C([N:3](CC)CC)C.ClC(OCC)=O.[CH3:14][O:15][C:16]1[CH:17]=[C:18]2[C:23](=[CH:24][CH:25]=1)[CH2:22][CH:21]([C:26]([OH:28])=O)[CH2:20][CH2:19]2.[NH4+].[OH-]>CC(C)=O>[CH3:14][O:15][C:16]1[CH:17]=[C:18]2[C:23](=[CH:24][CH:25]=1)[CH2:22][CH:21]([C:26]([NH2:3])=[O:28])[CH2:20][CH2:19]2A solution of triethylamine (2.7 ml, 0.019 mol) and ethyl chloroformate (2 ml, 0.021 mol) in acetone (40 ml) is added to a solution of the acid obtained in step (i) (3 g, 0.014 mol) in acetone (50 ml) cooled to -10° C. After 1,5 hours at -10° C., concentrated NH4OH (4.5 ml, 0.036 mol) is added dropwise and the reaction mixture is allowed to stand at -10° C. for 1 hour and at room temperature overnight. The solution is concentrated under vacuum, ethyl acetate (150 ml) is added to the obtained residue and the solution is washed sequentially with water, a saturated sodium bicarbonate solution, 6N hydrochloric acid, and water, then it is dried and concentrated to dryness. The residue is triturated with isopropyl ether and filtered thus affording 1.7 g of the above indicated amide; m.p. 136°-138° C.; [α]=+40.2° (c= 1.4%, CHCl3).
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