Iopanoic Acid → Methyl 2-cyanomethyl-2-phenylmethylbutanoate

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Methyl 2-phenylmethylbutyrate (9.60 g, 50 mmol) was reacted with bromoacetonitrile (7.20 g, 60 mmol) in the presence of lithium diisopropylamide in THF (150 mL) and HMPA (4.3 mL, 25 mmol), as described above in the preparation of Example 4, to give 12.08 g of the crude product as a dark colored liquid. Methyl 2-phenylmethylbutyrate was prepared as in Colombo M, De Amici M, De Micheli C, Pitre D, Carrea G, Riva S (1991) "Chemoenzymatic synthesis of the enantiomers of iopanic acid" Tetrahedron:Asymmetry, 2, 1021-1030. Column chromatography over silica gel (hexanes-CH2Cl2, 3:2) afforded 5.98 g (52%) of the nitrile as a colorless viscous liquid. Analytical sample was prepared by bulb-to-bulb distillation (pot temp. 105° C. (0.5 mmHg)). Lithium diisopropylamide was prepared by treating diisopropylamine (5.56 g, 55 mmol) with butyllithium in hexanes (2.5 M, 22 mL, 55 mmol).

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