Tonalensin,a 5,10-seco-neoclerodane diterpenoid

We report the X-ray study on the structure of a newseco-neoclerodane diterpenoid, tonalensin, isolated from the aerial parts ofSalvia tonalensis. The compound crystallizes in the monoclinic space groupP2₁ witha=10.146(2),b=7.620(2),c=11.316(2) Å, =109.58(2)°. Thetrans,cis,cis-cyclodeca-1,3,5-triene ring adopts a boat-chair conformation in which the ^1,3,5-triene system is no longer coplanar. The -lactone and furan rings are essentially planar, while both five-membered rings of the dioxabicylooctane moiety arecis-fused and adopt a twist conformation.Contribution No. 1339 of Instituto de Química, UNAM.