Structure-based design, synthesis, and biological evaluation of inhibitors of Mycobacterium tuberculosis type II dehydroquinase

Article abstract of DOI:10.1021/jm0501836

The syntheses by Suzuki cross-coupling of 12 5-aryl analogues of the known inhibitor (LR,3/2,4R)-1,3,4-trihydroxycyclohex-5-en-1-carboxylic acid are reported. These compounds were found to be reversible competitive inhibitors against Mycobacterium tubercu

Full text of DOI:10.1021/jm0501836

J. Med. Chem. 2005, 48, 4871-4881
4871
Structure-Based Design, Synthesis, and Biological Evaluation of Inhibitors of
Mycobacterium tuberculosis Type II Dehydroquinase
Cristina Sa´nchez-Sixto,† Vero´nica F. V. Prazeres,† Luis Castedo,† Heather Lamb,§ Alastair R. Hawkins,§ and
Concepcio´n Gonza´lez-Bello*,†
Departamento de Quı´mica Orga´nica y Unidad Asociada al C.S.I.C., Facultad de Qu´ımica, Universidad de Santiago de
Compostela, 15782 Santiago de Compostela, Spain, and Institute of Cell and Molecular Biosciences, Catherine Cookson
Building, Medical School, University, Newcastle upon Tyne, Framlington Place, Newcastle upon Tyne NE2 4HH, U.K.
Received February 25, 2005
The syntheses by Suzuki cross-coupling of 12 5-aryl analogues of the known inhibitor
(1R,3R,4R)-1,3,4-trihydroxycyclohex-5-en-1-carboxylic acid are reported. These compounds were
found to be reversible competitive inhibitors against Mycobacterium tuberculosis type II
dehydroquinase, the third enzyme of the shikimic acid pathway. The most potent inhibitor,
the 3-nitrophenyl derivative, has a Ki of 54 nM, over 180 times more potent than the reported
inhibitor (1R,3R,4R)-5-fluoro-1,3,4-trihydroxycyclohex-5-en-1-carboxylic acid and more than 700
times lower than the KM of the substrate, making it the most potent known inhibitor against
any type II dehydroquinase. Docking studies using GOLD (version 2.2) indicated a key
electrostatic binding interaction between the aromatic rings and Arg19, a residue that has
been identified as essential for enzyme activity.
Introduction
ridium parvum.6 The absence of the pathway in mam-
mals, combined with its essential nature in certain
microorganisms, makes the shikimic acid pathway
enzymes attractive targets for the development of new
antibiotics and herbicides. In fact, glyphosate [N-(phos-
phomethyl)glycine], the active ingredient in the well-
known herbicides RoundUp and Tumbleweed and a
specific inhibitor of the sixth enzyme of the shikimate
pathway (EPSP synthase),7 was shown to be active in
vitro against malaria.6a Also, (6R)- and (6S)-6-fluo-
roshikimic acids have shown antimicrobial activity
against Escherichia coli, the latter being the most potent
one.8 Here, we report a series of compounds active
against Mycobacterium tuberculosis type II dehydro-
quinase, the third enzyme of the shikimic acid pathway.
The enzyme dehydroquinase (3-dehydroquinate de-
hydratase, EC 4.2.1.10) catalyzes the reversible dehy-
dration of 3-dehydroquinic acid (1) to form 3-dehy-
droshikimic acid (2) (Scheme 1). This reaction is part
of two metabolic pathways: the biosynthetic shikimate
pathway and the catabolic quinate pathway.9 There are
two distinct types of enzymes, known as type I and type
II, which have different biochemical and biophysical
properties and show no sequence similarity. The type I
enzyme (typically Salmonella typhi and Escherichia
coli)10 found in plants, fungi, and many bacterial species
is exclusively biosynthetic, whereas the type II enzyme
(Streptomyces coelicolor, Mycobacterium tuberculosis,
Aspergillius nidulans, Helicobacter pylori, Neurospora
crassa)11 has both biosynthetic and catabolic roles. More
importantly, these enzymes utilize completely different
mechanisms to catalyze the same overall reaction. The
type I enzyme mechanism involves covalent imine
intermediates between the enzyme (Lys170 in E. coli)
and the substrate and proceeds with syn stereochem-
istry.12 In contrast, type II reaction proceeds through
an enol intermediate with overall anti stereochemistry
Although effective chemotherapeutic agents have
been developed, Mycobacterium tuberculosis, the caus-
ative agent of tuberculosis (TB), continues to be the
greatest single infectious cause of mortality worldwide,
killing roughly two million people annually (one person
dies every 10 s).1 The World Health Organization
(WHO) has estimated that one-third of the world’s
population is infected with Mycobacterium tuberculosis.2
Each untreated person with active TB disease will infect
on average of 10-15 people every year, but people
infected with TB bacilli will not necessarily become sick
with the disease. The TB bacilli may remain in the body
for decades without causing the symptoms of tubercu-
losis.3 TB is a leading cause of death among people who
are HIV-positive (13% of AIDS deaths worldwide).4 The
synergy between tuberculosis and the AIDS epidemic
and the surge of multidrug-resistant isolates of M.
tuberculosis have reaffirmed tuberculosis as a primary
public health threat. It has been predicted that by 2020
one billion people will be newly infected if new anti-TB
treatments are not developed. It is therefore necessary
to discover new, safe, and more efficient antibiotics
against this disease.
The shikimate pathway is the biosynthetic route to
the aromatic amino acids L-phenylalanine, L-tryptophan,
and L-tyrosine, as well as precursors to the folate
coenzymes, alkaloids, and vitamins, and many other
aromatic compounds.5 This pathway is present in
bacteria, fungi, and plants and has been recently
discovered in apicomplexan parasites Plasmodium fal-
ciparum (malaria), Toxoplasma gondii, and Cryptospo-
* To whom correspondence should be addressed. Phone: +34 981
563100, extension 14368. Fax: +34 981 595012. E-mail:
cgb1@lugo.usc.es.
† Universidad de Santiago de Compostela.
§ Medical School, University, Newcastle upon Tyne.
10.1021/jm0501836 CCC: $30.25 © 2005 American Chemical Society
Published on Web 06/25/2005

4872 Journal of Medicinal Chemistry, 2005, Vol. 48, No. 15
Sa´nchez-Sixto et al.
Scheme 1. Conversion of 3-Dehydroquinic Acid (1) to
3-Dehydroshikimic Acid (2) Catalyzed by
Dehydroquinase
Results and Discussion
Synthesis of Compounds 4a-l. The strategy used
involved the introduction of the aromatic ring in 4a-l
by Suzuki cross-coupling reactions between diverse
substituted phenyl- and arylboronic acids and vinyl
triflate 6, which was synthesized from a cheap and
commercially available (-)-quinic acid (5)21 as a chiral
template (Scheme 3).
The synthesis of the key intermediate, the vinyl
triflate 6, was achieved in four steps from previously
reported benzyl lactone 7,22 as outlined in Scheme 4.
First, treatment of diol 7 with TBSOTf in pyridine
afforded silyl ether 8 in 97% yield. Deprotection of the
equatorial secondary hydroxyl group in 8 was achieved
by catallytic hydrogenolysis. Although the reaction can
be carried out using palladium-on-carbon, the best
results were obtained using palladium hydroxide in
methanol. The free hydroxyl group in 9 was readily
oxidized using PDC in the presence of 4 Å activated
molecular sieves to afford ketone 10 in 95% yield.
Finally, the key intermediate 6 was synthesied by
enolization of the ketone 10 and reaction with triflimide.
Different bases (LDA, KHMDS, LHMDS), temperatures,
and solvents (THF, DMF, DMF/toluene) were employed.
Using KHMDS in a mixture of DMF/toluene (1:1.1) gave
the desired vinyl triflate 6 in 80% yield.
The key step of the synthesis was the carbon-carbon
bond formation between the vinyl triflate 6 and diverse
boronic acids. The reaction was performed in THF in
the presence of Et3N (3 equiv) and (dba)3Pd2‚CHCl3
catalyst (7.5%).23 The corresponding vinylaryl deriva-
tives 11 were obtained in good yields of 61-96% after
column chromatography (Scheme 5, Table 1). Attempts
to synthesize 11k using the above conditions afforded
mainly starting material. However, by use of a 3-pyri-
dine boronic acid ester, Pd(PPh3)4 as catalyst in the
presence of K3PO4 afforded the desired pyridine 11k in
good yield (Table 1, entry 11).
(Scheme 2).13 Two residues, Arg19 and Tyr24, have been
identified by chemical modification and site-directed
mutagenesis studies as being essential for enzyme
activity.14 Both residues are on the flexible loop that
closes over the active site upon substrate binding. It has
been suggested that Arg19 is involved in stabilization
of the enol intermediate. A conserved molecule of water
close to the carbonyl group stabilizes the enol interme-
diate, and it is held in a specific orientation by hydrogen
bonds to Asn12, the carbonyl group of Pro11, and the
main chain amide of Gly77. The final step is the acid-
catalyzed elimination of the C1 hydroxyl group cata-
lyzed by His101. These mechanistic and stereochemical
distinctions have allowed the design and the synthesis
of compounds that are specific to either type I15 or type
II16 enzymes.
Because the elimination mechanism of the type II
enzymes proceeds via an enol intermediate character-
ized by ring-flattening due to the π-system formed
between C2 and C3 and by the increased H-bonding of
the enol oxygen formed, compounds that mimicked the
enol intermediate were likely to show inhibitory proper-
ties. Both of these features have been exploited for the
design of the first generation of inhibitors. Abell et al.
reported that analogues 3a, 3b, and 3c are competitive
reversible inhibitors of M. tuberculosis type II dehy-
droquinase with a Ki of 200 µM, 10 µM, and 20 µM,
respectively (Figure 1).16a,c,17 The crystal structures of
M. tuberculosis dehydroquinase apoenzyme18 and the
enzyme in complex with inhibitors 3a19 and 3c20 have
been recently solved. The important observation that
compounds with a double bond between C5 and C6 bind
in a manner predicted for transition-state mimics
encouraged us to design the next generation of inhibi-
tors.
Finally, conversion of the cross-coupling products 11
to the desired acids 4 was achieved by a two-step
reaction sequence. The first step is deprotection of the
TBS groups with TBAF (60-97%), and the second step
is basic hydrolysis of the corresponding lactone, followed
by treatment with Amberlite IR-120 (H+) ion-exchange
resin (83-99%).
We have reported previously that the incorporation
of substituted benzyl moieties in C1 or C4 hydroxyl
groups of the inhibitor 3a results in the competitive
inhibition of Streptomyces coelicolor type II dehydro-
quinase.16d The key binding interactions for the benzyl
groups appear to be π-stacking against Tyr28 and
possibly electrostatic interactions with Arg23. Tyr28
performs the proton abstraction, and its pKa is mediated
by the proximity of the side chain of Arg113 and possibly
of Arg23. We therefore decided to explore the idea of
making more potent inhibitors against M. tuberculosis
type II dehydroquinase by incorporating substituted
aryl groups in the C5 of inhibitor 3a. Herein, we
describe the synthesis of 12 new analogues 4a-l (Figure
1) using palladium-catalyzed cross-coupling reactions.
The results of inhibition studies of these compounds
against M. tuberculosis type II dehydroquinase and the
molecular docking studies using GOLD (version 2.2) are
also described.
Assay Results. The 12 acids 4a-l were assayed in
the presence of 3-dehydroquinic acid (1) for their inhibi-
tory properties against M. tuberculosis type II dehy-
droquinase. The inhibition data are summarized in
Table 2. The UV spectrophotometric assay was used to
measure the initial rate of product formation, detecting
the enone-carboxylate chromophore at 234 nm in
3-dehydroshikimic acid (2). The Ki values were obtained
from Dixon plots (1/v vs [I]).
All the compounds were shown to be reversible
competitive inhibitors of M. tuberculosis type II dehy-
droquinase. All the analogues, except three of them,
4-CF3 4c, 3-OH 4f, and 3-CO2H 4h, were found to be
more potent than the original inhibitors 3a (200 µM),
3b (10 µM), and 3c (20 µM). The 3-nitro derivative 4g
was the most potent compound with a low Ki of 54 nM
compared to the reported inhibitors 3a, 3b, and 3c and
considerably below the KM of the substrate (40 µM). The
thiophene derivative 4j also had a high affinity of 590

Inhibitors of Type II Dehydroquinase
Journal of Medicinal Chemistry, 2005, Vol. 48, No. 15 4873
Scheme 2. Proposed E1CB Mechanism for the Enzymatic Conversion of 3-Dehydroquinic Acid (1) to
3-Dehydroshikimic Acid (2) Catalyzed by Type II Dehydroquinase Indicating the Residues Involved in the Catalysis
Scheme 3
nM. No significant differences in activity were found
between fluorophenyl analogues, the 3-substituted being
slightly more potent than the 4-substituted. The 3-car-
boxy derivative 4h was a surprisingly poor inhibitor
with a Ki of 150 µM.
Docking Studies. Ligands 4a-l were docked in the
active site of M. tuberculosis type II dehydroquinase
using the program GOLD (version 2.2).24
The apoenzyme structure indicates that the catalyti-
cally important domain is disordered with no interpret-
able electron density visible between residues 19 and
26, where Arg19 and Tyr24 are located. Both residues
have been previously identified by chemical modification
and site-directed mutagenesis studies as being essential
for enzyme activity.25 Arg19 is not observed as well in
the crystal structure of the enzyme complexed with the
inhibitor 3a.19 However, in the crystal structures of the
enzyme complexed with sulfate26 and with the oxime
inhibitor 3c,20 this arginine is visible and is positioned
in the active site of the enzyme. Therefore, the latter
crystal structure was used for this study.
The molecule of inhibitor 3c and all the water
molecules were removed from the structure. No energy
minimization was performed on the enzyme. The struc-
tures of the inhibitors were prepared using Gaussian
98W27 and energy-minimized using AM1. All the inhibi-
tors were docked as their carboxylate anions, and 25
independent GOLD runs were performed for each
ligand. The GoldScore scoring function was used.
Ligands 3a and 3c were docked as a control, and the
results were compared to the enzyme-inhibitor com-
plex. Both ligands docked similarly at the same site, and
their positions in the active site coincided with the
position of the oxime inhibitor 3c in the crystal structure
Figure 1. M. tuberculosis type II dehydroquinase inhibitors.
to within 0.5 Å.

4874 Journal of Medicinal Chemistry, 2005, Vol. 48, No. 15
Sa´nchez-Sixto et al.
Scheme 4a
Table 2. Inhibition Results for Assays with M. tuberculosis
Type II Dehydroquinasea
compd
R
Ki (nM)
4a
4b
4c
4d
4e
4f
4g
4h
4i
phenyl
1500
1800
17000
1500
2125
95000
54
150000
2440
590
(4-F)phenyl
(4-CF3)phenyl
(3-F)phenyl
(3-CF3)phenyl
(3-OH)phenyl
(3-NO2)phenyl
(3-CO2H)phenyl
(3,5-diF)phenyl
tiophen-3-yl
pyridin-3-yl
4j
4k
4l
45000
830
furan-3-yl
a KM value of 40 µM was obtained at the assay conditions.
a Reagents and conditions: (i) ref 22; (ii) TBSOTf, Py, DCM, 0
°C f room temp; (iii) H2, Pd(OH)2, MeOH, room temp; (iv) PDC,
4 Å molecular sieves, DCM, room temp; (v) (1) KN(TMS)2, DMF,
toluene, -78 °C, (2) triflimide, -78 °C f room temp.
Figure 2. Docking results of the highest score solution of
ligand 4j (green).
Scheme 5a
same site as 3c in the crystal structure of the enzyme-
inhibitor complex. The predicted binding puts the
aromatic ring of the ligands into the pocket formed
between the three arginines of the active site, Arg19,
Arg108, and Arg112. However, differences were ob-
served in the position of the aromatic ring of the ligands,
leading to some differences in the predicted relative
binding of the analogues.
a Reagents and conditions: (i) (dba)3Pd2‚CHCl3, DCM, THF,
Et3N, ArB(OH)2, -78 °C f room temp; (ii) TBAF, THF, 0 °C f
room temp; (iii) (1) LiOH, THF, room temp, (2) Amberlite IR-120
(H+); (iv) (3-Py)B(OR)2, Pd(PPh3)4, dioxane, aqueous K3PO4, ∆.
The key binding association for the aromatic ring
appeared to be its electrostatic interaction with Arg19.
The aromatic rings of the inhibitors are located parallel
to Arg19, with the exception of pyridine 4k and thiophene
4j, which are orientated perpendicularly (Figure 2). This
may be due to stronger electrostatic interactions be-
tween the heteroatom (N, S) and Arg19 than between
the aromatic ring π-system and Arg19. This hetero-
atom-arginine interaction should be stronger in 4j than
in 4k because the sulfur still has a free electron pair
not implicated in the π-system and may be responsible
for the inhibitory potency of the thiophene analogue 4j.
The docking results of fluoro (4b, 4d, and 4i) and
trifluoromethyl derivatives (4c, 4e) were quite similar,
suggesting that these substituents do not introduce
significant changes in the π-system of the aromatic ring.
The predicted binding for the most potent inhibitor,
the 3-nitrophenyl analogue 4g (Figure 3), suggests a
strong electrostatic interaction between the nitro group
and Arg19, which may be responsible for the low Ki
value observed.
Table 1. Synthesis of Compounds 11, 12, and 4a
6 f 11
11 f 12
12 f 4
yield
(%)
yield
(%)
yield
(%)
entry
R
11
12
4
1
2
phenyl
11a
11b
11c
11d
11e
11f
93
61
96
89
77
90
88
62
77
69
70
71
12a
12b
12c
12d
12e
12f
12g
12ha
12i
76
88
81
87
94
60
79
89
97
82
94
79
4a
4b
4c
4d
4e
4f
4g
4hb
4i
84
89
92
99
98
93
99
83
87
93
96
98
(4-F)phenyl
3
(4-CF3)phenyl
(3-F)phenyl
4
5
(3-CF3)phenyl
(3-OH)phenyl
(3-NO2)phenyl
6
7
11g
8
(3-CO2R′)phenyl 11ha
(3,5-diF)phenyl 11i
9
10
11
12
3-thiophenyl
3-pyridinyl
3-furanyl
11j
11k
11l
12j
12k
12l
4j
4k
4l
a R′ ) Me. b R′ ) H.
All 25 GOLD runs for all ligands showed the carboxyl
group binding to the backbone amides of Ile102 and
Ser103, and the C-1 hydroxyl binding to His101 and
Asn75 as in the enzyme-inhibitor complex. The cyclo-
hexene ring of the inhibitors occupied approximately the
Conclusions
Suzuki cross-coupling between a vinyl triflate deriva-
tive from (-)-quinic acid and diverse arylboronic acids

Inhibitors of Type II Dehydroquinase
Journal of Medicinal Chemistry, 2005, Vol. 48, No. 15 4875
quinic acid (1) were calibrated by equilibration with type II
dehydroquinase and measurement of the change in the UV
absorbance at 234 nm due to the formation of the enone-
carboxylate chromophore of 3-dehydroshikimic acid (2).
Docking. The receptor and ligands were used as MOL2
files. Each ligand was docked using GOLD (version 2.2) in 25
independent genetic algorithm (GA) runs, and for each of these
a maximum number of 100 000 GA operations were performed
on a single population of 50 individuals. Operator weights for
crossover, mutation, and migration in the entry box were used
as default parameters (95, 95, and 10, respectively), as well
as the hydrogen bonding (4.0 Å) and van der Waals (2.5 Å)
parameters. The position of the active site was introduced, and
the radius was set to 15 Å, with the automatic active-site
detection on. The “flip ring corners” flag was switched on, while
all the other flags were off.
Figure 3. Docking results of the highest score solution of
ligand 4g (yellow).
(1S,3R,4R,5R)-3-Benciloxy-1,4-di(tert-butyldimethylsi-
lyloxy)cyclohexan-1,5-carbolactone (8). To a stirred solu-
tion of the diol 722 (1.00 g, 3.79 mmol) in dry DCM (13 mL)
and pyridine (1.1 mL, 13.27 mmol) under an inert atmosphere
at 0 °C was added tert-butyldimethylsilyl trifluorosulfonate
(2.6 mL, 11.37 mmol). The resultant solution was stirred at
room temperature for 12 h and then diluted with DCM and
water. The aqueous layer was acidified with HCl (10%), and
the organic phase was separated. The aqueous phase was
extracted twice with DCM. All the combined organic extracts
were dried (anhydrous Na2SO4), filtered, and evaporated. The
obtained residue was purified by flash chromatography, eluting
with 10% ethyl acetate-hexanes to yield silyl ether 8 (1.81 g,
has been used for the synthesis of 12 5-aryl analogues
of the known inhibitor 3a. These compounds were
assayed against Mycobacterium tuberculosis type II
dehydroquinase and showed competitive inhibition
against this enzyme. Nine of them were more potent
than the reported inhibitors 3a, 3b, and 3c. The most
potent inhibitor, 3-nitrophenyl derivative 4g, has a Ki
of 54 nM, over 180 times more potent than the original
5-fluoro inhibitor 3b and more than 700 times lower
than the KM of the substrate, making it the most potent
known inhibitor against any type II dehydroquinase.
Docking studies using GOLD (version 2.2) indicated a
key electrostatic binding interaction between the aro-
matic rings as well as the nitro group in the case of
compound 4g and Arg19, a residue that has been
identified as being essential for enzyme activity. These
docking studies need to be supported with structural
studies of enzyme-inhibitor complexes, which are un-
derway and should be considered for the design of the
next generation of inhibitors.
97%) as a colorless oil. [R]20 -14° (c 1.4, CHCl3); 1H NMR
D
(250 MHz, CDCl3) δ (ppm) 7.31 (m, 5H), 4.45 (t, 1H, J 5.6),
4.42 (s, 2H), 4.11 (t, 1H, J 4.6), 3.42 (ddd, 1H, J 11.7, 6.2 and
4.1), 2.43 (d, 1H, J 11.4), 2.13-1.98 (m, 2H), 1.76 (t, 1H, J
11.9), 0.70 (s, 9H), 0.69 (s, 9H), -0.07 (s, 3H), -0.09 (s, 3H),
-0.15 (s, 3H) and -0.16 (s, 3H); 13C NMR (63 MHz, CDCl3) δ
(ppm) 176.3, 137.8, 128.3 (2×), 127.7, 127.6 (2×), 75.9, 74.1,
73.7, 71.1, 65.7, 38.1, 37.5, 25.7 (3×), 25.6 (3×), 18.1, 18.0, -2.9
(2×), -4.5, and -5.0.
(1S,3R,4R,5R)-1,4-Di(tert-butyldimethylsilyloxy)-3-hy-
droxycyclohexan-1,5-carbolactone (9). A suspension of the
disilyl ether 8 (270 mg, 0.55 mmol) and 20% palladium
hydroxide on carbon (50 mg) in methanol (15 mL) was shaken
under hydrogen atmosphere at room temperature for 48 h. The
mixture was filtered over Celite, and the residue was washed
with methanol. The filtrate and washings were evaporated
under reduced pressure to yield a white solid that was purified
by flash chromatography, eluting with 10% ethyl acetate-
hexanes to yield alcohol 9 (218 mg, 99%) as white needless.
Mp 107-108 °C; [R]20D -1° (c 1.1, CHCl3); 1H NMR (250 MHz,
CDCl3) δ (ppm) 4.49 (t, 1H, J 5.5), 3.95 (t, 1H, J 4.8), 3.75-
3.61 (m, 1H), 2.24 (d, 1H, J 11.4), 2.08 (m, 2H), 1.87 (d, 1H, J
11.6), 1.53 (t, 1H, J 12.6), 0.73 (s, 9H), 0.67 (s, 9H), -0.06 (s,
3H), -0.08 (s, 3H), -0.10 (s, 3H), and -0.11 (s, 3H); 13C NMR
(63 MHz, CDCl3) δ (ppm) 175.9, 75.6, 73.6, 67.0, 66.1, 41.4,
37.8, 25.7 (3×), 25.5 (3×), 18.0 (2×), -2.9 (2×), -4.6, and -4.9.
Experimental Section
General Procedures. All starting materials and reagents
were commercially available and used without further puri-
fication. FT-IR spectra were recorded as NaCl plates or KBr
disks. [R]D values are given in 10-1 deg cm2 g-1 1H NMR
.
spectra (250, 300, and 500 MHz) and 13C NMR spectra (63,
75, and 100 MHz) were measured in deuterated solvents. J
values are given in hertz. NMR assignments were made by a
combination of 1D, COSY, and DEPT-135 experiments. All
procedures involving the use of ion-exchange resins were
carried out at room temperature and used Mili-Q deionized
water. Amberlite IR-120 (H+) (cation exchanger) was washed
sequentially with water, 10% NaOH, water, 10% HCl, and
finally water before use. The purity of carboxylic acids was
analyzed by HPLC and by NMR. HPLC was performed on a
preparative (300 mm × 16 mm) Bio-Rad Aminex ion exclusion
HPX-87H organic acids column. The eluent used for these
columns was 100 mM aqueous formic acid at a flow rate of
(1S,4S,5R)-1,4-Di(tert-butyldimethylsilyloxy)-3-oxocy-
clohexan-1,5-carbolactone (10). To a stirred suspension of
the alcohol 9 (1.24 g, 3.09 mmol) and 4 Å activated powder
molecular sieves (1.24 g) in dry DCM (31 mL) was added
pyridinium dichromate (1.40 g, 3.71 mmol). The resultant
suspension was stirred vigorously at room temperature. After
3 h, more 4 Å activated powder molecular sieves (750 mg) were
added and the resultant suspension was stirred for an ad-
ditional 2 h. The reaction mixture was filtered over a plug of
Celite and silica gel, and the residue was washed with diethyl
ether. The filtrate and the washings were concentrated under
reduced pressure. The brown solid obtained was redisolved in
hot hexane and treated with activated carbon. The black
suspension was filtered over Celite, and the residue was
washed with hot hexane. The filtrate and the washings were
concentrated and recrystallized to afford the ketone 10 (1.17
g, 95%) as white needless. Mp 50-51 °C (hexanes); [R]20D -24°
0.6 mL min-1
.
Dehydroquinase Assay. M. tuberculosis type II dehydro-
quinase was purified as described previously.28 A concentrated
solution (0.7 mg mL-1) was stored in potassium phosphate
buffer (50 mM, pH 7.2), DTT (1 mM), and NaCl (150 mM).
When required for assays, aliquots of the enzyme stocks were
diluted in water and buffer and stored on ice.
Dehydroquinase was assayed in the forward direction by
monitoring the increase in the absorbance at 234 nm in the
UV spectrum due to the absorbance of the enone-carboxylate
chromophore of 3-dehydroshikimic acid (2) (ꢀ ) 12 000 M-1
cm-1). Standard assay conditions for type II dehydroquinase
were pH 8.2 at 25 °C in Tris/HOAc (50 mM). Each assay was
initiated by addition of the substrate. Solutions of 3-dehydro-
1
(c 1.1, CHCl3); H NMR (250 MHz, CDCl3) δ (ppm) 4.51 (dd,
1H, J 5.9 and 4.1), 3.81 (br d, 1H, J 4.1), 2.74 (d, 1H, J 17.6),

4876 Journal of Medicinal Chemistry, 2005, Vol. 48, No. 15
Sa´nchez-Sixto et al.
2.60 (ddd, 1H, J 17.6, 2.7, and 0.9), 2.50 (d, 1H, J 12.3), 2.44-
2.35 (ddd, 1H, J 12.3, 5.9, and 0.9), 0.67 (s, 9H), 0.66 (s, 9H),
-0.04 (s, 3H), -0.09 (s, 3H), -0.11 (s, 3H), and -0.15 (s, 3H);
13C NMR (63 MHz, CDCl3) δ (ppm) 203.2, 175.2, 74.1, 73.1,
71.0, 50.9, 37.0, 25.5 (3×), 25.5 (3×), 18.0, 17.9, -3.1, -3.4,
-4.9, and -5.3.
115.2 (2×, JCF 21), 75.9, 74.8, 67.5, 36.4, 25.6 (3×), 25.5 (3×),
18.0, 17.8, -3.0, -3.0, -4.6, and -5.1; 19F NMR (282 MHz,
CDCl3) δ (ppm) -118.2 (m, 1F).
(1R,3R,4R)-1,4-Di(tert-butyldimethylsilyloxy)-5-(4-tri-
fluoromethyl)phenylcyclohex-5-en-1,3-carbolactone (11c).
Vinyl triflate 6 (61 mg, 0.12 mmol), (dba)3Pd2‚CHCl3 (9 mg,
8.6 µmol), DCM (0.5 mL), 4-trifluoromethylphenylboronic acid
(44 mg, 0.23 mmol), THF (1 mL), and triethylamine (50 µL,
0.35 mmol) were combined to produce a mixture. After 1 h a
solution of 4-trifluoromethylphenylboronic acid (23 mg, 0.12
mmol) in dry THF (0.5 mL) was added. Chromatographic
(1R,3R,4S)-1,4-Di(tert-butyldimethylsilyloxy)cyclohex-
5-en-1,3-carbolactone trifluoromethane Sulfonate (6). To
a solution of potassium bis(trimethylsilyl)amide (0.5 M in
toluene) (3 mL, 1.5 mmol) in dry DMF (1.7 mL) under an inert
atmosphere at -78 °C, a solution of the ketone 10 (500 mg,
1.25 mmol) in dry DMF (2.5 mL) and toluene (1.7 mL) was
added dropwise. The resultant mixture was stirred for 1 h at
this temperature, and a solution of 2-[N,N-bis(trifluorometh-
ylsulfonyl)amino]-5-chloropyridine (735 mg, 1.87 mmol) in dry
DMF (1.9 mL) was then added dropwise. The resultant
reaction mixture was stirred for 15 h, during which period it
was allowed to warm until room temperature. Water and
diethyl ether were added, the organic layer was separated, and
the aqueous layer was extracted twice with diethyl ether. All
the combined organic layers were dried (anhydrous Na2SO4),
filtered, and evaporated. The obtained light-yellow oil was
purified by flash chromatography (eluent, 50% DCM-hexanes)
to afford vinyl triflate 6 (665 mg, 80%) as a colorless oil that
solidifies on standing. [R]20D -32° (c 0.6, CHCl3); 1H NMR (250
MHz, CDCl3) δ (ppm) 6.05 (s, 1H), 4.45 (dd, 1H, J 6.6 and 3.7),
4.20 (d, 1H, J 3.7), 2.24 (m, 2H), 0.71 (s, 9H), 0.71 (s, 9H),
-0.03 (s, 3H), -0.05 (s, 3H), -0.07 (s, 3H), and -0.07 (s, 3H);
13C NMR (63 MHz, CDCl3) δ (ppm) 173.7, 146.1, 126.1, 118.3
(JCF 318), 74.5, 73.6, 67.3, 36.8, 25.5 (3×), 25.4 (3×), 17.9, 17.8,
-3.3 (2×), -5.1 and -5.1; 19F NMR (282 MHz, CDCl3) δ (ppm)
-73.7 (s, 3F).
General Procedure of Suzuki Coupling. To a stirred
solution of the vinyl triflate 6 (1 equiv) and (dba)3Pd2‚CHCl3
(0.075 equiv) in dry DCM under inert atmosphere at -78 °C,
2 equiv of a solution of the boronic acid in dry THF (0.15 M)
and 3 equiv of dry triethylamine were added. The dry ice bath
was removed, and after 1 h at room temperature more boronic
acid (1-1.5 equiv) in dry THF was added to the reaction
mixture cooled at -78 °C. The reaction mixture was stirred
at room temperature between 14 and 16 h. The solvents were
removed under reduced pressure, and the crude residue was
purified by flash chromatography.
(1R,3R,4R)-1,4-Di(tert-butyldimethylsilyloxy)-5-phen-
ylcyclohex-5-en-1,3-carbolactone (11a). Vinyl triflate 6 (50
mg, 0.09 mmol), (dba)3Pd2‚CHCl3 (7 mg, 7.0 µmol), DCM (0.5
mL), phenylboronic acid (23 mg, 0.19 mmol), THF (1.25 mL),
and triethylamine (40 µL, 0.29 mmol) were combined to
produce a mixture. After 1 h a solution of phenylboronic acid
(11.5 mg, 0.09 mmol) in dry THF (0.6 mL) was added.
Chromatographic eluent: DCM-hexanes (50%). 11a (40 mg,
93%) as a light-orange oil. [R]20D -199° (c 1.2, CHCl3); 1H NMR
(250 MHz, CDCl3) δ (ppm) 7.29-7.16 (m, 5H), 5.97 (d, 1H, J
1.8), 4.55-4.50 (m, 2H), 2.41 (d, 1H, J 10.7), 2.35-2.27 (m,
1H), 0.87 (s, 9H), 0.65 (s, 9H), 0.13 (s, 3H), 0.12 (s, 3H), -0.03
(s, 3H), and -0.36 (s, 3H); 13C NMR (63 MHz, CDCl3) δ (ppm)
175.6, 139.5, 138.0, 132.9, 128.3 (2×), 128.0, 127.1 (2×), 76.0,
74.9, 67.3, 36.5 (3×), 25.6 (3×), 25.5, 18.0, 17.8, -3.0, -3.1,
-4.7, and -5.2.
eluent: DCM-hexanes (35%). 11c (58 mg, 96%) as a colorless
1
oil. [R]20 -159° (c 1.3, CHCl3); H NMR (250 MHz, CDCl3) δ
D
(ppm) 7.60 (d, 2H, J 8.4), 7.39 (d, 2H, J 8.4), 6.08 (d, 1H, J
1.5), 4.52 (m, 2H), 2.32 (m, 2H), 0.75 (s, 9H), 0.52 (s, 9H), 0.00
(s, 3H), -0.03 (s, 3H), -0.17 (s, 3H), and -0.49 (s, 3H); 13C
NMR (63 MHz, CDCl3) δ (ppm) 175.3, 141.6, 138.4, 134.7, 130.2
(JCF 32), 127.5 (2×), 125.2 (2×, JCF 4), 124.0 (JCF 270), 75.8,
74.9, 67.3, 36.4, 25.6 (3×), 25.4 (3×), 18.0, 17.8, -3.0, -3.1,
-4.6, and -5.2; 19F NMR (282 MHz, CDCl3) δ (ppm) -62.7 (s,
3F).
(1R,3R,4R)-1,4-Di(tert-butyldimethylsilyloxy)-5-(3-fluo-
ro)phenylcyclohex-5-en-1,3-carbolactone (11d). Vinyl tri-
flate 6 (50 mg, 0.09 mmol), (dba)3Pd2‚CHCl3 (7 mg, 7.0 µmol),
DCM (0.5 mL), 3-fluorophenylboronic acid (26 mg, 0.19 mmol),
THF (1.25 mL), and triethylamine (40 µL, 0.29 mmol) were
combined to produce a mixture. After 1 h a solution of
3-fluorophenylboronic acid (14 mg, 0.09 mmol) in dry THF (0.6
mL) was added. Chromatographic eluent: DCM-hexanes
(50%). 11d (40 mg, 89%) as a colorless oil. [R]20D -197° (c 1.3,
CHCl3); 1H NMR (250 MHz, CDCl3) δ (ppm) 7.27-7.20 (m, 1H),
6.99-6.90 (m, 3H), 6.00 (d, 1H, J 1.6), 4.53 (m, 2H), 2.37 (d,
1H, J 10.7), 2.33 (ddd, 1H, J 10.7, 5.1, and 1.6), 0.87 (s, 9H),
0.66 (s, 9H), 0.13 (s, 3H), 0.11 (s, 3H), -0.01 (s, 3H), and -0.3
(s, 3H); 13C NMR (63 MHz, CDCl3) δ (ppm) 175.4, 162.6 (JCF
245), 140.1 (JCF 8), 138.3 (JCF 2), 133.9, 129.8 (JCF 8), 122.7
(JCF 3), 114.9 (JCF 21), 114.2 (JCF 22), 75.8, 74.8, 67.3, 36.4,
25.6 (3×), 25.5 (3×), 18.0, 17.8, -3.0, -3.0, -4.6, and -5.1;
19F NMR (282 MHz, CDCl3) δ (ppm) -113.7 (m, 1F).
(1R,3R,4R)-1,4-Di(tert-butyldimethylsilyloxy)-5-(3-tri-
fluoromethyl)phenylcyclohex-5-en-1,3-carbolactone (11e).
Vinyl triflate 6 (133 mg, 0.25 mmol), (dba)3Pd2‚CHCl3 (24 mg,
23 µmol), DCM (1.1 mL), 3-trifluoromethylphenylboronic acid
(95 mg, 0.50 mmol), THF (3.3 mL), and triethylamine (105 µL,
0.76 mmol) were combined to produce a mixture. After 1 h a
solution of 3-trifluoromethylphenylboronic acid (71 mg, 0.38
mmol) in dry THF (1.6 mL) was added. Chromatographic
eluent: DCM-hexanes [(1) 20%, (2) 35%]. 11e (102 mg, 77%)
as a pale-yellow oil. [R]20D -135° (c 1.3, CHCl3); 1H NMR (250
MHz, CDCl3) δ (ppm) 7.59-7.46 (m, 4H), 6.12 (d, 1H, J 1.5),
4.63 (m, 2H), 2.52-2.40 (m, 2H), 0.95 (s, 9H), 0.73 (s, 9H), 0.22
(s, 3H), 0.20 (s, 3H), 0.06 (s, 3H), and -0.25 (s, 3H); 13C NMR
(63 MHz, CDCl3) δ (ppm) 175.3, 138.8, 138.2, 134.6, 130.7 (JCF
32), 130.6, 128.9, 124.8 (JCF 4), 124.0 (JCF 4), 123.9 (JCF 271),
75.8, 74.9, 67.4, 36.4, 25.6 (3×), 25.4 (3×), 18.0, 17.7, -3.0,
-3.1, -4.6, and -5.4; 19F NMR (282 MHz, CDCl3) δ (ppm)
-63.1 (s, 3F).
(1R,3R,4R)-1,4-Di(tert-butyldimethylsilyloxy)-5-(3-hy-
droxy)phenylcyclohex-5-en-1,3-carbolactone (11f). Vinyl
triflate 6 (50 mg, 0.09 mmol), (dba)3Pd2‚CHCl3 (7 mg, 7 µmol),
DCM (0.5 mL), 3-hydroxyphenylboronic acid (26 mg, 0.19
mmol), THF (1.3 mL), and triethylamine (40 µL, 0.29 mmol)
were combined to produce a mixture. After 1 h a solution of
3-hydroxyphenylboronic acid (13 mg, 0.09 mmol) in dry THF
(0.6 mL) was added. Chromatographic eluent: diethyl ether-
hexanes [(1) 25%, (2) 50%]. 11f (40 mg, 90%) as a colorless oil.
[R]20D -88° (c 1.0, CHCl3); 1H NMR (250 MHz, CDCl3) δ (ppm)
7.12 (td, 1H, J 7.7 and 0.8), 6.75-6.70 (m, 3H), 6.00 (d, 1H, J
1.7), 4.60-4.50 (m, 2H), 2.49-2.28 (m, 2H), 0.86 (s, 9H), 0.68
(s, 9H), 0.12 (s, 3H), 0.10 (s, 3H), 0.00 (s, 3H), and -0.68 (s,
3H); 13C NMR (63 MHz, CDCl3) δ (ppm) 176.2, 155.7, 139.4,
139.3, 132.7, 129.5, 119.4, 115.1, 114.1, 76.2, 74.9, 67.2, 36.5,
25.6 (3×), 25.5 (3×), 18.0, 17.8, -2.9, -3.0, -4.7, and
-5.1.
(1R,3R,4R)-1,4-Di(tert-butyldimethylsilyloxy)-5-(4-fluo-
ro)phenylcyclohex-5-en-1,3-carbolactone (11b). Vinyl tri-
flate 6 (55 mg, 0.10 mmol), (dba)3Pd2‚CHCl3 (8 mg, 7.5 µmol),
DCM (0.4 mL), 4-fluorophenylboronic acid (28 mg, 0.20 mmol),
THF (1.4 mL), and triethylamine (42 µL, 0.30 mmol) were
combined to produce a mixture. After 1 h a solution of
4-fluorophenylboronic acid (14 mg, 0.10 mmol) in dry THF (0.4
mL) was added. Chromatographic eluent: DCM-hexanes
(35%). 11b (29 mg, 61%) as a colorless oil. [R]20 -37° (c 0.6,
D
1
CHCl3); H NMR (250 MHz, CDCl3) δ (ppm) 7.52 (ddd, 2H, J
9.0, 3.8, and 1.7), 7.29 (t, 2H, J 8.9), 6.25 (d, 1H, J 1.6), 4.78
(m, 2H), 2.60 (d, 1H, J 10.8), 2.52 (ddd, 1H, J 10.8, 5.4, and
1.4), 1.02 (s, 9H), 0.81 (s, 9H), 0.27 (s, 3H), 0.25 (s, 3H), 0.10
(s, 3H), and -0.20 (s, 3H); 13C NMR (63 MHz, CDCl3) δ (ppm)
175.5, 162.6 (JCF 246), 138.5, 134.0, 133.2, 128.8 (2×, JCF 8),

Inhibitors of Type II Dehydroquinase
Journal of Medicinal Chemistry, 2005, Vol. 48, No. 15 4877
(1R,3R,4R)-1,4-Di(tert-butyldimethylsilyloxy)-5-(3-ni-
tro)phenylcyclohex-5-en-1,3-carbolactone (11g). Vinyl tri-
flate 6 (168 mg, 0.32 mmol), (dba)3Pd2‚CHCl3 (24 mg, 24 µmol),
DCM (1.4 mL), 3-nitrophenylboronic acid (107 mg, 0.64 mmol),
THF (4.1 mL), and triethylamine (140 µL, 0.97 mmol) were
combined to produce a mixture. Chromatographic eluent:
DCM-hexanes (35%). 11g (142 mg, 88%) as a pale-yellow oil.
[R]20D -141° (c 1.1, CHCl3); 1H NMR (300 MHz, CDCl3) δ (ppm)
8.15 (d, 2H, J 5.5), 7.68-7.49 (m, 2H), 6.19 (s, 1H), 4.64 (m,
2H), 2.48 (m, 2H), 0.95 (s, 9H), 0.73 (s, 9H), 0.23 (s, 3H), 0.20
(s, 3H), 0.10 (s, 3H), and -0.18 (s, 3H); 13C NMR (75 MHz,
CDCl3) δ (ppm) 174.8, 148.0, 139.4, 137.2, 135.4, 133.0, 129.4,
122.8, 122.0, 75.7, 74.9, 67.3, 36.4, 25.7 (3×), 25.5 (3×), 18.1,
17.9, -2.9, -2.9, -4.3, and -4.9.
(anhydrous Na2SO4), filtered, and concentrated under reduced
pressure. The crude reaction was purified by flash chroma-
tography, eluting with diethyl ether-hexanes [(1) 25%, (2)
50%] to afford pyridine 11k (30 mg, 70%) as pale-yellow
1
needles. Mp 78-80 °C; [R]20 -189° (c 1.0, CHCl3); H NMR
D
(250 MHz, CDCl3) δ (ppm) 8.84 (m, 2H), 7.87 (dt, 1H, J 8.0
and 0.5), 7.55 (m, 1H), 6.41 (d, 1H, J 1.1), 4.89 (m, 2H), 2.75
(m, 2H), 1.23 (s, 9H), 1.02 (s, 9H), 0.50 (s, 3H), 0.48 (s, 3H),
0.35 (s, 3H), and 0.06 (s, 3H); 13C NMR (63 MHz, CDCl3) δ
(ppm) 175.2, 149.2, 148.3, 136.4, 134.9, 134.4, 133.6, 123.0,
75.7, 74.8, 67.2, 36.3, 25.6 (3×), 25.4 (3×), 18.0, 17.7, -3.0,
-3.1, -4.6, and -5.1.
(1R,3R,4R)-1,4-Di(tert-butyldimethylsilyloxy)-5-(furan-
3-yl)cyclohex-5-en-1,3-carbolactone (11l). Vinyl triflate 6
(150 mg, 0.28 mmol), (dba)3Pd2‚CHCl3 (22 mg, 21 µmol), DCM
(1.5 mL), 3-furaneboronic acid (63 mg, 0.56 mmol), THF (3.8
mL), and triethylamine (120 µL, 0.86 mmol) were combined
to produce a mixture. After 1 h a solution of 3-furaneboronic
acid (32 mg, 0.28 mmol) in dry THF (1.9 mL) was added.
Chromatographic eluent: DCM-hexanes (35%). 11l (90 mg,
71%) as a white amorphous solid. Mp 97-99 °C; [R]20D -166°
(c 1.1, CHCl3); 1H NMR (250 MHz, CDCl3) δ (ppm) 7.46 (br s,
1H), 7.36 (t, 1H, J 1.75), 6.42 (dd, 1H, J 1.75 and 0.75), 6.07
(d, 1H, J 1.75), 4.60 (dd, 1H, J 5.75 and 3.25), 4.41 (d, 1H, J
3.25), 2.46 (d, 1H, J 10.75), 2.38 (ddd, 1H, J 10.75, 5.75, and
1.75), 0.94 (s, 9H), 0.86 (s, 9H), 0.21 (s, 3H), 0.17 (s, 3H), 0.15
(s, 3H), and 0.08 (s, 3H); 13C NMR (63 MHz, CDCl3) δ (ppm)
175.4, 143.1, 139.8, 131.4, 130.5, 123.3, 108.7, 75.8, 74.9, 67.6,
36.8, 25.6 (6×), 18.0, 17.9, -3.0 (2×), -4.1, and -4.6.
(1R,3R,4R)-1,4-Di(tert-butyldimethylsilyloxy)-5-(3-car-
boxymethyl)phenylcyclohex-5-en-1,3-carbolactone (11h).
Vinyl triflate 6 (50 mg, 0.09 mmol), (dba)3Pd2‚CHCl3 (7 mg,
7.0 µmol), DCM (0.5 mL), 3-carboxymethylphenylboronic acid
(51 mg, 0.28 mmol), THF (1.9 mL), triethylamine (40 µL, 0.29
mmol). Chromatographic eluent: DCM-hexanes [(1) 35%, (2)
50%]. 11h (30 mg, 62%) as a light-yellow oil. [R]20 -150° (c
D
1.3, CHCl3); 1H NMR (250 MHz, CDCl3) δ (ppm) 8.00-7.96
(m, 2H), 7.48 (dt, 1H, J 8.0 and 1.5), 7.41 (dd, 1H, J 8.0 and
7.8), 6.12 (d, 1H, J 1.5), 4.64 (m, 2H), 3.92 (s, 3H), 2.51 (d, 1H,
J 10.8), 2.42 (ddd, 1H, J 10.8, 5.2, and 1.5), 0.95 (s, 9H), 0.73
(s, 9H), 0.22 (s, 3H), 0.20 (s, 3H), 0.07 (s, 3H), and -0.25 (s,
3H); 13C NMR (63 MHz, CDCl3) δ (ppm) 175.4, 166.7, 138.4,
138.1, 134.0, 131.6, 130.2, 129.2, 128.5, 128.2, 75.9, 74.9, 67.2,
52.2, 36.4, 25.6 (3×), 25.5 (3×), 18.0, 17.8, -3.0, -3.1, -4.6,
and -5.2.
General Procedure for TBS Deprotection. To a stirred
solution of the silyl ether 11 (1 equiv) in dry THF (75 mM)
under argon at 0 °C was added tetrabutylammonium fluoride
(2.2-2.6 equiv, ca. 1.0 M in THF). After the mixture was
stirred for 30 min, dilute HCl was added and the organic layer
was extracted with ethyl acetate (×3). The combined organic
extracts were dried (anhydrous Na2SO4), filtered, and concen-
trated under reduced pressure. The crude reaction was purified
by flash chromatography.
(1R,3R,4R)-1,4-Dihydroxy-5-phenylcyclohex-5-en-1,3-
carbolactone (12a). The reaction was carried out as described
above. Silyl ether 11a (110 mg, 0.24 mmol), tetrabutylammo-
nium fluoride (0.53 mL, 0.53 mmol), and THF (3.4 mL) were
combined to produce a mixture. Chromatographic eluent: ethyl
acetate-hexanes (75%). 12a (42 mg, 76%) as a light-orange
oil. [R]20D -257° (c 1.1, CH3OH); 1H NMR (250 MHz, CD3OD)
δ (ppm) 7.48 (d, 2H, J 7.5), 7.31 (m, 3H), 6.28 (s, 1H), 4.70-
4.66 (m, 2H), and 2.39 (m, 2H); 13C NMR (63 MHz, CD3OD) δ
(ppm) 178.5, 139.8, 138.2, 131.8, 129.6 (2×), 129.3, 127.3 (2×),
78.0, 74.3, 66.4, and 36.8.
(1R,3R,4R)-1,4-Di(tert-butyldimethylsilyloxy)-5-(3,5-di-
fluoro)phenylcyclohex-5-en-1,3-carbolactone (11i). Vinyl
triflate 6 (139 mg, 0.26 mmol), (dba)3Pd2‚CHCl3 (20 mg, 20
µmol), DCM (1.1 mL), 3,5-difluorophenylboronic acid (82 mg,
0.52 mmol), THF (3.4 mL), and triethylamine (110 µL, 0.79
mmol) were combined to produce a mixture. Chromatographic
eluent: DCM-hexanes (35%). 11i (100 mg, 77%) as a colorless
1
oil. [R]20 -170° (c 1.1, CHCl3); H NMR (300 MHz, CDCl3) δ
D
(ppm) 6.85-6.71 (m, 3H), 6.12 (d, 1H, J 1.5), 4.61 (m, 1H),
4.54 (d, 1H, J 3.3), 2.45 (m, 2H), 0.96 (s, 9H), 0.78 (s, 9H),
0.23 (s, 3H), 0.20 (s, 3H), 0.10 (s, 3H), and -0.13 (s, 3H); 13C
NMR (75 MHz, CDCl3) δ (ppm) 174.9, 162.7 (2×, JCF 247 and
13), 141.1 (JCF 9), 137.4, 134.7, 110.1 (2×, JCF 21), 103.4 (JCF
21), 75.7, 74.8, 67.3, 36.4, 25.7 (3×), 25.5 (3×), 18.1, 17.9, -2.8,
-2.9, -4.3, and -4.9; 19F NMR (282 MHz, CDCl3) δ (ppm)
-73.9 (s, 2F).
(1R,3R,4R)-1,4-Di(tert-butyldimethylsilyloxy)-5-
(thiophen-3-yl)cyclohex-5-en-1,3-carbolactone (11j). Vinyl
triflate 6 (50 mg, 94 µmol), (dba)3Pd2‚CHCl3 (7 mg, 7 µmol),
DCM (0.5 mL), 3-thiopheneboronic acid (24 mg, 0.19 mmol),
THF (1.3 mL), and triethylamine (40 µL, 0.29 mmol) were
combined to produce a mixture. After 1 h a solution of
3-thiophene boronic acid (12 mg, 94 µmol) in dry THF (0.6 mL)
was added. Chromatographic eluent: DCM-hexanes (50%).
11j (30 mg, 69%) as a white amorphous solid. Mp 98-100 °C;
[R]20D -186° (c 1.1, CHCl3); 1H NMR (250 MHz, CDCl3) δ (ppm)
7.28 (dd, 1H, J 5.0 and 3.0), 7.20 (dd, 1H, J 3.0, and 1.3), 7.08
(dd, 1H, J 5.0, and 1.3), 6.14 (d, 1H, J 1.9), 4.61 (dd, 1H, J
5.7, and 3.5), 4.56 (d, 1H, J 3.5), 2.50 (d, 1H, J 10.6), 2.40 (ddd,
1H, J 10.6, 5.7, and 1.9), 0.94 (s, 9H), 0.80 (s, 9H), 0.21 (s,
3H), 0.18 (s, 3H), 0.12 (s, 3H), and -0.05 (s, 3H); 13C NMR (63
MHz, CDCl3) δ (ppm) 175.5, 138.9, 134.1, 132.1, 126.2, 125.7,
122.1, 75.9, 74.8, 67.6, 36.6, 25.6 (6×), 18.0, 17.9, -3.0 (2×),
-4.3, and -4.8.
(1R,3R,4R)-1,4-Di(tert-butyldimethylsilyloxy)-5-(pyri-
dine-3-yl)cyclohex-5-en-1,3-carbolactone (11k). To a stirred
solution of the vinyl triflate 6 (50 mg, 0.09 mmol) in dioxane
(0.5 mL) was added Pd(PPh3)4 (3 mg, 2.35 µmol), 3-(1,3,2)-
dioxaborinan-2-ylpyridine (17 mg, 0.10 mmol), and 0.2 mL of
an aqueous solution of K3PO4 (0.8 M). The resultant reaction
mixture was heated under reflux for 2 h. After the mixture
was cooled to room temperature, DCM was added and the
organic layer was separated. The aqueous phase was extracted
with DCM (2×). The combined organic extracts were dried
(1R,3R,4R)-1,4-Dihydroxy-5-(4-fluoro)phenylcyclohex-
5-en-1,3-carbolactone (12b). Silyl ether 11b (156 mg, 0.33
mmol), tetrabutylammonium fluoride (0.86 mL, 0.86 mmol),
and THF (4.7 mL) were combined to produce a mixture.
Chromatographic eluent: ethyl acetate-hexanes (60%). 12b
1
(72 mg, 88%) as colorless oil. [R]20 -237° (c 1.1, CH3OH); H
D
NMR (250 MHz, CD3OD) δ (ppm) 7.55 (m, 2H), 7.07 (m, 2H),
6.29 (s, 1H), 4.74 (dd, 1H, J 6.3, and 3.3), 4.65 (d, 1H, J 3.3),
and 2.41 (m, 2H); 13C NMR (63 MHz, CD3OD) δ (ppm) 178.5,
164.1 (JCF 245), 138.7, 134.5, 131.8, 129.3 (2×, JCF 8), 116.2
(2×, JCF 22), 77.9, 74.3, 66.5, and 36.8; 19F NMR (282 MHz,
CD3OD) δ (ppm) -116.2 (m, 1F).
(1R,3R,4R)-1,4-Dihydroxy-5-(4-trifluoromethyl)phen-
ylcyclohex-5-en-1,3-carbolactone (12c). Silyl ether 11 (174
mg, 0.33 mmol), tetrabutylammonium fluoride (0.86 mL, 0.86
mmol), and THF (4.7 mL) were combined to produce a mixture.
Chromatographic eluent: ethyl acetate-hexane (60%). 12c (80
mg, 81%) as pale-yellow needles. Mp 133-134 °C; [R]20D -198°
(c 1.2, CH3OH); 1H NMR (250 MHz, CD3OD) δ (ppm) 7.70 (m,
4H), 6.48 (s, 1H), 4.78 (dd, 1H, J 6.2 and 3.2), 4.73 (d, 1H, J
3.2), and 2.45 (m, 2H); 13C NMR (63 MHz, CD3OD) δ (ppm)
178.2, 142.1, 138.6, 134.2, 131.0 (JCF 32), 128.0 (2×), 126.4 (2×,
JCF 4), 125.6 (JCF 262), 77.9, 74.4, 66.6, and 36.7; 19F NMR
(282 MHz, CD3OD) δ (ppm) -64.5 (s, 3F).

4878 Journal of Medicinal Chemistry, 2005, Vol. 48, No. 15
Sa´nchez-Sixto et al.
(1R,3R,4R)-1,4-Dihydroxy-5-(3-fluoro)phenylcyclohex-
5-en-1,3-carbolactone (12d). Silyl ether 11d (88 mg, 0.18
mmol), tetrabutylammonium fluoride (0.41 mL, 0.41 mmol),
and THF (2.6 mL) were combined to produce a mixture.
Chromatographic eluent: ethyl acetate-hexanes (75%). 12d
(40 mg, 87%) as a white solid. [R]20D -275° (c 1.0, CH3OH); 1H
NMR (250 MHz, CD3OD) δ (ppm) 7.50-7.28 (m, 3H), 7.15-
7.02 (m, 1H), 6.48 (s, 1H), 4.75 (dd, 1H, J 6.3 and 3.4), 4.62 (d,
1H, J 3.4), and 2.46 (m, 2H); 13C NMR (63 MHz, CD3OD) δ
(ppm) 178.3, 164.4 (JCF 242), 140.8 (JCF 8), 138.7, 133.1, 131.3
(JCF 8), 123.2 (JCF 3), 115.9 (JCF 21), 114.2 (JCF 23), 77.9, 74.3,
66.4, and 36.8; 19F NMR (282 MHz, CD3OD) δ (ppm) -115.6
(m, 1F).
(1R,3R,4R)-1,4-Dihydroxy-5-(3-trifluoromethyl)phen-
ylcyclohex-5-en-1,3-carbolactone (12e). Silyl ether 11e
(137 mg, 0.26 mmol), tetrabutylammonium fluoride (0.68 mL,
0.68 mmol), and THF (3.7 mL) were combined to produce a
mixture. Chromatographic eluent: ethyl acetate-hexanes
(60%). 12e (73 mg, 94%) as pale-yellow needles. Mp 142-145
°C; [R]20D -212° (c 1.0, CH3OH); 1H NMR (250 MHz, CD3OD)
δ (ppm) 7.80 (m, 2H), 7.56 (m, 2H), 6.43 (s, 1H), 4.76 (dd, 1H,
J 6.3 and 3.4), 4.70 (d, 1H, J 3.4), and 2.44 (m, 2H); 13C NMR
(63 MHz, CD3OD) δ (ppm) 178.2, 139.4, 138.6, 133.7, 131.9
(JCF 32), 131.1 (JCF 1), 130.4, 125.8 (JCF 4), 125.6 (JCF 270),
124.1 (JCF 4), 77.9, 74.3, 66.5, and 36.8; 19F NMR (282 MHz,
CD3OD) δ (ppm) -64.5 (s, 3F).
(JCF 26), 77.8, 74.3, 66.4, and 36.7; 19F NMR (282 MHz, CD3-
OD) δ (ppm) -112.1 (t, 2F, J 8.7).
(1R,3R,4R)-1,4-Dihydroxy-5-(thiophen-3-yl)cyclohex-5-
en-1,3-carbolactone (12j). Silyl ether 11j (120 mg, 0.26
mmol), tetrabutylammonium fluoride (0.6 mL, 0.60 mmol), and
THF (3.7 mL) were combined to produce a mixture. Chromato-
graphic eluent: ethyl acetate-hexanes (60%). 12j (50 mg, 82%)
as amorphous white solid. Mp 147-149 °C; [R]20D -261° (c 1.0,
CH3OH); 1H NMR (250 MHz, CD3OD) δ (ppm) 7.69 (dd, 1H, J
2.9 and 1.3), 7.40 (dd, 1H, J 2.9 and 5.1), 7.32 (dd, 1H, J 1.3
and 5.1), 6.42 (d, 1H, J 1.3), 4.75 (dt, 1H, J 3.3 and 1.3), 4.58
(d, 1H, J 3.3), and 2.45 (m, 2H); 13C NMR (63 MHz, CD3OD)
δ (ppm) 178.6, 139.7, 134.8, 130.4, 126.7, 126.4, 123.4, 78.0,
74.2, 67.1, and 37.2.
(1R,3R,4R)-1,4-Dihydroxy-5-(pyridine-3-yl)cyclohex-5-
en-1,3-carbolactone (12k). Silyl ether 11k (126 mg, 0.27
mmol), tetrabutylammonium fluoride (0.6 mL, 0.60 mmol), and
THF (3.9 mL) were combined to produce a mixture. Chromato-
graphic eluent: acetone. 12k (60 mg, 94%) as white needles.
Mp 44-46 °C; [R]20D -213° (c 1.0, CH3OH); 1H NMR (250 MHz,
CD3OD) δ (ppm) 8.64 (m, 1H), 8.38 (dd, 1H, J 1.6 and 4.7),
7.93 (ddd, 1H, J 2.2, 1.6, and 8.0), 7.36 (dd, 1H, J 4.7 and 8.0),
6.40 (s, 1H), 4.70 (m, 1H), 4.63 (d, 1H, J 3.2), and 2.38 (m,
2H); 13C NMR (63 MHz, CD3OD) δ (ppm) 178.1, 149.4, 148.0,
136.8, 136.0, 134.8, 134.2, 125.2, 77.8, 74.4, 66.3, and 36.8.
(1R,3R,4R)-1,4-Dihydroxy-5-(furan-3-yl)cyclohex-5-en-
1,3-carbolactone (12l). Silyl ether 11l (150 mg, 0.33 mmol),
tetrabutylammonium fluoride (0.7 mL, 0.73 mmol), and THF
(4.8 mL) were combined to produce a mixture. Chromato-
graphic eluent: (1) diehyl ether-hexanes (75%), (2) diethyl
ether. 12l (58 mg, 79%) as colorless oil that solidifies on
(1R,3R,4R)-1,4-Dihydroxy-5-(3-hydroxy)phenylcyclohex-
5-en-1,3-carbolactone (12f). Silyl ether 11f (130 mg, 0.27
mmol), tetrabutylammonium fluoride (0.6 mL, 0.60 mmol), and
THF (4 mL) were combined to produce a mixture. Chromato-
graphic eluent: ethyl acetate-hexanes (75%). 12f (41 mg, 60%)
standing. [R]20 -240° (c 1.1, CH3OH); 1H NMR (250 MHz,
1
D
as a colorless oil. [R]20 -219° (c 1.1, CH3OH); H NMR (250
D
CD3OD) δ (ppm) 7.45 (s, 1H), 7.46 (t, 1H, J 1.75), 6.62 (dd,
1H, J 1.75 and 0.75), 6.20 (s, 1H), 4.69 (m, 1H), 4.38 (d, 1H, J
3.25), and 2.39 (m, 2H); 13C NMR (63 MHz, CD3OD) δ (ppm)
178.7, 144.6, 141.9, 132.1, 129.7, 124.5, 108.8, 78.1, 74.2, 67.3,
and 37.6.
MHz, CD3OD) δ (ppm) 7.30 (br d, 1H, J 2.3), 7.15 (t, 1H, J
7.8), 6.97 (m, 2H), 6.95 (ddd, 1H, J 7.8, 2.3, and 0.9), 6.25 (s,
1H), 4.69 (m, 1H), 4.54 (d, 1H, J 3.3), and 2.42 (m, 2H); 13C
NMR (63 MHz, CD3OD) δ (ppm) 179.0, 159.0, 140.2, 140.1,
132.1, 131.0, 119.1, 116.8, 114.6, 78.4, 74.7, 66.9, and 37.2.
General Procedure of Lactone Hydrolysis. A solution
of the lactone 12 (1 equiv) in THF (0.1 M) and aqueous lithium
hydroxide (2.5 equiv, 0.5 M) was stirred at room temperature
for 30 min. Water was added, the THF was removed under
reduced pressure, and the resultant aqueous solution was
washed with diethyl ether (×2). The aqueous extract was
treated with Amberlite IR-120 until pH 6 was attained. The
resin was filtered and washed with water. The filtrate and
the washings were lyophilized.
(1R,3R,4R)-1,3,4-Trihydroxy-5-phenylcyclohex-5-en-1-
carboxylic Acid (4a). Lactone 12a (42 mg, 0.18 mmol), THF
(1.6 mL), and aqueous lithium hydroxide (0.9 mL) were
combined to produce a mixture. 4a (40 mg, 88%) as an
amorphous white solid. Retention time: 33 min. Mp 147-149
°C; [R]20D -121° (c 1.1, H2O); 1H NMR (400 MHz, D2O) δ (ppm)
7.3 (m, 5H), 5.78 (s, 1H), 4.51 (dd, 1H, J 7.6 and 1.6), 3.95
(ddd, 1H, J 11.2, 7.6, and 3.8), 2.16 (dd, 1H, J 13.4 and 11.2),
and 2.05 (dd, 1H, J 13.4 and 3.8); 13C NMR (100 MHz, D2O) δ
(ppm) 181.1, 147.0, 141.0, 131.5 (2×), 131.2, 130.1 (2×), 128.8,
76.1, 74.8, 72.6, and 41.3.
(1R,3R,4R)-1,4-Dihydroxy-5-(3-nitro)phenylcyclohex-
5-en-1,3-carbolactone (12g). Silyl ether 11g (148 mg, 0.29
mmol), tetrabutylammonium fluoride (0.62 mL, 0.62 mmol),
and THF (4 mL) were combined to produce a mixture.
Chromatographic eluent: ethyl acetate-hexanes (60%). 12g
(63 mg, 79%) as pale-yellow amorphous solid. Mp 142-148 °C;
1
[R]20 -179° (c 1.2, CH3OH); H NMR (300 MHz, CD3OD) δ
D
(ppm) 8.41 (t, 1H, J 2.0), 8.17 (ddd, 1H, J 8.0, 2.0, and 0.9),
7.94 (ddd, 1H, J 8.0, 2.0 and 0.9), 7.60 (t, 1H, J 8.0), 6.52 (s,
1H), 4.78 (dd, 1H, J 6.0 and 3.6), 4.73 (d, 1H, J 3.6), and 2.46
(m, 2H); 13C NMR (75 MHz, CD3OD) δ (ppm) 177.8, 149.7,
140.0, 137.8, 134.4, 133.3, 130.7, 123.7, 122.1, 77.8, 74.3, 66.5,
and 36.8.
(1R,3R,4R)-1,4-Dihydroxy-5-(3-carboxymethyl)phenyl-
cyclohex-5-en-1,3-carbolactone (12h). Silyl ether 11h (120
mg, 0.23 mmol), tetrabutylammonium fluoride (0.50 mL, 0.50
mmol), and THF (3.3 mL) were combined to produce a mixture.
Chromatographic eluent: ethyl acetate-hexanes (75%). 12h
(60 mg, 89%) as a colorless oil. [R]20 -201° (c 1.1, CH3OH);
D
1H NMR (250 MHz, CD3OD) δ (ppm) 8.12 (t, 1H, J 1.6), 7.88
(dt, 1H, J 7.8, and 1.2), 7.72 (dt, 1H, J 7.8 and 1.2), 7.41 (t,
1H, J 7.8), 6.37 (s, 1H), 4.73 (dd, 1H, J 6.2 and 3.2), 4.67 (d,
1H, J 3.2), 3.86 (s, 3H), and 2.40 (m, 2H); 13C NMR (63 MHz,
CD3OD) δ (ppm) 178.4, 168.3, 138.9, 138.7, 133.1, 132.0, 131.6,
130.2, 129.9, 128.4, 77.9, 74.4, 66.4, 52.8, and 36.8.
(1R,3R,4R)-1,3,4-Trihydroxy-5-(4-fluoro)phenylcyclo-
hex-5-en-1-carboxylic Acid (4b). Lactone 12b (73 mg, 0.29
mmol), THF (2.6 mL), and aqueous lithium hydroxide (1.5 mL)
were combined to produce a mixture. 4b (69 mg, 89%) as a
white amorphous solid. Retention time: 33 min. Mp 118-122
°C; [R]20 -69° (c 1.2, CH3OH); 1H NMR (300 MHz, D2O) δ
D
(1R,3R,4R)-1,4-Dihydroxy-5-(3,4-difluoro)phenylcyclo-
hex-5-en-1,3-carbolactone (12i). Silyl ether 11i (142 mg,
0.29 mmol), tetrabutylammonium fluoride (0.75 mL, 0.75
mmol), and THF (4.1 mL) were combined to produce a mixture.
Chromatographic eluent: ethyl acetate-hexanes (60%). 12i
(ppm) 7.25 (dd, 2H, J 7.8 and 5.7), 6.99 (dd, 2H, J 8.4 and
8.7), 5.72 (s, 1H), 4.44 (d, 1H, J 7.3), 3.92 (m, 1H), and 2.09
(m, 2H); 13C NMR (75 MHz, D2O) δ (ppm) 178.1, 162.5 (JCF
243), 143.4, 134.3 (JCF 3), 129.1 (2×, JCF 9), 125.8, 115.3 (2×,
JCF 21), 73.2, 72.0, 69.7, and 38.4; 19F NMR (282 MHz, D2O) δ
(ppm) -115.2 (m, 1F).
(76 mg, 97%) as a pale-yellow oil. [R]20 -185° (c 1.1, CH3-
D
1
OH); H NMR (250 MHz, CD3OD) δ (ppm) 7.16 (m, 2H), 6.88
(1R,3R,4R)-1,3,4-Trihydroxy-5-(4-trifluoromethyl)phen-
ylcyclohex-5-en-1-carboxylic Acid (4c). Lactone 12c (74
mg, 0.25 mmol), THF (2.3 mL), and aqueous lithium hydroxide
(1.3 mL). 4c (73 mg, 92%) as a white amorphous solid.
(tt, 1H, J 9.0 and 2.3), 6.44 (s, 1H), 4.74 (dd, 1H, J 6.1 and
3.4), 4.62 (d, 1H, J 3.4), and 2.42 (m, 2H); 13C NMR (63 MHz,
CD3OD) δ (ppm) 178.1, 164.5 (2×, JCF 245 and 13), 142.0 (JCF
10), 137.9 (JCF 3), 134.3, 110.4 (JCF 17), 110.3 (JCF 17), 104.2
Retention time: 50 min. Mp 117-120 °C; [R]20 -89° (c 1.0,
D

Inhibitors of Type II Dehydroquinase
Journal of Medicinal Chemistry, 2005, Vol. 48, No. 15 4879
CH3OH); 1H NMR (250 MHz, D2O) δ (ppm) 7.44 (d, 2H, J 8.2),
7.27 (d, 2H, J 8.2), 5.70 (s, 1H), 4.39 (d, 1H, J 7.4), 3.84 (m,
1H), and 2.01 (m, 2H); 13C NMR (63 MHz, D2O) δ (ppm) 178.0,
143.5, 142.1, 129.5 (JCF 32), 127.9 (2×), 127.4, 125.6 (2×, JCF
3), 124.5 (JCF 270), 73.3, 72.1, 69.8, and 38.6; 19F NMR (282
MHz, D2O) δ (ppm) -62.7 (s, 3F).
(1R,3R,4R)-1,3,4-Trihydroxy-5-(3-fluoro)phenylcyclo-
hex-5-en-1-carboxylic Acid (4d). Lactone 12d (40 mg, 0.16
mmol), THF (1.5 mL), and aqueous lithium hydroxide (0.8 mL)
were combined to produce a mixture. 4d (42 mg, 99%) as a
white amorphous solid. Retention time: 31 min. Mp 117-120
°C; [R]20D -81° (c 1.1, H2O); 1H NMR (300 MHz, D2O) δ (ppm)
7.28 (m, 1H), 7.11-6.95 (m, 3H), 5.81 (s, 1H), 4.46 (d, 1H, J
7.3), 3.93 (ddd, 1H, J 11.1, 7.3 and 3.8), 2.13 (dd, 1H, J 11.1
and 13.5), 2.03 (dd, 1H, J 13.5 and 3.5); 13C NMR (75 MHz,
D2O) δ (ppm) 178.4, 162.6 (JCF 241), 143.0, 140.6 (JCF 8), 130.3
(JCF 9), 126.9, 123.2 (JCF 3), 114.9 (J 21), 114.1 (J 22), 73.2,
71.9, 69.7, and 38.4; 19F NMR (282 MHz, D2O) δ (ppm) -114.5
(m, 1F).
110.4 (JCF 17), 110.3 (JCF 17), 103.3 (JCF 25), 73.0, 71.7, 69.6,
and 38.3; 19F NMR (282 MHz, D2O) δ (ppm) -111.2 (t, 2F, J
8.7).
(1R,3R,4R)-1,3,4-Trihydroxy-5-(thiophen-3-yl)phenyl-
cyclohex-5-en-1-carboxylic Acid (4j). Lactone 12j (40 mg,
0.17 mmol), THF (1.5 mL), and aqueous lithium hydroxide (0.8
mL) were combined to produce a mixture. 4j (40 mg, 93%) as
a white amorphous solid. Retention time: 29 min. Mp 147-
1
149 °C; [R]20 -74° (c 1.2, H2O); H NMR (300 MHz, D2O) δ
D
(ppm) 7.32 (m, 1H), 7.28-7.26 (m, 1H), 7.10 (m, 1H), 5.86 (s,
1H), 4.34 (d, 1H, J 6.3), 3.91-3.86 (m, 1H), and 2.02 (m, 2H);
13C NMR (75 MHz, D2O) δ (ppm) 182.4, 142.2, 140.2, 129.3,
129.2, 128.7, 125.7, 76.3, 74.2, 72.8, and 40.2.
(1R,3R,4R)-1,3,4-Trihydroxy-5-(pyridine-3-yl)cyclohex-
5-en-1-carboxylic Acid (4k). Lactone 12k (50 mg, 0.21
mmol), THF (1.9 mL), and aqueous lithium hydroxide (1.1 mL)
were combined to produce a mixture. The aqueous extract was
treated with Amberlite IR-120 until pH 5 and filtered. The
resin was washed with 0.5 M ammonia until pH 8, filtered,
and washed with water. The filtrate and the washings were
lyophilized. 4k (50 mg, 96%) as a white amorphous solid. Mp
196-198 °C; [R]20D -15° (c 1.1, H2O); 1H NMR (250 MHz, D2O)
δ (ppm) 8.70 (br s, 1H), 8.58 (br s, 1H), 8.50 (d, 1H, J 8.25),
7.93 (dd, 1H, J 7.75 and 6.0), 6.07 (s, 1H), 4.50 (d, 1H, J 6.75),
3.92 (m, 1H), and 2.07 (m, 2H); 13C NMR (125 MHz, D2O) δ
(ppm) 183.6, 150.6, 149.9, 142.2, 139.1, 132.8, 130.3, 126.9,
76.9, 74.6, 73.0, and 41.5.
(1R,3R,4R)-1,3,4-Trihydroxy-5-(3-trifluoromethyl)phen-
ylcyclohex-5-en-1-carboxylic Acid (4e). Lactone 12e (46
mg, 0.15 mmol), THF (1.5 mL), and aqueous lithium hydroxide
(0.76 mL) were combined to produce a mixture. 4e (47 mg,
98%) as a beige amorphous solid. Retention time: 42 min. Mp
1
122-125 °C; [R]20 -41° (c 1.0, CH3OH); H NMR (300 MHz,
D
D2O) δ (ppm) 7.50 (m, 4H), 5.86 (s, 1H), 4.51 (dd, 1H, J 7.8
and 1.5), 3.95 (ddd, 1H, J 11.1, 7.8, and 4.2), and 2.09 (m, 2H);
13C NMR (75 MHz, D2O) δ (ppm) 177.9, 143.2, 139.0, 131.0,
130.1 (JCF 32), 129.2, 127.0, 124.9 (JCF 4), 124.3 (JCF 270), 124.0
(JCF 4), 73.1, 71.9, 69.6, and 38.5; 19F NMR (282 MHz, D2O) δ
(ppm) -62.8 (s, 3F).
(1R,3R,4R)-1,3,4-Trihydroxy-5-(furan-3-yl)phenylcy-
clohex-5-en-1-carboxylic Acid (4l). Lactone 12l (53 mg, 0.24
mmol), THF (2.2 mL), and aqueous lithium hydroxide (1.2 mL)
were combined to produce a mixture. 4l (56 mg, 98%) as a
white amorphous solid. Retention time: 17 min. Mp 73-75
(1R,3R,4R)-1,3,4-Trihydroxy-5-(3-hydroxy)phenylcy-
clohex-5-en-1-carboxylic Acid (4f). Lactone 12f (40 mg, 0.16
mmol), THF (1.5 mL), and aqueous lithium hydroxide (0.8 mL)
were combined to produce a mixture. 4f (40 mg, 93%) as a
white amorphous solid. Retention time: 21 min. Mp 120-122
°C; [R]20D -116° (c 1.2, H2O); 1H NMR (500 MHz, D2O) δ (ppm)
7.21 (t, 1H, J 8.0), 6.91 (d, 1H, J 7.5), 6.83 (t, 1H, J 2.0), 6.78
(dd, 1H, J 8.0 and 2.5), 5.79 (s, 1H), 4.50 (dd, 1H, J 7.0 and
1.0), 3.97 (ddd, 1H, J 11.0, 7.0, and 3.5), 2.17 (dd, 1H, J 13.5
and 11.0), and 12.07 (dd, 1H, J 13.5 and 4.0); 13C NMR (100
MHz, D2O) δ (ppm) 182.2, 158.4, 145.9, 143.1, 132.9, 129.8,
122.3, 118.0, 117.0, 76.4, 74.7, 72.8, and 41.2.
(1R,3R,4R)-1,3,4-Trihydroxy-5-(3-nitro)phenylcyclohex-
5-en-1-carboxylic Acid (4g). Lactone 12g (61 mg, 0.22
mmol), THF (2 mL), and aqueous lithium hydroxide (1.1 mL)
were combined to produce a mixture. 4g (64 mg, 99%) as a
pale-beige amorphous solid. Retention time: 37 min. Mp 138-
140 °C; [R]20D -62.5° (c 1.3, CH3OH); 1H NMR (250 MHz, D2O)
δ (ppm) 7.87 (m, 2H), 7.50 (d, 1H, J 7.4), 7.29 (t, 1H, J 7.8),
5.76 (s, 1H), 4.38 (d, 1H, J 7.2), 3.84 (m, 1H), and 2.02 (m,
2H); 13C NMR (63 MHz, D2O) δ (ppm) 178.3, 147.9, 142.2,
139.9, 134.1, 129.8, 128.2, 123.1, 122.2, 73.4, 72.0, 69.9, and
38.6.
1
°C; [R]20 -59° (c 1.1, MeOH); H NMR (300 MHz, CD3OD) δ
D
(ppm) 7.66 (s, 1H), 7.39 (br s, 1H), 6.54 (br s, 1H), 5.91 (s, 1H),
4.22 (d, 1H, J 6.9), 3.96 (m, 1H), and 2.18-2.02 (m, 2H); 13C
NMR (75 MHz, D2O) δ (ppm) 177.8, 143.6, 141.2, 135.0, 123.3,
123.0, 108.7, 73.0, 71.7, 69.7, and 37.7.
Acknowledgment. Financial support from the
Xunta de Galicia (Grant PGIDIT02RAG20901PR) and
the Spanish Ministry of Education and Culture (Grant
CTQ2004-04238) is gratefully acknowledged.
Supporting Information Available: IR, MS, and HRMS
1
data for all compounds, elemental analysis results for 4, H
NMR, 13C NMR, and DEPT spectra of 4a-l, and 19F NMR
spectra of 4b-e,i. This material is available free of charge via
the Internet at http://pubs.acs.org.
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1
168 °C; [R]20 -80° (c 1.1, H2O); H NMR (250 MHz, D2O) δ
D
(ppm) 7.73 (m, 2H), 7.45 (d, 1H, J 7.5), 7.30 (t, 1H, J 7.7), 5.78
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1
°C; [R]20 -134° (c 1.1, CH3OH); H NMR (300 MHz, D2O) δ
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(ppm) 6.85-6.71 (m, 3H), 5.79 (s, 1H), 4.38 (d, 1H, J 7.6), 3.90
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