[CH3:1][N:2]1[CH2:7][CH2:6][NH:5][CH2:4][CH2:3]1.CCN(CC)CC.Cl[S:16]([CH2:19][C@H:20]([CH3:31])[C:21]([O:23][CH2:24][C:25]1[CH:30]=[CH:29][CH:28]=[CH:27][CH:26]=1)=[O:22])(=[O:18])=[O:17]>C(Cl)Cl>[CH3:1][N:2]1[CH2:7][CH2:6][N:5]([S:16]([CH2:19][C@H:20]([CH3:31])[C:21]([O:23][CH2:24][C:25]2[CH:30]=[CH:29][CH:28]=[CH:27][CH:26]=2)=[O:22])(=[O:18])=[O:17])[CH2:4][CH2:3]1A 100 mL round bottom flask equipped with magnetic stir bar was charged with 0.42 mL (1.05 eq) N-methyl-piperazine, 1 mL NEt3 and 20 mL CH2Cl2. The solution was cooled to 0° C. and 1.0 g of benzyl 3-chlorosulfonyl-2(R)-methylpropionate from Example 3 in 5 mL CH2Cl2 was added. After 1 hour reaction was concentrated in vacuo. The residue was partioned between EA/H2O and the organic phase was washed with saturated aqueous bicarb., brine, dried, and concentrated in vacuo to yield benzyl 3-[(4-methylpiperizin-1-yl)sulfonyl]-2(R)-methylpropionate which was used without further purification.
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