Yeast-based process for production of l-pac

DETAILED DESCRIPTION OF THE INVENTION The invention will now be described in detail by way of reference only to the following non-limiting examples.
EXAMPLE 1 Yeast-Mediated Acyloin Condensation of Benzaldehyde Using Pyruvic Acid Pyruvic acid buffer was prepared by dissolving pyruvic acid (10.
44 g, 119 mmol) in 100 ml of 0.
05 M sodium citrate.
Ammonium acetate was added to give a pH of 5.
45.
Benzaldehyde (106 mg, 1 mmol), petroleum ether (80 ml), ethanol (0.
5 ml), baker's yeast (5 g) and the pyruvic acid buffer (5 ml) were stirred at 50.
degree.
C.
for 24 h.
The mixture was then filtered and the yeast washed with diethyl ether.
The combined organic layers were then washed with 10% sodium carbonate.
After removal of the solvent in vacuo the product was purified by flash distillation (200.
degree.
C.
/1 mm) to give phenylacetylcarbinol (30 mg, 20% yield).
Gas chromatography (GC) of the product showed pure PAC (11.
88 min.
).
Chiral GC showed a ratio of 95:5, 90% ee.
[.
alpha.
].
sub.
D =-262.
6 (c=0.
745, CHCl.
sub.
3).
.
sup.
1 H NMR (CDCl.
sub.
3) .
delta.
7.
33-7.
52, M, Ph; .
delta.
5.
12, s, CH; .
delta.
2.
06, s, CH.
sub.
3.
EXAMPLE 2 Yeast-Mediated Acyloin Condensation of Benzaldehyde Using Sodium Pyruvate 9.
5 ml of 0.
1 M citric acid and 40.
5 ml of 0.
1 M tri-sodium citrate were diluted to 100 ml to give a pH 6 citrate buffer solution.
(Ref.
: Buffers for pH and Metal Ion Control, D.
D.
Perrin and B.
Dempsey, Publ.
John Wiley and Sons, pg 103).
Petroleum spirit (40 ml), ethanol (0.
5 ml), the pH 6 citrate buffer (5 ml) and sodium pyruvate (2.
5 g, 23 mmol) were stirred at room temperature for 1 h.
Benzaldehyde (127 mg, 1.
2 mmol) and baker's yeast (5 g) were then added and the reaction stirred at 5.
degree.
C.
for 24 h.
The mixture was then filtered and yeast washed with diethyl ether.
After removal of the solvent in vacuo the product was purified by flash distillation (200.
degree.
C.
/1 mm) to give phenylacetylcarbinol (44 mg, 24%).
The GC of the product showed pure PAC (11.
88 min.
).
Chiral GC showed a ratio of 97