PENTACOVALENT PHOSPHORUS-CONTAINING MODELS OF P(V) H2O- OR ENZYME CAMP ADDUCTS - NONCHAIR CONFORMATIONS OF THE PHOSPHORUS-CONTAINING RINGS AS DETERMINED BY H-1-NMR SPECTROSCOPY AND X-RAY CRYSTALLOGRAPHY - YU, JHH; ARIF, AM; BENTRUDE, WG (AMER CHEMICAL SOC, 1990)