.beta.-Rubromycin 27267-70-5 AIDS-001777 AIDS001777 Spiro[benzo[1,2-b:5,4-c']dipyran-2(3H),2'(3'H)-naphtho[2,3-b]furan]-7-carboxylic acid, 4,4',9,9'-tetrahydro-8',10-dihydroxy-5',7'-dimethoxy-4',9,9'-trioxo-, methyl ester, (2S)-