2. Experimental
Evaporations were carried out on a Buchi rotary evaporator (Model RE 111) at bath temperatures less than 40 °C. Analytical thin layer chromatography (TLC) was accomplished on Analtech plates coated with avicel. Autoradiography was done at 0 °C after spraying with 2,5-diphenyloxazole and exposing the plates to X-ray film. TLC plates were also scanned for radioactivity (~370 kBq) using a Vanguard Autoscanner. Analytical high pressure liquid chromatography (HPLC) was performed on a PerkinElmer instrument with peak detection done simultaneously by UV (280 nm) and a IN/US Systems Beta RAM Model 3 radioactivity detector. Solution radioassays were conducted with a PerkinElmer Tri-Carb 3100T instrument. The NMR spectrum was recorded on a Bruker 300 MHz instrument with chemical shifts being reported as parts per million (ppm) downfield from internal tetramethylsilane. All chemicals used were reagent grade.