N-alpha-(9-Fluorenylmethyloxycarbonyl)-O-trityl-D-threonine

The Trt group can be removed with 1% TFA in dichloromethane (silanes as scavengers) while tBu-type protecting groups stay intact. Resin bound Hse(Trt), Ser(Trt), Thr(Trt), and Tyr(Clt) are versatile building blocks for on-resin side chain modifications, like phosphorylation, sulfonation or PEGylation. References: 1. Preparation and application of N-Fmoc-O-Trt-hydroxy amino acids for solid-phase synthesis of peptides; K.Barlos, D.Gatos, S.Koutsogianni, W.Schafer, G.Stavropoulos, Y.Wenqing; Tetrahedron Lett. 1991; 32(4): 471-474. 2. Fmoc/Trt-amino acids: comparison to Fmoc/tBu-amino acids in peptide synthesis; K.Barlos, D.Gatos, S.Koutsogianni; J. Pept. Res. 1998; 51(3): 194-200.