[CH:1]([C:3]1[CH:8]=[C:7]([O:9][CH3:10])[CH:6]=[CH:5][C:4]=1[NH:11][CH:12]=O)=O.[NH2:14][C@H:15]([C:21]([OH:23])=[O:22])[CH2:16][CH2:17][C:18](=[O:20])[NH2:19].[BH4-].[Na+]>CO.[OH-].[Na+]>[C:18]([CH2:17][CH2:16][CH:15]([N:14]1[CH2:1][C:3]2[C:4](=[CH:5][CH:6]=[C:7]([O:9][CH3:10])[CH:8]=2)[N:11]=[CH:12]1)[C:21]([OH:23])=[O:22])(=[O:20])[NH2:19]A solution of 0.79 g of the product from stage 3 in 30 ml of methanol was added to a solution of 0.58 g of L-glutamine in 10 ml of methanol and 2 ml of 2N sodium hydroxide solution. After stirring for 1 hour at 20° C., the mixture was cooled to 0° C. and 0.103 g of sodium borohydride was added in portions within 30 minutes. The mixture was stirred for 12 hours at 0° C., then adjusted to pH 2 to 3, and stirred for a further 4 hours at 20° C. After neutralizing the solution with sodium hydroxide, the methanol was distilled off. The aqueous residue was washed twice with 15 ml of diethyl ether each time, and then concentrated by evaporation in vacuo. The residue was taken up in 25 ml of methanol and freed from insoluble constituents by filtration. The residue obtained by evaporating the filtrate in vacuo was directly reacted further as described in stage 5, without purification.
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