Halogenation enantioselective inverse

Novel approach for optically pure alcohol from racemic compounds is the use of dehalogenases.24 For example, L-2-halo acid dehalogenase Pseudomonas putida was used for the synthesis of D-3-chlorolactic acid from racemic 2,3-dichloropropionic acid (Figure 23(a)).24ad The enzyme catalyzed hydrolytic release of halogen from 2-halocarboxylic acids and produces 2-hydroxy acids with inversion of the configuration. L-2-Halo acid dehalogenase acted on the L-isomer of 2-halo acids and produces D-2-hydroxy acid with an excellent enantioselectivity. 

NaBr/H20, LiBr on Amberlyst-15 resin, TiCU-LiCl, " SiCL, I2 with a Sml2 catalyst, and Lil on silica gel. Epoxides can be converted directly to 1,2-dichloro compounds by treatment with SOCI2 and pyridine, or with Ph3P and CCl4. These are two-step reactions a halohydrin is formed first and is then converted by the reagents to the dihalide (10-48). As expected, inversion is found at both carbons. Meso epoxides were cleaved enantioselectively with the chiral B-halodiisopinocampheylboranes (see 15-16), where the halogen was Cl, Br, or I. ° Diatomic iodine gives an iodohydrin with a 2,6-bis[2-(o-aminophenoxy) methyl]-4-bromo-l-methoxybenzene catalyst. ... 

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