Purpuromycin

4,5',8',9-Tetrahydro-4,4',9',10-tetrahydroxy-7'-methoxy-5',8',9-trioxospiro[benzo[1,2-b:5,4-c']dipyran-2(3H),2'(3'H)-naphtho[2,3-b]furan]-7-carboxylic acid methyl ester