[O:1]1[C:6]2[CH:7]=[CH:8][CH:9]=[C:10]([N:11]([CH2:19][CH2:20]OS(C)(=O)=O)[CH2:12][CH2:13]OS(C)(=O)=O)[C:5]=2[O:4][CH2:3][CH2:2]1.[NH2:26][C@@H:27]([CH2:29][OH:30])[CH3:28].[Br-].[Li+].C(=O)([O-])[O-].[K+].[K+]>C(#N)C>[O:1]1[C:6]2[CH:7]=[CH:8][CH:9]=[C:10]([N:11]3[CH2:12][CH2:13][N:26]([CH:27]([CH3:28])[CH2:29][OH:30])[CH2:20][CH2:19]3)[C:5]=2[O:4][CH2:3][CH2:2]1
Dimesylate III (67.0 g, 0.17 mol), D-alaninol (14.0 g, 0.19 mol), lithium bromide (31.0 g, 0.35 mol), and potassium carbonate (74.8 g, 0.54 mol) are mixed together with acetonitrile (750 mL). The resulting suspension is refluxed (82° C.) for 27 h with monitoring by HPLC. The reaction mixture is cooled, filtered, and insoluble residue washed with acetonitrile. Mother liquor is concentrated to a small volume, filtered through 200 cm3 of silica gel, and eluted with 1.5 L of MeOH 10% in EtOAc. After removing solvent on rotary evaporator, the residue is redissolved in EtOAc (200 mL). This solution is washed with water (2×50 mL), dried with MgSO4 and concentrated to produce IV as thick golden oil that slowly crystallizes upon standing; yield 29.4 g (63%) and purity 88.3 area % (LC-MS). Melting point=91-92° C. 1H NMR (CDCl3) δ6.78 (t, J=7.5 Hz, 1H), 6.55 (m, 2H), 4.29 (m, 4H), 3.45 (dd, J=11, 5 Hz, 1H), 3.38 (t, J=11 Hz, 1H), 3.10 (br m, 4H), 2.86 (m, 3H), 2.63 (m, 2H), 0.96 (d, J=7.5 Hz, 3H).
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