E«/-Atisanes

E. Atisane-Aconane Conversion and Stereospecific Skeletal Rearrangements 75... 

Chart 34. e /-Atisane type diterpenes found in the filicopsida... 

The numbering system for the alkaloids used in this chapter is based upon the standard skeletons atisane, kaurane, and aconane and corresponds with the proposal suggested by J. W. Rowe and endorsed by O. E. Edwards, K. Wiesner, and the author. Thus the atisine, veatchine, and lycoctonine systems are numbered as in (1), (2), and (3), respectively.1... 

Atisane is the basic skeleton of various diterpene alkaloids (aconitum-alkaloids) found in the plant families of Ranunculaceae and Garryaceae. (-)-Atisine, as a typical representative, was isolated from the Atis plant Aconitum heterophyllum (Ranunculaceae), which also contains (-)-15,20-dihydroxy-16-atisen-19-oic acid as the lactone (19,20-olide). Erythroxylon monogynum and related speeies are reported to contain (-)-16-atisene. Euphorbiaceae such as Euphorbia acaulis and E. fidjiana produce (-)-16a,17-dihydroxyatisan-3-one. (+)-13-Atisene-16p,17-diol is known as serradiol due to its natural occurrence in Sideritis serrata (Labiatae). 

Walker found that rearrangement occurred to give mainly e/i/-(16i )-atisan-15-one (450). The epoxy-6-lactone (451), containing a 7a- or 7j5-hydroxy-group, under the catalytic effect of BFg readily isomerized, with C-8 methyl migration, to the olefin (452). ii... 

The kaurane and atisane diterpenes, in a variety of forms, serve as substrates for the elaboration of an array of complex, highly functionalized natural products including the gibberellins, the grayanotoxins, and the aconite alkaloids e.g., talatizidine, 286). The biogenesis of each of these... 

The overall transformation of the atisane skeleton e.g. atiserene, 274) to the Ci9 aconite alkaloids, apart from oxidative and functionalization steps, requires three principal structural alterations C7-C20 bond connection, removal of one carbon (C17), and rearrangement of the Cg-Cg bond to C15. Although the order of these alterations is not known, the isolation of the atisine-type alkaloid, denudatin (285), which possesses the C7-C20 link, indicates that this step may occur first. 

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