4-Methyl-2-oxovaleric acid → (R)-2-hydroxy-4-methylpentanoic acid

Participants

Reaction Steps

Ten 500 ml Erlenmeyer flasks provided with a baffle and containing in each case 100 ml of medium B were inoculated with Coryneform strain NRS-130KH20B (FERM-P No. 3657, NRRL B-11088) from a slant culture and incubated for 24 hours under the same conditions as described in Example 1. 8.19 g of sodium DL-2-hydroxy-4-methylvalerate were added to each flask as the substrate and the fermentation was continued for 120 hours under the same conditions. According to the method described earlier it was found that 120 hours after the addition of the substrate 35 mg/ml of 4-methyl-2-oxovaleric acid and 37mg/ml of pure D-hydroxy-acid were present. The fermentation was therefore discontinued and the fermentation broth were combined and centrifuged. The supernatant was acidified to pH 1.5 with 38 ml of 50% sulphuric acid and extracted three times with 1 liter of diethyl ether. The combined ether extracts were washed three times with 10 ml of saturated sodium chloride solution and evaporated under reduced pressure. 100 ml of toluene were added to the residue and the mixture was concentrated under reduced pressure in order to remove the water. The yellowish-brown oily residue was dissolved in 400 ml of petroleum ether and the solution was stored overnight in the refrigerator. The crystallisate was collected by filtration, washed with 50 ml of cold petroleum ether and dried in vacuo. There were obtained 28.1 g of D-2-hydroxy-4-methylvaleric acid in the form of colourless crystals of melting point 79.9° C.; [α]D20 =+26.67° (c=2 in 1-N sodium hydroxide).

Provenance & Evidence