Synthesis of Adiponectin

• Applicant: Dr. Manuel Johannes
• Subject Area: Organic Molecular Chemistry - Synthesis and Characterisation
• Term: from 2012 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 233156836

Adiponectin, a 30 kDa-protein consisting of 244 amino acids, is a hormone produced mainly by white adipose tissue, which circulates at high concentration in the blood. It has shown to play vital roles in the regulation of fuel metabolism, cardiovascular biology and type-2-diabetes. Adiponectin consists of several isoforms: a trimeric structure, a hexamer and especially a high molecular weight oligomer, which shows bioactivity against diabetes. This isoform is only developed after post translational modifications, namely the presence of alpha1,2-glucosylgalactosyl disaccharide moieties anchored to 5-hydroxylysyl residues within the collagen domain of adiponectin. Furthermore, recombinant production of adiponectin is extremely difficult, unlikely to be commercially feasible and does not contain the translational modifications described above. However, chemical synthesis provides all tools needed for preparation of adiponectin and following structure-activity relationship analysis to develop potential drugs for diabetes and furthermore proof whether the dissacharide moiety is indeed the significant structural feature responsible for the observed biological activity.First a new concise and stereoselective synthesis of 5-hydroxy lysine will be developed where first two fragments are synthesized, namely an allylic alcolol and vinylglycine. These two fragments then are coupled by means of cross metathesis with subsequent palladium catalysed hydrogenation of the resulting double bond. After protecting group manipulation a short and stereoselective synthesis of the desired modified amino acid is feasible. An alternative procedure is conceivable where the chiral William`s auxiliary and an organocatalytic chlorination of an aldehyde will serve as a tool to synthesis the amino acid. Orthogonal protection of all functional groups again would sets the stage for the following glycosylation with 2-Chloroacetyl-3,4,6-tribenzyl-galactosylbromide, which can be prepared in a seven steps synthesis starting from galactose. After the beta-selective Koenigs-Knorr-glycosylation, the protecting group at 2-position is removed and 2,3,4,6-Tetrabenzyl-glucosylbromide is attached via an alpha-selective Schmidt-glycosylation to finish the desired synthesis of the amino acid building block for solid phase peptide synthesis.For the completion of the synthesis of adiponectin native chemical ligation is used to connect five different oligopeptides prepared by solid phase synthesis, where the N-termini contain a thiol group and react with a thioester at the C-terminus. After coupling of all required fragments, which also contain the described 5-hydroxy-lysin, a mild desulphurisation reaction will be carried out to remove all redundant sulphur atoms, installed for the coupling reactions. Finally all remaining protecting groups will be removed and adiponectin should be obtained for further structure-activity-relationship analysis and potential use as drug against typ-2 diabetes.

• DFG Programme: Research Fellowships
• International Connection: New Zealand
• Host: Professorin Margaret A. Brimble, Ph.D.