Acetic Acid → 1,1-Dimethylethyl 6-cyano-3,5-dihydroxyhexanoate

Participants

Reaction Steps

Crude 5R 1,1-dimethylethyl 6-cyano-5-hydroxy-3-oxohexanoate (about 150 moles) from Step (1) is dissolved in 325 L of tetrahydrofuran containing about 20 kg of triethylborane, stirred for about 2 hours at room temperature, cooled to −75° C.±20° C. and diluted with 25 L of methanol and 8 kg of acetic acid. Sodium borohydride (8 kg) as a solution in methanol and aqueous sodium hydroxide is added slowly. After the addition, the reaction mixture is warmed to 0° C.±25° C. The reaction mixture is optionally quenched by the addition of 3 kg of acetic acid and 10 L of methanol and concentrated by vacuum distillation, saving the distillate. The residue is dissolved in methanol and acetic acid, optionally diluted with water, and concentrated by vacuum distillation, keeping this distillate separate from the first one. The residue is dissolved in methanol and concentrated by vacuum distillation. The residue is dissolved in a mixture of water and ethyl acetate, and the aqueous layer separated. The organic layer is concentrated by vacuum distillation. The residue is dissolved in methanol and acetic acid and concentrated by vacuum distillation. The residue is dissolved in ethyl acetate and concentrated by vacuum distillation affording crude [R-(R*,R*)]-1,1-dimethylethyl 6-cyano-3,5-dihydroxyhexanoate.

Provenance & Evidence