N-alpha-(9-Fluorenylmethyloxycarbonyl)-S-p-methoxytrityl-L-cysteine

The Mmt function can be cleaved selectively in the presence of t-butyl type protecting groups and of 4-methyl benzhydryl resin (see BR-1180), Wang resin or Rink amide MBHA resin (Product code BR-1300, BR-1305, BR-1360, BR-1365, and BR-1366). The liberated thiol function then selectively reacts with various compounds, such as haloacyl or haloalkyl PEG derivatives or can be oxidized, in order to form disulfide bridges. Cleavage conditions for Cys(Mmt): 1 g of resin-bound peptide is washed 4 times with dichloromethane. Then 10 ml of an 1.1 % TFA mixture of dichloromethane/triethylsilane (97:3) are added and the mixture is shaken for 10 min at RT and filtered. The cleavage is repeated 1-3 times until no more Mmt can be detected. The Mmt detection is easily performed by applying a spot of the cleavage mixture on a TLC plate and exposes it a few seconds to gaseous HCl coming from conc. HCl. The presence of the Mmt-cation is visualized immediately by the orange coloration of the spot. The highly acid labile S-Mmt group is preferred over the StBu group for the SPS of S-palmitoyl transmembrane peptides since the latter give rise to quantitative desulphurization during on resin deprotection. Literature: 1. K. Barlos et al. in “Peptides 1992, Proc. 22nd European Peptide Symposium”, C.H. Schneider and A. N. Eberle (Eds), ESCOM, Leiden 1993. 2. K. Barlos, et al. (1996) Int. J. Peptide Protein Res. 47,148. 3. D. T. S. Rijkers, et al. Tetrahedron Letters 46 (2005) 3341-3345.