Gelozymes in organic synthesis. Part IV: Resolution of glycidate esters with crude Mung bean (Phaseolus radiatus) epoxide hydrolase immobilized in gelatin matrix

A crude extract of Mung bean meal (Phaseolus radiatus) possessing epoxide hydrolase activity immobilized in gelatin gel (gelozyme) is employed in the stereoselective epoxide ring opening of glycidate esters. Thus, ethyl trans-(±)-3-phenyl glycidate 1a and methyl trans-(±)-3-(4-methoxyphenyl) glycidate 1b gave (2S,3R)-glycidate esters (ee >99% and 45% yield) with gelatin immobilized enzyme in diisopropyl ether. The corresponding (2R,3S)-enantiomer of 1a was hydrolyzed by an epoxide hydrolase to predominantly give the anti-product, ethyl (2R,3R)-2,3-dihydroxy-3-phenylpropanoate, with a diastereomeric excess of 78% and ee 94% (40%). A small amount (5%) of racemic syn-product was also obtained as a result of the spontaneous hydrolysis. In the case of 1b, the hydrolysis product was racemic due to high reactivity of the glycidate toward water.

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Ethyl (2S,3R)-3-phenyloxirane-2-carboxylateC11H12O3Ee >99%[α]D25=156 (c 1, CHCl3)Source of chirality: enzymatic resolutionAbsolute configuration: (2S,3R)

Methyl (2S,3R)-3-(4-methoxyphenyl)oxirane-2-carboxylateC11H12O4Ee >99%[α]D25=196 (c 1, ethanol)Source of chirality: enzymatic resolutionAbsolute configuration: (2S,3R)

Ethyl (2R,3R)-2,3-dihydroxy-3-phenylpropanoateC11H14O4Ee = 94%De = 78%[α]D25=-22 (c 1, CHCl3)Source of chirality: enzymatic hydrolysisAbsolute configuration: (2R,3R)

Ethyl (4R,5R)-2,2-dimethyl-5-phenyl-1,3-dioxolane-4-carboxylateC14H18O4Ee >94%De = 78%[α]D25=-52 (c 1, CH2Cl2)Source of chirality: enzymatic hydrolysisAbsolute configuration: (4R,5R)