Portentol

Portentol
Names
	Preferred IUPAC name (1S,2S,3S,3′R,4R,4′R,5′S,6′R,8R)-4′-Hydroxy-1,3,3′,5′,6′,8-hexamethyl-5-oxaspiro[bicyclo[2.2.2]octane-2,2′-oxane]-6,7-dione
Identifiers
CAS Number	21795-25-5 ;
3D model (JSmol)	Interactive image;
ChemSpider	10192631;
PubChem CID	177166;
UNII	0726883SQG ;
CompTox Dashboard (EPA)	DTXSID10944401 ;
	InChI InChI=1S/C17H26O5/c1-7-11(5)22-17(9(3)12(7)18)10(4)13-8(2)14(19)16(17,6)15(20)21-13/h7-13,18H,1-6H3/t7-,8-,9-,10+,11-,12-,13+,16+,17+/m1/s1 Key: CVPVGRDVSAJUQS-ACMDZGLISA-N;
	SMILES C[C@@H]1[C@H](O[C@@]2([C@@H]([C@@H]1O)C)[C@H]([C@@H]3[C@H](C(=O)[C@]2(C(=O)O3)C)C)C)C;
Properties
Chemical formula	C17H26O5
Molar mass	310.390 g·mol−1
Melting point	260-261 °C (500-502 °F; 533-534 K)
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Portentol is a complex polyketide first isolated in 1967 from the lichen Roccella portentosa and has since been extracted from various other lichen. It has exhibited moderate activity toward several cancer cell lines. Of greater interest is the structural skeleton and chemical space the molecule possesses, which were ultimately determined by detailed NMR studies and X-ray analysis. The spiro tricyclic core contains nine consecutive stereocenters, two of which are adjacent quaternary centers, and a β-keto-δ-lactone moiety. The densely functionalized natural product offered an exciting challenge to total synthesis.