JMS Letters

Abstract

ESI mass spectrometry of amino acid trimethylsilylethyl estersIn complex peptide synthesis, such as cyclopeptides 1,2 and cyclodepsipeptides, 3 multiple protection strategies are required to build the desired structure. 4 Exotic protecting groups cleaved under unusual conditions are chosen to mask a specific reactive site. Among such protections, trimethylsilylethyl (TMSE) esters were found satisfactory in terms of compatibility with classical solidphase urethane protections such as tert-butyloxycarbonyl (Boc) or 9-fluorenylmethoxycarbonyl (Fmoc) groups. Indeed, silyl esters are selectively deprotected in the presence of a Boc group using tetrabutylammonium fluoride. 5 NaH deprotection ensures selectivity with fluoride-labile Fmoc groups. 6 Soft ionization fast atom bombardment (FAB) and electrospray ionization (ESI) mass spectrometric (MS) techniques are effective analytical tools to identify and sequence peptides. 7 Specific fragmentations encountered in FAB mass spectrometry for the most common protecting groups Boc, 8 Fmoc 9 and Z 10 are also relevant in ESI-MS under collision-activated induced dissociation (CAD) conditions. We investigated the specific fragmentation of the TMSE protecting group in ESI-MS.

Derivatization in Mass Spectrometry—1. Silylation

“…Nevertheless, application of silylation in LC/MS is also expected and an atmospheric pressure ionization study has appeared in the recent literature. 107 It is clear that the majority of investigations have been made with the use of TMS and TBDMS derivatives. However, flophemesyl, isopropyldimethylsilyl, allyldimethylsilyl and many other silyl groups can be used for protection in solving particular problems, especially where the reagents are commercially available.…”