[OH:1][CH:2]([CH:11]=[CH2:12])[CH2:3][C:4]([O:6][C:7]([CH3:10])([CH3:9])[CH3:8])=[O:5].C(C(C(C)C)=C[CH2:18][B:19]([O-])[O-:20])(C)C>C(Cl)Cl.Cl[Ru](=CC1C=CC=CC=1)([P](C1CCCCC1)(C1CCCCC1)C1CCCCC1)([P](C1CCCCC1)(C1CCCCC1)C1CCCCC1)Cl>[OH:20][B:19]1[CH2:18][CH:12]=[CH:11][CH:2]([CH2:3][C:4]([O:6][C:7]([CH3:8])([CH3:10])[CH3:9])=[O:5])[O:1]1To a solution of tert-butyl 3-hydroxypent-4-enoate, XLVI (674 mg, 3.92 mmol) in DCM (15 mL) was added diisopropylallylboronate XLV (2 g, 11.76 mmol) via syringe. To the mixture was then added Grubbs' first generation catalyst (260 mg, 0.31 mmol, 7.5 mol %) and the vessel was purged with argon. The reaction was heated at 65° C. under nitrogen for 18 h. The mixture was concentrated under vacuum and the residue was purified by flash column chromatography (100% hexane→30% EtOAc/hexane) to afford tert-butyl 2-(2-hydroxy-3,6-dihydro-2H-1,2-oxaborinin-6-yl)acetate XLVII (770 mg, 3.63 mmol, 92.7% yield).
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