[CH:1]([Mg]Cl)([CH3:3])[CH3:2].[CH3:6][C:7]1[O:12][CH2:11][N:10]([C:13]([CH3:17])([CH3:16])[CH:14]=[O:15])[C:9](=[O:18])[C:8]=1[C:19]1[CH:24]=[CH:23][CH:22]=[CH:21][CH:20]=1.[Cl-].[NH4+]>O1CCCC1>[CH3:6][C:7]1[O:12][CH2:11][N:10]([C:13]([CH3:16])([CH:14]([OH:15])[CH:1]([CH3:3])[CH3:2])[CH3:17])[C:9](=[O:18])[C:8]=1[C:19]1[CH:24]=[CH:23][CH:22]=[CH:21][CH:20]=1Isopropylmagnesium chloride (5 ml of a 2M solution in tetrahydrofuran) was added during 10 minutes to a stirred solution of 2-(2,3-dihydro-6-methyl-4-oxo-5 -phenyl-4H-1,3-oxazin-3-yl)-2-methylpropionaldehyde (2 g) in tetrahydrofuran at 0° C. under an inert atmosphere. The mixture was allowed to warn to 10° C. over 1 hour, poured onto saturated ammonium chloride solution and extracted (ether). The organic phase was dried (magnesium sulphate) and evaporated to give 2-(2,3-dihydro-6-methyl-4-oxo-5-phenyl-4H-1,3-oxazin-3-yl)-2,4-dimethylpentan-3-ol (2.26 g) as a yellow gum, m.p. 42-54° C., NMR 1H δ0.85(d,3H), 0.95(d,3H), 1.4(s,3H), 1.5(s,3H), 1.65(m,1H), 1.85(s,3H), 3.25(dd,1H), 5.0(d,1H), 5.1(d,1H), 5.25(d,1H), 7.15-7.35(m,5H).
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