(S)-mandelic acid → (2s)-Cyclohexyl(hydroxy)acetic acid

(S)(+)-Mandelic acid (76.0 g) was dissolved in 440 ml methanol containing 5 ml glacial acetic acid. The phenyl ring was entirely reduced in the presence of 5 gm. of 5% rhodium-on-alumina catalyst under 100 psi H2 pressure in 10 hrs. Following filtration of the solution through Celite® (diatomaceous earth) to remove the catalyst, the methanol was removed via a rotary evaporator. The resulting white solid was dissolved in 1 liter (l) of hot diethyl ether and filtered while hot. The volume of the solution was reduced to 400 ml and 250 ml cyclohexane was added. The ether was then removed and the resultant cyclohexane solution was stored several hours under refrigeration. White crystals of the desired product formed and were collected via filtration. The solid was dried overnight in vacuo at 40° C. Seventy-one grams of (S)(+)-hexahydromandelic acid were obtained for a 90% yield: m.p. 128°-129° C. (lit., 129° C.) and [α]D23 =+23.5° (1, HOAc) (lit. [α]D23 =+25.5 (1.1, HOAc) for the (R) (+) isomer.

1. filtrationfiltration of the solution through Celite® (diatomaceous earth)
2. customto remove the catalyst
3. customthe methanol was removed via a rotary evaporator
4. dissolutionThe resulting white solid was dissolved in 1 liter (l) of hot diethyl ether
5. filtrationfiltered while hot
6. additionwas added
7. customThe ether was then removed
8. waitthe resultant cyclohexane solution was stored several hours under refrigeration

ORD-Eintrag

ord-f1240b5e56bb4cf5a6c06de7f5075edc

Quelldatensatz

uspto-grants-1982_05

DOI

10.6084/m9.figshare.5104873.v1

Patentnummer

US04331818