Solid-phase synthesis of longer peptides is potentially limited by chemical instability of the phosphonamido group to repetitive cycles of piperidine treatment required for Fmoc-based solid-phase protocols (Boutselis et al. 2007). In the broader sense, there’s a paucity of reagents obtainable for the solid-phase synthesis of polypeptides containing prodrug-protected pThr mimetics. The pivaloyloxymethyl (POM) group is an esterase-labile moiety that has been extensively applied to phosphoryl prodrug protection of nucleotides (Hecker and Erion 2008) and phosphate and phosphonic acid functionality in smaller molecules and peptide mimetics (Stankovic et al. 1997; Mandal et al. 2009; Mandal et al. 2011; Zhao and Etzkorn 2007). On the other hand, in spite of its usefulness in these latter contexts, you can find no prior reports of polypeptides containing pThr, pSer or their phosphonic acid-based mimetics, bearing POM protection. Provided the value of pThr within a huge variety of biological processes (Elia and Yaffe 2005), a reagent that would permit the solid-phase synthesis of polypeptides containing POM-protected pThr mimetics will be extremely desirable. We had previously reported the preparation of N-Fmoc-(2S,3R)-2-amino-3-methyl-4phosphonobutyric acid bis-tert-butyl phopshoryl ester [Fmoc-Pmab(But2)-OH, 1, Fig. 1] as a hydrolytically-stable pThr mimetic bearing orthogonal protection suitable for the standard Fmoc-based synthesis of peptides containing Pmab. Even so this reagent yields peptides in which the Pmab residue has its phosphonic acid moiety inside the free di-anionic type (Liu et al. 2009). To date, there have already been no reports of Pmab suitably derivatized for the solid-phase synthesis of polypeptides that maintained the phosphonic acid inside a prodrug-protected type. Inside the existing paper we describe the first preparation of Fmoc-Pmab having the phosphonic acid group masked as its POM bis-esters [Fmoc-Pmab(POM)2-OH, 2, Fig. 1] and demonstrate its use in the solid-phase synthesis of a peptide bearing complete POM protection in the Pmab residue.NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author ManuscriptMaterials and methodsGeneral techniques All experiments involving moisture-sensitive compounds were conducted below anhydrous conditions. Fmoc-Ser(Trt)-OH, and Fmoc-His(Mtt)-OH had been bought from NovaChioChem. All solvents were bought in anhydrous type (Aldrich) and applied straight. Analytical TLCs have been performed employing Analtech precoated plates (Uniplate, silica gel GHLF, 250 nm) containing a fluorescence indicator.Batoclimab NMR spectra were recorded employing a Varian Inova 400 MHz spectrometer.Trimethoprim Coupling constants are reported in hertz, and peak shifts are reported in (ppm) relative to TMS.PMID:23554582 Low-resolution mass spectra (ESI) had been measured with an Agilent 260 1200 LC/MSD-SL program. High resolution mass spectra (HRMS) were obtained by positive ion, ESI evaluation on a Thermo Scientific LTQ-XL Orbitrap mass spectrometer with HPLC sample introduction making use of a short narrow-bore CAmino Acids. Author manuscript; offered in PMC 2014 November 01.Qian and BurkePagereversed-phase column with CH3CN – H2O gradients. Reported m/z values would be the typical of eight or far more scans over the chromatographic peak of interest.NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author ManuscriptSynthesis of Fmoc-Pmab(POM)2-OH (two) (2S,3R)-Benzyl 2-(((benzyloxy)carbonyl)amino)-4-(di-tert-butoxyphosphoryl)-3methylbutanoate (4)–To a resolution of 3 (Liu et al. 2009) (0.26 g, 0.57 mmol) in THFH2.