To a solution of 11-acetyl-8-carbamoyloxymethyl-4-formyl-6-hydroxy-14-oxa-1,11-diazatetracyclo[7.4.1.02,7.010,12 ]tetradeca-2,4,6-trien-9-yl acetate (25 mg) in a mixture of acetone (1 ml) and methyl iodide (1 ml) was added potassium carbonate (50 mg), and the mixture was stirred for 3 hours at 45° C. The reaction mixture was subjected to preparative thin layer chromatography, which was developed with a mixture of chloroform and methanol (15:1, v/v) to afford 11-acetyl-8-carbamoyloxymethyl-4-formyl-6-methoxy-14-oxa-1,11-diazatetracyclo[7.4.1.02,7.010,12 ]tetradeca-2,4,6-trien-9-yl acetate (25 mg).
