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Proceedings of the 31 st European Peptide SymposiumMichal Lebl, Morten Meldal, Knud J. Jensen, Thomas Hoeg-Jensen (Editors)European Peptide Society, 2010Solid-Phase Synthesis of the Lipopeptide Myr-HBVpreS/2-78;A Hepatitis B Virus Entry InhibitorAlexa Schieck 1 , Thomas Müller 1 , Uwe Haberkorn 1 , Stephan Urban 2 ,and Walter Mier 11 Department of Nuclear Medicine, University Hospital Heidelberg, Heidelberg, 69120,Germany; 2 Department of Infectious Diseases, Molecular Virology, University HospitalHeidelberg, Heidelberg, 69120, GermanyIntroductionChronic HBV infection is the leading cause of liver cirrhosis and hepatocellular carcinoma(HCC). Synthetic peptides derived from the Hepatitis B Virus envelope, have been shownto efficiently inhibit an HBV infection in vitro [1] and in vivo [2]. Myr-HBVpreS/2-78 isthe parent compound of these lipopeptides. It is a 77 amino acid peptide representing theN-terminal part of the viral L-protein. As the region 3-77 of the L-protein is required forHBV infectivity in primary human hepatocytes [3,4], the corresponding peptide is expectedto address a cellular receptor on hepatocytes to block the HBV entry.Constituting a novel class of anti HBV drugs an efficient synthesis of this peptide isrequired. The solid phase synthesis of the N-terminal 77 amino acids of the viral L-proteinwas studied in detail [5]. Difficult sequence regions were identified by using a softwarebased on the Chou and Fasman secondary structure prediction algorithm. Based on theidentification of difficult synthetic sections, the aim was to optimize the synthesis throughthe use of pseudoproline dipeptides, additional coupling steps (double couple), and the useof elevated temperature during the solid phase synthesis.Results and DiscussionThe analysis of the aggregation potential revealed that the sequence is prone to be difficultfrom position 43 to 47 of the peptide sequence (Figure 1B). The changes of the Fmoccleavage signal are in perfect agreement with the predicted structured properties andprovide an indicator for significant aggregations of the growing peptide (Figure 2A). Massspectrometric analysis of the crude peptide products showed a number of terminatedpeptide by-products all blocked with a N -acetyl group (Figure 2, grey chromatogram).These acetylated by-products arise in the regions identified to have a higher aggregationpotential.Different strategies were pursued to overcome the difficulties within the synthesis. Itwas tried to increase the coupling yield by double coupling of the corresponding aminoacid and using HATU instead of HBTU. To avoid a truncation of the peptide chain atposition 35, the pseudoproline dipeptide Fmoc-Asp(OtBu)-Thr(ΨMe,Mepro)-OH wasinserted at position 40 of the peptide sequence. Analytical RP-HPLC and massUV absorbance at 301 nmaggregation potential(a)320024001600200100015 202 5 2510 30 35 40 45 50 55 60 65 70 75 78GQNLSTSNPLGFFPDHQLDPAFRANTANPDWDFNPNKDTWPDANKVGAGAFGLGLTPPHGGLLGWSPQAQGILQTLPYK1.21.00.8synthesis direction(b)Fig. 1. (a) UV measurement of the peptide synthesizer (FMOC cleavage) and (b)prediction of the difficult sequences according to the aggregation potential (softwarePeptide Companion).172