Neo-clerodane diterpenoids from Scutellaria altissima and S-albida

Three new neo-clerodane derivatives, scutalbins A-C, have been isolated from the acetone extract of the aerial parts of Scutellaria albida, in addition to the previously known diterpenes scutecolumnins A and B, jodrellin B and clerodin. S. altissima provided a new neo-clerodane, scutalsin, as the sole detectable diterpene constituent. The structures of the new compounds were established by chemical and spectroscopic means as (11S,13S,15R and S,16R,19R)-6 alpha-acetoxy-19-isobutyryloxy-2 alpha;19;4<alpha, 18,11;16;15,16-tetraepoxy-neo-clerodan-15-ol (scutalsin), (11S,13S,16S,19S)-6 alpha-acetoxy-2 alpha,19;4 alpha,18;11,16;15,16-tetraepoxy-neo-clerod-14-en-19-ol (scutalbin A), (11S,13S,15R and S,16R,19R)-6 alpha-acetoxy-19-(2'-methyl)butyryloxy-2 alpha, 19;4 alpha,18;11,16;15,16-tetraepoxy-neo-clerodan-15-ol (scutalbin B) and (11S,13S,15R and S,16R,19S)-6 alpha-acetoxy-2 alpha, 19;4 alpha,18;11,16;15,16-tetraepoxy-neo-cleroda-15,19-diol (scutalbin C). Scutalsin and scutalbins B and C were isolated as 1:1 mixtures of the C-15 epimers.