Protein phosphorylation is a post translational modification of proteins in which a serine, a threonine or a tyrosine residue is phosphorylated by an enzyme, kinase. Phosphorylation of proteins is a reversible and very important regulatory mechanism that occurs in both prokaryotes and eukaryotes. Phosphorylation turns many protein enzymes on and off, preventing or causing many diseases such as diabetes, cancer and rheumatoid arthritis. The phosphorylation on tyrosine residues of proteins is essential for transmission of signals for cell growth, proliferation and differentiation. Protein tyrosine phosphatases (PTPs) in concert with protein tyrosine kinases (PTKs) regulate many signal transduction pathways by controlling the degree of phosphorylation of tyrosine residues within the protein. While the roles and mechanisms of protein tyrosine kinases are well documented, our present understanding of protein tyrosine phosphatases is very limited. In this regard we still have much more to learn about PTPs. Here we propose the design and synthesis of novel protein tyrosine phosphatase mimetics and their activity against tyrosine phosphatases. Chapter two describes the synthesis of 2-aminopyrimidine chlorides, sulfonamides and the sequence of reactions to make its amino acid analog. Chapter three describes the synthesis of α-aryl, α,β-epoxy carboxylates, phosphonates and their biological activity against tyrosine phosphatases. These compounds could be very helpful in significantly improving the current understandings about the roles and mechanisms of the PTPs. These proposed tyrosine phosphatase inhibitors are believed to work effectively in treating the diseases by modulating the phosphorylation in signal transductions pathways. Chapter four describes the design and the synthesis of Peptide Nucleic Acids (PNAs) both standard as well as hybrid PNAs with novel cysteine based monomers that are aimed to increase the cellular uptake by introducing positively charged or amphipathic species attached to cysteine thiol functional group.