Total Synthesis of Human Follicle Stimulating Hormone

The human Follicle Stimulating Hormone (hFSH) is involved in the regulation and maintenance procedures of essential reproductive processes, such as gametogenesis, follicular development and ovulation. Like other glycoproteins, hFSH exists as a family of isohormones which have been identified within the anterior pituitary, serum and urine, differing in their oligosaccharide structures, including the degree of terminal sialylation or sulfatation. The exceptional therapeutic value of hFSH is displayed in its integral role in medical practices for treatment of anovulatory disorders as well as in assisted reproductive technologies such as intra uterine insemination (IUI). It is our objective to develop a route to fully synthetic homogeneous Human Follicle Stimulating Hormone in order to bypasses complicated separation and to allow for determination of the biological consequences of a specific state of glycosidation. The retrosynthesis for the 92 amino acids and 2 glycanes containing FSH devides the glycoprotein into two glycoprotein and two protein fragments. In a similar fashion the ß-Unit of FSH - consisting of 111 amino acids and 2 glycanes - is divided into four fragments, where two are glycosylated. The required amino acid sequences will be synthesized on solid support employing standard techniques. The carbohydrate part to be attached at the four aspartame residues (AA52 and AA78 in FSHa and AA7 and AA24 in FSHß respectively) will be the most abundantly in hFSH found dodecasaccharide containing one fucose and two sialic acid residues. The merging of the proteins and the deprotected glycane will be accomplished by asparylations following the Lansbury protocol. Penultimately, the highly convergent unification of the peptide and glycopeptide fragments will be achieved by the use of glycopeptide ligation methods (including those developed in the laboratory of Danishefsky) such as native chemical ligation (NCL) or its phenolic ester variation. In addition to this, the described outline will allow for the preparation of differently glycosylated derivatives of hFSH, in order to study the biological role of the glycosidation state with regard to the option of further applications in medicine.