Spirodesertols A and B, two highly modified spirocyclic diterpenoids with an unprecedented 6-isopropyl-3H-spiro[benzofuran-2,1′cyclohexane] motif from Salvia deserta

Two highly modified spirocyclic diterpenoids with an unprecedented 6-isopropyl-3H-spiro[benzofuran2,1'-cyclohexane] motif, spirodesertols A (1) and B (2), four new icetexane diterpenoids, salviadenones A-D (3-6), together with their biogenetic precursor, 20-deoxocarnosol (7), were isolated from the root extract of Salvia deserta. Their structures were elucidated by spectroscopic analysis, quantum chemical calculations including the 13C chemical shift calculations with DP4+ probability analysis and electronic circular dichroism (ECD) calculations, and single-crystal X-ray diffraction analysis. The plausible biogenetic pathways for 1-6 were proposed. Compounds 1-7 were evaluated for their cytotoxicity against five cancer cell lines. Spirodesertol A (1) showed more potent cytotoxicity against the A-549, SMMC-7721, and MCF-7 cancer cell lines than the positive control, cisplatin.