Purity of all final compounds was ≥95% as determined on an Agilent LC/MS (Agilent Technologies, Santa Clara, CA) using a 7-minute gradient of 4% to 100% acetonitrile (containing 0.025% trifluoroacetic acid) and water (containing 0.05% trifluoroacetic acid) with an 8-minute run time at a flow rate of 1 mL/min. A Phenomenex Luna C18 column (3 micron, 3 x 75 mm) was used at a temperature of 50 °C using an Agilent Diode Array Detector. Mass determination was performed using an Agilent 6130 mass spectrometer with electrospray ionization in the positive mode.