N ‐Tetrachlorophthaloyl (TCP) Protection for Solid‐Phase Peptide Synthesis

The N ‐tetrachlorophthaloyl‐(TCP‐)amino protecting group has been evaluated for use in solid‐phase peptide synthesis. The TCP group was unaffected by exposure to either piperidine or N , N ‐diisopropylethylamine (DIEA), which suggests compatibility with both Fmoc and Boc solid‐phase synthesis protocols. Quantitative TCP removal was achieved by treatment with hydrazine/DMF (3:17) at 35 °C for 30 min or with ethylenediamine/DMF (1:200) at 50 °C for 30 min. Several C‐terminal peptide amides were synthesized successfully by following protocols that use hydrazine/DMF (3:17) at 40 °C for 1 h for repetitive deprotection. Treatment of TCP‐amines with methylamine or with diamines did not give the corresponding amines (deprotected), but rather the appropriate N , N′ ‐disubstituted tetrachlorophthalamides, which corresponds to a single ring‐opening step. This observation was harnessed to prepare linear and macrocyclic peptide−arene hybrids based on the mild reaction of the parent TCP compound with 1,3‐diaminopropane/DMF (1:49) at 25 °C for 5 min. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)