This investigation involved the synthesis of potential CA clan cysteine inhibitors of m-calpain and cathepsin B. Inhibitors 2.1.3a-j were based on the SJA-6017 construct containing the N-(4-fluorobenzenesulfonyl) moiety at the P₃ address region. The inhibitor 2.1.3k was based on CAT-0059 a novel dipeptide dialdehyde inhibitor containing the 5-formyl pyrrole moiety at the P₃ address region. Chapter 1 introduces proteases in particular m-calpain and cathepsin B implicated in human pathologies cataract and tumour metastasis respectably. Structure, disease processes and known inhibitors for m-calpain and cathepsin B are presented and described. The chapter also describes drug design and rational including the requirement of the β-strand conformation for enzyme substrate binding. Chapter 2 details the synthesis of m-calpain and cathepsin B inhibitors, N-(4-fluorobenzenesulfonyl) peptide aldehyde 2.1.3a-j and the dipeptide dialdehyde 2.1.3k. The synthesis involved the preparation of the N-(4-fluorobenzenesulfonyl) α-amino acids 2.1.8a-f, the N-(4-fluorobenzenesulfonyl) peptide esters of 2.1.10a-g, the peptide alcohols 2.1.11a-k and the peptide aldehydes 2.1.3a-k. Specific coupling reagents for amide bond formation are also discussed. The oxidation of the alcohols 2.1.11a-k with sulfur trioxide and pyridine complex are also addressed. The results from molecular modelling and enzymatic assays of the inhibitors 2.1.3a-k with m-calpain and cathepsin B are presented and discussed.