| Studies toward the synthesis a repeat glycopeptide unit of the Pir protein are described in this thesis. Efforts were employed toward the construction of the proposed glycosidic ester linkage between the beta-1,3-glucan and the side chain of the glutamic acid residue in a nonapeptide. A brief review of naturally distributed glycosyl esters, currently existing chemical methods for the preparation of glycosyl esters, and general methods for the preparation of glycopeptides are presented at the beginning of this thesis.;The beta-1,3-glucan was prepared by developing a specific O2-ester protecting group that can be removed under hydrogenolysis conditions. This protecting group employed a simplified trimethyl-lock group and was proven to function efficiently in sugar-sugar glycosylations, sugar-amino acid glycosylations, and in subsequent hydrogenolysis reactions. Using this newly developed protecting group in conjunction with O3-2-naphthylmethyl and O4, O6-dibenzyl protecting groups, a beta-1,3-glucotetraose was prepared in a satisfactory yield.;A new carboxamide side-chain protecting group (the 2-naphthylmethylsulfonyl group) and a new fluorenylmethyloxycarbonyl-based solid phase peptide synthesis linker, again based on the trimethyl-lock, were developed and applied to the preparation of the nonapeptide needed for the glycosylation with the beta-1,3-glucotetraose and the subsequent global hydrogenolys.;Various attempts at the coupling of the beta-1,3-glucotetraose and the nonapeptide were unsuccessful, although promising results were obtained by carbodimide coupling of the peptideyl acid with the reducing tetraose. |
