methyl 4-oxo-5H-furo[5,4-b][1,5]benzothiazepine-2-carboxylate 4-oxo-5H-furo[5,4-b][1,5]benzothiazepine-2-carboxylic acid methyl ester 4-keto-5H-furo[5,4-b][1,5]benzothiazepine-2-carboxylic acid methyl ester NCI60_032071 AIDS-150826 AIDS150826 Methyl 4-oxo-4,5-dihydrofuro[2,3-b][1,5]benzothiazepine-2-carboxylate NSC688998