Chemical synthesis of o‐thiophosphotyrosyl peptides

Abstract

The synthon for O‐thiophosphotyrosine, Fmoc‐Tyr[PS(OBzl)2]‐OH (1c), was prepared in 63%;, yield from Fmoc‐Tyr‐OH by first transient protection as the tBuMe2Si‐ester and phosphinylation with (BzlO)2PNiPr2/ tetrazole followed by oxidation of P(III) to P(V) vith S8x in CS2. Building block 1cwas incorporated in the Fmoc solid‐phase synthesis of two O‐thiophosphotyrosine‐containing peptides H‐Thr‐Glu‐Pro‐Gln‐Tyr(PS)‐Gln‐Pro‐Gly‐Glu‐OH (2) and H‐Thr‐Arg‐Asp‐Ile‐Tyr(PS)‐Glu‐Thr‐Asp‐Phe‐Phe‐Arg‐Lys‐OH (3), corresponding to sequences of the p60src (523–531) protein and an insulin receptor (IR) (1142–1153) analogue, respectively. An alternative approach of synthesis, the global phosphorylation of a resin‐bound peptide, also proved useful. Thus, the free tyrosyl side‐chain containing‐peptide IR (1142–1153) on support was phosphinylated with the above phosphoramidite reagent followed by oxidation with either S8/CS2 or tetraethylthiuram disulfide/CH3CN solutions. Deprotection and peptide‐resin cleavage was performed with a TFA/thiophenol (H2O) mixture. Crude peptides 2 and 3 were stable to the acidolytic deprotection. Preparative RP(C18)HPLC was initially performed using 0.1% TFA(aq) EtOH solvents. However, analyses of fractions resulting from the purification step indicated significant decomposition of thiophosphopeptide in solution. Stability measurements both as a function of time and pH. further confirmed this initial finding. Purifications performed at intermediate pH using a triethylammonium acetatc (pH 7.5) CH3CN solvent system overcame this problem.

Thiophosphopeptides Instantly Targeting Golgi Apparatus and Selectively Killing Cancer Cells

“…Our observations agree with several known facts: (i) CRPs are enriched in Golgi, [36][37][38] (ii) a significant level of oxidation occurs in the Golgi membrane, 39 (iii) ALP, as an "almost perfect" enzyme 40 being anchored on the cell membrane by glycosylphosphatidylinositol (GPI) and overexpressed on certain cancer cell, 23,[41][42] is known to be sorted as oligomers at the Golgi before secretion. [28][29] Since thiophosphopeptides [43][44][45] are much less developed than phosphopeptides, replace NBD with other functional motifs (e.g. 10-hydroxycamptothecine) 46 may lead to new discoveries.…”