premarrubiin

(2''aS,3R,5'R)-3',3'',4',4'',5'',5''a,7'',8'',8''aα,8''bα-Decahydro-2''aα,5''aβ,7''α-trimethyldispiro[furan-3(2H),2'(5'H)-furan-5',6''-[6H]naphtho[1,8-bc]furan]-2''(2''aH)-one

(2''aS,3R,5'R)-2''a,3',3'',4',5'',5''a,7'',8'',8''aα,8''bα-Decahydro-2''aα,5''aβ,7''α-trimethyldispiro[furan-3(2H),2'(5'H)-furan-5',6''-[6H]naphtho[1,8-bc]furan]-2''(4''H)-one