The synthesis on solid phase of a new derivative of the anticoagulant protein hirudin is described (see Scheme and Fig. I , I). The henicosapeptide is a bivalent conjugate of the C-terminus of hirudin and of the active-site-binding tetrapeptide D-Phe-Pro-Arg-Pro linked via a tetraglycine spacer. The peptide, for which the name hirufos was coined, incorporates a stable phosphono derivative of L-phenylalanine which, combined with the other structural modifications, leads to a potent anticoagulant agent. Synthesis was readily achieved by the (9H-fluoren-9-yl)-methoxycarbonyl (Fmoc) strategy followed by acidolytic cleavage from the resin and deprotection, including the liberation of the crucial phosphonic group on L-phenylalanine.Introduction. -Hirudin is a 0-sulfonated peptide of 65 amino acids firstly isolated from the salivary glands of the blood-sucking leech Hirudo medicinalis [I] and endowed with strong anticoagulant properties. The polypeptide binds tightly to the fibrinogenrecognizing site of a-thrombin, thus leading to an efficient inhibition of the protease [2]. X-Ray data analysis of the cocrystal convincingly demonstrated an interaction between the carboxy-terminal tail of hirudin (residues 48 to 65) and a long groove on the surface of the enzyme [3]. In addition, hirudin binds with its N-terminal part (Val-Val-Tyr) to the thrombin active sit cleft. The therapeutic potential of hirudin was soon realized, and the peptide (desulfohirudin) is currently produced on large scale by biotechnological means [4], and a number of advantages of recombinant hirudin over heparins are reported [5].
The asymmetric synthesis of derivatives of the new amino acid (2S)-2-amino-3-(4-hydroxy-3-phosphonopheny1)propionic acid (3'-phosphono-~-tyrosine; ,]) is described. The protected amino acid 13 is obtained oia a Schdlkopfsynthesis by coupling of the rearranged orrho-phosphonophenolic side chain (see Scheme I, 6a) with the lithiated bis-lactim ether 8 of cyclo(-o-valyl-glycyl-) (see Scheme 2). The incorporation of the protected amino acid 14 in a biologically active dodecapeptide is successfully achieved by the [(9H-fluoren-9-yl)-methoxylcarbonyl (Fmoc) strategy of solid-phase peptide synthesis. Differential protection of ,] provides four levels of selective deprotection of, in the order, the N2-amino, the carboxyl (cleavage from the resin), the phenol, and the phosphono function (+peptide 16).Introduction. -Phosphorylation of tyrosine residues in proteins plays an important role in signal-transduction pathways during cell transformation and hormone-induced cell growth [I] [2]. Together protein tyrosine kinases and phosphatases catalyze the reversible transfer of phosphate to tyrosyl residues of enzymes and other proteins. Peptides containing analogs of phosphotyrosine may serve either as product inhibitors of kinases or as substrate inhibitors of phosphatases and, therefore, have potential as anticancer drugs. Both as a building block during peptide synthesis and as a constitutive residue in the final peptide, phosphotyrosine suffers from being easily hydrolyzable under acidic conditions [3], and several attempts were made to stabilize the attachment of the phosphate group on the aryl moiety, including the replacement of the phenolic 0-atom by a CH, or CF, group [4-61, or the replacement of the aryl C-0 bond by a C-P bond [7]. However, these methods either introduce an additional methylene group between the aromatic ring and the phosphate group or eliminate the phenolic function of tyrosine. We report here on the enantioselective preparation of a new phosphono derivative of tyrosine in which the free phenolic function is maintained in position 4' and the phosphono group attached to the aromatic ring in position 3' by a stable C-P bond. We describe several protected derivatives suitable for peptide synthesis and the incorporation of one deriva-
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.