The crystal structure of Hop-17(21)-en-3β-yl acetate of pluchea pteropoda Hemsl. from Vietnam

C 32 H 52 O 2 (293K): monoclinic space group C2, a= 13.227(7), b= 6.600(1), c= 32.514(2) A, β=96.18(5)°, V=2821.9(16) A 3 , D x = 1.103 g.cm -3 , Z=4, F(000)= 1040, λ(CuKα)=1.5418 A, μ=0.499 mm -1 . The title compound isolated from the roots of a Vietnamese plant and being known for its activity against fever was identified by this X-ray analysis to be a pentacyclic triterpene of hopanoide type with a C17=C21 endocyclic double bond in the five membered ring. The presence of several axially substituted methyl groups on both the a and β side causes the so called mid-molecule strain having already been reported in the literature for other hopane type ring systems.