[OH:1][CH2:2][C:3]1[CH:8]=[C:7]([O:9][CH2:10][CH2:11][NH:12][CH2:13][CH2:14][C:15]([O:17][C:18](C)(C)C)=[O:16])[CH:6]=[C:5]([CH2:22][OH:23])[N:4]=1.C(O)(C(F)(F)F)=O.C[Si](C=[N+]=[N-])(C)C.C(O)(=O)C>C(Cl)Cl.CO.CCCCCC.O.CCOC(C)=O>[OH:23][CH2:22][C:5]1[CH:6]=[C:7]([O:9][CH2:10][CH2:11][NH:12][CH2:13][CH2:14][C:15]([O:17][CH3:18])=[O:16])[CH:8]=[C:3]([CH2:2][OH:1])[N:4]=1
To a solution of 670 mg of tert-butyl 3-[2-(2,6-bis-hydroxymethyl-pyridin-4-yloxy)-ethylamino]-propanoate in 20 ml of DCM was added 2 ml of TFA. The mixture was stirred for 6 hours at room temperature and then concentrated under reduced pressure, taken up in DCM and concentrated again under reduced pressure. To the residue obtained, dissolved in 10 ml of MeOH, was added, at 5° C., 7 ml of a 2M solution of (trimethylsilyl)diazomethane in hexane. The mixture was stirred for 1 hour 30 minutes at 5° C. and then 200 μl of acetic acid were added. The mixture was taken up in 30 ml of water and 30 ml of EtOAc. The aqueous phase was extracted 2× with 30 ml of EtOAc. The organic phases were combined, washed with saturated NaCl solution, concentrated under reduced pressure and purified by flash chromatography on silica (Analogix Super Flash SiO2 SF15-24g), using a gradient of 0 to 10% MeOH in DCM. The fractions containing the desired product were combined and concentrated under reduced pressure. 155 mg of methyl 3-[2-(2,6-bis-hydroxymethyl-pyridin-4-yloxy)-ethylamino]-propanoate were obtained. LC/MS (C): tr=2.56 min; [M+H]+: m/z 470.
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