[CH3:1][C:2]1[CH:3]=[N:4][C:5]2[CH:6]=[CH:7][CH:8]=[C:9]([C:12](O)=[O:13])[C:10]=2[CH:11]=1.C(N(CC)CC)C.ClC(OCC)=O.[BH4-].[Na+]>O.COCCOC>[CH3:1][C:2]1[CH:3]=[N:4][C:5]2[C:10]([CH:11]=1)=[C:9]([CH2:12][OH:13])[CH:8]=[CH:7][CH:6]=235.0 g (187 mmol) of the compound from example 21A are introduced into 440 ml of 1,2-dimethoxyethane, 32.3 ml (233 mmol) of triethylamine are added, and the mixture is stirred at room temperature for 30 min Then 22.3 ml (233 mmol) of ethyl chloroformate are added dropwise at 15° C., and the mixture is stirred at room temperature for 15 min. The precipitated solid is filtered off and washed with 1,2-dimethoxyethane. The filtrate is then concentrated, and the residue is taken up in 440 ml of ethanol. 13.1 g (345 mmol) of sodium borohydride are added dropwise as a solution in 210 ml of water to the solution obtained in this way. After a reaction time of 16 h at room temperature, the precipitated solid is filtered off with suction and washed with ethanol, and the filtrate is concentrated in a rotary evaporator. The resulting residue is taken up in 800 ml of water and 600 ml of dichloromethane/methanol (8:2). The aqueous phase is again extracted with 600 ml of dichloromethane/methanol (8:2), and the combined organic phases are washed with saturated sodium chloride solution. Concentration and drying result in 23.0 g (71% of theory) of the title compound.
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