The present invention relates to a method of making novel dipeptidyl peptidase-IV ("DPP-IV') inhibitor compounds useful for treating, inter alia, diseases that are associated with proteins that are subject to processing by DPP-IV, such as Type 2 diabetes mellitus, metabolic syndrome (Syndrome X or insulin resistance syndrome), hyperglycemia, impaired glucose tolerance, glucosuria, metabolic acidosis, cataracts, diabetic neuropathy, diabetic nephropathy, diabetic retinopathy, diabetic cardiomyopathy, Type 1 diabetes, obesity, hypertension, hyperlipidemia, atherosclerosis, osteoporosis, osteopenia, frailty, bone loss, bone fracture, acute coronary syndrome, infertility due to polycystic ovary syndrome, short bowel syndrome and to prevent disease progression in Type 2 diabetes. The invention also relates to a method of making 3,3,4,4-tetrafluoropyrrolidine, a starting material utilized in the afore-mentioned method for preparing DPP-IV compounds.