Wenger, R. M. (1992) “Structure of Cyclosporine and Its Metabolites: Total Synthesis of Cyclosporine Metabolites Formed by Oxidation at Positions 4 and 9 of Cyclosporine. Preparation of Leucine-4-cyclosporine, (γ-Hydroxy)-N-methyl-leucine-9-cyclosporine and Leucine-4-(γ-hydroxy)-N-methyl-leucine-9-cyclosporine”, CHIMIA, 46(7-8), p. 314. doi: 10.2533/chimia.1992.314.