A Synergic Blend of Newly Isolated Pseudomonas mandeliiKJLPB5 and [hmim]Br for Chemoselective 2� Aryl AlcoholOxidation in H2O2: Synthesis of Aryl Ketone or Aldehydesvia Sequential Dehydration-Oxidative C=C Cleavage

Nandini Sharma • Upendra K. Sharma •

Richa Salwan • Ramesh C. Kasana •

Arun K. Sinha

Received: 9 September 2010 / Accepted: 19 December 2010 / Published online: 5 January 2011

� Springer Science+Business Media, LLC 2011

Abstract Pseudomonas mandelii KJLPB5 is reported for

the oxidation of aryl alcohols in ionic liquid [hmim]Br

(1-hexyl-3-methyl imidazolium bromide) with H2O2. With

a slight alteration of reaction conditions, the developed

protocol leads either to (i) chemoselective oxidation of 2�aryl alcohols over 1� and aliphatic counterparts or (ii)

direct one pot-two step sequential conversion of 2� aryl

alcohols into corresponding one or two carbons shorter aryl

aldehydes through oxidative cleavage pathway, thus pro-

viding a new facet to metal-free oxidations. The key

operational parameters such as substrate concentration,

incubation temperature, incubation time, ionic liquid type

and ionic liquid concentration are also optimized.

Keywords Biocatalysis � Pseudomonas mandelii �Ionic liquid � Alkene cleavage � Oxidation

1 Introduction

The carbonyl group is one of the most prevalent functional

groups and is entailed in many important chemical reac-

tions. Generally, alkenes and alcohols are used as precur-

sors for the generation of carbonyls [1–5], and selective

oxidation of alcohols to carbonyl containing moieties

remains one of the fundamental processes in organic syn-

thesis [6–8]. A plethora of reagents are available for this

interconversion, but most of these are often expensive,

toxic and must be used in stoichiometric quantities [9, 10].

Consequently, both from the environmental and economi-

cal points of view, catalytic oxidations particular involving

clean oxidants such as O2 and H2O2 are promising [11–18].

On the similar grounds, catalysis in ionic liquids (IL) as an

alternative to organic solvents is gaining significance due

to their negligible vapour-pressure, excellent solvent

properties and high stability [19, 20].

Furthermore, in the heightened context of developing

green chemical methodologies, dynamic efforts to exploit

the potential of biocatalysts (whole cell as well as

enzymes) is on rise due to their simple processing

requirements, high selectivity and mild reaction conditions.

A number of biocatalytic reports are available for the

synthesis of carbonyls either by oxidation of alcohols

[21–24] or by oxidative alkene cleavage [25–27]. Still, the

development of chemoselective methods that efficiently

discriminate among various functional groups remains

challenging. Our group has been involved in the explora-

tion of practical green chemistry procedures for various

organic transformations [21, 28–30]. In continuation of our

interest in the use of ionic liquids in biocatalytic synthesis

and taking into account the encouraging results of our

previous study on alcohol oxidation with lipase and

[hmim]Br [21], we were interested to explore microbial

IHBT Communication No. 2060.

Electronic supplementary material The online version of thisarticle (doi:10.1007/s10562-010-0542-6) contains supplementarymaterial, which is available to authorized users.

N. Sharma � U. K. Sharma � A. K. Sinha (&)

Natural Plant Products Division, Institute of Himalayan

Bioresource Technology (CSIR), Palampur,

Himachal Pradesh 176061, India

e-mail: aksinha08@rediffmail.com

R. Salwan � R. C. Kasana

Hill Area Tea Science Division, Institute of Himalayan

Bioresource Technology (CSIR), Palampur,

Himachal Pradesh 176061, India

123

Catal Lett (2011) 141:616–622

DOI 10.1007/s10562-010-0542-6

catalyst from Western Himalayan region for metal free

oxidative transformations, especially those involving user

friendly reagent H2O2 which generally requires metal

activation [21]. Such whole cell transformations are pref-

erable as they eliminate the need for enzyme purification

and coenzyme addition/regeneration [31].

Thus herein, we report a new bacterial strain Pseudo-

monas mandelii KJLPB5 for oxidation of aryl alcohols. The

developed protocol uses culture supernate of P. mandelii

KJLPB5 in IL [hmim]Br with 30% H2O2 as oxidant. Besides,

the same protocol provides a novel and facile approach for

direct conversion of 2� aryl alcohols into corresponding one

or two carbon shorter aryl aldehydes (Scheme 1), which is

the first report of such bioconversions.

2 Experimental

2.1 Materials

Substrates were obtained from commercial sources (Merck

or Acros). Ionic liquid ([hmim]Br) was synthesized

according to reported method [31–33]. The solvents used

for isolation/purification of compounds were obtained from

Merck and used without further purification.

2.2 General Procedure

Experiments were carried out in duplicate. Bacterial cul-

tures used in the study were isolated from the soils of

Western Himalayan region by following standard proce-

dures [34]. The strains capable of oxidation were rapidly

screened through HPLC analysis. Isolates found positive

for bioconversion of 4-methoxyphenylpropanol (1a) in

initial screening were grown in nutrient broth (NB) med-

ium at 28 �C and 220 rpm. 1a was added in final concen-

tration of 1–3 g L-1 and incubated at 20–40 �C and

220 rpm for 24, 36, 48, 72 and 96 h. Samples were

withdrawn periodically and extracted with ethyl acetate.

Organic extracts were filtered, dried over anhydrous

sodium sulphate and concentrated at 40 �C in vacuo to

remove solvent. 1 mL of HPLC grade methanol (Merck)

was added to the concentrated extract and filtered through

0.22 lM filter prior to analysis.

For the preparation of culture supernate, culture having

OD550 0.8 were harvested, centrifuged at 10,0009g at 4 �C

for 25 min and supernatant (culture supernate) was sepa-

rated from the pellet. The pellet constituting resting cells

was re-suspended in 50 mM tris HCl buffer (pH 7) and

stored at 4 �C till further experiments. The protein content

of culture supernate was determined according to Bradford

method using BSA as standard.

2.3 Analysis of Biotransformed Products

Analysis was performed using a Shimadzu HPLC (Model

LC-20AT pump, DGU-20A5 degasser) equipped with auto

sampler (SIL-20AC), photo diode array detector (CBM-20A;

Shimadzu, Kyoto, Japan) and interfaced with IBM Pentium 4

personal computer. The separation was performed on a

Purospher star RP-18e column (150 9 4.6 mm id, 5 lM;

Merck) at 30 �C. The mobile phase consisted of (A) 0.05%

TFA (Trifluoroacetic acid) in H2O and (B) methanol/aceto-

nitrile (in 70/30 v:v) with gradient elution (0–5 min, 40–70%

B; 5–10 min, 70–100% B; 10–12 min, 100–40% B;

12–20 min, 40% B) with a flow rate of 1 mL min-1. Analysis

wavelength was set at 280 nm. The quantification was per-

formed using external standard method. GC–MS analysis was

undertaken using Shimadzu-2010. 1H (300 MHz) and 13C

(75.4 MHz) NMR spectra were recorded on Bruker Avance-

300 spectrometer wherever mentioned.

2.4 Identification of Bacterial Strain

Strain KJLPB5 showing oxidation and oxidative alkene

cleavage activity was then subsequently identified based on

R'

R

OH

1. [hmim]Br, MWCHO

R (yield upto 85%)

P. mandelii strain KJLPB5

30% H2O2, [hmim]BrR'

R

O

(yield upto 46%)

2. P. mandelii strain KJLPB5 30% H2O2

R= OCH3, Cl, NO2, BrR'= CH3, CH2CH3 etc.

Scheme 1 2� aryl alcohol

oxidations catalyzed by cell free

supernate of P. mandeliiKJLPB5 in [hmim]Br with

H2O2

Pseudomonas mandelii KJLPB5 Catalyzed Oxidations in Ionic Liquid 617

123

its 16S rDNA sequencing [35]. The primers used for

amplification were 50-AGAGTTTGATCATGGCTC-30 and

50-GTTACCTTGTTACGACTT-30. Amplification reaction

was performed in a 50 lL reaction volume containing 1 lL

(5 U) of Taq DNA polymerase (Sigma), 5 lL of 109 Taq

buffer, 1 lL of 10 mM dNTPs mix, 1 lL of each 10 lM

primer and 50–100 ng of template DNA. The reaction was

performed in a thermal cycler for 4 min at 94 �C and then

subjected to 35 amplification cycles of 20 s at 94 �C, 1 min

at 52 �C, for 2 min at 72 �C followed by a final extension

step of 8 min at 72 �C. The amplified PCR product was

electrophoresed on 0.8% agarose gel and amplicon of

1.5 kb was gel purified using Gen Elute gel extraction kit

(Sigma, USA). The purified 16S rRNA gene was cloned

into the pGEM-T easy vector system (Promega). The

nucleotide sequencing of the gene was done by using Big

Dye� Terminator Cycle Sequencing Kit (Applied Biosys-

tems) and 3130 9 l Genetic Analyzer (Applied Biosys-

tems). The BLASTN program (http://www.ncbi.nlm.nih.

gov/BLAST/, NCBI, Bethesda, MD) was used for homol-

ogy searches with the standard program default. Multiple

alignments of the sequences were performed using CLUS-

TAL W program [36]. 16S rRNA gene sequence of

P. mandelii KJLPB5 is provided as supplementary data.

3 Results and Discussions

3.1 Screening of Microbial Strains

Using 4-methoxyphenylpropanol (1a) as a model substrate,

the strains capable of oxidation were rapidly screened

through high performance liquid chromatography (HPLC)

by comparison with reference standard. The products

obtained from bioconversion were confirmed through

GC–MS and NMR. Accordingly, a strain showing good

conversion was selected, subsequently identified by 16S

rDNA sequencing and hereafter named as P. mandelii

KJLPB5 (EMBL # FN811901). The strain is currently

deposited with Institute of Microbial Technology, Chan-

digarh, India.

3.2 Biotransformation Studies with Culture Supernate

of KJLPB5

10 mL of culture supernate of KJLPB5 was taken and

0.12 mM of 1a (final conc. in medium 2.0 g L-1), 30%

H2O2 (6 equiv.) and 0.5 mL [hmim]Br was added to it. The

reaction mixture was incubated up to 96 h at 37 �C. Bio-

transformation products were analyzed with HPLC. The

pellet constituting of resting cells was also checked for

targeted enzyme activity, however maximum conversion

was observed in culture supernate clearly indicating the

exogenous nature of the enzyme. So this culture supernate

was inevitably used for further reaction. The protein con-

tent of culture supernate was found to be 0.064 mg mL-1

(For SDS page analysis, see supplementary data).

3.3 Optimization of Biotransformation Procedure

Optimization experiments for the conversion of 1a into

4-methoxyphenylpropanone (1b) were carried out to find the

best suitable conditions. [hmim]Br was initially taken as

ionic liquid of choice based on the encouraging results of our

previous study [21]. To begin with, reaction mixture

(0.12 mM substrate ? 0.5 mL IL ? 6 equiv. H2O2 ? 10 mL

culture supernate) was incubated up to 96 h at 37 �C. 200 lL

of sample was withdrawn at different time intervals (12, 24,

36, 48, 72 and 96 h) and analyzed with HPLC. It was found

that best yield was obtained at 72 h (about 46%) after which

there was no significant increase. For optimization of sub-

strate concentration, initially 1a was added in concentration

of 1.0 g L-1 and gradually increased up to 3.0 g L-1.

Maximum conversion of 1a to 1b was observed with 2.0 g

L-1; yield declining correspondingly with increase of sub-

strate concentration to 2.5 g L-1. No bioconversion was

observed above 3.0 g L-1. Figure 1 shows the effect of

substrate concentration and varying incubation time at

37 �C.

The effect of incubation temperature (20, 28 and 37 �C)

on the oxidation of 4-methoxyphenylpropanol was also

studied at concentration 2 g L-1. The conversion increased

from 24 to 46% with the increase of temperature from 20 to

37 �C. Thus, from the results it was ascertained that 2.0 g

L-1 of substrate concentration, 37 �C of incubation tem-

perature and 72 h of incubation time was optimum for the

conversion.

In our efforts to increase the yield, we shifted our

attention to evaluate the dependence of the above reaction

05

101520253035404550

0 24 48 72 96

Incubation time (h)

Yie

ld (

%)

Fig. 1 Effect of substrate concentration and incubation time on the

yield of 1b by P. mandelii KJLPB5. The reactions are performed with

4-methoxyphenylpropanol as substrate in concentrations (g L-1): 1.0

(filled diamonds), 2.0 (filled squares), 2.5 (filled triangles) and 3.0

(times) at temperature 37 �C in 0.5 mL IL and 6 equiv. of 30% H2O2

618 N. Sharma et al.

123

on the composition of the ionic liquid (Table 1). We found

that, apart from [hmim]Br, ionic liquids [bmim]Br

(Table 1, entry 2) and [bmim]Cl (entry 3) were also able to

provide 1b in more than 40% yield. On the other hand,

acidic ionic liquids like [Hmim]pTSA and [bmim]PF6

provided low yields of 1b (entries 4 and 5) while moderate

conversion (1b in 26% yield) was achieved with

[bmim]BF4 (entry 6). Interestingly, replacement with basic

ionic liquid [bmim]OH (entry 7) gave only 10% yield of

1b. Subsequently, we studied the effect of ionic liquid

amount and oxidant amount on reaction performance. It

was observed that any change in the amount of ionic liquid

or H2O2 led to decrease in product yield (Table 1, entries

8–10). We also explored the effectiveness of urea-hydrogen

peroxide (UHP), an adduct of H2O2, for the above con-

version. Significantly lower yield of 1a (entry 11) was

observed along with a number of side products, emphasiz-

ing the benefit of using H2O2 in [hmim]Br. Further, control

experiment carried out in absence of [hmim]Br did not

show any conversion into 1b, ascertaining the role of ionic

liquid for above reaction.

3.4 Substrate Spectrum

To elucidate the scope and structural requirements for

substrates to be converted, a variety of structurally diver-

gent alcohols were subjected to the oxidation under opti-

mized conditions. As shown in Table 2 the best substrate

for oxidation with P. mandelii KJLPB5 was 4-methoxy-

phenylpropanol (1a), affording 46% yield with excellent

selectivity. In case of electron withdrawing chloro- (4a)

and nitro- (5a) substitution, lower yields were obtained

(Table 2, entries 4 and 5). When the acetylated 2� aryl

alcohols were subjected to oxidation, corresponding

deacetylated compound was obtained as the major product

(Table 2, entries 6 and 7). On the other hand, 1� aryl

alcohol (8a) was found to be very less reactive, while

cyclic alcohols (9a) and aliphatic alcohols were not con-

verted at all (Table 2).

These findings suggested the promising use of reaction as

a chemoselective method for oxidizing 2� aryl alcohols in

the presence of 1� aryl alcohols, cyclic and acyclic ones. To

further ascertain this, equimolar mixture of 4-methoxy-

phenylpropanol (1a) and 1� aryl alcohol (Table 3, entry 1)

was treated under developed condition where 1b was

obtained in 46% yield without any significant conversion of

1� aryl alcohol (3%). Similarly, oxidation of 1a in presence

of cyclic alcohol (Table 3, entry 2) and aliphatic alcohol

(Table 3, entry 3) led to the facile oxidation of only aryl

alcohol without any conversion or interference by other

alcoholic substrates.

Our quest to increase the yield prompted us to explore

several variants in the above reaction. In one such variant,

instead of adding IL and culture in single step, firstly IL

was added to 1a with constant stirring at 40 �C. After 7 h,

cell free supernate of KJLPB5 was added along with H2O2

and reaction mixture was incubated for 72 h at 37 �C.

Surprisingly, 4-methoxybenzaldehyde was obtained in 25%

yield along with desired 1a which hinted on the possible

Table 1 Effect of ionic liquid type, ionic liquid amount and con-

centration of H2O2 on the oxidation of 1a

H3C O

OH

Ioni c liquid (0.5 m L),37 oC, 72 h1a

P. mandelii KJLPB 530 % H2O2 (6 equiv.)

H3C O

O

1b

Entry Ionic liquid Yield (%)a

1 [hmim]Br 46

2 [bmim]Br 42

3 [bmim]Cl 41

4 [Hmim]pTSA 6

5 [bmim]PF6 11

6 [bmim]BF4 26

7 [bmim]OH 10

8b [hmim]Br 39

9c [hmim]Br 18

10d [hmim]Br 29e

11f [hmim]Br 17e

a Yield on the basis of HPLC conversion with comparison to refer-

ence standard; b amount of ionic liquid increased from 0.5 to 1 mL;c amount of ionic liquid decreased from 0.5 to 0.25 mL; d amount of

30% H2O2 increased from 6 to 8 equiv.; e multiple products were

observed; f with urea-hydrogen peroxide (6 equiv.) as oxidant

Table 2 Oxidation of aryl alcohols/acetates catalyzed by P. mandeliiKJLPB5 and [hmim]Br with H2O2

(a) (b)R 1 R 2

OR 3

R 1 R 2

OP . m an d e lii K JL P B 5

[hm im ]B r, 3 7 oC

Entry R1 R2 R3 Time (h) Yield (%)a

1 4-MeOC6H4 C2H5 H 72 46

2 3,4-(MeO)2C6H3 CH3 H 72 42

3 C6H5 C2H5 H 72 35

4 4-ClC6H4 CH3 H 72 28

5 4-NO2C6H4 CH3 H 72 13

6 4-MeOC6H4 C2H5 COCH3 72 16 (59b)

7 4-NO2C6H4 CH3 COCH3 72 12 (57b)

8 4-MeOC6H4 H H 72 5

9 Cyclohexanol – – 120 nd

Reaction conditions: 0.12 mM substrate, 10 mL cell free supernate,

0.5 mL IL, 30% H2O2

a Product identification with HPLC in comparison to standard and by

GC–MS; b deacetylated compound as major product

Pseudomonas mandelii KJLPB5 Catalyzed Oxidations in Ionic Liquid 619

123

role of KJLPB5 for oxidative cleavage. Based on the above

observation and our previous finding [30] we envisaged the

direct conversion of aryl alcohols into corresponding one

or two carbon shorter aldehydes employing P. mandelii and

H2O2 in ionic liquid [hmim]Br. For this, in the initial step,

a mixture of 4-methoxyphenylpropanol (1a) (0.12 mM)

and [hmim]Br (0.5 mL) was irradiated for 15 min in a

round bottom flask in a focused microwave system

(150 W, 120 �C), which yielded corresponding dehydrated

product (confirmed by TLC and HPLC) [30]. In the next

step, 10 mL of culture supernate of KJLPB5 and 6 equiv.

of 30% H2O2 was added to the same pot and reaction

mixture was incubated for 72 h at 37 �C. To our delight,

various structurally divergent 2� aryl alcohols were suc-

cessfully converted affording quantitative yield (85%) with

excellent selectivity in one pot-two step protocol (Table 4).

Fascinated by this flexible oxidizing ability of KJLPB5,

we sought to exploit the same for oxidative alkene cleavage

since this area is currently the subject of numerous studies

for development of metal-independent ‘‘green’’ oxidations

[8]. t-anethole was chosen as substrate of choice. Initially,

0.12 mM of the compound was incubated with 10 mL cell-

free supernate of P. mandelii KJLPB5, 0.5 mL [hmim]Br

and 30% H2O2 (6 equiv.) at 37 �C for 72 h resulting in

89% conversion to anisaldehyde (Table 5, entry 1). To rule

out any background activity from IL, control reaction with

[hmim]Br and H2O2 was carried out whereby the yield was

obtained in traces only. Similarly, when the reaction was

carried out without IL, low yield was obtained (about 66%)

hinting at the possible role of IL in activation or stabil-

ization of enzymes [37, 38]. Further, testing of various

alkenes allowed us to elucidate the substrate scope for the

reaction (Table 5). It was clear that the developed system

could not cleave double bond non-conjugated to aromatic

ring, or bulky 1,2-disubstituted alkenes such as trans-

or cis-stilbene (Table 5).

Table 3 Selective oxidation of aryl alcohols catalyzed by P. mandelii KJLPB5 and [hmim]Br with H2O2

Entry Alcoholsa Time (h) Products Yield (%)b

1 OH

H 3COOH

H 3CO+

72 O

H 3CO

CHO

H 3CO+

(46 ? 3)

2 OH

H 3CO

OH

+

72 O

H 3CO

O

+

(43 ? 0)

3 OH

H 3COOH+

72 O

H 3COO+

(45 ? 0)

General conditions: 10 mL cell free supernate of P. mandelii KJLPB5, 0.5 mL IL, 6 equiv. of 30% H2O2, 37 �Ca Equimolar mixture of alcohol; b product identification with HPLC in comparison to reference standard and by GC–MS

Table 4 Oxidative conversion of 2� aryl alcohols to one or two

carbon shorter benzaldehydes by P. mandelii KJLPB5 with H2O2

(a) (b)R1 R2

OR 3

R1 H

O

2. P. mandelii KJLPB5, H2O2, 37 oC

1. [hmim]Br, 15 min M.W.

Entry R1 R2 R3 Time (h) Yield (%)a

1 4-MeOC6H4 C2H5 H 72 85

2 3,4-(MeO)2C6H3 CH3 H 72 77

3 4-MeC6H5 CH3 H 72 72

4 4-ClC6H4 C2H5 H 72 45

5 3-NO2C6H4 C2H5 H 72 36

6 4-MeOC6H4 C2H5 COCH3 72 69

8 4-BrC6H4 C2H5 H 72 35

Reaction conditions: (1) 0.12 mM substrate, 0.5 mL IL, MW for

15 min at 150 W and 120 �C; (2) 10 mL cell free supernate of P.mandelii KJLPB5, 30% H2O2

a Product identification with HPLC in comparison to standard and by

GC–MS

Table 5 Oxidative cleavage of aryl alkenes catalyzed by P. mandeliiKJLPB5 and [hmim]Br with H2O2

P. mandelii KJLP B5

[hm im ]Br, H2O 2, 37 oC

(b)

R1

R2

R1 H

O

(a)

Entry R1 R2 Time (h) Yield (%)a

1 4-MeOC6H4 CH3 72 89

2 4-MeC6H4 CH3 72 52

3 4-ClC6H4 CH3 72 44

4 3-NO2C6H4 CH3 72 30

5 4-BrC6H4 CH3 72 36

6 2-ClC6H4 CH3 72 36

7 4-MeOC6H4 H 72 65

8 C6H5 C6H5 72 nd

Reaction conditions: 0.12 mM substrate, 10 mL cell free supernate,

0.5 mL IL, 30% H2O2

a Product identification with HPLC with comparison to standard and

by GC–MS

620 N. Sharma et al.

123

3.5 Effect of Some Inhibitors on Biotransformation

In some preliminary experiments, effects of metal chelators

(EDTA and EGTA), and sulfhydryl reducing agents (DTT

and Iodoacetamide) on oxidative cleavage reaction, with

t-anethole as model substrate, were studied for an insight

into the identity of components in the supernatant. At

5 mM concentration of each supplement used, more than

50% reduction in the product yield was observed with

metal chelators. Similarly, significant inhibition was

caused by Iodoacetamide resulting in very low product

yield (\20%) however, DTT (Dithiothreitol) has no

inhibitory effect on the transformation.

3.6 Proposed Mechanism

To demonstrate that above oxidation is biocatalysed, the

transformation of 1a into 1b was carried out with culture

supernate inactivated by heat which resulted in no reaction

at all. Furthermore, neither corresponding epoxide nor diol

was detected during the reaction course leaving out the

possibility of these as intermediates in a possible pathway.

Moreover, the inability of culture supernate to convert

t-anethole epoxide into the corresponding aldehyde hinted

out that the alkene cleavage is a one step mechanism

employing molecular oxygen as oxidant [26]. Further, the

culture supernate was found positive for the catalase

activity. Mechanistically for oxidative-cleavage, it was

presumed that ionic-liquid promotes dehydration through

an initial polarization of the C–O bond by the imidazolium

cation of the ionic liquid [30]. At the same time, molecular

oxygen released by the disproportionation of hydrogen

peroxide by the catalase enzyme present in supernatant

attacks the double bond resulting in formation of corre-

sponding aldehyde via alkene cleavage. The detailed

characterization of reaction mechanism for the above

conversion is under progress.

3.7 Preparative Scale Evaluation of Oxidative

Biotransformation

To evaluate the practical use of isolated strain, oxidative

biotransformation was carried out on preparative scale. For

it, five flasks each containing 0.36 mg of 1a was micro-

waved in 1 mL of IL for 15 min and then 30 mL of

P. mandelii KJLPB5 supernate and 6 equiv. H2O2 was

added to it. Flasks were incubated for 72 h at 37 �C.

Product was extracted with ethyl acetate and analyzed with

HPLC where quantitative conversion was confirmed. Col-

umn chromatography of the crude sample over silica gel

with hexane/ethyl acetate (8:2, v/v) gave anisaldehyde with

76% yield.

4 Conclusions

In summary, a green biocatalytic approach is reported for

the metal-free H2O2 activation using culture supernate of

P. mandelii KJLPB5 in neutral IL [hmim]Br for the oxi-

dation of 2� aryl alcohols and sequential synthesis of aryl

aldehydes through alkene cleavage. Although the catalytic

system provided a modest yield for 2� aryl alcohol oxida-

tion, it offers a promising platform for the hitherto

unknown biocatalytic direct synthesis of one or two carbon

shorter aldehydes from 2� aryl alcohols. Further efforts for

enhancement of yield and substrate scope are in progress.

Acknowledgments NS and UKS are indebted to CSIR New Delhi

for the award of research fellowships. CSIR Delhi is acknowledged

for financial support (NWP0006, MLP0025 and MLP0034). The

authors are grateful to the Director, IHBT Palampur, for his kind

cooperation and encouragement.

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