A chemical study of Burley tobacco flavour (Nicotiona tobacum L.) V. Identification and synthesis of the novel terpenoid alkaloids 1, 3, 6, 6-petramethyl-5, 6, 7, 8-tetrahydro-isoquinolin-8-one and 3, 6, 6-trirnethyl-5, 6-dihydro-7H-2-pyrindin-7-one - Demole, E; Demole, C (Helv Chim Acta, 1975)