The present invention is directed to novel methods for production of 5-epi-.beta.-vetivone, 2-isopropyl-6,10-dimethyl-spiro[4.5]deca-2,6-dien-8-one and 2-isopropyl-6,10-dimethyl-spiro[4.5]deca-1,6-dien-8-one, which are useful for their fragrant qualities. In one embodiment the present invention describes a method for production of 5-epi-.beta.-vetivone by the use of premnaspirodiene as starting material. In another embodiment the present invention describes a method for production of 2-isopropyl-6,10-dimethyl-spiro[4.5]deca-2,6-dien-8-one and 2-isopropyl-6,10-dimethyl-spiro[4.5]deca-1,6-dien-8-one by the use of premnaspirodiene as starting material. In yet another embodiment the present invention describes a novel method for production of premnaspirodiene from a terpene substrate.