The focus of this research is the synthesis of labeled leupeptin derivatives containing 1-13C-argininal. Enzyme activity as proteinase inhibitors will be probed by 13-C-NMR to identify the structures in solution that can possibly act as transition-state analogs. %%% With this Standard Grant RUI award, the Synthethic Organic Program is supporting the research of Dr. Rose M. McConnell of the Department of Natural Sciences at the University of Arkansas, Monticello. Professor McConnell will focus her research of the preparation of 13C-labeled leupeptin derivatives that will be studied by NMR to determine the role of the compounds as proteinase inhibitors. The research is especially ammenable to the involvement of undergraduates.