[CH3:1][O:2][CH2:3][C:4]1O[CH:6]=[CH:7][C:8](=[O:18])[C:9]=1[O:10][CH2:11][C:12]1[CH:17]=[CH:16][CH:15]=[CH:14][CH:13]=1.O.[CH2:20]([NH2:22])[CH3:21].[OH-].[Na+]>C(O)C>[CH2:20]([N:22]1[CH:6]=[CH:7][C:8](=[O:18])[C:9]([O:10][CH2:11][C:12]2[CH:13]=[CH:14][CH:15]=[CH:16][CH:17]=2)=[C:4]1[CH2:3][O:2][CH3:1])[CH3:21]
To a solution of 2-methoxymethyl-3-benzyloxy-pyran-4(1H)-one (2.46 g, 10 mmol, 1 eq.) in ethanol (10 ml)/water (10 ml) was added 1.93 g (30 mmol, 3 eq.) of 70% aqueous ethylamine followed by 2N sodium hydroxide solution until pH 13 was obtained. The reaction mixture was sealed in a thick-walled glass tube and stirred at 70° C. overnight. After adjustment to pH 1 with concentrated hydrochloric acid, the solvent was removed by rotary evaporation prior to addition of water (50 ml) and washing with diethyl ether (3×50 ml). Subsequent adjustment of the aqueous fraction to pH 7 with 10N sodium hydroxide solution was followed by extraction into dichloromethane (4×50 ml), the combined organic layers then being dried over anhydrous sodium sulphate, filtered and the solvent removed in vacuo. The residue was purified by column chromatography on silica gel (eluant: 15% CH3OH/85% CHCl3) to afford the title compound (2.05 g, 75.1 %) as a yellow oil.
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