(+)-Petasin 2-Butanoic acid, 2-methyl-, 1,2,3,4,6,7,8,8a-octahydro-1,8a-dimethyl-7-(1-methylethenyl)-6-oxo-2-naphthalenyl ester, (1R-(1alpha,2beta(Z),7beta,8aalpha))- 26577-85-5