Emmanuel Skordalakes

Design of a novel class of bifunctional thrombin inhibitors, synthesised by the first application of peptide boronates in solid phase chemistry

Abstract Borologs containing peptide boronates are new bifunctional biologically active molecules which bind to and inhibit thrombin. These compounds are designed based on the C-terminal sequence of hirudin. The inhibitors consists of four parts, i) an active site inhibitor, D-Phe Pro-Boro(aa)-OPin. ii) an anion binding exosite association moiety, Hirudin, iii) a spacer to link these components and iv) a novel ‘flexor’ non-peptide unit to allow correct orientation. The bivalent nature of the inhibitor [-D-PheProBoroBpgOPin]CO(CH 2 ) 3 COGly 2 Hir enhanced binding up to 10 fold greater than the corresponding native peptide Z-D-PheProBoroBpgOPin or the mixture of non covalently linked units, and resulted in a potent and selective inhibitor of thrombin having a Ki of 0.6nM. For the synthesis of these compounds suitably protected aminoboronate derivatives were shown to be compatible with FMOC solid phase chemistry.

The facile synthesis of O,O-Dialkyl α-halobenzylphosphonates from O,O-Dialkyl α-hydroxybenzylphosphonates

Abstract O,O-Dialkyl α-hydroxybenzylphosphonates (1) can be easily converted in their corresponding α-bromo (2) or α-iodo (3) phosphonates, in quantitative yield, using N ,N′-carbonyldiimidazole (CDI) in the presence of allyl bromide or methyl iodide.

Rhodium(I)-catalysed hydroboration of 1-halo-1-alkenes

Abstract The hydroboration of 1-halo-1-alkenes by catecholborane is accelerated by a catalytic amount of Wilkinsons catalyst {RhCl(PPh 3 ) 3 } to give α-halo boronic esters in good yields.

Substrate Related O,O-Dialkyldipeptidylaminophosphonates, A New Type of Thrombin Inhibitor

Abstract The facile reduction of O,O-dialkyl 1-hydroxyiminoalkanephosphonate precursors, using LiBH4/Me3SiCl in THF at ambient temperature, conveniently affords O,O-dialkyl 1-aminoalkanephosphonates in good yield and high state of purity. O,O-Dialkyl 1-aminobenzylphosphonates may be prepared in high yield and purity from catalytic hydrogenolysis of their 1-benzylaminobenzylphosphonate precursors. These biologically active aminophosphonates, when coupled to substrate derived dipeptides, produced a range of novel phosphonotripeptides based upon the ‘fibrinogen-like’ sequence H-D-Phe-Pro-Arg; where the phosphorus structural units replace the ‘Pl’Arg. These tripeptides showed a marked inhibitory specificity towards the trypsin-like serine protease thrombin, a ubiquitous enzyme that plays a crucial role in the cardiovascular system. The compounds possess an initial Ki in-vitro in the micromolar range against thrombin. Further enzyme kinetic analysis of the compound Z-D-Dpa-Pro-PglP(OiPr)2 (IC50 11.7 micromolar...

SUBSTRATE RELATED O,O-DIALKYLDIPEPTIDYLY ψ CARBOXYBENZYLPHOSPHONATES, A NEW TYPE OF THROMBIN INHIBITOR

Abstract O,O-Dialkyl α-hydroxybenzylphosphonates (1) were coupled to substrate derived dipeptides (2). using an active ester methodology approach to generate a series of phosphonotripeptides (3) with a carboxy ester linkage between the “P1” and “P2” positions of the molecule. These compounds inhibit thrombin in the micromolar range.

X-Ray Crystallographic Analyses of Human α-Thrombin Complexed to Peptidyl Aminophosphonates: Evidence of a Binding Mechanism

We sought to study O,O-Diphenyl dipeptidylaminophosphonates and their interaction with the coagulation protease, human α-thrombin. The ‘fibrinogen-like’ recognition sequence D-Phe-Pro-Arg, is a template of high affinity for thrombin. This was modified by replacing the ‘PI’ Arg by a neutral side chain, and the unnatural amino acid diphenylalanine was used in place of the ‘P3’ Phe. The tripeptides of general formula D-Dpa-Pro-NHCHRP(OPh)2 are highly selective for thrombin amongst other serine proteases; and, more importantly for the design of an efficacious anti-thrombotic agent, show particularly low activity toward other coagulation serine proteases of the cascade. However the kinetics of thrombin inhibition were seen to be dependent on the compounds structure. To explain this we have studied compounds (1), where R is pentyl and compound (2) where R is (3-methoxy)propyl, for which the kinetics of inhibition were analysed as competitive (2 μM) and slow, tight-binding (final Ki 20nM) respectively. Analysis...

THE FACILE SYNTHESIS OF 1-AMINOPHOSPHONATES FROM 1-NITROPHOSPHONATE PRECURSORS

Abstract l-Aminophosphonates may be generated in high yield and spectroscopic purity by the treatment of l-nitrophosphonates with LiBH4/Me3SiCl in THF at room temperature.

THE SYNTHESIS AND FAB MASS ANALYSIS OF O,O-DIALKYL 1-BENZYLAMINOBENZYLPHOSPHONATES, PRECURSORS OF IMPORTANT STRUCTURAL UNITS IN ANTI-THROMBOTIC TRIPEPTIDES

Abstract O,O-Dialkyl 1-benzylaminobenzylphosphonates (3) formed in quantitative yield at R.T. by the nucleophilic addition of dialkyl phosphite (1) to benzylidenebenzylamines (2) in CH2C12 give highly characteristic fragmentation patterns in their positive ion FAB mass spectrum. Catalytic hydrogenolysis of these precursors produces ‘P1’ structural units which when incorporated into substrate-like peptides, form potent inhibitors of thrombin.