1. Review
L-Phenylacetylcarbinol (L-PAC): biosynthesis and industrial applications
V.B. Shukla and P.R. Kulkarni*
Food and Fermentation Technology Division, University Department of Chemical Technology (UDCT),
University of Mumbai, Nathalal Parekh Marg, Matunga, Mumbai ± 400 019, India
*Author for correspondence: Tel.: 91224145 616, Fax: 91224145 5614, E-mail: rss@€t.udct.ernet.in
Received 18 October 1999; accepted 18 June 2000
Keywords: Benzaldehyde, bioreactor, biotransformation, downstream processing, L-ephedrine, free and immobi-
lized yeast cells, L-phenylacetycarbinol, pyruvate decarboxylase
Summary
L-Phenylacetylcarbinol (L-PAC), an important drug intermediate, can be produced by biotransformation of
benzaldehyde, mainly by yeast cultures but also by Zymomonas mobilis. The biotransformation by free cells,
immobilized cells, mutant organisms, puri®ed pyruvate decarboxylase as well as the use of bioreactors, the
downstream processing of L-PAC and the industrial applications have been reviewed.
Introduction
L-(À)Phenylacetylcarbinol (L-PAC), also known as
1-hydroxy-1-phenyl-2-propanone or Neuberg's ketol
(90-63-1) or 1-hydroxy-1-phenylacetone or a-hydroxyb-
enzyl methylketonehasthe structureasshown inFigure 1.
It acts as a key intermediate for the synthesis
of L-ephedrine, pseudoephedrine, norephedrine, nor-
pseudoephedrine as well as adrenaline, amphetamine,
methamphetamine, phenylpropanolamine and phenyl-
amine (Ellaiah & Krishna 1987). L-PAC can be
produced by chemical synthesis from cyanohydrins
(Brusse et al. 1988; Jacson et al. 1990a, b) but the
biotransformation route for its production from benz-
aldehyde is preferred industrially.
Production of L-PAC by biotransformation
The biotransformation of benzaldehyde to L-PAC by
brewer's yeast was ®rst described by Neuberg &
Liberman (1921) and later on by Neuberg & Ohle
(1922). The exact pathway for production of L-PAC and
associated products is shown Figure 2. Pyruvic acid, a
product of glycolysis is decarboxylated to `active acet-
aldehyde' that reacts with benzaldehyde to produce
L-PAC (Mahmoud et al. 1990a).
Using yeasts like Saccharomyces cerevisiae, S. carls-
bergensis and Candida utilis as transforming organisms
under optimal physico-chemical conditions, quantitative
conversion of benzaldehyde into L-PAC has never been
achieved (Gupta et al. 1979; Agrawal et al. 1987), but
has been reported to be associated with formation
of byproducts like benzyl alcohol and 1-phenyl 1,2
propenediol (PAC-diol) (Shin & Roger 1996a).
Biotransformation of benzaldehyde to L-PAC
using free microbial cells
Microorganisms producing L-PAC
Bacteria like Zymomonas mobilis (Bringer-Meyer &
Sahm 1988; Cardillo et al. 1991) and moulds like
Aspergillus niger (Cardillo et al. 1991) have been report-
ed to biotransform benzaldehyde to benzyl alcohol as
the major product, but their ability to produce L-PAC
by this route is poor. Different yeast species have been
reported to produce L-PAC (Becvarova & Hanc 1963).
Comparison of following six yeast species viz. Hansenula
anomala, Brettanomyces vini Paynaud et Domer cq.
Strain X, S. carlsbergensis, S. cerevisiae R XII, S.
ellipsoideus and Torula utilis for production of L-PAC
after a single addition of benzaldehyde (0.2 g/100 ml)Figure 1. Structure of L-phenylacetylcarbinol.
World Journal of Microbiology & Biotechnology 16: 499±506, 2000. 499
Ó 2000 Kluwer Academic Publishers. Printed in the Netherlands.

2. brought out that the highest yield of 0.092±0.103 g of
L-PAC/100 ml was given by Hansenula anomala,
S. carlsbergensis and S. cerevisiae, suggesting that the
productivity of L-PAC depends on the organism as well
as its metabolic status. With four additions of 0.2 g
benzaldehyde/100 ml each time Hansenula anomala
produced 0.4 g/100 ml whereas S. carlsbergensis could
produce 0.56 g L-PAC/100 ml. In studies on production
of L-PAC using baker's yeast [Neuberg & Libermann
(1921); Hanc & Kabac (1956); Groeger et al. (1966);
Voet et al. (1973); Vojtisek & Netrval (1982)], and 38
other yeast species, mainly of the genera Saccharomyces
and Candida only four yeast strains could yield L-PAC
as high as S. carlsbergensis, which is considered as the
best producer (Netrval &Vojtisek 1982). Addition of
sucrose, benzaldehyde and acetaldehyde resulted in
0.6 g of L-PAC/100 ml in the strain S. carlsbergensis
`Budwar'. Cardillo et al. (1991) reported S. cerevisiae
CBS 818 and S. delbrueckii CBS 1146 to give maximum
yield of L-PAC (56 and 60 wt.% respectively). Out of
the three yeast species viz. S. cerevisiae ATCC 834,
Zygosaccharomyces rouxii ATCC 2615 and Z. rouxii var
mallis ATCC 10685, only the S. cerevisiae strain was
able to grow in presence of benzaldehyde and produce
L-PAC (Mohamoud et al. 1990a).
E€ect of process parameters
The e€ect of process parameters on the production of L-
PAC has been thoroughly studied. Low voltage alter-
Figure 2. The pathway for production of L-PAC and associated by-products (Shin & Rogers 1999a).
500 V.B. Shukla and P.R. Kulkarni

3. nating current between 9 and 15 V has a stimulatory
effect on growth of S. cerevisiae and L-PAC production
but temperature below 35
C has no effect (Ellaiah
Krishna 1988). Maximum L-PAC formation has been
reported with S. cerevisiae with a culture having an age
of 18 h, concentration of cell mass at 160 g/l and
benzaldehyde at 16 mM concentration (Agrawal et al.
1987). In shaken cultures of S. cerevisiae, more produc-
tion of L-PAC during the ®rst 5 h of fermentation
followed by a slow production on further incubation,
suggests high activity of pyruvate decarboxylase in the
initial phase and reduction in its productivity due to
toxic effect of the product and substrate thereafter (Voet
et al. 1973).
Starved yeast (5% suspension aerated at 37
C for
several hours in a weak solution of inorganic salts
without sugar) converted L-PAC into benzoic acid and
a-methyl a-phenyl ethylene glycol suggesting that in the
absence of any carbon source L-PAC may be utilized for
metabolism. Studies by Groeger et al. (1966) on L-PAC
formation by using baker's yeast in a molasses medium
with simultaneous addition of benzaldehyde and acet-
aldehyde (50%) in a ratio of 1:1.5 brought out that
acetaldehyde stimulated L-PAC production. Whey and
beer wort also stimulated L-PAC synthesis, giving
maximum yield upto 0.78 g L-PAC/100 ml. Similarly
the the yield of L-PAC was increased when acetone was
added to the culture medium as a competitive hydrogen
acceptor, probably making more benzaldehyde available
for L-PAC formation (Yashio 1952). Ose et al. (1960)
reported that addition of acetaldehyde increased the
yield of L-PAC by acting as hydrogen acceptor and
inhibiting hydrogenation of benzaldehyde to benzyl
alcohol and diverting more benzaldehyde towards
L-PAC formation using pressed beer. According to
a Czech patent (Jaromir 1969) L-PAC production at
higher scale is possible with an acid-resistant yeast
strain, 350 kg molasses, 150 kg sucrose and 5 kg
MgSO4, in 7000 l H2O at pH 5.2 with 12 h shaking of
70 l benzaldehyde. Effect of inoculum size, sugar con-
centration and different complex nitrogen sources on L-
PAC formation in Saccharomyces cerevisiae CBS 1171
has also been reported (Gupta et al. 1979). Reduced
aeration (100 l/min), low temperature (23
C), arsenate
(0.156 M), cyanide (0.3 mM) and sodium ¯uoride
(0.02 M) have been reported to inhibit L-PAC formation
in S. cerevisiae (Zeeman et al. 1992). Netraval
Vodnansky (1982) reported production of L-PAC using
waste brewer's yeast where pyruvic acid was found to be
stimulatory for L-PAC production. The cofactors like
diphosphothiamine, Mg‡‡
, NAD and coenzyme-A were
required for L-PAC formation, while arsenate (0.01±
0.02 M) was inhibitory (Smith Hendlin 1953). Addi-
tion of a-naphthoxyacetic acid and EDTA enhances
L-PAC production by S. cerevisiae (Ellaiah Krishna
1987). Aleksander et al. (1987) reported culturing bak-
er's yeast at 31.2 g/l molasses medium with 8 g benzal-
dehyde/l for 8 h under aeration and agitation which
gave L-PAC 4.5 g/l and benzyl alcohol 1.8 g/l.
According to a recent report, a respiratory quotient
(RQ) of 4±5 was optimum in Candida utilis for growth
as well as L-PAC production (Shin Roger 1996a).
Sambamurthy et al. (1984) reported increase in yield of
PAC using di€erent aeration rates. The highest L-PAC
production of 2.86 g/100 ml was achieved at 7 U of
pyruvate decarboxylase activity/ml and 200 mM benz-
aldehyde. The ratio of pyruvate to benzaldehyde was
two. From fed-batch culture studies, continuation of the
fermentation process over 600 h has been established
(Agrawal Basu 1989) with a two-fold increase in
productivity. From studies on continuous cultivation of
a S. cerevisiae strain for biotransformation, Tripathi
et al. (1988) have reported that the speci®c transforma-
tion rate is higher for cells which have been grown at
higher dilution rates attributed to oxygen limitation.
According to a Czech patent for production of L-PAC
by S. coreanus, cell mass is grown ®rst followed by
biotransformation with reduced aeration (Cuilk et al.
1984).
Since benzaldehyde is a substrate for both L-PAC and
benzyl alcohol formation, inhibition of the reduction of
aldehyde to alcohol by different nicotinic acid analogues
could improve L-PAC yield due to inhibition of benzyl
alcohol formation 0±24% (Smith Hendlin 1954).
Observations by Long Ward (1989a) have suggested
that pulse feeding of benzaldehyde resulted in higher
overall product formation. Also as benzaldehyde con-
centration was increased, cell growth of S. cerevisiae was
reduced at 0.05 g/100 ml, inhibited at 0.2 g/100 ml or
cell viability reduced at 0.3 g/100 ml of benzaldehyde.
Benzaldehyde was also found to alter the cell perme-
ability barrier to substrate and product. Semicontinuous
feeding of benzaldehyde has proved to increase yield of
L-PAC (Becvarova et al. 1963). A maximum biotrans-
formation rate of S. cerevisiae with concentrations of
benzaldehyde, sucrose and yeast at 6, 40 and 60 g/l
respectively and a pH range of 4±4.5 has been reported
(Long Ward 1989a), while chemically modi®ed
benzaldehyde resulted in much lower yields of aromatic
carbinols. Addition of b-cyclodextrin resulted in entrap-
ment and controlled release of benzaldehyde and pro-
tection to cells of S. cerevisiae from the toxic e€ects of
benzaldehyde, thereby increasing the L-PAC yield
(Coughlin et al. 1991). The total L-PAC production is
reported to be in¯uenced by pyruvate decarboxylase
activity and pyruvate concentration in the cells of S.
carlsbergensis (Vojtisek Netraval 1982) the later being
actually the rate-limiting factor, so the organism for
biotransformation should be maintained in the meta-
bolic status in which higher PDC activity should be
there supplying an optimal level of pyruvate. Pyruvate
decarboxylase was substantially resistant to inactivation
by benzaldehyde at concentrations as high as 7 g/l.
Alcohol dehydrogenase was found to be more suscep-
tible to inactivation by benzaldehyde (Long Ward
1989a). Thus in biotransformation the loss of produc-
tivity of cells is due to enzyme inactivation as well as the
loss in integrity of the cells by action on the cell
Review: L-Phenylacetylcarbinol 501

4. membrane. Partially puri®ed pyruvate decarboxylase
from C. utilis, at levels above 7 units/ml was greatly
a€ected by free acetaldehyde (Shin Roger 1996b). In
C. utilis the L-PAC formation rates were signi®cantly
increased with higher levels of benzaldehyde up to
120 mM. With 150 mM benzaldehyde and 1.5 substrated
(pyruvate) molar ratio, a maximum yield of L-PAC of
2.71 g/100 ml was observed. Typical biotransformation
kinetics with immobilization suggested a rapid increase
in L-PAC formation rate in the ®rst 1±2 h, declining
together with accumulation of by-products, acetalde-
hyde and acetoin (Shin Roger 1996b).
The addition of corn steep liquor and yeast hydroly-
sate to the medium in¯uenced favourably both the
pyruvate decarboxylase activity and L-PAC production
(Vojtisek Netraval 1982). Recently concentrations of
more than 2.2 g/100 ml have been obtained using a wild
type strain of C. utilis through optimal control of yeast
metabolism (via microprocessor control of RQ) in order
to enhance pyruvate production and induce pyruvate
decarboxylase activity (Rogers et al. 1998).
Recent studies from our laboratory using a new yeast
isolate identi®ed as Torulaspora delbrueckii showed
reusability of free cells for at least nine cycles. Volume
of biotransformation medium, level of benzaldehyde,
adaptation of cells to biotransformation medium,
growth medium ingredients, feeding patterns of sub-
strate and co-substrate have all been shown to be
essential process parameters for good L-PAC yield in
shake ¯ask (Unpublished results).
Biotransformation of benzaldehyde to L-PAC
using immobilized cell mass
Immobilized yeast cell mass has been used for produc-
tion of L-PAC. With use of benzaldehyde at 12±15 g/l,
solvents like ethanol or other monohydric solvents,
short-chain and long-chain polyols like ethylene glycol
and glycerol were found to stimulate PAC production.
Polyethylene glycol-1000 was found to be a better
solvent. This may be due to enhancing the solubility of
benzaldehyde as well as L-PAC in the biotransformation
medium (Seely et al. 1990b). Nikolova Ward (1994)
have also studied the e€ect of various support matrices
on the ratio of product to by-product formation as
individual enzymes respond di€erently to a change in
the microenvironment.
The highest concentration of L-PAC (3.75 mM) pro-
duced by immobilized cells of S. cerevisiae was observed
in the ENT-4000 matrix (containing poly-ethylene
glycol having hydrophilic properties from M/s A.
Tanaka, Japan). The highest concentration of benzyl
alcohol (2.5 mM) was produced by cells immobilized in
ENTP-2000 (containing poly-propylene glycol giving
water-insoluble hydrophobic gel from M/s. A. Tanaka,
Japan). The effect of support material on ratio of
product (L-PAC) and by-product (benzyl alcohol) was
found to be maximum for the support material poly-
propylene glycol i.e. PU-3 (1:0.8) and minimum for
ENTP-2000 (1:1.8) (Nikolova Ward 1994). L-PAC
production by immobilized cells of Saccharomyces
cerevisiae ATCC 834 was 1.4-, 2.5- and 7.5-fold higher
than that by free cells using initial concentrations of 0.2,
0.4 and 0.6% of benzaldehyde respectively, but benzal-
dehyde above 0.6% caused a decrease in benzyl alcohol
as well as L-PAC (Mahmoud et al. 1990a). Though
L-PAC production by semicontinuous fermentation
using the same beads was possible only upto the third
cycle, reimmobilization of cells could give effective
biotransformations over seven cycles yielding a 5-fold
increase in L-PAC compared to a single batch yield
(Mahmoud et al. 1990b). Using b-cyclodextrin, produc-
tion of L-PAC by immobilized cells of S. cerevisiae with
semicontinuous operation over more than 200 h of
production has been possible (Mahmoud et al. 1990c).
According to a US patent by Coughlin et al. (1991)
extracting cyclodextrin with a solvent after biotransfor-
mation could make the process economically viable.
Studies on L-PAC production using calcium alginate-
immobilized S. cerevisiae cells in shake ¯asks as well as
conical ¯uidized bed reactors proved that the highest
speci®c transformation rates were achieved with low
residence time and high ¯ow rates in the continuous
fermentation system (Tripathi et al. 1991). Reusability
of Torulaspora delbrueckii yeast cells immobilized in
barium alginate for nine cycles has been successfully
achieved recently in our laboratory (Unpublished data).
Application of mutant organisms for biotransformation
During the production of L-PAC, some amount of
benzaldehyde is also reduced to benzyl alcohol and low
levels of benzoic acid may also be produced (Agrawal
et al. 1987; Long Ward 1989a). Several attempts have
been made to reduce these byproducts to almost zero
level as well as make the cells resistant to higher levels of
benzaldehyde. Nitrous acid was found to be the best
mutagen, giving a strain with good biotransformation
activity and enhanced yield (Ellaiah Krishna 1987).
Mutation of S. cerevisiae and C. ¯areri by u.v. and
c radiation to a strain resistant to acetaldehyde and
L-ephedrine, producing maximum L-PAC is successful
(Seely et al. 1990b). A mutant strain of S. cerevisiae
producing ethanol and benzyl alcohol in the absence of
ADH I, II and III suggested the presence of an
additional isoenzyme like ADH IV (Nikolova Ward
1991).
A patent (Seely et al. 1990b) on an immobilized mutant
of S. cerevisiae has described L-PAC production at 1.2±
1.5 g/100 ml and benzyl alcohol at 0±0.2 g/100 ml using
benzaldehyde at concentration of 1.2±1.5 g/100 ml, with
pyruvate and benzaldehyde proportion preferably at 1:1
to 1.2:1 and a temperature of 15
C. An increase in
productivity with higher concentrations of L-PAC by
mutant cells of S. cerevisiae with endogenous pyruvate
decarboxylase, immobilized on polyazetidine is described
502 V.B. Shukla and P.R. Kulkarni

5. in a patent from M/s Hercules Inc., USA (Seely et al.
1990a). The process of obtaining an induced mutant
strain of S. cerevisiae using N-methyl-NH
-nitro-N-nitros-
oguanidine and a mutant resistant to chemically modi®ed
benzaldehyde as well as ephedrine has been also patented
(Seely et al. 1990a), while in the case of pyruvate
decarboxylase of Zymomonas mobilis, site-directed mu-
tagenesis is reported to be a powerful tool to improve
synthesis of L-PAC (Bruhn et al. 1995).
Biotransformation using pyruvate decarboxylase enzyme
Puri®ed yeast pyruvate decarboxylase has been success-
fully used for L-PAC production (Bringer-Meyer Sahm
1988; Crout et al. 1991). Highly puri®ed pyruvate decar-
boxylase from yeast has been shown to catalyse the
condensation between pyruvate and a wide range of
substituted benzaldehydes to give hydroxy ketones (acy-
loins) of the same (R) enantiomer series and of high
optical activity as determined by chiral GC using a novel
cyclodextrin-based stationary phase like Lipodex A, D1,
D2 (Kren et al. 1993). Production of various acyloins
using pyruvate decarboxylase and various aliphatic,
aromatic and heterocyclic aldehydes has also been re-
ported (Ohata et al. 1986; Fuganti Grasseli 1977;
Fuganti et al. 1988). Pyruvate decarboxylase of Z. mobilis
and that from S. carlsbergensis catalyse acetoin and
phenylacetylcarbinol synthesis from pyruvate and acet-
aldehyde or benzaldehyde (Bringer-Meyer Sahm 1988).
Biotransformation in non-conventional media
In many biotransformations, implementation of the
biocatalytic reactions in non-conventional media, using
organic solvents, has been investigated due to advanta-
ges o€ered such as ease of product and catalyst recovery
and shift of thermodynamics in favor of synthesis.
Studies on the biotransformation of benzaldehyde to L-
PAC by cells of baker's yeast in two-phase systems using
various organic solvents proved that maximum L-PAC
formation occurred in hexane and hexadecane and the
lowest bioconversion rate was with toluene and chloro-
form (Nikolova Ward 1992d, 1993a). A 10% moisture
content in hexane was found to be optimal for main-
tenance of cell integrity and for L-PAC production
(Nikolova Ward 1992c).
Biotransformation using bioreactors
Tripathi et al. (1988) reported use of a stirred tank
reactor of 1 1 capacity with 1 v/v/min aeration, 400 rev/
min for growth of S. cerevisiae and this biotransforma-
tion, with higher dilution rates proved useful in enhanc-
ing the biotransformation of benzaldehyde to L-PAC.
Using a stirred tank reactor having a capacity of
100 l, with 40 l medium with molasses (10% sugar),
ammonium sulphate (0.1%) and agitation at 200 rev/
min at a temperature of 29 Æ 1
C 30% yield of L-PAC
has been reported by Subramanian et al. (1987). Semi-
continuous production of L-PAC using calcium algi-
nate-immobilized S. cerevisiae ATCC 834 in an air
bubble column reactor showed that immobilized cells
adapted for repeated exposure to benzaldehyde over a
period of more than 200 h produce more L-PAC than
wild type cells (Mahmoud et al. 1990b). Batch and
continuous transformation in a conical ¯uidized bed
reactor (Tripathi et al. 1991) proved that the speci®c
production rate was higher for cells which were grown at
higher dilution rates. The use of a continuous membrane
bioreactor (CMB) with cera¯o ceramic micro®lter has
been reported recently (Liew et al. 1995) . As compared
to classical continuous fermentation, the CMB process
was shown to have higher biomass concentration (from
40 to 400% increase) and greater growth rate (from 3- to
9-fold) at dilution rates varying from 0.03 to 0X23 hÀ1
.
Very recently scaling up of the biotransformation for
L-PAC production to 5 l in a fermentor with a dual
impeller (disk turbine-pitched blade turbine down ¯ow)
in our laboratory yielded 0.7 g of L-PAC/100 ml using
semicontinuos feeding of benzaldehyde and acetalde-
hyde and cells of T. delbrueckii (Unpublished data).
Downstream processing and estimation of L-PAC
from biotransformation broth
Isolation and puri®cation of L-PAC from fermentation
broth have been studied but have not been adequately
described. (Gupta et al. 1979; Juni 1952; Smith
Hendlin 1953). A modi®cation of the earlier method
(Smith Hendlin 1953) by Long Ward (1989a) has
recommended puri®cation of L-acetyl aromatic carbi-
nol from biotransformation broth using derivatized
aromatic aldehydes like p-anisaldehyde, m-tolualdehyde
and p-hydroxybenzaldehyde. Extraction of broth with
ether, removal of acid by aq. NaHCO3, complex
formation of carbinol and aldehyde with sodium
metabisulphite; production of free carbinol and alde-
hyde by addition of solid NaHCO3 and separation of
them on a silica gel column have also been described
by the same authors. A bisulphite adduct preparation
method for puri®cation of L-PAC includes extracting
the broth with ether and shaking with (5%) sodium
bicarbonate solution for removing acid, followed by
shaking with 25% aqueous sodium metabisulphite
solution and treatment of the aqueous extract with
sodium bicarbonate till the evolution of carbon dioxide
ceases (Subramanian et al. 1987). Very recently a
detailed protocol for extraction of L-PAC from the
biotransformation broth using diethyl ether followed
by ion exchange resin treatment, preparation of bisul-
phite adduct in cold conditions followed by separation
of adduct and recovery of L-PAC by the breakdown of
the adduct has been reported (Shukla Kulkarni
1999).
Review: L-Phenylacetylcarbinol 503

6. The methods reported for estimation of L-PAC and
its byproducts include spectrophotometric (Gupta et al.
1979), polarographic (Netraval Vojtisek 1982b; Bec-
varova et al. 1963), and titrimetric methods (Smith
Hendlin 1953), which su€er from poor sensitivity due to
possible interferences, especially while analysing a com-
plex system like biotransformation broth. In older
methods u.v. absorbance as well as the iodoform
method have been used for estimation of benzaldehyde
and benzyl alcohol (Smith Hendlin 1954). Application
of the Voges±Prauskaur reaction has been tried for
estimation of L-PAC (Groeger Erge 1965). According
to Nikolova Ward (1991) a GC method with a DB-1-
15XW column having 1X5 lm 100% methylpolysiloxane
®lm could give retention times for benzaldehyde, benzyl
alcohol and L-PAC of 1.32, 2.19 and 5.45 min respec-
tively. Separation of L-PAC has also been reported with
a column of silica megabore coated with 1 lm thickness
of 25% cynopropyl, 25% phenyl, 50% methyl poly-
siloxane and helium as a carrier gas (Nikolora Ward
1992b). Estimation of benzaldehyde and benzyl alcohol
on a GC using helium as a carrier gas and colorimetric
estimation of L-PAC also have been reported (Long
Ward 1989). Recently a gas chromatograph column
packed with WHr/SE 30 WTX 10 and use of nitrogen
gas as a carrier has been found to be useful for
estimation of L-PAC and benzaldehyde (Shin Rogers
1996a). The GC methods used so far have used costlier
capillary columns and helium as a carrier gas. Recently a
simple GC method using 5%OV-17 and nitrogen gas as
a carrier has also been developed for analysis of the
biotransformation products (Shukla Kulkarni 1999).
An HPLC method using a 250-mm ultrasphere ODS
column and MCH-10 microguard (Agrawal et al. 1987)
and also with a reverse phase column by Bringer-Meyer
Sahm (1988) or Delta PAC C-18, 300 ÊA column
(Mahmoud et al. 1990a) are known.
Industrial applications
L-PAC is not a marketed product. It is produced by
the industries which use it as a synthon for various
drugs having a, b adrenergic properties. These include
L-ephedrine, pseudoephedrine, norephedrine, nor-
pseudoephedrine. These can be used as nasal deconges-
tants, antiasthmatics, for treatment of hypotension, as
for L-ephedrine. L-Ephedrine is a natural product found
in various species of plants of genus Ephedra such as
E. indica, E. distachya, E. vulgaris, E. sincasta€,
E. equisetina. It is obtained from dried plant material
by initial treatment with alkali, followed by extraction
with organic solvent. While D-pseudoephedrine is also
found in nature, it is more easily obtained in high yields
from L-ephedrine by the Welsh rearrangement (Seely
et al. 1990b). Extraction, puri®cation and isolation of
these drugs is tedious, time-consuming, laborious, costly
and accompanied by many undesired products. Kherad-
mandy (1990) reported the production of L-PAC and its
conversion to ephedrine or norephedrine in the presence
of PtO2 depending on whether MeNH2 or NH3 was
added. Conversion of L-PAC to ephedrine by using
Raney nickel and NH3 has also been described. Pro-
duction of ephedrine by the semisynthetic route from
L-PAC produced by yeast biotransformation has been
proved to be more advantageous than the extraction
route The L-PAC could be converted by a chemical
reductive amination with methylamine to optically pure
L-ephedrine and D-pseudoephedrine (Figure 3) (Seely
et al. 1990a). The combination of yeast transformation
of benzaldehyde to produce L-PAC and chemical
conversion of the L-PAC to L-ephedrine was described
in a US patent (Hinderbrandt Klavehn 1934).
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Figure 3. Chemical conversion of L-PAC to L-(À)-ephedrine and D-(+)-pseudoephedrine.
504 V.B. Shukla and P.R. Kulkarni

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