Melting points were cletermined on a Thomas-Hoover capillary melting point apparatus and have not been corrected. Microanalyses were performed by Galbraith Laboratories, Inc., Knoxville, Tenn. IR spectra were recorded on a Perkin-Elmer Model 700 spectrophotometer. NMR spectra were recorded on a Varian Associates T-60 spectrometer or a Hitachi Perkin- Elmer R-22B instrument. Silica gel for column chromatography was Davison Chemicals ...