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The enzymatic hydrolysis of methyl 2-fluoro-2-arylpropionates was performed using lipases from Candida rugosa and Candida cylindracea (OF-360). A careful analysis of the reaction products revealed that racemic 2-hydroxy-2-arylpropionic acid and traces of 2-arylacrylic acid are formed, in addition to the expected 2-aryl-2-fluoropropionic acid. The presence of powerful electron-releasing groups in the aromatic ring of the substrate increase the amount of 2-hydroxypropionic acid. A mechanistic hypothesis has been formulated according to which the enzyme facilitates the elimination of fluoride ion from the hydrolysed acid with the formation of an α-carboxy-stabilized carbocation which provides 2-hydroxypropionic acids by nucleophilic attack of H2O and 2-arylacrylic acids by a β-elimination process.

The enzymatic kinetic resolution of (±)-4-acetoxy[2.2]paracyclophane by Candida cylindracea lipase was investigated in water and in a two-phase aqueous organic system. The (+)-(R)-4-hydroxy- and (+)-(S)-4-acetoxy[2.2]-paracyclophanes were isolated in excellent yields and high enantiomeric excesses. The resolution was carried out on multi-gram scale in hexane-water at 40° C.

1-Oxa-2,3-cyclohexadiene (I) can be readily generated by treatment of 5-bromo-3,4-dihydro-2H-pyran with potassium tert-butoxide in the presence of 18-crown-6 and can be trapped with dienes or olefins. Thus, the treatment of I with furan gave 50% yield of Diels-Alder adduct II, whereas with 1,1-diphenylethylene I gave 43% of the [2+2]cycloadduct III. The remarkable regio- and stereoselectivities with which [4+2] and [2+2] adducts are formed suggests a concerted, non-radical cycloaddn. mechanism. [on SciFinder (R)]