Deprotection sulfonic acid, polymer-supported

Scheme 18.5 Steps in the synthesis of trilobolide requiring orthogonal protection and deprotection using polymer-supported sulfonic acid.

In general one has to realize that each deprotection reaction is specifically influenced by the chain length of the polymer-bound peptide and by the acutal N-terminal amino acid residue, because of the differences in solvation of the individual amino acids and of the whole peptide in relation to the properties of the support. For this reason, for example, 5.35 N HCl in dimethylsulfoxide/dichloromethane (1 1) was employed [ 115] to deal with the problem of different solvations. In another example, mercaptoethane sulfonic acid [116] was utilized in diluted solution to deprotect N-terminal Boc-tryptophane without harming the indole moiety. 

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