Baccharis oxide

Baccharis Oxide.—The interesting structure (79) has been proposed for baccharis oxide, from Baccharis halimifolia. In biogenetic terms baccharis oxide is readily derivable from the cation (80), which leads to ebelin lactone (81) and shionone (82). On treatment with boron trifluoride dihydro-baccharis oxide rearranged to (83). 

To date more than 100 species from the large genus Baccharis have been investigated chemically. The most widespread compounds are clerodane diterpene derivatives, but labdane derivatives have also been isolated. Furthermore, typical acetylenic compounds, baccharis oxide, a unique triterpene, and derivatives of hydroxyacetophenone are present, although it is mainly other biologically active constituents, e.g. flavonoids, sesquiterpenes and essential oils that have been reported in the last years. The constituents of Baccharis species compiled from different sources are presented below. 

Reports on the triterpene composition of Baccharis genus are recorded in the literature. Baccharis oxide, Fig. (21) is a common and unique triterpene found in many Baccharis species, such as Baccharis halimifolia L. [54] and B. salicifolia [55], The NMR spectra of this compound was assigned ambiguously [56], but recently Nurnberg et al. [57] established the total NMR chemical shift assignments of baccharis oxide. 

The structure of Baccharis oxide has been revised biosynthetically this is close to the previous structure (Vol. 2, p. 168) and therefore of comparable interest. The total laboratory synthesis of lupeol is a notable further achievement in the synthesis of unsymmetrical triterpenoids. 

The structure of baccharis oxide (see Vol. 2, p. 168) has been revised to (95) on the basis of a direct A"-ray analysis. Baccharan-3-one (96) was found to be identical with 18,19-secolupan-3-one, prepared via cleavage of (97), the mercuric acetate oxidation product of lupenyl acetate. This provides direct chemical proof of the configuration at C-17 in baccharis oxide. 

C30H50, D C-friedo-B A -neo-Gammacer-9 11)-ene, 46B, 572 C30H50O, Baccharis oxide, 39B, 407 C30H50O, Campanulin, 43B, 728... 

An alternative biogenesis of baccharis oxide is suggested by the boron trifluoride-induced rearrangement of 3p,4p-epoxyshionane (393) to 24,25-dihydrobaccharis oxide 485). However, the 5- 04 methyl migration in this rearrangement occurs syn to the epoxide group. The... 

Anthonsen, T., T. Bruun, E. Hemmer, D. Holme, A. Lamvik, E. Sunde, and N. A. Sorensen Baccharis Oxide, a new Triterpenoid from Baccharis halimifolia L. Acta Chem. Scand. 24, 2479 (1970). 

Mo, F., T. Anthonsen, and T. Bruun Revised Structure of the Triterpenoid Baccharis Oxide. Acta Chem. Scand. 26, 1287 (1972). 

Tachibana, K., and T. Takahashi The Conversion of Shionone into Dihydro-baccharis Oxide. Tetrahedron Letters 1975, 1857. 

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