[O:1]=[S:2](Cl)Cl.[Br:5][C:6]1[CH:7]=[C:8]([C:12]([NH:16][C:17](=[O:23])[O:18][C:19]([CH3:22])([CH3:21])[CH3:20])([CH3:15])[CH2:13][OH:14])[CH:9]=[CH:10][CH:11]=1.N1C=CC=CC=1>CC#N>[C:19]([O:18][C:17]([N:16]1[C:12]([C:8]2[CH:9]=[CH:10][CH:11]=[C:6]([Br:5])[CH:7]=2)([CH3:15])[CH2:13][O:14][S:2]1=[O:1])=[O:23])([CH3:20])([CH3:21])[CH3:22]To a solution of SOCl2 (5.7 mL, 2.5 eq) in dry CH3CN (37 mL) under argon was cooled to −40° C. was added tert-butyl 2-(3-bromophenyl)-1-hydroxypropan-2-ylcarbamate (DC3; R4=Me) (10.3 g, 31 mmol) in dry CH3CN (27 mL) was added dropwise, followed by the addition of dry pyridine (12.4 mL, 160 mmol, 5 eq). The mixture was then allowed to warm to RT in 1 h. The mixture was concentrated to about 30 mL. EtOAc (30 mL) was added and the precipitate was filtered off. The filtrate was concentrated in vacuo to give 10.4 g (89%) of 3-(tert-butoxycarbonyl)-4-(3-bromophenyl)-4-methyl-[1,2,3]-oxathiazolidine-2-oxide as a colorless oil. 1H NMR (CDCl3) 7.64 (t, J=2.0 Hz, 1H), 7.36-7.53 (m, 2H), 7.24 (m, 1H), 4.52 (q, J=9.5 Hz, 2H), 1.86 (s, 3H), 1.42 (br s, 9H).
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