.gamma.-Rubromycin 27267-71-6 AIDS-001778 AIDS001778 Spiro[benzol[1,2-b:5,4-c']dipyran-2(3H),2'(3'H)-naphthol[2,3-b]furan]-7-carboxylic acid, 4,5',8',0-tetrahydro-4',9',10-trihydroxy-7'-methoxy-5',8',9-trioxo-, methyl ester