Reversal of regioselectivity in acetylation and deacetylation of aryl-naphthalene diols and diacetates by Amano lipase

Article abstract of DOI:10.1039/c4ra10503f

The regioselectivity of hydrolysis by Amano lipase (AK lipase) from Pseudomonas fluorescens of aryl naphthalene 4′,7-diacetates 1a-c prepared by the Garratt-Braverman cyclization of bis-propargyl sulfones, ethers and sulfonamides and acetylation of the co

Full text of DOI:10.1039/c4ra10503f

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ARTICLE TYPE
Reversal of Regioselectivity in Acetylation and Deacetylation of Aryl-Naphthalene
Diols and Diacetates by Amano Lipase
Arpita Panja, Deb Ranjan Banerjee and Amit Basak*
Department of Chemistry, Indian Institute of Technology Kharagpur 721 302 India
5
Received (in XXX, XXX) XthXXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
DOI: 10.1039/b000000x
Abstract— The regioselectivity of hydrolysis by Amano Lipase (AK Lipase) from Pseudomonas fluorescens of aryl naphthalene 4’,7ꢀ
diacetates 1a-c prepared by GarrattꢀBraverman Cyclization of bisꢀpropargyl sulfones, ethers and sulfonamides and acetylation of the
corresponding diol 2a-c were studied. In all these cases selectivity of hydrolysis and acetylation were both excellent. However, the
10 pattern of selectivity was found to be dependent upon the nature of the fused heterocyclic ring, namely dihydrothiophene dioxide
(sulfolene), dihydrofuran (phthalan) or dihydro isoindole (indoline). For the isoindole system, the hydrolysis as well as acetylation
occurred at Cꢀ7 while for the furan derivative, the reaction took place entirely at the Cꢀ4’. Interestingly, for dihydrothiophene dioxide,
reversal of selectivity was observed in hydrolysis and acetylation. The results are in contrast with those reported for similar reactions on
aryl naphthalene 2’, 5ꢀdiacetates and corresponding diols. The observed results can be explained by molecular docking using PCL crystal
15 structure representing the Pseudomonas lipase family.
an enzymatic acetylation/deacetylation route to
differentially protected aryl naphthalenes where the
1. Introduction
Aryl naphthalene is regarded as a privileged skeleton
because of its presence in natural products like the 45 functional groups were at C2’ and C5 positions. The
justicidin class of lignans1 as well as in several unnatural
20 products with the diverse array of optical and electronic
properties.2 Several methods have been reported for the
synthesis of such skeletons which include intramolecular
binding mode was the same for acetylation and for
deacetylation reactions (Scheme 2). We were curious to
know whether similar regioselectivity would be observed
for substrates having the acetoxymethyl or hydroxymethyl
FriedelꢀCrafts and DielsꢀAlder reactions.3 In recent years 50 groups at other positions. With this in mind, we studied the
use of GarrattꢀBraverman (GB) cyclization4 (Scheme 1) for
25 efficient construction of aryl naphthalenes has been
reported along with several mechanistic details.5
hydrolysis of aryl naphthalene sulfones/ethers/sulfonamide
4’,7ꢀdiacetates by Amano lipase (AK lipase)7 Pseudomonas
fluorescens and acetylation of the corresponding diols. In all
cases, the reactions are highly regioselective. However, the
55 pattern of selectivity was found to be dependent upon the
nature of the fused heterocyclic ring, namely
dihydrothiophene dioxide (sulfolene), dihydrofuran
(phthalan) or isoindole (indoline). For the isoindole
system, the hydrolysis as well as acetylation occurred at
60 the Cꢀ7 while for the furan derivative, the reactions took
place entirely at the C4’. For sulfones, reversal of
selectivity for hydrolysis and acetylation was observed.
The hydrolysis occurred selectively at Cꢀ7 while Cꢀ4’ was
the preferred position for acetylation. The results are in
65 contrast with those reported for similar reactions on 2’, 5 ꢀ
disubstituted aryl naphthalenes where hydrolysis/
acetylation both occurred at Cꢀ5. The observed results have
been explained by molecular docking using the
O
O
O
O
O
O
S
S
S
O
O
O
S
S
O
C
C
30
Scheme 1: GarrattꢀBraverman Cyclization
The usual starting materials for GB cyclization are bisꢀ
propargyl sulfones, ethers or sulfonamides. The
35 symmetrical starting materials lead to aryl naphthalenes
with the same functional groups at different locations.
Unsymmetrical bispropargyl systems with different
functionalities at the two ends upon GB cyclization often
lead to a mixture of isomers. Thus there is a need to
40 regiochemically differentiate similar functional groups in
arylnaphthalenes obtained via GB cyclization of
symmetrical systems. In a recent paper,6 we had reported
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Pseudomonas cepacia lipase crystal structure8 as the
representative class of lipases of the Pseudomonas family.
The hydrolytic behavior of the aryl naphthalene bisꢀ
acetates 1a-c was then studied. Attempted chemical
hydrolysis, even under mild conditions (LiOH, THF),10
produced a mixture of monoacetates thereby demonstrating
45 lack of selectivity. Enzymatic hydrolysis was attempted
next using various hydrolytic enzymes. While Candida
cylindracea (CCL)11 and Porcine pancreatic lipase (PPL)12
failed to induce hydrolysis of the diacetates or acetylation
of the diols, Amano Lipase AK was able to hydrolyze the
OAc
OAc
OH
OH
4
5
5
X
X
X
ii
X
1
OH
OAc
OAc
OH
2'
5
2'
A1, X = SO2
B1, X = NTs
C1, X = O
A3, X = SO2
B3, X = NTs
C3, X = O
A2, X = SO2
B2, X = NTs
C2, X = O
A4, X = SO2
B4, X = NTs
C4, X = O
i = AK lipase, buffer-acetone
For X =SO2/NTs/O
ii = AK lipase, vinyl acetate, THF
50 diacetates 1a-c to the monoacetates 12a-c in
a
Scheme 2: Previous results of hydrolysis and acetylation
regioselective manner (Scheme 4). The products of
hydrolysis from the diacetates are shown in Table 1.
4
4
X
10
X
7
1
7
OAc
1
OH
SO2
SO2
c
SO2
OHC
OHC
HOH2C
AcOH2C
AcOH2C
a. X = SO2
b. X = N-SO2Ar
c. X = O
4'
OH
4'
OAc
1 a-c
55
CH2OAc
NTs
14a
14b
CH2OAc
CH2OAc
NTs
1a
12a
2 a-c
NTs
Figure 1: Aryl naphthalene diacetates and diols used for enzymatic
c
a
a
HOH2C
15 hydrolysis and acetylation respectively
CH2OAc
O
The starting diols 2a-b were prepared by NaBH4 reduction
of the corresponding diesters11a-b9; the other diol 2c by
deprotection of the THP protected diol 11c. The diesters
and the diol, in turn, were obtained from the bisꢀpropargyl
20 sulfone, ether and sulfonamide by GarrattꢀBraverman
cyclization. The diols were then bisꢀacetylated with acetyl
chloride in the presence of triethylamine (Scheme 3).
12b CH2OAc
CH2OAc
O
1b
60
O
c
AcOH2C
AcOH2C
AcOH2C
CH2OH
CHO
14c
1c
12c
CH2OAc
a = acetone-phosphate buffer (pH 7.00 (1:3 by v/v), Amano Lipase (AK), r.t.; c =
Dess-Martin Reagent, CH2Cl2, r.t., 30 min
65 Scheme 4: Hydrolysis of diacetates and subsequent oxidation
CO2Me
S
I
OH
Br
i
i
i
94%
MeO2C
50%
MeO2C
Substrate
Product
12a
Enzyme
Yield(%)
75
MeO2C
9
3
5
4
MeO2C
Amano Lipase AK
1a
1b
1c
25
i
65%
i
94%
Amano Lipase AK
Amano Lipase AK
68
72
12b
O
S
Ts
O
CO2Me
CO2Me
N
NHTs
12c
iii
MeO2C
90%
Table 1: Enzymatic hydrolysis of the diacetates
10a
MeO2C
OTHP
10b
6
MeO2C
OH
i
O
SO2
Br
SO2
SO2
HOH2C
v
OHC
AcOH2C
OHC
b
c
HOH2C
90%
70%
7
10c
OTHP
OTHP
8
OTHP
CH2OAc
NTs
CH2OAc
12a
13b
15a
15b
2a CH2OH
NTs
30
10a
10b
10c
b
NTs
c
iv
ii 92%
90%
vi
90%
AcOH2C
HOH2C
O
O
NTs
O
S
THPOH2C
MeO2C
CH2OH
O
CHO
MeO2C
CH2OH
2b
11b
CH2OTHP
CO2Me
O
11a
vii
11c
c
CO2Me
b
HOH2C
O
HOH2C
35
CH2OAc
CH2OH
1a, 2a X = SO2
1b, 2b X = NTs
1c, 2c X = O
CH2OAc
CH2OAc
13c
11a
11b
2c
15c
CH2OH
X
X
ix
80%
90%
viii
85%
b = vinyl acetate, THF, Amano lipase (AK), r.t. c = Dess-Martin Reagent, CH2Cl2,
r.t., 30 min
CH2OAc
CH2OH
11c
Ts = 4-methylbenzene sulfonyl
THP = Tetrahydropyranyl
2a-c
1a-c
Scheme 5: Acetylation of diols and subsequent oxidation
i = ref.13; ii = Et3N, CHCl3, rt; iii = K2CO3, DMF, 5; iv = DBU, Toluene, reflux; v = NaH,
THF, 7; vi = KOBut, Toluene, reflux; vii = NaBH4, THF, MeOH, reflux; viii = PPTS, EtOH,
50 oC; ix = AcCl, Et3N, DMAP (cat), CH2Cl2, 0 o
C
The acetylation was next carried out using vinyl acetate
and Amano Lipase AK (Scheme 5). Again the reaction
40 Scheme 3: Synthesis of naphthalene derivatives 1 and 2
2
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proceeded with a high degree of selectivity and the various
monoacetates were isolated in high yields (Table 2).
Inspection of the results shown in Tables 1 and 2 revealed
many important attributes to these enzyme catalyzed
reactions. Although all the hydrolysis/acetylation reactions
were highly regioselective, the pattern of selectivity is
55 dependent upon the nature of heterocyclic ring. Normally
the orientation of substrate binding to the active site of the
enzyme for hydrolysis or acetylation is expected to be
similar. This is indeed found to be true in case of the furan
or isoindole derivative. Howerver, for furan, the substrate
60 binding takes place in such a way that the C4’ꢀacetate or
hydroxymethyl is near the active site serine/acetylated
serine. For the sulfonamide (1a and 2a) it is the other
acetate/hydroxymethyl at C5 that is placed near to the
active site serine/acetylated serine upon binding. The
65 hydrolytic/acetylation behaviour of the sulfones is
interesting. The orientation of binding for hydrolysis is
different from that of acetylation. The hydrolysis is taking
place preferentially at C5’ꢀacetate while the acetylation has
occurred at the C4’ꢀhydroxy methyl. All these aspects are
70 schematically represented in Scheme 6.
Substrate
Product
Enzyme
Yield(%)
Amano Lipase AK
Amano Lipase AK
Amano Lipase AK
82
75
75
2a
2b
2c
13a
13b
13c
Table 2: Enzymatic acetylation of the diols
The structure of the various monoacetates obtained upon
hydrolysis/esterification could not be confirmed by Xꢀray
crystallography as we failed to obtain good quality
5
1
crystals. The H NMR also failed to reveal the location of
the acetate. Finally the structures could be confirmed by
studying the shift of aryl hydrogens upon oxidation to the
10 aldehydes which exerted deshielding effect on the aryl
hydrogens to which the aldehyde functionality is attached.
As an example, the aldehyde 14c obtained from 12c, the
hydrogens in the pendant aryl ring experienced downfield
shift. For the other aldehyde 15c derived from 13c, the aryl
15 hydrogens in ring A of the naphthalene moiety underwent
downfield shift (Figure 2).
-----Serine---
-----Serine---
OH
OAc
CH2OAc
CH2OH
CH2OAc
CH2OAc
O
O
75
80
85
20
25
30
35
40
45
-----Serine---
OAc
-----Serine---
OH
CH2OAc
CH2OH
CH2OH
CH2OH
NTs
NTs
-----Serine---
-----Serine---
OH
OAc
CH2OH
CH2OAc
CH2OH
CH2OAc
O
S
S
O
O
O
90 Scheme 6: Mode of binding of acetate/hydroxymethyl functionality based
on the experimental results.
Docking Studies: Explanation of the results
Docking studies have been performed to find insight on
95 binding of our synthesized compounds. The structure of
Pseudomonas fluorescens lipase (PFL) is yet to be solved;
therefore, we have performed these docking studies with
Pseudomonas cepacia lipase (PCL). PCL is homologous to
50 Figure 2: 1H NMR of alcohol and corresponding aldehyde
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the PFL and has 22% sequence identity.14The active site of
45
PCL is constituted by Ser87, His286 and Asp264, while
the Leu17 and Gln88 residues also take part in catalysis.15,
16 PCL have two binding pockets; one is large hydrophobic
binding pocket which lies above the active site Ser87 and
an “alternate binding pocket” lying below the Ser87. This
alternate binding pocket is lined with hydrophobic amino
acids Tyr23, Leu27, Tyr29, Phe146, Ile290, and Leu293
(Figure 3). Researchers have shown that “extra hydrogen
10 bonds” with Tyr29 or Tyr 23 residues helped the binding
of ligand in this alternate groove and play crucial role in
the selective catalysis.15 Lang et al.17 also suggested that
Tyr29 remain hydrogen bonded with active site residues in
native state and during catalysis. Although crystal structure
15 of PFL is not known, alignment of sequence of PFL with
PCL suggests a tyrosine (Tyr50) in same position and
indicates the presence of ‘alternate binding site’ in PFL.15
5
50
55
60
65
70
20
Figure 3: A. PCL active site (PDB ID: 3LIP) with catalytic triad and
25 other crucial residues; B. Surface representation of PCL representing the
main large binding cavity and alternate binding cavity.
The pattern of selectivity was found to be dependent upon
the nature of the fused heterocyclic ring; hence, the
differences in their electronic natures, sizes and position of
30 substituent should have effect in their binding modes at
lipase’s active site cavity.
Figure 4: Comparative 1H NMR of PFL and PCL catalyzed reactions; a:
Starting diacetate or diol; b, d: Regioꢀisomeric monoacetate from PFL
75 catalyzed acetylation and hydrolysis; c: PCL catalyzed reactions
(acetylation or hydrolysis).
Before proceeding with the docking study, it would be
worth to explore the hydrolysis/acetylation behaviour of
some of the representative substrates with PCL and find
35 out whether similar selectivity is followed. Thus the
substrates were treated with Lipase, immobilized in Solꢀ
GelꢀAK from Pseudomonas cepacia. Although the
reactions were very sluggish, the hydrolysis of diacetate B1
and acetylation of diols C2 and 2a followed similar
40 regioselectivity as revealed by 1H NMR (Figure 4)
Based on these rationales, we have performed the docking
studies. Regioꢀselective catalysis of similar type of arylꢀ
naphthalenes has been reported previously from this group.
80 As PCL has limited homology with PFL, we have tried to
standardize and validate current in silico approach by using
previously reported compounds. Interaction or proximity
of ligand part with active site residue Ser87 has been noted
with priority because Ser87 is the most crucial residue and
85 involved in the first step of the catalysis.
Compounds with fused dihydrofuran ring: In case of
previously reported compounds, the hydrolysis as well as
acetylation occurred at Cꢀ5 position of naphthalene ring.
4
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This previous finding has been supported by current
We have studied these previous finding as model study.
docking study (Details are included in SI). Substituent at 50 Docking study suggests that the regionꢀselectivity of these
Cꢀ5 position of naphthalene ring is more exposed than
sterically crowded Cꢀ2’ position of aryl ring. In case of
both the hydrolysis and acetylation reactions, the
respective compound docked at main binding cavity. The
class compounds has been guided by the positioning of Nꢀ
tosyl group at binding cavity of lipase. The large and
hydrophobic Nꢀtosylgoup always acquires the “alternate
binding cavity and force the naphthalene ring pointing
5
acetate/alcohol linked to Cꢀ5 has been found to interact 55 towards the active site cavity. Hence, the reaction takes
with crucial residues line Tyr29/Ser117 and remain in
close proximity to the Ser87/acylatedꢀSer87. Interactions
10 of the substituent with lipase have been found to be major
driving force behind regionꢀselectivity of this class
compounds.
In case of current compounds, the hydrolysis as well as
acetylation occurred at Cꢀ4’ position of aryl ring. The
15 substituent linked to Cꢀ4’ position of aryl ring is more
exposed than Cꢀ2’ position of the previous cases. Docking
studies indicate that the naphthalene ring docked at main
binding cavity; while the acetate/alcohol linked to Cꢀ4’
drag the aryl ring towards active site via interacting with
20 crucial residues like Tyr29 and leu17 (Figure 5 and 6).
place at Cꢀ5 position. (Details are included in SI)
In case of current compounds, the hydrolysis as well as
acetylation occurred at Cꢀ7 position of naphthalene ring.
From docking study, we have found similar results as of
60 model study. The bulky and hydrophobic Nꢀtosyl unit
position in an alternate binding cavity and force the
naphthalene ring to point towards active site cavity. Hence,
reactions take place at Cꢀ7 position regioꢀselectively
(Figure 7 and 8).
65
70
25
Figure 7: Docked image of 1b with PCL; A. PCL represented as surface,
Nꢀtosyl ring docked in another binding cavity; force the naphthalene ring
to point towards active site cavity. B. 2D diagram of PClꢀ1b interaction,
Acetate linked to Cꢀ7 interacts with Tyr29 and remain in close proximity
75 to active site residue Ser87.
30 Figure 5: Docked image of 1c with PCL; A. PCL represented as surface,
naphthalene docked at main binding cavity while aryl drag near to active
site via alternate cavity. B. 2D diagram of PClꢀ1c interaction, Acetate
linked to Cꢀ4’ interacts with Tyr29 while aryl ring form πꢀcation
interaction with active site residue His286.
35
80
Figure 8: Docked image of 2b with PCL; A. PCL represented as surface,
Nꢀtosyl ring docked in alternate binding cavity; force the naphthalene ring
to point towards active site cavity. B. 2D diagram of PClꢀ2b interaction,
85 Alcohol linked to Cꢀ7 interacts with Leu167 and remain in close
proximity to active site residue acylatedꢀSer87.
Compounds with dihydrothiophene dioxide ring:
Docking study of this class of compounds is intriguing.
Docking study suggests that both the sulfone group and
90 substituent present at ligand molecule can cause sufficient
interaction with lipase receptor which can govern the
regioselectivity. In case of previously reported compounds,
the hydrolysis as well as acetylation occurred at Cꢀ5
position of naphthalene ring. But docking study predicts
95 that the reactions should occur at Cꢀ2’ position (Details are
40
Figure 6: Docked image of 2c with PCL; A. PCL represented as surface,
naphthalene docked at main binding cavity while aryl drag near to active
site via alternate cavity. B. 2D diagram of PClꢀ2c interaction, Alcohol
linked to Cꢀ4’ interacts with Tyr29 and Leu17 while aryl ring form πꢀ
45 cation interaction with active site residue His286.
Compounds with fused dihydroisoindole ring: In case of
previously reported compounds, the hydrolysis as well as
acetylation occurred at Cꢀ5 position of naphthalene ring.
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included in SI). We have got same trend of regioꢀ
selectivity with alternate positioning. This is may be due to
the fact that we have preformed this computational study
From the above exercise, it is clear that the docking can
successfully explain the observed regioselectivity in the
case of the isoindole and furan derivatives. While
with PCL and we have done experiments with PFL. 50 interaction of the substituent with lipase has been the major
5
Sulfone group itself can cause strong interaction with
protein residues unlike furan/tosyl, hence small change in
sequences or cavity size between PCL and PFL can trigger
the position alternation. If we take this result as a model
driving force for furans, the positioning of the bulky Nꢀ
tosyl group drives the selectivity in case of isoindole
derivatives. The docking results of sulfone derivatives are
more intriguing. The study has suggested that the
study, then we should get similar result in case of current 55 combined interactions of the sulfone group and the
10 sulfones too.
substituent may be the probable reason behind reversal of
selectivity for hydrolysis and acetylation. In case of
hydrolysis, the polar sulfone is the main binding force
unlike furan/tosyl, while in acetylation, free alcohol group
In case of current compounds, reversal of selectivity for
hydrolysis and acetylation was observed experimentally.
Docking study supports this reversal of selectivity with
alternate positioning like our model study. The hydrolysis 60 is involved is the major interaction. Though docking
15 reaction takes place at Cꢀ7 position; while docking study
predicts the reaction to take place at Cꢀ4’ position. The
sulfone group strongly interacts with Tyr29 and drag the
aryl ring towards active site cavity (Figure 9). The
studies could not explain the position alternation, it is
likely that the sulfone group itself can cause strong
interaction with protein residues. A small change between
PCL and PFL structures can cause the position alternation.
acetylation reaction takes place at Cꢀ4’ position; while 65 This was observed in acetylation of diol 2a catalysed by
20 docking study suggests the reaction to take place at Cꢀ7
position. In acetylation process, sulfone group does not
interact with lipase, but alcohol group at Cꢀ7 position
interacts directly with acylated Ser87 residue and governs
the reaction (Figure 10).
AK lipase and PCL (Figure 10).
25
70
30
75
Figure 9: Docked image of 1a with PCL; A. PCL represented as surface,
Aryl ring point towards the active site cavity. B. 2D diagram of PClꢀ1a
interaction, Sulfone causes driving force via interacting with Tyr29 and
35 drags the aryl ring towards active site cavity.
Figure 10: Comparative 1H NMR of PFL and PCL catalyzed acetylation;
a: Starting diol; b, d: Regioꢀisomeric monoacetate from PFL catalyzed
acetylation; c: PCL catalyzed reactions acetylation.
80 In conclusion, we have shown that differently
functionalized aryl naphthalenes can be prepared by
Amino Lipase AK catalyzed hydrolysis or acetylation of
the corresponding diacetates or diols respectively. It has
also been demonstrated that a change in the fused
85 heterocycle can affect the nature of binding to the active
site. Future work will address the issue of axial chirality
during the enzyme catalyzed hydrolysis/acetylation of
substrates capable of showing atropisomerism.
40
Figure 10: Docked image of 2a with PCL; A. PCL is represented as
surface. Sulfone docked away from active site; naphthalene enters into
active site cavity; B. 2D diagram of PCLꢀ2a interaction. Sulfone does not
45 interacts with PCL residues. Alcohol linked to Cꢀ7 of naphthalene ring
causes the driving force via interacting directly with Ser87.
Acknowledgement
90
The author AB is grateful to DST, Govt. of India, for
research funding and the JC Bose fellowship. AP and DB
thanks CSIR, Govt. of India for a research fellowship
6
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(NET). DST is also thanked for the funds for a 400 MHz 50 = 8 4Hz), 4.63 (2H, s), 4.25 (2H, s), 4.02 (3H, s), 3.89 (3H,
NMR facility under the IRPHA programme.
S); δC (100 MHz, CDCl3) 166.7, 166.5, 137.3, 137.0,
134.0, 132.4, 131.3, 131.0, 130.7, 130.5, 129.9, 129.7,
129.4, 128.6, 126.7, 126.6, 126.4, 57.0, 56.4, 52.5.
EXPERIMENTAL SECTION
DOCKING DETAILS
Synthesis of 11b
55 DBU (1.4 mmol) was added to the solution of bisꢀ
propargyl tosyl amine 10b (0.7 mmol) in dry toluene, and
refluxed for 48 h. After completion of the reaction, toluene
was removed under vacuo. The crude was extracted with
ethyl acetate and after removing the solvent, it was purified
60 by column chromatography using petroleum ether: ethyl
acetate (3:1) as eluent. State: Sticky mass; Yield: 90%;δH
(400 MHz, CDCl3) 8.25ꢀ8.23(3H, m), 8.07 (1H, d, J = 8.4
Hz), 7.89 (1H, d, J = 8.4 Hz), 7.77ꢀ7.73 (3H, m), 7.38 (2H,
d, J = 8.4 Hz), 7.33 (2H, d, J= 8.4 Hz), 4.83 (2H, s), 4.47
65 (2H, s), 4.03 (3H, s), 3.88 (3H, s), 2.41 (3H, s); δC (100
MHz, CDCl3) 167.0, 166.8, 144.0, 141.6, 137.0, 135.7,
134.8, 134.5, 133.3, 130.7, 130.3, 130.2, 130.0, 129.6,
128.4, 128.3, 128.0, 127.7, 125.7, 121.2, 53.6, 52.9, 52.5,
52.4, 21.6.
5
Advanced and widely used molecular gridꢀbased docking
program Autodock4.2 was used to predict the binding
modes and approximate binding free energies of all the
designed inhibitors in lead library. The Xꢀray crystal
10 coordinates of PCL was obtained from the Protein Data
Bank (http://www.rcsb.org), PDB ID 3LIP. Receptor
structure had been edited and hydrogen atoms added prior
to docking. AutoDock Tools was used to assign Gasteiger
charges to the receptor. Ligand structures were built up
15 using Accelrys Discovery studio 3.1 client. Energy
minimization of ligand structures was performed by
applying CHARMM force field. The conformer with best
binding energy was evaluated for designing purpose.
70 Synthesis of 11c
20 CHEMISTRY DETAILS
To the solution of bisꢀpropargyl ether (0.6 mmol) in
toluene, potassium tꢀbutoxide (1.2 mmol) was added and
was allowed to reflux for 6 h. After completion of the
reaction, toluene was removed under vacuo. The reaction
75 mixture was partitioned between water and ethyl acetate.
The organic layer was washed with brine and dried over
Na2SO4. The crude product was purified by column
chromatography over Si gel, using petroleum ether: ethyl
acetate (3:1) as eluent. State: Gummy liquid; Yield: 90%;
80 δH (400 MHz, CDCl3) 7.88 (1H, d, J = 8.4 Hz), 7.69 (2H,
s), 7.53 (3H, d, J = 8.1 Hz), 7.37 (2H, d, J = 6.6 Hz), 5.30
(2H, s), 5.05 (2H, s), 4.94 (1H, d, J = 12 Hz), 4.88ꢀ4.84
(2H, m), 4.72ꢀ4.70 (1H, m), 4.64ꢀ4.57 (2H, m), 3.99ꢀ3.89
(2H, m ), 3.66ꢀ3.52 (2H, m), 1.68ꢀ1.52 (12 H, m); δC (100
All reactions were conducted with ovenꢀdried glassware
under nitrogen. All common reagents were commercial
grade reagents and used without further purification. The
solvents were dried by standard methods and purified by
25 distillation before use. Silica gel (60–120 and 230–400
mesh) was used for column chromatography. TLC was
performed on aluminumꢀbacked plates coated with Silica
gel 60 with F254 indicator. Locally available UVꢀlamp
chamber and I2ꢀblower were used as the TLC spot
30 indicator. For solid compounds melting point (MP) was
measured in melting point apparatus twice and reported
without further calibration. The NMR spectra were
recorded using 200 MHz and 400 MHz The following
abbreviations are used to describe peak patterns: s =
35 singlet, d = doublet, t = triplet, q = quartet, m = multiplet, 85 MHz, CDCl3) 138.0, 137.8, 137.4, 137.3, 136.0, 133.4,
dd = double doublet, ABq = AB quartet.
132.6, 131.9, 129.7, 128.5, 128.1, 126.0, 124.6, 118.8,
98.3, 98.0, 73.6, 73.2, 69.2, 68.9, 62.4, 30.8, 25.7, 20.0,
19.6.
Procedure for Garratt-Braverman Cyclization:
Synthesis of 11a
General procedure for the reduction of diester
40 To the solution of bisꢀpropargylsulfone10a (1.4 mmol) in 90 To the solution of diesters 11a and 11b in THF (15 mL),
dry CHCl3, Et3N (2.8 mmol) was added and stirred for 1 h.
at room temperature. The reaction mixture was partitioned
between waterꢀdichloromethane. The organic layer was
washed with brine and dried over Na2SO4. After
finely powdered NaBH4 (2 eq) was added and stirred for
15 min at 65◦C. Methanol (2 mL) was then added drop
wise and stirred at 65◦C for 5 h. The reaction mixture was
cooled to room temperature and quenched with saturated
45 evaporation of the solvent the crude product was purified 95 NH4Cl. The organic layer was extracted with ethyl acetate
by column chromatography over Si gel, using petroleum
ether: ethyl acetate (2:1) as eluent. State: Sticky mass;
Yield: 92%;δH (400 MHz, CDCl3) 8.28ꢀ 8.24 (3H, m), 8.14
(1H, d, J = 8.8 Hz), 7.95 (2H, d, J = 8.4 Hz), 7.43 (2H, d, J
(40 mL) and dried over Na2SO4. After evaporation of the
solvent, diols 2a and 2b was purified by column
chromatography over Si gel, using petroleum ether: ethyl
acetate.
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Compound 2a: State: White solid; Yield: 90%; mp: 200
˚C; δH (400 MHz, CDCl3) 7.88 (1H, d, J = 8.5 Hz), 7.85
(1H, s), 7.59ꢀ7.52 (4H, m), 7.29 (2H, d, J = 8.0 Hz), 4.83
(2H, s), 4.73 (2H, s), 4.59 (2H, s), 4.22 (2H, s); δC (100
MHz, CDCl3) 141.2, 139.8, 138.0, 136.9, 133.0, 132.3,
130.0, 128.7, 128.7, 128.6, 127.8, 127.7, 126.5, 125.0,
123.9, 65.5, 65.2.
4.81 (2H, s), 4.49 (2H, s), 2.42 (3H, s), 2.23 (3H, s), 2.06
(3H, s); δC (100 MHz, CDCl3) 171.2, 171.0, 144.0, 137.4,
136.0, 135.0, 134.3, 134.1, 133.9, 133.6, 133.4, 131.7,
130.1, 129.8, 129.0, 128.7, 127.9, 126.3, 125.3, 120.9,
55 66.6, 66.2, 53.7, 53.3, 21.7, 21.3, 21.2.
5
Compound 1c: State: Gummy liquid; Yield: 70%; δH
(400 MHz, CDCl3) 7.87 (1H, d, J = 8.4 Hz), 7.69 (1H, s),
7.61 (1H, s), 7.51ꢀ7.46 (3H, m), 7.35 (2H, d, J = 8.0 Hz),
5.28 (2H, s), 5.22 (2H, s), 5.14 (2H, s), 5.01 (2H, s), 2.18
Compound 2b: State: White solid; Yield: 90%;mp: 220
˚C; δH (400 MHz, CDCl3) 7.81 (1H, d, J = 8.4 Hz), 7.73
10 (2H, d, J = 8.0 Hz), 7.63 (1H, s), 7.52ꢀ7.47 (4H, m), 7.31ꢀ 60 (3H, s), 2.06 (3H, s); δC (100 MHz, CDCl3) 171.1, 171.0,
7.24 (4H, m), 4.83 (2H, s), 4.78 (2H, s), 4.69 (2H, s), 4.45
(2H, s), 2.39 (3H, s); δC (100 MHz, CDCl3) 143.7, 140.5,
138.6, 136.7, 134.3, 134.0, 133.8, 133.0, 131.7, 129.8,
129.5, 128.4, 127.6, 127.4, 125.4, 123.3, 120.5, 65.4, 65.0,
15 53.5, 53.1, 22.4.
Procedure for the synthesis of 2c: To the solution of 11c
in ethanol PPTS and drop of water were added and allowed
to stir at 50 oC for 8 h. Ethanol was removed under vacuo.
The mixture was partitioned between waterꢀethyl acetate.
20 The organic layer was washed with brine and dried over
Na2SO4. After removing the solvent, the pure product was
obtained by column chromatography over Si gel,
petroleum ether: ethyl acetate (1:2) as eluent.
138.3, 137.9, 137.6, 135.6, 133.5, 133.5, 132.3, 131.6,
129.8, 129.0, 128.8, 128.7, 126.0, 125.3, 119.0, 73.5, 73.0,
66.6, 66.2, 21.2, 21.1.
General procedure for enzymatic catalysis
65 General procedure for hydrolysis of the diacetate: To
the solution of diacetates 1a-c (0.14 mmol) in acetoneꢀ
phosphate buffer (1:3 v/v, pH 7), the enzyme Amano lipase
(18 mg) was added and stirred at room temperature for 6 h.
The reaction mixture was filtered and acetone was
70 removed under vacuo. The crude was extracted with ethyl
acetate. The organic layer was washed with brine and dried
over Na2SO4. After removal of the solvent the crude was
purified by column chromatography over Si gel, using
petroleum ether and ethyl acetate (2:1) as eluent to get the
75 pure monoacetates12a-c.
State: Sticky mass; Yield: 85%; δH (400 MHz, CDCl3)
25 7.89 (1H, d, J = 8.4 Hz), 7.71 (1H, s), 7.63 (1H, s), 7.51
(3H, d, J = 8.0 Hz), 7.34 (2H, d, J = 7.6 Hz), 5.31 (2H, s),
5.0 (2H, s), 4.81 (2H, s), 4.73 (2H, s); δC (100 MHz,
CDCl3) 140.5, 138.5, 137.8, 137.5, 137.4, 133.4, 132.5,
131.9, 129.8, 128.8, 127.5,125.4,123.5,118.9, 73.5, 73.1,
30 65.7, 65.3.
General procedure for di-acetylation: Et3N (6 eq),
DMAP (catalytic amount), AcCl (3 eq) were added
successively to the solution of diol 2a-c in CH2Cl2 (20 mL)
at 0 oC and stirred at room temperature for 1 h. The
State: Sticky mass; Yield: 75%; δH (400 MHz, CDCl3)
7.88 (1H, d, J = 8.4 Hz), 7.83 (1H, s), 7.58ꢀ7.51 (4H, m),
7.31ꢀ7.29 (2H, m), 5.24 (2H, s), 4.75 (2H, s), 4.59 (2H, s),
4.23 (2H, s), 2.19 (3H, s); δC (100 MHz, CDCl3) 171.1,
80 139.8, 137.6, 137.4, 136.3,132.8, 132.0, 129.8, 128.9,
128.6, 128.5, 128.4, 127.6, 126.4, 124.9, 123.7, 65.9,65.3,
57.2,56.6, 21.2.
State: Semi solid; Yield: 68%; δH (400 MHz, CDCl3) 7.82
(1H, d, J = 8.9 Hz), 7.74 (2H, d, J = 8.0 Hz), 7.64 (1H, s),
35 reaction mixture was partitioned between waterꢀ 85 7.50 (4H, d, J = 9.4 Hz), 7.31 (4H, d, J = 8.1 Hz), 5.23
dichloromethane. The organic layer was washed with
brine, dried over Na2SO4. After evaporation of the solvent
the pure diacetate was isolated by column chromatography.
Compound 1a: State: Sticky yellow mass; Yield:80%; δH
(2H, s), 4.78 (2H, s), 4.71 (2H, s), 4.46 (2H, s), 2.39 (3H,
s), 2.21 (3H, s); δC (100 MHz, CDCl3) 171.2, 144.0, 138.9,
137.6, 135.9, 134.5, 133.5, 134.1, 133.2, 131.8, 130.1,
129.8, 129.0, 128.7, 127.9, 125.7, 123.5, 120.9, 66.2, 65.7,
40 (400 MHz, CDCl3) 7.90 (1H, d, J = 8.4 Hz), 7.85 (1H, s), 90 53.7, 53.3, 21.8, 21.4.
7.57ꢀ7.54 (3H, m), 7.50 (1H, s), 7.33ꢀ7.29 (2H, m), 5.25
(2H, s), 5.15 (2H, s), 4.61 (2H, s), 4.25 (2H, s), 2.20 (3H,
s), 2.08 (3H, s); δC (100 MHz, CDCl3) 171.0, 170.8, 137.7,
137.2, 136.4, 134.8, 133.0, 131.9, 129.8, 129.1, 128.9,
45 128.6, 127.0, 125.6, 124.9, 66.3, 65.9, 57.2, 56.5, 21.2,
21.0.
State: Sticky mass; Yield: 72%; δH (400 MHz, CDCl3)
7.88 (1H, d, J = 8.4 Hz), 7.69 (1H, s), 7.62 (1H, s), 7.52
(2H, d, J = 7.8 Hz), 7.47 (1H, d, J = 8.4 Hz), 7.35 (2H, d, J
= 7.7 Hz), 5.29 (2H, s), 5.14 (2H, s), 5.01 (2H, s), 4.83
95 (2H, s), 2.06 (3H, s); δC (100 MHz, CDCl3) 171.1, 140.5,
138.4, 137.6, 137.4, 133.5, 132.6, 131.8, 129.9, 128.9,
127.6, 126.0, 125.6, 124.7, 124.2, 119.3, 118.9, 73.6, 73.1,
66.9, 65.4, 21.2.
Compound 1b: State: Sticky mass; Yield: 70%; δH (400
MHz, CDCl3) 7.84 (1H, d, J = 8.4 Hz), 7.77 (2H, d, J = 8.0
Hz), 7.66 (1H, s), 7.55ꢀ7.46 (4H, m), 7.33 (2H, d, J = 7.6
General procedure for the acetylation of the diol: Vinyl
50 Hz), 7.28 (2H, d, J = 7.6 Hz),5.26 (2H, s), 5.13 (2H, s), 100 acetate (0.68 mmol) and Amano lipase (44 mg) was added
8
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[5]. (a) Maji, M.; Mallick, D.; Mondal, S.; Anoop, A.; Bag, S. S.; Basak,
A.; Jemmis, E. D. Org. Lett. 2011, 13, 888.
55 [6]. Panja, A.; Ghosh, D.; Basak, A. Bioorg. Med. Chem. Lett. 2013, 23,
893.
[7]. Gupta, R.; Gupta, N.; Rathi, P. Appl. Microbiol. Biotechnol. 2004, 64,
763.
[8]. Kim, K. K.; Song, K. Y.; Shin, D. H.; Hwang, K. Y.; Suh, S. W.
60 Structure 1997, 5,173.
[9]. (a) Saeed, A; Ashraf, Z. J. Chem. Sci. 2006, 118, 419; (b) Prugh, J.
D.; Deana, A. A. Tetrahedron Lett. 1988, 29, 37.
[10]. (a) Evans, D. A.; Miller, S. J.; Ennies, M. D.; Ornstein, P. L. J. Org.
Chem.1992, 57, 1067; (b) Smith, A. B.; Chen, S. SꢀY.; Nelsen, F. C.;
65 Reichert, J. M.; Salvatore, B. A. J. Am. Chem. Soc. 1997, 119, 10953; (c)
Nazare, M.; Waldman, H. Chem. Eur. J. 2001, 7, 3363.
[11]. (a) Sharma, R.; Chisti, Y.; Banerjee, U. C. Biotechnology
Advances2001, 19, 627; (b) Linko, Y. Y.; Lamsa, M.; Huhtala, A.;
Rantanen, O. J. Am. Oil. Chem. Soc.1995, 72, 129.
70 [12]. Zaks, A.; Klibanov, A. M. Science 1984, 224, 1291.
[13]. (a) Mandal, S.; Maji, M.; Basak, A. Tetrahedron Lett. 2011, 52,
1183; (b) Mukherjee, R.; Mandal, S.; Basak, A.; Mallick, D.; Jemmis, E.
D. Chem. Asian J. 2012, 7, 957; (c) Mukherjee, R.; Basak, A. Synlett
2012, 877; (d) Mondal; S.; Mukherjee, R.; Anoop, A.; Basak, A.
75 Tetrahedron 2012, 68, 7202.
to the THF solution of diol 2a-c (0.34 mmol). The reaction
mixture was allowed to stir at room temperature until the
reaction was complete (6 h for 2a; 4 h for 2b and 2c). It
was then filtered and THF was removed under vacuo. The
pure monoacetates 12a and 13b-c were isolated by column
chromatography of the crude residue over Si gel, using
petroleum ether and ethyl acetate (2:1) as eluent.
5
State: Sticky mass; Yield: 82%;δH (400 MHz, CDCl3)
7.87 (1H, d, J = 8.4 Hz), 7.81 (1H, s), 7.56ꢀ7.49 (4H, m),
10 7.29ꢀ7.28 (2H, m) 5.22 (2H, s), 4.73 (2H, s), 4.58 (2H, s),
4.21 (2H, s), 2.18 (3H, s); δC (100 MHz, CDCl3) 171.2,
139.9, 137.7, 137.5, 136.4, 132.9, 132.2, 129.9, 129.0,
128.7, 128.6, 128.5, 126.5, 125.1, 123.8, 66.1, 65.4, 57.3,
56.7, 21.3.
15 State: Semi solid; Yield: 75%;δH (400 MHz, CDCl3) 7.81
(1H, d, J = 9.6 Hz), 7.73 (2H, d, J = 8.0 Hz), 7.63 (1H, s),
7.53ꢀ7.49 (3H, m), 7.43 (1H, d, J = 8.0 Hz), 7.29 (3H, d, J
= 8.0 Hz), 7.23 (1H, s), 5.09 (2H, s), 4.83 (2H, s), 4.78
(2H, s), 4.46 (2H, s), 2.39 (3H, s), 2.04 (3H, s); δC (100
20 MHz, CDCl3) 170.8, 143.7, 140.6, 136.4, 134.7, 134.1,
134.0, 133.6, 133.4, 133.1, 131.5, 129.8, 129.5, 128.4,
127.6, 127.4, 126.0, 125.2, 120.5, 65.0, 64.4, 53.5, 53.0,
21.5, 20.9.
[14]. Tan, Y.; Miller, K. J. Cloning, expression, and nucleotide sequence
of a lipase gene from Pseudomonas fluorescens; B52. Appl. Environ.
Microbiol. 1992, 58, 1402.
[15]. Tuomi, W. V.; Kazlauskas, R. J. J. Org. Chem. 1999, 64, 2638.
80 [16]. (a) Hof, R. P.; Kellogg, R. M. J. Chem. Soc. Perkin Trans. 1 1996,
2051. (b) Lemke, K., Lemke, M., Theil, F. J. Org. Chem. 1997, 62, 6268.
[17]. Lang, D.; Hofmann, B.; Haalck, L.; Hecht, H. J.; Spener, F.;
Schmid, R. D.; Schomburg, D. J. Mol. Biol. 1996, 259, 704.
State: Sticky mass; Yield: 75%; δH (400 MHz, CDCl3)
25 7.86 (1H, d, J = 8.4 Hz), 7.68 (1H, s), 7.60 (1H, s), 7.50ꢀ
7.47 (3H, m), 7.35ꢀ7.33 (2H, m), 5.27 (2H, s), 5.21 (2H, s),
4.99 (2H, s), 4.73 (2H, s), 2.17 (3H, s); δC (100 MHz,
CDCl3) 171.0, 138.5, 138.0, 137.7, 137.3, 135.4, 133.2,
132.1, 131.7, 129.7, 128.6, 128.5, 125.2, 123.3, 118.8,
30 73.3, 72.9, 66.0, 65.5, 21.1.
85
References
[1]. (a) Hui, Y. H.; Chang, C. J.; Mclaughlin, J. L.; Powell, R. G. J. Nat.
Prod. 1986, 49, 1175; (b) Chen, C. C.; Hsin, W. C.; Ko, N. F.; Huang, Y.
L.; Ou, C. J.; Teng, C. M. J. Nat. Prod. 1996, 59, 1149; (c)
35 Mohagheghzadeh, A.; Schmidt, T. J.; Alfermann, A. W. J. Nat. Prod.
2002, 65, 69; (d) Vasile, N.; Elfahmi; Boss, R.; Kayser, O.; Momekov,
G.; Konstantinov, S.; Ionkova, I. J. Nat. Prod. 2006, 69, 1014.
90
[2]. (a) Tyson, D. S.; Carbaugh, A. D.; Ilhan, F.; SantosꢀPerez, J.;
Meader, M. A. Chemistry of Materials2008, 20, 6595. (b) Meader, M. A.;
40 Tyson, D. S.; Ilhan, F. U.S. Pat. Appl. Publ. 2008, US 20080242870 A1
20081002. (c) Meader, M. A.; Tyson, D. S.; Carbaugh, A. D. PMSE
Preprints 2008, 98, 130; (c) Facchetti, A.; Marks, T. J.; Yan, H. PCT Int.
Appl. 2008, WO.2008085942 A2 20080717.
[3]. (a) Kobayashi, S. Cycloaddition Reactions in Organic Synthesis;
45 WileyꢀVCH, 2001; (b) Carruthers, W. Cycloaddition Reactions in
Organic Synthesis; Pergamon Press: Oxford, 1990.
[4]. (a) Braverman, S.; Segev, D. J. Am. Chem. Soc. 1974, 96, 1245; (b)
Garratt, P. J.; Neoh, S. B. J. Org. Chem. 1979, 44, 2667; (c) Cheng, Y. S.
P.; Garratt, P. J.; Neoh, S. B.; Rumjanek, V. H. Isr. J. Chem 1985, 26,
50 101; (d) Braverman, S.; Duar, Y.; Segev, D. Tetrahedron Lett. 1976, 17,
3181; (e) Zafrani, Y.; Gottlieb, H. E.; Sprecher, M.; Braverman, S. J. Org.
Chem. 2005, 70, 10166.
This journal is © The Royal Society of Chemistry [year]
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Graphical Abstract
Reversal of Regioselectivity in Acetylation
and Deacetylation of Aryl-Naphthalene
Diols and Diacetates by Amano Lipase Arpita Panja, Deb Ranjan Banerjee and Amit
Basak*
X
HOH2C
X
HOH2C
C
X
CH2OAc
X
X
I
II
A
HOH2C
AcOH2C
CH2OAc
X
CH2OH
CH2OAc
AcOH2C
AcOH2C
D
X = SO2, C is the product
X = NTs, D is the product
X = O, C is the product
X = SO2, A is the product
X = NTs, A is the product
X = O, B is the product
B
CH2OH
CH2OH
I = acetone-phosphate buffer (pH 7.00 (1:3 by v/v), Amano Lipase (AK), r.t.; II = vinyl acetate, THF,
Amano lipase (AK), r.t.

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1