Stereochemical evaluation and complete H-1 and C-13 NMR assignment of the chamigrenes johnstonol (1), pacifenediol (2), pacifidiene (3), pacifenol (4), isolated from the Brazilian mollusc Aplysia dactilomela, were performed using 2D NMR techniques including COSY, NOESY, HSQC and HMBC, combined with AMI calculations and H-1 NMR spectrum simulations. Copyright (C) 2001 John Wiley & Sons, Ltd.