Taraxeranes, Multiflorane, Glutinanes, Friedelanes, Isoursane, Phyllanthane Bauerane, and Shionanes

Taraxeranes, Multiflorane, Glutinanes, Friedelanes, Isoursane, Phyllanthane, Bauerane, and Shionanes 

Under more forcing conditions the parent hydrocarbon A -oleanene (352, R = H) undergoes isomerization to the equilibrium mixture of Ai ( )-oleanene and A -18oc-oleanene (365 + 366) 452). The regiospe-cific elimination into the A position is attributable to either steric inaccessibility of the tertiary Cis hydrogen or unfavorable alignment of 

It proved possible to effect a second methyl rearrangement (C8 Ci4) through chlorination of taxarene derivative (379) (as acetate) in the presence of zinc acetate (469). The resulting chloro epoxide (380) was converted to multiflorenol (372) by reductive removal of the extraneous functionality at Cn, C12, and C15. 

A relevant biogenetic-type rearrangement is observed in the acid-catalyzed cyclization of the terminal epoxide (386) of 7-farnesyloxy-coumarin (umbelliprenin) 480). The friedelin-like, monocyclic ketone (388), obtained in 4% yield along with several other products, presumably arises from the monocyclic carbon ion intermediate (389) through a sequence of 1,2-shifts. Sesquiterpene derivatives of this type e.g., asco-chlorin, 390) are, in fact, mold metabolites 481). The pattern of in- 

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 

---