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This thesis reports the development of potent and selective inhibitors of m-calpain for the treatment of cataract. SJA6017 has been proven to prevent lens opacity in rat and has been our lead compound. A series of Val-Leu peptidyl aldehyde inhibitors (33a-e, 33g, 33i and 35) have been designed, synthesized, and tested for therapeutic potential as cataract inhibitors. Chapter 1 is an introduction to calpain and the diseases associated with it's over activation. A review of the literature on calpain inhibition is given. Structure activity relationship (SAR) theory is presented. The techniques that have been applied in our research group to drug design include molecular modeling, synthesis, assay and animal studies which are all briefly discussed. The importance of a -strand conformation for an inhibitor to bind to calpain is discussed. Chapter 2 describes the synthesis of m-calpain inhibitors. This comprises the preparation of the Val-Leu dipeptide core 29, Val-Leu dipeptidyl alcohols 31a-g and 31i, and the synthesis of dipeptidyl aldehydes 33a-e, 33g, 33i and 35. The choice of coupling regents and conditions in the coupling reactions is investigated. Sulfur trioxide pyridine oxidation for the conversion of Val-Leu dipeptidyl alcohols to aldehydes is discussed. The molecular modeling and biological assay results are presented.

The preparation of 11 new oxytocin analogs is described. The synthesis of the protected peptides were performed using solid phase peptides synthetic methodology. The protected peptides were deprotected and cyclized using sodium in liquid ammonia followed by aqueous potassium ferricyanide treatment. The purification of each peptide was accomplished using partition chromatography followed by gel filtration. Final purity was checked using high-performance liquid chromatography. Several amino-acid derivatives were prepared and incorporated as racemates into the synthetic peptides. The synthetic diastereomeric peptides were separated and purified by high pressure liquid chromatography using aqueous trifluoroacetic acid:acetonitrile mixtures. The oxytocin analogs prepared in this dissertation were divided into 2 classes: oxytocin agonists and oxytocin antagonists. The oxytocin agonist analogs prepared are [2-cycloleucine]oxytocin and [8-cycloleucine]oxytocin. The oxytocin antagonists described in this dissertation are [Pen¹,Cle²]oxytocin, [Pen¹,Cle⁸]oxytocin, [Pen¹,L-TyrMe²,Thr⁴,Orn⁸]oxytocin, [Pen¹,L-TyrEt²,Thr⁴,Orn⁸]oxytocin, [Pen¹,D-TyrEt²,Thr⁴,Orn⁸]oxytocin, [Pen¹,L-PheMe²,Thr⁴,Orn⁸]oxytocin, [Pen¹,L-PheEt²,Thr⁴,Orn⁸]oxytocin, [Pen¹,D-PheMe²,Thr⁴,Orn⁸]oxytocin and [Pen¹,D-PheEt²,Thr⁴,Orn⁸]oxytocin. A conformational study of the synthetic peptides was also undertaken in order to determine possible solution conformations for the various peptides. Two biophysical methods were used in the conformational study of these peptides; they include nuclear magnetic resonance spectroscopy (H-1 and C-13) and circular dichroism spectroscopy. Two somewhat different solution conformations were discovered for peptides containing all L-amino acids and for peptides containing a D-amino acid residue in position 2. A possible correlation between biological potency and observed solution conformation is suggested; the proposed models may aid in the design of more potent peptide inhibitor analogs.

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