also lend itself to automation. 

Polystyrene resin with a hydroxymethylphenoxy linker (Wang resin)1 was originally developed for solid-phase peptide synthesis... 

Hydroxymethylphenoxy base resin was treated with BzCl (0.3 M) and pyridine (0.4 M) in CH2CI2 (lOmL-g" resin) for 30 min at 25 °C and then the resin was washed with CH2CI2, DMF, and CH2C12.I ... 

Another alternative for incorporation of the first protected amino acid onto hydroxymethyl base resins without activation of the carboxy group is by a Mitsunobu reac-tion.f l The esterification of 4-hydroxymethylphenoxy-type resins by Fmoc-protected amino acids using this method was first reported by Sieber,P l who observed the presence of an unidentified hydrophobic impurity in the amino acids cleaved from the resin however, independent studies by the groups of Krchnak and Spatola l have shown that the esterification of 4-hydroxymethylphenoxy-type PSty and PEG-PS resins using this procedure proceeds rapidly with acceptable to good yields, with practically no racemization and without the presence of additional contaminants in the final product. On the other hand, this method did not provide satisfactory results for cellulose supports.P l... 

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