ORIENTATIONS OF PHENYL SUBSTITUENT IN ISOMERIC 1-ETHYL-2,5-DIMETHYL-4-PHENYLPIPERIDIN-4-OLES BY 2-DIMENSIONAL NUCLEAR OVERHAUSER SPECTROSCOPY (NOESY) - CONFORMATION OF BETA-ISOMER OF 1,2,5-TRIMETHYL-4-PHENYLPIPERIDIN-4-OLE