A dichloromethane solution containing 395 mg of (1S,4aS,6S,7R,7aR)-6,7-epoxy-1,4a,5,6,7,7a-hexahydro-7-methyl-1-(methylcarbamoyloxy)cyclopenta[c]-pyrane-4-carboxylic acid described in Example 1 was cooled with ice followed by addition of 0.49 ml of triethylamine, 0.38 ml of diphenylphosphate azide and 118 mg of methylamine hydrochloride and stirring for 15 hours at room temperature. The reaction mixture was then extracted with dichloromethane. After washing the organic phase with dilute hydrochloric acid, saturated aqueous sodium bicarbonate and brine, it was dried over anhydrous magnesium sulfate. After distilling off the solvent under reduced pressure, the residue was purified by silica gel chromatography to obtain colorless needles from the dichloromethane-methanol eluate in the form of (1S,4aS,6S,7R,7aR)-6,7-epoxy-1,4a,5,6,7,7a-hexahydro-7-methyl-1-(methylcarbamoyloxy)cyclopenta[c]-pyrane-4-carboxylic acid methylamide (194 mg, yield: 47%). The physicochemical properties of this compound are described in Table 3, Compound No. 15.
