Conversion of the Gai.i.ya alkaloids garryfoline (I) and veatchine (II) into the 17-nor-16-ketones VIII and SSII established the absolute configuration at C-8 and C-13, since their rotatory dispersion curves were very similar to that of the 17 nor-16-ketone XI of the phyllocladene (X) series of established absolute configuration. A multistage degradation of garryfoline (I) via the azomethine XXVI of cuauchichicine led to the hydrocarbon XXXII, which proved to be identical with a degradation product of steviol (XXXIY) as well as with ( - )-"P"-dihpdrokaurene obtainable from the diterpene hydrocarbon kaurene (XXXIII). When combined with earlier rotatory dispersion evidence and conformational deductions, these results lead to the complete absolute configurational representations I and II for the principal Gavvya alkaloids. In view of the chemical interconversion of veatchine (II) with atisine (III), the present absolute configurational assignment also applies to the Aconitum alkaloids related to atisine (III). It is noteworthy that these diterpene alkaloids and hence the diterpenes ( - )-kaurene (XXXIII) and steviol (XSXIV) represent another group of natural products with the antipodal A/B stereochemistry as compared to the steroids or diterpenoids of the abietic acid class.