SOLID-PHASE SYNTHESIS OF H-PHOSPHONOPEPTIDES AND METHYLPHOSPHONOPEPTIDES

We introduce solid-phase syntheses of H- and methylphosphonopeptides, giving access for the first time to a new class of mimics for o-phosph oamino acids. The model peptides H-GlyGlyXaaAla-OH (Xaa=Ser, Thr) were synthesized on a solid-phase using Fmoc/(t)Bu strategy and HBTU/HOBt activation by incorporation of hydroxyl-protected serine and threonine . As selectively cleavable hydroxyl-protecting groups we used tripheny lmethyl and tel t-butyldimethylsilyl for both amino acids, as describe d in the literature. All peptides were phosphitilated with O,O-di-tert -butyl-N,N-diethylphosphoramidite and yielded H-phosphonopeptides afte r trifluoroacetic acid cleavage. Alternatively we phosphonylated the p eptides with O-tert-butyl-N,N-diethyl-P-methylphosphonamidite, which w as synthesized by a two-step one-pot procedure starting from commercia lly available chemicals. All H- and methylphosphonopeptides were obtai ned in high purities and yields, as shown by reversed-phase high-perfo rmance liquid chromatography and anion-exchange chromatography. The ph osphonopeptides were characterized by H-1 and P-31 NMR. We confirmed t heir molecular masses by electrospray mass spectrometry and analyzed t heir fragmentation schemes, which seemed to be characteristic for each class of analogues. The H-phosphonopeptides lost phosphonic acid (H3P O3, 82 mass units) and the methylphosphonopeptides lost methylphosphon ic acid (MeH(2)PO(3), 96 mass units). Both H- and methylphosphonopepti des represent a new and simply accessible class of mimics for phosphop eptides. Compared with the corresponding phosphopeptides all phosphono peptides were synthesized in higher yields and purities (>80%). (C) Mu nksgaard 1996.