The difluoromethylenesulfonic acid group as a monoanionic phosphate surrogate for obtaining PTP1B inhibitors

Article abstract of DOI:10.1016/S0968-0896(02)00062-7

Three peptides, 7-9, bearing sulfono(difluoromethyl)phenylalanine (F₂Smp, 2), a nonhydrolyzable, monoanionic phosphotyrosine mimetic, were prepared and evaluated as PTP1B inhibitors. The most effective inhibitor was the nonapeptide, ELEF(F₂Smp)MDYE-NH₂, (9) which exhibited a K_i of 360 nM. A comparison of F₂Smp-bearing peptides 7 [DADE(F₂Smp)LNH₂, K_i=3.4 μM] and 8 [EEDE(F₂Smp)LNH₂, K_i=0.74 μM] with their phosphono(difluoromethyl)phenylalanine (F₂Pmp)-bearing analogues indicated that F₂Smp is not as effective a pTyr mimetic as F₂Pmp by 100- to 130-fold. Although F₂Smp is not as effective as F₂Pmp, a comparison of peptide 7 with analagous peptides bearing other monoanionic pTyr mimetics recently reported in the literature indicates that F₂Smp is about 65-fold more effective than any other non-hydrolyzable, monanionic pTyr mimetic reported to date. To further assess the difluoromethylenesulfonic acid (DFMS) group as a monoanionic phosphate mimetic, a series of 24 nonpeptidyl biaryl compounds bearing the DFMS group were prepared using polymer-supported methodologies and screened for PTP1B inhibition. Several of these compounds were selected for further study and their IC₅₀'s compared to their difluoromethylenephosphonic (DFMP) analogues. The differences in IC₅₀'s between the DFMS and DFMP non-peptidyl compounds was not as great as with the F₂Smp- and F₂Pmp-bearing peptides. Possible reasons for this and its implication to the design of small molecule PTP1B inhibitors is discussed.

Full text of DOI:10.1016/S0968-0896(02)00062-7

Bioorganic & Medicinal Chemistry 10 (2002) 2309–2323
The Difluoromethylenesulfonic Acid Group as a Monoanionic
Phosphate Surrogate for Obtaining PTP1B Inhibitors
Carmen Leung, Justyna Grzyb, Jason Lee, Natalie Meyer, Gabriel Hum, Chenguo Jia,
Shifeng Liu and Scott D. Taylor*
Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
Received 6 November 2001; accepted 10 January 2002
Abstract—Three peptides, 7–9, bearing sulfono(difluoromethyl)phenylalanine (F2Smp, 2), a nonhydrolyzable, monoanionic phos-
photyrosine mimetic, were prepared and evaluated as PTP1B inhibitors. The most effective inhibitor was the nonapeptide,
ELEF(F2Smp)MDYE-NH2, (9) which exhibited a Ki of 360 nM. A comparison of F2Smp-bearing peptides 7 [DADE(F2Smp)LNH2,
Ki=3.4 mM] and 8 [EEDE(F2Smp)LNH2, Ki=0.74 mM] with their phosphono(difluoromethyl)phenylalanine (F2Pmp)-bearing
analogues indicated that F2Smp is not as effective a pTyr mimetic as F2Pmp by 100- to 130-fold. Although F2Smp is not as effective
as F2Pmp, a comparison of peptide 7 with analagous peptides bearing other monoanionic pTyr mimetics recently reported in the
literature indicates that F2Smp is about 65-fold more effective than any other non-hydrolyzable, monanionic pTyr mimetic reported
to date. To further assess the difluoromethylenesulfonic acid (DFMS) group as a monoanionic phosphate mimetic, a series of 24
nonpeptidyl biaryl compounds bearing the DFMS group were prepared using polymer-supported methodologies and screened for
PTP1B inhibition. Several of these compounds were selected for further study and their IC50’s compared to their difluoro-
methylenephosphonic (DFMP) analogues. The differences in IC50’s between the DFMS and DFMP non-peptidyl compounds was
not as great as with the F2Smp- and F2Pmp-bearing peptides. Possible reasons for this and its implication to the design of small
molecule PTP1B inhibitors is discussed. # 2002 Elsevier Science Ltd. All rights reserved.
Introduction
type 2 diabetes and obesity and numerous papers have
appeared in recent years describing inhibitors of this
enzyme.2
There are numerous signal transduction pathways that
rely on protein tyrosine phosphorylation/dephos-
phorylation for signal transmission. The phosphoryla-
tion event is catalyzed by protein tyrosine kinases
(PTKs) while the dephosporylation reaction is catalyzed
by protein tyrosine phosphatases (PTPs). Due to their
potential for the treatment of a variety of disease states,
inhibitors of both the PTKs and PTPs have been pur-
sued with considerable vigour over the last decade.1,2
Among the PTPs, human protein tyrosine phosphatase
1B (PTP1B) has received the most attention. PTP1B is
widely expressed in insulin-sensitive tissues and has been
implicated in the attenuation of insulin signaling.3
Recent studies with a PTP1B knock-out mouse has
demonstrated that PTP1B plays a key regulatory role in
modulating both insulin sensitivity and resistance to
diet-induced obesity.4 Thus, PTP1B is now recognized
as a potential therapeutic target for the treatment of
Since the phosphate group is crucial for PTP-substrate
binding,5 an effective non-hydrolyzable phosphate
mimetic is an important aspect of PTP inhibitor design.
The most effective phosphate mimetic reported to date
is the difluoromethylenephosphonic acid (DFMP) group.
Peptides bearing phosphono(difluoromethyl)phenyla-
lanine (F2Pmp, 1) bind better than the analogous pep-
tide substrates and can be up to three orders of
magnitude more effective than their non-fluorinated
analogues.2,6aꢀd The DFMP group also been found to
be effective for the development of non-peptidyl PTP
inhibitors.7aꢀg
Although the DFMP group has proven to be useful for
obtaining inhibitors of PTP1B, its dianionic nature may
compromise cell permeability.7a Consequently, there has
been considerable interest in the development of less
highly charged pTyr mimics.8,9 A variety of other
phosphate mimetics have been examined but none have
proven to be as effective as the DFMP group.8,9 Several
*Corresponding author. Tel.: +1-519-888-4567x3325; fax: +1-519-
746-0435; e-mail:
0968-0896/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S0968-0896(02)00062-7

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C. Leung et al. / Bioorg. Med. Chem. 10 (2002) 2309–2323
years ago, Liotta and co-workers reported that a syn-
thetic tri-sulfotyrosyl dodecapeptide analogue of the
insulin receptor kinase domain was an inhibitor of
PTP1B.10 Later, Desmarais and co-workers performed
a more detailed analysis of sulfotyrosyl peptides as
PTP1B inhibitors.11 These workers found that peptides
bearing acidic residues N-terminal to the sTyr residue
exhibited IC50’s in the low mM region11 which indicates
that these peptides bind almost as well as the best pep-
tide substrates.6d However, the hydrolytic lability of
phenyl sulfates makes them unsuitable as phosphate
mimetics for drug development. Since the effect of the
fluorines in DFMP-bearing compounds is believed to be
due to H-bonding of the fluorines with residues in the
active site and not pKa effects,6c,7b we reasoned that the
difluoromethylsulfonic acid (DFMS) group would be an
effective hydrolytically stable, monoanionic phosphate
mimetic. We developed a method for constructing
a-fluorosulfonic acids using electrophilic fluorina-
tion12,13 and evaluated compounds 3 and 5 as inhibitors
of PTP1B.14 These compounds were found to be mod-
erate inhibitors of PTP1B (3, IC50=175 mM; 5,
IC50=115 mM) and were approximately 5- to 8-fold less
potent than their DFMP analogues 4 and 6 (4,
IC50=35 mM; 6, IC50=15 mM)14,15 Since this work
appeared, several other monanionic pTyr mimetics have
been reported and evaluated on peptidyl scaffolds.8,9 In
order to compare the DFMS group as a phosphotyr-
osine mimetic to those reported by other workers,8,9 we
decided to prepare several peptides bearing the DFMS
group. We recently reported an enantioselective synth-
esis of sulfono(difluoromethyl)phenylalanine (F2Smp, 2)
suitably protected for peptide synthesis and its incor-
poration into a peptide.16 Here we report the evaluation
of three F2Smp-containing peptides as PTP1B inhibitors
and a comparison of the potency of one of these pep-
tides with analagous peptides bearing other pTyr
mimetics reported by other workers. The synthesis of 24
non-peptidyl compounds bearing the DFMS group,
prepared using soluble polymer supported organic
synthesis (SPSOS) methodologies, is also reported.
Their evaluation as PTP1B inhibitors and a comparison
of the inhibitory potency of selected DFMS compounds
with their DFMP analogues is also reported.
other pTyr mimetics. Peptide 8 was prepared since
Huyer et al. have shown that the peptide
EEDE(F2Pmp)M exhibits a Ki of 7.2 nM, making it the
most potent peptide-based PTP1B inhibitor reported to
date.6d Finally, using a reverse alanine scan to find high-
affinity substrates for PTP1B, Vetter et al. discovered
that AcELEFpYMDYENH2 is one of the best peptide
substrates, in terms of kcat/Km, for PTP1B ever repor-
ted.17 Consequently, we anticipated that its F2Smp
analogue (9) would be a good PTP1B inhibitor.
Peptides 7–9 were constructed using the procedure
described previously for peptide 7.16 The results from
the inhibition studies with peptide 7–9 are shown in
Table 1. All of the peptides were competitive inhibitors.
The most potent of these three peptides was the non-
apeptide 9 which exhibited a Ki of 360 nM which is
consistent with AcELEFpYMDYENH2 being an out-
standing peptide substrate.17 The Ki for peptide 9 is
approximately 2 times lower than the Ki for peptide 8
and about 10-fold lower than that for peptide 7. Com-
paring peptides 7 and 8 with similar F2Pmp-bearing
peptides 10 and 11 (Table 1), it can be seen that F2Smp
is not as effective a pTyr mimetic as F2Pmp by at least
100- to 130-fold. This was somewhat surprising since
Desmarais et al.’s results with sTyr-containingꢀpeptide
inhibitors11 suggested that the monoanionic SO4 group
binds almost as well as the POꢀ4 2 group. For example,
the tripeptide AcDE(sY)L (10) has a Ki of 5.0 mM,
which is approximately the same as the Km (3.2 mM) of
the pentapeptide substrate, AcDADE(pY)LNH2 (11).11
Although the sTyr analogue of peptides 7–9 have not
been reported, it is clear that substituting the labile
oxygen in sTyr-bearing peptide inhibitors with a
difluoromethylene group does not result in an increase
in inhibitory potency. This is in contrast to F2Pmp
bearing peptides which have Ki’s that are 26- to 75-fold
lower than the Km’s of their substrate analogues.6d Our
earlier inhibition studies with compounds 3 and 5 and
their non-fluorinated analogues indicated that the
fluorines are essential for good inhibition.14 Sulfonates,
whether bearing a-fluorines or not, are highly acidic and
should be completely ionized at the pH under which
these studies were performed (pH 6.5). This suggests
that the enhanced effect of the fluorines with the CF2-
sulfonates is most likely a result of a direct interaction
of the fluorines with residues in the enzyme active site
and is not due to pKa effects. It is possible that the
Table 1. Inhibition of PTP1B with F2Smp- and F2Pmp-bearing
peptides
Peptide
Ki (uM)
Results and Discussion
DADE(F2Smp)LNH2 (7)
EEDE(F2Smp)LNH2 (8)
ELEF(F2Smp)MDYENH2 (9)
DADE(F2Pmp)L (10)
EEDE(F2Pmp)L (11)
3.4
0.74
0.36
Studies with F2Smp-bearing peptides
0.026a
0.0072a
5.0b
Three F2Smp-bearing peptides, 7–9, were prepared and
then examined as PTP1B inhibitors (Table 1). Peptide 7
was constructed since the DADE-X-L sequence has
been used extensively for examining phosphotyrosine
mimetics for obtaining inhibitors of PTP1B.9 This pep-
tide would allow us to compare the F2Smp moiety to
AcDE(sY)L (12)
AcDADE(pY)LNH2 (13)
Km=3.2c
aFrom ref 6d.
bFrom ref 11.
cFrom ref 18.

C. Leung et al. / Bioorg. Med. Chem. 10 (2002) 2309–2323
2311
Scheme 1.
Scheme 2.
Table 2. Inhibition of PTP1B with non-phosphorus, monoanionic
and dianionic phenylphosphate mimeticsa
unusually strong H-bond that has been proposed to
account for the high affinity of DFMP-bearing inhibi-
tors7b may not be able to form in an optimal manner in
the F2Smp-bearing peptides due to overall size and/or
geometric constraints. Nevertheless, whether due to pKa
effects or H-bonding, it is clear that the DFMS group is
poorer phosphate mimetic than the DFMP group.
R (monoanionic)
IC50 (mM)
R (dianionic)
IC50 (mM)
Although F2Smp is not as effective as F2Pmp, a com-
parison of F2Smp-bearing peptide 7 with similar pep-
tides bearing other monoanionic pTyr mimetics recently
reported in the literature,9 indicates that the DFMS
group is about 65-fold more effective than any other
non-hydrolyzable, monanionic phosphate mimetic repor-
ted to date (14–20, Table 2). F2Smp compares very
favorably even to non-phosphorus, dianionic pTyr
mimics (21–27, Table 2) and only the fluoromalonyl
group (21) is more effective.19
DADE(F2Smp)LNH2 7
10
1
650
1200
10
19
Synthesis of non-peptidyl compounds bearing the DFMS
group on a soluble polymer support
It is interesting to note that in contrast to the above
peptide inhibitors, small molecule inhibitors 3 and 5
were only 5- to 8-fold less potent than their DFMP
analogues 4 and 6.14 This prompted us to investigate
non-peptidyl compounds bearing the DFMS group in
more detail. We recently described a method by which
non-peptidyl DFMP compounds could be prepared
using non-crosslinked polystyrene (NCPS), a soluble
polymer, as a support.20 This procedure was used to
prepare a small library of biaryl DFMP’s (Scheme 1).21
We wished to prepare the same or similar DFMS-bear-
ing compounds and compare the inhibitory potency of
these compounds to some of their DFMP analogues.
We anticipated that our polymer-supported methodol-
ogy would be a rapid approach to the synthesis of the
DFMS compounds (Scheme 2). Indeed, we felt that our
polymer-supported methodology would be even better
suited to preparing DFMS compounds as opposed to
DFMP compounds, since the DFMS compounds could
be removed from the support by simple hydrolysis,
rather than with the more harsh TMSBr or TMSI as
was the case with the DFMP compounds.
2500
430
4400
800
4600
1500
3700
5300
13,000
Before preparing the DFMS compounds, a rapid screen
of the compounds obtained from the previously repor-
ted DFMP library20 was performed by assaying PTP1B
in the presence of 150 mM of each compound. The
aAll values were obtained from ref 9 with the exception of compound
7, which was obtained from these studies.

2312
C. Leung et al. / Bioorg. Med. Chem. 10 (2002) 2309–2323
Scheme 3.
Table 3. Percent inhibition of PTP1B with DFMP compounds
results of these studies are shown in Table 3. The meta
series of compounds were better inhibitors than the para
series and none of the para series of compounds was
particularly good inhibitors. This is consistent with our
earlier finding that compound 6 was a 6-fold better
inhibitor than its para isomer.7c A number of the meta
compounds appeared to be promising with the excep-
tion of compounds 39 and 40, which bore ortho sub-
stituents on the distal aryl ring. Compounds 28–38 of
the meta series were rescreened using 50 mM of each
compound which enable us to better differentiate
between these inhibitors. The majority of the meta
compounds showed approximately the same level of
inhibition (between 70 and 80% inhibition at 50 mM)
with the exception of compounds 37 and 38 (59 and
65% inhibition at 50 mM, respectively) which bore a
para-t-butyl group (37) and a para-chloro group (38) on
the distal aryl ring and compounds 28 and 29 which
were substituted with the 2-naphthyl and biphenyl
groups, respectively, and were the best two inhibitors.
The IC50’s of 28 and 29 were determined to be 21 and
8 mM, respectively. The IC50 of compound 30 was also
determined and found to be 24 mM. Compound 29
represents an approximately 8-fold improvement in
inhibitory potency compared to the parent compound 6.
R
% Inhibition
para series 150 mM
% Inhibition meta series
150 mM
50 mM
80
99
89
NDa,b
98
94
91
90
89
88
88
87
92
85
60
24
87
80
50
43
75
41
74
61
74
For the DFMS library, we focused on the meta-sub-
stituted compounds since the above studies indicated
that the para biaryl compounds were not as effective
inhibitors as the meta series. We chose to construct of
the DFMS analogues of the above DFMP-meta series
as well as other biaryl compounds, some bearing het-
erocyclic rings. It was anticipated that the polymer-
bound DFMS compounds would be quite hydrolytically
labile and therefore, would have to be attached to the
polymer by a linker arm that would confer enough sta-
bility to enable chemistry to be performed on the aryl
ring, yet still allow the compounds to be removed by
mild hydrolysis. Our initial approach was to construct
sulfonyl chloride 41 and then attach it to NCPS mod-
ified with a 2,3-dimethylpentanol linker arm as outlined
in Scheme 3 (pathway A). It was anticipated that the
two methyl groups on the linker arm would help confer
some hydrolytic stability to the polymer-bound sulfo-
nates. However, attempts to prepare 41 from the corre-
sponding sulfonic acid or its salts using a variety of
different procedures were unsuccessful. This is in con-
trast to its nonfluorinated analogue (43, Scheme 4)
which was readily prepared by reaction of the corre-
sponding sodium salt with POCl3 in sulfolane/CH3CN.
Therefore, an alternative approach was investigated
38
74
54
70
38
70
50
65
41
59
56
NDa
NDa
29
aND, not determined.
bNot determined due to solubility problems.

C. Leung et al. / Bioorg. Med. Chem. 10 (2002) 2309–2323
2313
Scheme 4.
Scheme 5.
which involved attaching the linker arm to the sulfonate
first to give 42 and then attaching 42 to the support
(pathway B, Scheme 3). Sulfonyl chloride 43 was reac-
ted with mono-TBDMS-protected 2,3-dimethylpentane-
1,5-diol to give the sulfonate ester 44 in 86% yield.
equivalents TMAD and 4 equivalents PBu3 in THF/
CH2Cl2. After 24 h, the reaction was added directly to a
solution of MeOH and recovery of sulfonylated polymer
48 was 97%. The polymer loading was approximately
0.55 mmol/g as determined by NMR (see Experimental).
Reaction of 44 with
3
equiv N-fluorobenzene-
sulfonimide (NFSi), and 2.5 equivalents of NaHMDS in
THF at ꢀ78 ꢁC followed by warming to room tempera-
ture and stirring overnight gave the fluorinated sulfo-
nate 45 in 88% yield. Removal of the TBDMS group
was accomplished using AcOH/H2O/THF to give the
free alcohol 42 in 78% yield (Scheme 4).
The polymer-bound biaryls (49) were prepared using the
room temperature Suzuki reaction conditions we devel-
oped for the DFMP library.20 This involved reacting the
polymer-bound sulfonate 48 with 3 equivalents boronic
acid in the presence of 20 mol% (PhCN)2PdCl2, 3
equivalents K2CO3 and 10 equivalents water in degassed
DMF (Scheme 5). A total of 24 different aryl boronic
acids were used. The reactions were monitored by 19F
NMR and within 9 h or less, almost all of the reactions
had gone to completion, with the exception of 2-fur-
anboronic acid which required 24 h, and then another
24 h with fresh reagents. After the palladium catalyst
was removed by centrifugation, all polymer-bound
biaryl products were purified by diluting the reaction
mixture with CH2Cl2, precipitating out the polymer in
MeOH and a few drops of brine, filtering off the poly-
mer, and rinsing the collected polymer with MeOH. The
polymer recovery ranged from 90 to 95%. The products
were hydrolyzed off the polymer support with 3 equiva-
lents of K2CO3, 10 equivalents of H2O, in DMF, at
80 ꢁC for 17 h. The crude reaction mixture was then
The sulfonate was attached to the support by a hydro-
lytically stable ether linkage. Styrene was copolymerized
with 9 mol% of 4-acetoxystyrene in the presence of the
free radical initiator 1,10-azobis(cyclohexanecarboni-
trile) (VAZO) to obtain the 4-acetoxy-functionalized
NCPS, 46 (Scheme 5).21 The polymer was then saponi-
fied by refluxing it in an aqueous solution of NaOH in
THF for 24 h to give the 4-hydroxylated NCPS (47).21
At each step, the polymer was purified by diluting the
reaction mixture with CH2Cl2 and then precipitating
out the polymer in MeOH. The recovery of polymer 47
was 90%. Loading of the polymer was achieved using
Mitsonobu chemistry which involved reacting 47 with
approximately 4 equivalents of the sulfonate 42, 4

2314
C. Leung et al. / Bioorg. Med. Chem. 10 (2002) 2309–2323
Scheme 6.
Scheme 7.
diluted with CH2Cl2 and added to a solution of
MeOH and a few drops of brine. The precipitated
polymer was filtered off, leaving the filtrate which con-
tained the crude potassium salt of the biaryl DFMS
compounds. The filtrate was concentrated, redissolved
in 1 N NaOH, washed with CH2Cl2 to remove any resi-
dual polymer and organic impurities, and acidified to
pH of approximately 0.5. The sulfonic acids were then
extracted into EtOAc, concentrated, treated with an
aqueous solution of NH4HCO3, and then lyophilized
and this process was repeated until a constant weight
was obtained. This gave the biaryl DFMS com-
pounds, 50–73, as their ammonium salts in yields
ranging from 34 to 95% [from the polymer-bound sul-
fonate 48 (see Table 4)]. The variable yields were mainly
a result of the extraction step. Nevertheless, sufficient
amounts of each compound were obtained for inhibitor
studies. The structures of all of the compounds was
confirmed by low resolution and high resolution ESMS,
1H, 19F NMR. The vast majority of these 24 com-
pounds were obtained in 95% purity or better as deter-
mined by 19F NMR, analytical HPLC and ESMS and
could be used directly for PTP1B screening. Although
19F NMR and HPLC suggested that compound 65 was
obtained in about 96–98% purity, high resolution
ESMS revealed that it was contaminated with sig-
nificant amounts (ꢂ9%) of compound 74, which was
most likely a result of a double Suzuki coupling on the
aryl chloride product. Surprisingly, the doubly coupled
products did not form to any significant extent with
compounds 57, 59, 63 and 66 (as determined by mass
spectral analysis), which were also aryl chlorides. We
were unable to separate compound 74 from com-
pound 65 and so compound 65 was resynthesized in
pure form in solution using a procedure (Scheme 6)
which did not yield any of the doubly coupled pro-
duct. Compound 71, which was obtained in only 77%
purity (by HPLC), was also difficult to purify and
therefore, was resynthesized in pure form in solution
(Scheme 7).

C. Leung et al. / Bioorg. Med. Chem. 10 (2002) 2309–2323
2315
A rapid screen of 50–73 was conducted by determining
the percent inhibition of PTP1B inhibition in the pre-
sence of 50 mM of each compound (Table 5). All of the
DFMP compounds in Table 3 were better inhibitors
than their analogous DFMS compounds (50–62, Table
5). The majority of the compounds showed little inhibi-
tory potency. As with the DFMP compounds in Table
3, the best DFMS inhibitors were those bearing large
apolar aryl moieties (50, 51, 72, and 73). The enhanced
binding of these compounds compared to the rest of the
DFMS inhibitors is most likely a result of increased
hydrophobic interactions.
Again, the best inhibitor was the meta-biphenyl sub-
stituted compound 50 which displayed an IC50 of
26 mM. A comparison of the IC50’s of DFMP com-
pounds 28–30 to the analogous DFMS compounds (50–
52) indicates that the DFMP compounds are approxi-
mately 3- to 8-fold better inhibitors than DFMS com-
pounds. This difference is comparable to what we found
for the difference in inhibitory potency between inhibi-
tors 3 and 5 and inhibitors 4 and 6.14 Again, this is in
contrast to the large difference in inhibitory potency
(>100-fold) between F2Pmp- and F2Smp-bearing pep-
tide inhibitors. Also, it is interesting to note that peptide
7 is only an 8-fold better inhibitor than compound 50.
This disparity between the effectiveness of certain
phosphate mimetics in peptidyl scaffolds versus small
The IC50’s of the four best inhibitors (50, 51, 72, and 73)
as well as for compound 52, were determined (Table 6).
Table 4. Yields and purity of biaryl DFMS products
R
% Yield
% Purity
19F NMR
R
% Yield
% Purity
19F NMR
HPLC
99
HPLC
99
34
100
89
100
92
54
79
71
72
67
88
63
84
85
73
100
100
100
100
100
99
99
100
100
98
62
91
95a
81
92
64
72
39
54
56
82
100
100
90
100
98a
99
96a
100
99
94
95
95
100
100
100
90
100
100
100
77
100
100
100
99
100
100
100
100
93
100
100
98
100
100
aESMS revealed approximately 9% of compound 74 present.

2316
C. Leung et al. / Bioorg. Med. Chem. 10 (2002) 2309–2323
Table 5. Percent inhibitiona of PTP1B with DFMS compounds
Table 6. IC50’s of selected DFMS and DFMP compounds with
PTP1B
R
% inhibitiona
77
R
% inhibitiona
R0=DFMS
R0=DFMP
b
NI
R
IC50 (mM)
R
IC50 (mM)
26
8
62
8
36
40
41
44
10
NI
42
12
22
51
65
53
197
56
21
24
NI
7
49
5
5
5
scaffolds if the ultimate goal is the discovery of potent
small molecule inhibitors.
NI
NI
43
NI
In conclusion, this study has demonstrated that F2Smp
is the most potent non-hydrolyzable, monoanionic pTyr
mimetic reported to date for obtaining PTP1B inhibi-
tors. Although the F2Smp-bearing peptides were at least
100-fold poorer inhibitors than F2Pmp-bearing pep-
tides, on small molecule scaffolds, the difference
between DFMS-bearing inhibitors and their DFMP
analogues was much smaller (3- to 8-fold) which suggest
that the DFMS group may prove to be a very useful
monoanionic phosphate mimetic for preparing small
molecule inhibitors of PTP1B. We also demonstrated
that the polymer supported methodologies described
previously for the synthesis of DFMP compounds can
also be used for the synthesis of DFMS compounds.
a50 mM inhibitor.
bNI, no inhibition.
molecules has recently been noted by Burke and co-
workers with other phosphate mimetics.9 These workers
suggested that the non-peptidyl compounds may have
more freedom to orient the pTyr mimic in such a way
that results in optimal binding and this may be what is
taking place here.9 However, when comparing mimetics
within non-peptidyl platforms, it is possible that, in
certain instances (such as 28 vs 50), neither the DFMP
group nor the DFMS group can form optimal interac-
tions with the enzyme and so other factors (such as
hydrophobic interactions) are also important and so less
of a difference in inhibition is seen between the two
classes of compounds. In any case, these results reflect
the concerns of Burke and co-workers about assessing
the effectiveness of pTyr mimetics using peptidyl
Experimental
General
All starting materials were obtained from commercial
suppliers (Aldrich Chemical Company, Oakville, ON,
Canada or Lancaster Synthesis Incorporated, Windham,
NH, USA). Solvents were purchased from Caledon
Laboratories (Georgetown, ON, Canada), Lancaster
Synthesis Incorporated, or BDH Canada (Toronto,
Canada). Tetrahydrofuran (THF) was distilled from
sodium metal in the presence of benzophenone under
argon. Dichloromethane (CH2Cl2) was distilled from
calcium hydride under argon. Dimethylformamide
(DMF) was distilled under reduced pressure from cal-

C. Leung et al. / Bioorg. Med. Chem. 10 (2002) 2309–2323
2317
cium hydride and stored over 4 A sieves under argon.
Reactions involving moisture-sensitive reagents were
executed under an inert atmosphere of dry argon or
nitrogen. All glassware was pre-dried prior to use and
all liquid transfers were performed using dry syringes
and needles. Silica gel chromatography was performed
(solvent B). The following linear gradient was used:
95% A/5% B to 20% A/80% B over a period of 30 min.
EEDE(F2Smp)MNH2 (8). Analytical HPLC showed
only a single peak (retention time=11.1 min). ESMS m/z
calculated for C34H47F2N7O17S2 926.24, found 926.07.
ELEF(F2Smp)MDYENH2 (9). Analytical HPLC
showed only a single peak (retention time=15.8 min).
Negative ion ESMS m/z calculated for C34H47F2N7O17S2
1349.46, found 1349.14.
1
using silica gel 60A (Silicycle, 230–400 mesh). H, 19F,
31P, and 13C NMR spectra were recorded on a Varian
200-Gemini, Bruker AC-200, or Bruker AC-300 NMR
spectrometer. The abbreviations s, d, t, q, m, dd, dt, and
br are used for singlet, doublet, triplet, quartet, multi-
plet, doublet of doublets, doublet of triplets, and broad,
respectively. Coupling constants are reported in Hertz
Synthesis of DFMS library
(3-Bromophenyl)methanesulfonyl chloride (43). To a
solution of sodium (3-bromophenyl)methanesulfonate22
(12.05 g, 44 mmol, 1 equiv) in 1:1 acetonitrile/sulfolane
(44 mL) was added phosphorus oxychloride (17.3 mL,
28.46 g, 185.3 mmol, 4.2 equiv). The reaction was stirred
for 3 h at 70 ꢁC, cooled to room temperature, and then
poured into cold water (300 mL) which resulted in the
precipitation of the crude product. The precipitate was
filtered off and then dissolved in CH2Cl2 (50 mL) and
washed with water (3ꢃ100 mL). The organic layer was
dried (MgSO4), filtered, and concentrated by rotary
evaporation to give pure 43 as a white solid in 85%
1
(Hz). Chemicals shifts (d) for H NMR spectra run in
CDCl3 are reported in ppm relative to the internal
standard tetramethylsilane (TMS). Chemical shifts (d)
for H NMR spectra run in CD3OD are reported in
1
ppm relative to residual solvent protons (d 3.30). Che-
1
mical shifts (d) for H NMR spectra run in D2O are
reported in ppm relative to residual solvent protons (d
4.79). For 13C NMR spectra run in CDCl3, chemical
shifts are reported in ppm relative to the CDCl3 residual
carbons (d 77.0 for central peak). For 13C NMR spectra
run in CD3OD, chemical shifts are reported in ppm
relative to the CD3OD residual carbons (d 49.0 for cen-
tral peak). For 31P NMR spectra, chemical shifts are
reported in ppm relative to 85% phosphoric acid
(external). 19F NMR spectra, chemical shifts are repor-
ted in ppm relative to trifluoroacetic acid (external).
Low resolution electron impact (LREIMS) and high
resolution (HREIMS) electron impact mass spectra
were obtained on a Micromass 70-S-250 mass spectro-
meter. Low resolution electrospray mass spectra
(LRESMS) were obtained on a Micromass Quatro II
mass spectrometer. High resolution electrospray mass
spectra (HRESMS) were obtained on a Bruker Dal-
tonics Apex II fourier transform ion cyclotron reso-
yield: mp 90–91 ꢁC. H NMR (CDCl3) d 7.62 (1H, d,
1
J=6.6 Hz), 7.30–7.46 (3H, m), 4.82 (2H, s); 13C NMR
(CDCl3) d 134.21, 133.45, 130.68, 129.98, 128.45,
123.08, 70.09. LREIMS m/z (relative intensity) 268 (9),
169 (100), 90 (45), 63 (26). HR-EIMS calcd for
C7H6O2S1Cl1Br1 267.8960, found 267.8951.
5-{[1-(tert-Butyl)-1,1-dimethylsilyl]oxy}-2,2-dimethylpentyl
(3-bromophenyl)methanesulfonate (44). To a solution of
43 (9.00 g, 33.5 mmol, 1 equiv) and 5-{[1-(tert-Butyl)-
1,1-dimethylsilyl]oxy}-2,2-dimethyl-1-pentanol23 (12.40g,
50.3 mmol, 1.5 equiv) in anhydrous THF (60 mL) at
0 ꢁC was added a solution of triethylamine (4.43 g,
43.5 mmol, 1.3 equiv) in anhydrous THF (60 mL). The
reaction was stirred at room temperature overnight then
concentrated by rotary evaporation. Water (50 mL) was
added and then extracted with CH2Cl2 (3ꢃ50 mL). The
combined organic layers were dried (MgSO4), filtered,
and concentrated by rotary evaporation. Column chro-
matography (5:1 CH2Cl2/hexane) of the crude residue
gave pure 44 as a white solid in 86% yield: mp 41–43 ꢁC.
1H NMR (CDCl3) d 7.25–7.60 (4H, br m), 4.31 (2H, s),
3.80 (2H, s), 3.56 (2H, t, J=6.2 Hz), 1.15–1.55 (4H, m),
0.89 (15H, s), 0.05 (6H, s); 13C NMR (CDCl3) d 133.65,
132.10, 130.47, 130.27, 129.27, 122.71, 78.12, 63.50,
56.04, 34.83, 34.06, 27.24, 25.98, 23.80, 18.31, ꢀ5.26.
LREIMS m/z (relative intensity) 309 (3), 169 (28), 97
(100), 75 (21), 55 (71). HR-EIMS calcd for C20H36O4
Si1S1Br1 (M+H+) 479.1287, found 479.1293.
nance spectrometer equipped with
a
7.0 tesla
superconducting magnet. All ESMS were run in the
negative mode. All melting points were taken on a Mel-
temp melting point apparatus and are uncorrected.
Analytical HPLC was performed on a Waters LC 4000
System using a Vydac 218TP54 analytical C-18 reverse-
phase column and a Waters 86 tunable absorbance
detector set at 254 nm. Buffer chemicals were obtained
from Sigma Chemical Company. Enzyme assay solu-
tions were prepared with deionized/distilled water.
Fluorescein diphosphate (FDP) and human PTP1B
were gifts from Merck-Frosst Canada Inc (Montreal,
PQ, Canada).
Syntheses
Compounds 28–40 were prepared as previously
described.20
5-{[1-(tert-Butyl)-1,1-dimethylsilyl]oxy}-2,2-dimethylpentyl
(3-bromophenyl)-difluoromethanesulfonate (45). To
a
solution of 44 (0.50 g, 1.05 mmol, 1 equiv) and NFSi
(1.00 g, 3.15 mmol, 3 equiv) in anhyd THF (28 mL) at
ꢀ78 ꢁC was added NaHMDS (2.63 mL, 1.0 M,
2.63 mmol, 2.5 equiv) dropwise over a period of 1 h. The
reaction was stirred at ꢀ78 ꢁC for 2 h, warmed to room
temperature, and stirred overnight. The reaction was
then quenched with water (30 mL) and extracted with
Peptide syntheses
Peptides 8 and 9 were prepared using the procedure
previously described for peptide 6.16 Peptide purities
were assessed by ESMS and analytical reverse-phase
HPLC. The mobile phase consisted of acetonitrile with
0.25% TFA (solvent A) and water with 0.025% TFA

2318
C. Leung et al. / Bioorg. Med. Chem. 10 (2002) 2309–2323
ether (3ꢃ30 mL). The combined organic layers were
dried (MgSO4), filtered, and concentrated by rotary
evaporation. Column chromatography (1:99 EtOAc/
hexane) of the crude residue yielded pure 45 as a pale-
Determination of polymer loading
Polymer loading is defined as the number of anchoring
sites per gram of polymer and is expressed in units of
mmol per gram (mmol/g). To determine this, 10 stan-
dards solutions in CDCl3 (0.5 mL) were prepared with
varying amounts of styrene and [{5-(4-ethylphenoxy)-
2,2 - dimethylpentyl}(3 - bromophenyl)](difluoro)methane-
sulfonate (83). The total mass for each of the standards
was 25 mg and the ratio of mmol of 83 to grams of sty-
rene plus grams of 83 ranged from 0.1 to 1.0. Integra-
tion ratios of the averaged (–CH2O–) peak area to the
aromatic proton peak area were calculated and then
plotted against the mmol of 83/g of styrene and 83. A
linear relationship was obtained. Mitsonobu reactions
between polymer 47 and varying quantities of compound
42, TMAD and P(Bu)3 were performed. The polymer
loading was determined by calculating the integration
ratio of the CH2O(average)/Ar–H polymer protons and
then using the equation of the line from the above stan-
dard curve. The polymer loading was determined to be
approximately 0.50–0.55 mmol/g. A detailed description
of the coupling of 42 to polymer 47 is given below.
1
yellow oil in 88% yield. H NMR (CDCl3) d 7.83 (1H,
s), 7.71 (1H, d, J=7.9 Hz), 7.64 (1H, d, J=7.9 Hz), 7.38
(1H, t, J=8.2 Hz), 4.16 (2H, s), 3.60 (9H, s), 0.06 (6H,
s); 19F NMR (CDCl3) d ꢀ24.28; 13C NMR (CDCl3) d
135.54, 130.25, 130.06 (t, JCF=6.3 Hz), 129.95 (t,
JCF=23 Hz), 125.79 (t, JCF=5.8 Hz), 122.69, 119.98 (t,
JCF=285 Hz), 83.36, 63.34, 34.37, 34.33, 27.05, 25.91,
23.55, 18.28, ꢀ5.34. LREIMS m/z (relative intensity)
383 (3), 207 (100), 171 (11), 147 (23), 126 (41), 115 (14),
97 (49), 83 (63), 69 (27), 55 (70). HR-EIMS calcd for
C20H34O4F2Si1S1Br1 515.1099, found 515.1120.
5-Hydroxy-2,2-dimethylpentyl (3-bromophenyl)difluoro-
methanesulfonate (42). To a solution of 45 (1.15 g,
2.24 mmol, 1 equiv) in THF (6 mL) was added a mixture
of 3:1 acetic acid/water (24 mL). The reaction was stir-
red at room temperature for 3 h, diluted with ether
(25 mL), washed with water (3ꢃ25 mL), 5% NaHCO3
(3ꢃ25 mL), and brine (3ꢃ25 mL). The organic layer was
dried (MgSO4), filtered, and concentrated by rotary
evaporation. Column chromatography (1:3, EtOAc/
hexane) of the crude residue gave pure 42 as a pale-yellow
Coupling of 42 to polymer 47 (48). To a solution of 47
(12.3 g, 6.2 mmol, 1 equiv) in an anhydrous mixture of
1:1 CH2Cl2/THF (50 mL) was added TMAD (4.3 g,
24.8mmol, 4 equiv). The reaction was stirred until TMAD
was completely dissolved. A solution of 42 (10.0 g,
24.8mmol, 4 equiv) in an anhydrous mixture of 1:1
CH2Cl2/THF (25 mL) was then added, followed by tri-
butylphosphine (5.0 g, 24.8 mmol, 4 equiv) added drop-
wise over a period of 5 min. The reaction was stirred at
room temperature overnight, diluted with CH2Cl2
(35 mL), and then added dropwise, using an addition
funnel, to a solution of MeOH (650mL) and brine (7mL).
The resulting polymer (48) was stirred for 3 h, collected by
filtration, washed with MeOH (250 mL), and dried
under high vacuum to give a white solid (11.8 g, 96%
polymer recovery). 1H NMR (CDCl3) d 7.84 (br s), 7.66
(br t), 7.34 (br t), 6.20–7.22 (br d), 4.21 (br s), 3.84 (br s),
1.10–2.30 (br d), 1.02 (br s); 19F NMR (CDCl3) d ꢀ24.18.
1
oil in 70% yield. H NMR (CDCl3) d 7.82 (1H, s), 7.72
(1H, d, J=8.3 Hz), 7.63 (1H, d, J=7.9 Hz), 7.39 (1H, t,
J=7.8 Hz), 4.16 (2H, s), 3.62 (2H, t, J=6.4 Hz), 2.22
(1H, s), 1.49–1.59 (2H, m), 1.33–1.39 (2H, m), 0.98 (6H,
s); 19F NMR (CDCl3) d ꢀ24.28; 13C NMR (CDCl3) d
135.58, 130.27, 130.01 (t, JCF=6.3 Hz), 129.79 (t,
JCF=24 Hz), 125.77 (t, JCF=6.3 Hz), 122.67, 119.97 (t,
JCF=284 Hz), 83.22, 63.01, 34.32, 34.20, 26.77, 23.50.
LR-EIMS m/z (relative intensity) 205 (100), 126 (39),
115 (8), 101 (30), 83 (64), 69 (21), 55 (56). HR-EIMS
calcd for C14H19O4F2S1Br1 400.0156, found 400.0131.
4-Acetoxy non-crosslinked polystyrene polymer (46).21
A
solution of styrene (46 mL, 41.81 g, 401 mmol, 1 equiv),
4-acetoxystyrene (5.9 mL, 6.25 g, 37.02 mmol, 0.09
equiv), and VAZO (0.49 g, 2.01 mmol, 0.005 equiv) in
deoxygenated and anhydrous toluene (120 mL) was
heated at 95 ꢁC for 48 h under nitrogen. The reaction
was cooled to room temperature, then diluted with
CH2Cl2 (75 mL) and then added dropwise, using an
addition funnel, to a solution of MeOH (1.2 L) and
brine (10 mL). Polymer 46 was collected by filtration,
washed with MeOH (300 mL), and dried under high
vacuum to give a white solid (44 g). 1H NMR (CDCl3) d
6.30–7.60 (br d), 2.36 (br s), 1.30–2.25 (br d).
General method for Suzuki cross coupling on polymer 48
(general structure 49)
Polymer 48 (0.500 g, 0.27 mmol, 1 equiv), arylboronic
acid (0.81 mmol, 3 equiv), K2CO3 (0.112 g, 0.81 mmol, 3
equiv), and (PhCN)2PdCl2 (0.021 g, 0.054 mmol, 0.2
equiv) were placed in a round bottom flask, flushed with
nitrogen. Deoxygenated DMF (3 mL) was added fol-
lowed by the addition of water (0.049 mL, 2.7 mmol, 10
equiv). The reaction mixture was stirred at room tem-
perature and monitored by 19F NMR. Upon completion,
the reaction mixture was diluted with CH2Cl2 (10 mL)
and centrifuged twice to remove the palladium catalyst.
The supernatants were combined and concentrated by
rotary evaporation. The resulting polymer (general struc-
ture 49) was redissolved in CH2Cl2 (3 mL), precipitated
in a mixture of MeOH (25 mL) and a few drops of brine,
collected by filtration, and washed with MeOH. Percent
recovery of polymer ranged from 90–95%. Only a single
polymer-bound species was evident by 19F NMR.
4-Hydroxylated NCPS (47).21 To a solution of polymer
46 (5 g) in THF (40 mL) was added an aqueous solution
of NaOH (5 mL, 5 M). The reaction was refluxed for
24 h, cooled to room temperature, diluted with CH2Cl2
(10 mL), and then added dropwise, using an addition
funnel, to a solution of MeOH (300 mL) and brine
(3 mL). The polymer (47) was collected by filtration,
washed with MeOH (100 mL), and dried under high
vacuum to give a white solid (4.5 g, 90% polymer
1
recovered): H NMR (CDCl3) d 6.20–7.50 (br d), 4.48
(br s), 1.10–2.30 (br d).

C. Leung et al. / Bioorg. Med. Chem. 10 (2002) 2309–2323
2319
General method for cleaving the biaryl products from the
polymer
C14H8F5S1O3 351.0114, found 351.0120. HPLC reten-
tion time=16.0 min.
The polymer-bound biaryl derivatives (general structure
49, 1 equiv) and K2CO3 (3 equiv) were placed in a
50-mL test tube, equipped with a stir bar and stopper,
and dissolved in DMF (3 mL). Water (10 equiv) was
then added to the reaction mixture and heated at 80 ꢁC
for 17 h. The reaction was diluted with CH2Cl2 (3 mL)
and the polymer was precipitated out in a mixture of
MeOH (25 mL) and a few drops of brine. The polymer
was separated from the product by filtration, and the
filtrate was concentrated by rotary evaporation. To
remove trace amounts of polymer the following
wash procedure was performed. The crude reaction
product was dissolved in an aqueous solution of NaOH
(10 mL, 1.0 N) and washed with CH2Cl2 (3ꢃ10 mL).
The aqueous layer was acidified to pH ꢂ0.5 with HCl
(10 N). NaCl was added until a saturated solution was
obtained. The sulfonic acids were then extracted with
EtOAc (3ꢃ15 mL). The combined organic layers were
dried (MgSO4), filtered, diluted with toluene (50 mL),
and concentrated on a high vacuum rotary evaporator.
The sulfonic acids were then dissolved in water (3 mL)
and treated with NH4HCO3 (2.5 equiv). The solutions
were lyophilized and this procedure was repeated until a
constant weight was obtained. The biaryl sulfonates
[3 - (40 - Ethylphenyl)phenyl]difluoromethanesulfonic acid,
ammonium salt (54). H NMR (D2O) d 7.85 (1H, s),
7.61 (2H, d, J=8.0 Hz), 7.41–7.49 (3H, m), 7.16 (2H, d,
J=8.2 Hz), 2.49 (2H, q, J=7.67 Hz), 1.06 (3H, t,
J=6.7 Hz); 19F NMR (D2O) d ꢀ24.90. LR-ESMS m/z
(relative intensity) 311 (100). HR-ESMS calcd for
C15H13F2S1O3 311.0554, found 311.0559. HPLC reten-
tion time=18.2 min.
1
[3-(30 -Fluorophenyl)phenyl]difluoromethanesulfonic acid,
1
ammonium salt (55). H NMR (D2O) d 7.82 (1H, s),
7.83 (1H, d, J=7.0 Hz), 7.40–7.71 (5H, br m), 7.10–7.19
(1H, m); 19F NMR (D2O) d ꢀ25.25, ꢀ35.23. LR-ESMS
m/z (relative intensity) 301 (100). HR-ESMS calcd for
C13H8F3S1O3 301.0146, found 301.0152. HPLC reten-
tion time=13.7 min.
[3-(40 -Fluorophenyl)phenyl]difluoromethanesulfonic acid,
1
ammonium salt (56). H NMR (D2O) d 7.88 (1H, s),
7.78 (1H, d, J=7.4 Hz), 7.53–7.69 (4H, br m), 7.20 (2H,
t, J=8.92 Hz); 19F NMR (D2O) d ꢀ25.18, ꢀ37.15. LR-
ESMS m/z (relative intensity) 301 (100). HR-ESMS
calcd for C13H8F3S1O3 301.0146, found 301.0152.
HPLC retention time=13.8 min.
1
were obtained as off-white solids and analyzed by H
and 19F NMR, LRESMS, HRESMS and analytical
reverse-phase HPLC (for yields and purities, see Table
4). All HPLC analyses were performed using the fol-
lowing gradient (solvent A: acetonitrile; solvent B: water
with 0.1% TFA): 0–30 min: 77% A, 23% B; 30–35 min:
linear gradient of 77% A to 100% A; 35–45 min: 100%
A.
[3 - (30 - Chloro - 40 - fluorophenyl)phenyl]difluoromethane-
1
sulfonic acid, ammonium salt (57). H NMR (D2O) d
7.79 (1H, s), 7.43–7.66 (5H, br m), 7.22 (1H, t,
J=8.9 Hz); 19F NMR (D2O) d ꢀ25.15, ꢀ40.14. LR-
ESMS m/z (relative intensity) 335 (100). HR-ESMS
calcd for C13H7F3Cl1S1O3 334.9757, found 334.9762.
HPLC retention time=16.7 min.
[3 - (40 - Biphenyl)phenyl]difluoromethanesulfonic acid,
[3-(40-Methylphenyl)phenyl]difluoromethanesulfonic acid,
ammonium salt (58). H NMR (D2O) d 7.91 (1H, s),
7.80 (1H, d, J=7.6 Hz), 7.56–7.68 (4H, br m), 7.33 (2H,
d, J=7.9 Hz), 2.36 (3H, s); 19F NMR (D2O) d ꢀ25.02.
LR-ESMS m/z (relative intensity) 297 (100). HR-ESMS
calcd for C14H11F2S1O3 297.0397, found 297.0402.
HPLC retention time=16.0 min.
1
1
ammonium salt (50). H NMR (CD3OD) d 7.98 (1H, s),
7.65–7.82 (8H, br m), 7.33–7.57 (4H, br m); 19F NMR
(D2O) d ꢀ24.41. LR-ESMS m/z (relative intensity) 359
(100). HR-ESMS calcd for C19H13F2S1O3 359.0554,
found 359.0559. HPLC retention time=22.1 min.
[3 - (20 - Naphthyl)phenyl]difluoromethanesulfonic acid,
1
ammonium salt (51). H NMR (D2O) d 7.62–7.75 (5H,
[3 - (4ꢀ - Chlorophenyl)phenyl]difluoromethanesulfonic
1
m), 7.22–7.49 (6H, br m); 19F NMR (D2O) d ꢀ25.04.
LR-ESMS m/z (relative intensity) 333 (100). HR-ESMS
calcd for C17H11F2S1O3 333.0397, found 333.0402.
HPLC retention time=18.4 min.
acid, ammonium salt (59). H NMR (D2O) d 7.83 (1H,
s), 7.64 (2H, d, J=7.0 Hz), 7.47–7.54 (3H, m), 7.36 (2H,
d, J=8.3 Hz); 19F NMR (D2O) d ꢀ25.03. LR-ESMS m/
z (relative intensity) 317 (100). HR-ESMS calcd for
C13H8F2Cl1S1O3 316.9851, found 316.9856. HPLC
retention time=16.8 min.
[3-(40-Acetylphenyl)phenyl](difluoro)methylsulfonic acid,
1
ammonium salt (52). H NMR (D2O) d 7.75–7.79 (3H,
m), 7.64 (1H, d, J=7.5 Hz), 7.57 (1H, d, J=7.5), 7.44–
7.49 (3H, m), 2.50 (3H, s); 19F NMR (D2O) d ꢀ24.94.
LR-ESMS m/z (relative intensity) 325 (100). HR-ESMS
calcd for C15H11F2S1O4 325.0346, found 325.0352.
HPLC retention time=11.9 min.
[3 - (40 - tert - Butylphenyl)phenyl]difluoromethanesulfonic
1
acid, ammonium salt (60). H NMR (D2O) d 7.79 (1H,
s), 7.59 (1H, d, J=5.6 Hz), 7.08–7.34 (6H, br m), 0.95
(9H, s); 19F NMR (D2O) d ꢀ24.52. LR-ESMS m/z
(relative intensity) 339 (100). HR-ESMS calcd for
C17H17F2S1O3 339.0867, found 339.0872. HPLC reten-
tion time=22.3 min.
[3 - (40 - Trifluoromethylphenyl)phenyl]difluoromethane-
1
sulfonic acid, ammonium salt (53). H NMR (D2O) d
7.92 (1H, s), 7.69–7.80 (6H, m), 7.58 (1H, t, J=7.8 Hz);
19F NMR (D2O) d 16.21, ꢀ25.08. LR-ESMS m/z (rela-
tive intensity) 351 (100). HR-ESMS calcd for
[3 - (30 - Trifluoromethylphenyl)phenyl]difluoromethane-
1
sulfonic acid, ammonium salt (61). H NMR (D2O) d
7.93 (2H, d, J=6.4 Hz), 7.82 (2H, t, J=7.5 Hz), 7.55–

2320
C. Leung et al. / Bioorg. Med. Chem. 10 (2002) 2309–2323
7.70 (4H, br m); 19F NMR (D2O) d 16.10, ꢀ25.20. LR-
ESMS m/z (relative intensity) 351 (100). HR-ESMS
calcd for C14H8F5S1O3 351.0114, found 351.0120.
HPLC retention time=15.5 min.
[3 - (30 - Thiophene)phenyl]difluoromethanesulfonic acid,
ammonium salt (69). H NMR (D2O) d 7.95 (1H, s),
7.84 (1H, d, J=7.84 Hz), 7.71–7.73 (1H, m), 7.50–7.63
(4H, br m); 19F NMR (D2O) d ꢀ25.11. LR-ESMS m/z
(relative intensity) 289 (100). HR-ESMS calcd for
C11H7F2S2O3 288.9805, found 288.9810. HPLC reten-
tion time=12.8 min.
1
[3-(20-Methylphenyl)phenyl]difluoromethanesulfonic acid,
1
ammonium salt (62). H NMR (D2O) d 7.53–7.71 (4H,
br m), 7.29–7.39 (4H, br m), 2.23 (3H, s); 19F NMR
(D2O) d ꢀ25.08. LR-ESMS m/z (relative intensity)
297 (100). HR-ESMS calcd for C14H11F2S1O3
297.0397, found 297.0402. HPLC retention time=
15.2 min.
[3 - (20 - Furanphenyl)phenyl]difluoromethanesulfonic acid,
1
ammonium salt (70). H NMR (D2O) d 8.02 (1H, s, Ar-
H), 7.93 (1H, d, J=6.6 Hz, Ar–H), 7.56–7.64 (3H, m,
Ar–H), 6.93 (1H, d, J=3.6 Hz, Ar–H), 6.62 (1H, s, Ar–
H); 19F NMR (D2O) d ꢀ25.38. LR-ESMS m/z (relative
intensity) 273 (100). HR-ESMS calcd for C11H7F2S1O4
273.0033, found 273.0039. HPLC retention time=
12.1 min.
[3-(30-Chlorophenyl)phenyl]difluoromethanesulfonic acid,
ammonium salt (63). 1H NMR (D2O) d 7.89 (1H, d,
J=7.7 Hz), 7.68 (2H, d, J=8.0 Hz), 7.55–7.62 (2H, m),
7.40–7.43 (2H, m); 19F NMR (D2O) d ꢀ25.23. LR-
ESMS m/z (relative intensity) 317 (100). HR-ESMS
calcd for C13H8F2Cl1S1O3 316.9851, found 316.9856.
HPLC retention time=16.7 min.
[3-(50-Acetyl-20-thiophene)phenyl]difluoromethanesulfonic
acid, ammonium salt (71). Although HRESMS, 19F and
1H NMR indicated that 71 was obtained, HPLC analy-
sis indicated that it was only 77% pure. 19F NMR ana-
lysis indicated 90% purity. This compound was
resynthesized in solution (see below). For complete
characterization data, see below the description of
compound 71 synthesized using solution-phase meth-
odologies.
[3 - (10 - Naphthyl)phenyl]difluoromethanesulfonic acid,
1
ammonium salt (64). H NMR (D2O) d 7.88 (1H, s),
7.62 (2H, d, J=10.3 Hz), 7.18–7.54 (8H, br m); 19F
NMR (D2O) d ꢀ24.73. LR-ESMS m/z (relative inten-
sity) 333 (100). HR-ESMS calcd for C17H11F2S1O3
333.0397, found 333.0402. HPLC retention time=
18.9 min.
[3-(20-Benzo[b]thiophene)phenyl] difluoromethanesulfonic
1
acid, ammonium salt (72). H NMR (D2O) d 7.78 (1H,
[3 - (30,50 - Dichlorophenyl)phenyl]difluoromethanesulfonic
acid (65). Although HR-ESMS, 19F and 1H NMR
indicated that 65 was obtained, ESMS revealed
that a significant quantity (ꢂ9%) of compound
74 was also present. This compound was not evi-
dent by 19F NMR and HPLC analysis which indi-
cated that 65 was obtained in 96–98% purity. This
compound was resynthesized in solution. For com-
plete characterization data, see below description of
compound 65 synthesized using solution-phase
methodologies.
s), 7.50 (1H, d, J=7.3 Hz), 7.37 (1H, d, J=6.9 Hz), 7.29
(2H, m), 7.17 (1H, t, J=7.7 Hz), 7.08 (1H, s), 6.94–7.03
(2H, m); 19F NMR (D2O) d ꢀ24.91. LR-ESMS m/z
(relative intensity) 339 (100). HR-ESMS calcd for
C15H9F2S2O3 338.9961, found 338.9967. HPLC reten-
tion time=21.3 min.
[3-(20-Benzo[b]furan)phenyl]difluoromethanesulfonic acid,
1
ammonium salt (73). H NMR (D2O) d 7.87 (1H, s),
7.43–7.53 (2H, m), 7.09–7.27 (3H, br m), 6.88–7.00 (2H,
br m), 6.55 (1H, s); 19F NMR (D2O) d -25.06. LR-
ESMS m/z (relative intensity) 323 (100). HR-ESMS
calcd for C15H9F2S1O4 323.0190, found 323.0195.
HPLC retention time=17.0 min.
[3 - (30,40 - Dichlorophenyl)phenyl]difluoromethylsulfonic
1
acid, ammonium (66). H NMR (D2O) d 7.85 (1H, s),
7.67–7.75 (3H, m), 7.45–7.59 (3H, m); 19F NMR (D2O)
d ꢀ25.10. LR-ESMS m/z (relative intensity) 351 (100).
HR-ESMS calcd for C13H7F2Cl2S1O3 350.9461, found
350.9466. HPLC retention time=21.0 min.
Synthesis of 65 and 71 using solution-phase
methodologies
3,5-Dichloro-30-methyl-1,10-biphenyl (75). To a solution
of Pd(PPh3)4 (0.875 g, 0.75 mmol, 0.03 equiv) in DME
(100 mL) under nitrogen was added 3-bromotoluene
(3.0 mL, 25 mmol, 1 equiv) and the resulting solution
was stirred for 20 min. An aqueous solution of sodium
carbonate (2.78 g, 26 mmol, 1.05 equiv, 75 mL) was
added followed by the addition of a solution of 3,5-
dichlorobenzeneboronic acid (5.0 g, 25 mmol, 1 equiv)
in DME (75 mL). The mixture was refluxed 3 h. After
cooling to room temperature, the organic layer was
washed with 5% sodium bicarbonate (3ꢃ350 mL) and
once with brine. The organic layer was dried, filtered
and concentrated. Silica gel column chromatography in
100% hexanes gave pure 75 as white solid in 84% yield:
[3 - (40 - Methoxyphenyl)phenyl]difluoromethanesulfonic
acid, ammonium salt (67). H NMR (D2O) d 7.80 (1H,
s), 7.60 (2H, t, J=7.0 Hz), 7.43–7.50 (3H, m), 6.93 (2H,
d, J=8.7 Hz), 3.75 (3H, s); 19F NMR (D2O) d ꢀ24.98.
LR-ESMS m/z (relative intensity) 313 (100). HR-ESMS
calcd for C14H11F2S1O4 313.0346, found 313.0352.
HPLC retention time=13.8 min.
1
[3 - (20 - Thiophene)phenyl]difluoromethanesulfonic acid,
1
ammonium salt (68). H NMR (D2O) d 7.94 (1H, s),
7.84 (1H, d, J=7.0 Hz), 7.45–7.63 (4H, br m), 7.15 (1H,
t, J=4.4 Hz); 19F NMR (D2O) d ꢀ25.30. LR-ESMS m/z
(relative intensity) 289 (100). HR-ESMS calcd for
C11H7F2S2O3 288.9805, found 288.9810. HPLC reten-
tion time=13.4 min.
ꢁ
1
mp 43–45 C. H NMR (CDCl3) 7.2–7.45 (7H, m), 2.41
(3H, s). LR-EIMS m/z (relative intensity) 236 (100), 292

C. Leung et al. / Bioorg. Med. Chem. 10 (2002) 2309–2323
2321
(3). HR-EIMS calcd for C10H13Cl2 236.0160, found
400.0156.
HR-EIMS calcd for C18H20SO3Cl2 386.0510, found
386.0519.
3-(3,5-Dichlorophenyl)phenylmethanesulfonic acid, sodium
salt (76). To a solution of AIBN (16 mg, 0.1 mmol, 0.02
equiv) and N-bromosuccinimide (0.98 g, 5.5 mmol, 1.1
equiv) in benzene (25 mL) was added 75 (1.19 g, 5 mmol,
1 equiv) and the solution refluxed for 1 h. The reaction
was cooled to room temperature, the mixture was
washed with water (3ꢃ25 mL), and the organic layer
was dried (MgSO4) and concentrated. Column chroma-
tography in 100% hexanes yielded a white solid which
was a mixture of mono and dibrominated product as
determined by 1H NMR. No attempt was made to
separate these two compounds. To a solution of the
crude material (1.85 g, approx 5.85 mmol) in acetone
(15 mL) was added an aqueous solution of sodium sul-
fite (0.77 g, 6.11 mmol, 10 mL) and the mixture was
refluxed for 12 h. After cooling to room temperature,
the solution was concentrated in vacuo and filtered. The
filter cake was washed with water (5 mLꢃ2) and CH2Cl2
(20 mLꢃ2) and dried under high vacuum overnight to
give pure 76 as white solid in 66% yield. 1H NMR
(D2O) d 4.08 (s, 2H), 7.45–7.24 (m, 7H); 13C NMR
(D2O) d 56.78, 125.42, 126.46, 127.04, 128.85, 129.26,
130.35, 132.54, 134.75, 138.26, 143.13. LR-ESMS m/z
315 (100).
Neopentyl-[3-(3,5-dichlorophenyl)phenyl]difluoromethane-
sulfonate (79). To a solution of 78 (0.200 g, 0.52 mmol)
and NFSi (0.487 g, 1.56 mmol) in dry THF (12 mL) at
ꢀ78 ꢁC under nitrogen was added a 1 M solution of
NaHMDS in THF (1 M, 1.3 mL, 1.3 mmol) dropwise
over a period of 1 h. The solution was then maintained
at ꢀ78 ꢁC for another 2 h, an then allowed to warm to
room temperature. After stirring at room temperature
for 1 h, the reaction was quenched with saturated
NH4Cl, extracted with ether (3ꢃ30 mL), washed with
water (2ꢃ30 mL), dried (MgSO4) and concentrated to
give a white solid. Flash chromatography of the crude
(5:1Hexane/EtOAc) gave pure 79 as white solid in 87%
yield: mp 72–73 ꢁC. H NMR (CDCl3) d 1.01 (s, 9H),
1
4.15 (s, 2H), 7.37 (t, J=2.0 Hz, 1H), 7.45 (d, J=2.0 Hz,
2H), 7.59 (t, J=8.0 Hz, 1H), 7.72(m, 2H), 7.82 (s, 1H);
13C NMR (CDCl3) d 25.82, 32.30, 84.65, 120.58 (t,
J=284.2 Hz), 125.56 (t, J=5.8 Hz) 127.03 (t,
J=5.8 Hz), 128.04, 128.99 (t, J=22.0 Hz), 129.57,
131.06, 135.63, 139.36, 142.55; 19F NMR (CDCl3) d
ꢀ24.53. LR-EIMS m/z (relative intensity) 423 (2), 422
(5), 271 (100). HR-EIMS calcd for C18H18SO3Cl2F2
422.0322, found 422.0325.
[3 - (3,5 - Dichlorophenyl)phenyl]difluoromethanesulfonic
acid, ammonium salt (65). To a solution of 79 (0.15 g,
0.355 mmol) in DMF (5 mL) was added K2CO3 (0.147 g,
1.06 mmol) and water (0.1 mL) and the mixture was
heated to 80 ꢁC for 17 h. The mixture was allowed to
cool to room temperature and then concentrated by
high vacuum rotary evaporation. The residue was dis-
solved in water (15 mL), acidified to pH 0.5 with 3 N
HCl saturated with NaCl, extracted with ethyl acetate
(5ꢃ30 mL), the organic were dried (MgSO4), and then
concentrated to give an off-white solid. The solid was
dissolved in an aqueous solution of NH4HCO3 (4 mL of
0.25 N) and lyophilized. This process was repeated until
a constant weight was obtained. This gave pure 65 as a
white solid in 99% yield: dec. 165 ꢁC. 1H NMR (D2O) d
6.75 (s, 1H), 6.89 (m, 3H), 7.02 (t, J=7.4 Hz, 1H), 7.36
(d, J=8.0 Hz, 1H), 7.44 (s, 1H); 13C NMR (D2O) d
122.55 (t, J=277.4 Hz), 127.44 (t, J=6.7 Hz), 127.83,
129.20 (t, J=6.7 Hz), 129.89, 131.74, 132.17, 133.68 (t,
J=23.8 Hz),137.40, 140.56, 144.72; 19F NMR (D2O) d
ꢀ27.57. LR-ESMS m/z (relative intensity) 351 (100).
HR-ESMS calcd for C13H7F2Cl2S1O3 350.9461, found
350.9466. HPLC retention time=22.1 min.
3-(3,5-Dichlorophenyl)phenylmethanesulfonyl chloride (77).
To a suspension of 76 (1.00 g, 2.95 mmol) in acetonitrile
(10 mL) under nitrogen was added freshly distilled
POCl3 (1.37 mL, 14.75 mmol). After refluxing for 10 h,
the reaction was cooled to room temperature and dilu-
ted with ether (30 mL), and then poured into a mixture
of ether (70 mL) and ice (ꢂ30 g). The ether layer was
washed with cold water (2ꢃ20 mL) and brine (20 mL),
and dried over MgSO4 and concentrated to give 77 as
an off-white solid 77% yield: mp 79–80 ꢁC. H NMR
1
(CDCl3) d 4.91 (s, 1H), 7.35 (t, J=7.4 Hz, 1H), 7.43 (d,
J=7.4 Hz, 2H), 7.45 (m, 2H), 7.62 (m, 2H); 13C NMR
(CDCl3): d 70.67, 125.81, 127.17, 127.90, 129.05, 130.03,
130.09, 131.34, 135.59, 139.79, 142.89; LR-EIMS m/z
(relative intensity) 334 (32), 336 (33), 235 (55), 165 (30).
HR-EIMS calcd for C13H9SO2Cl3 333.9389, found
333.9401.
Neopentyl 3-(3,5-dichlorophenyl)phenylmethanesulfonate
(78). To a solution of 77 (0.70 g, 2.09 mmol) in dry
THF (10 mL) under nitrogen was added neopentyl
alcohol (0.37 g, 4.2 mmol). The solution was cooled to
0 ꢁC, and 2,6-lutidine (0.5 mL, 4.2 mmol) was added.
The mixture was warmed to room temperature and
stirred overnight. The reaction was diluted with ether
(60 mL), washed with 0.1 N HCl and water, dried
(MgSO4) and concentrated to give a white solid.
Flash chromatography (5:1, hexane/EtOAc) of the
crude mixture yield pure 78 as white solid in 72%
Neopentyl 3-bromophenylmethanesulfonate (80). Prepared
in 70% yield from 43 using the same procedure as that
used for preparing 78 from 77. Pure product was
obtained by recrystallization in hexane/EtOAc (white
crystals): mp 87–88 ꢁC. 1H NMR (CDCl3) d 0.90 (s,
9H), 3.74 (s, 2H), 4.29 (s, 2H), 7.26 (t, J=7.9 Hz, 1H),
7.34 (d, J=7.9 Hz, 1H), 7.50 (d, J=7.9 Hz, 1H), 7.55 (s,
1H); 13C NMR (CDCl3) d 25.91, 31.78, 55.76, 79.60,
122.65, 129.27, 130.07, 130.32, 132.12, 133.59. LR-
EIMS m/z (relative intensity) 321 (3), 320 (18), 320
(18),169 (100), 171 (100). HR-EIMS calcd for
C12H17SO3Br, 320.0081, found 320.0095.
yield: mp 69–70 ꢁC. H NMR (CDCl3) d 0.93 (s, 9H),
1
3.81 (s, 2H), 4.41 (s, 2H), 7.36 (t, J=1.5 Hz, 1H), 7.42–
7.56 (m, 6H); 13C NMR (CDCl3) d 25.94, 31.77, 56.26,
79.42, 125.61, 127.51, 127.62, 128.93, 129.32, 129.53,
130.62, 135.36, 139.19, 143.17. LR-EIMS m/z (relative
intensity) 387 (5), 386 (22), 388 (17), 235 (100), 165 (37).

2322
C. Leung et al. / Bioorg. Med. Chem. 10 (2002) 2309–2323
Neopentyl (3-bromophenyl)difluoromethanesulfonate (81).
Prepared in 87% yield from 80 using the same proce-
dure as that used for preparing 79 from 78 (colorless
7.84 (1H, s, Ar–H), 7.72 (1H, d, J=8.0 Hz, Ar–H), 7.64
(1H, d, J=7.3 Hz, Ar-H), 7.39 (1H, t, J=8.1 Hz, Ar–
H), 7.11 (2H, d, J=8.0 Hz, Ar–H), 6.82 (2H, d,
J=8.8 Hz, Ar–H), 4.19 (2H, s, CH2O), 3.93 (2H, t,
J=6.2 Hz, CH2), 2.59 (2H, q, J=7.6 Hz, CH2), 1.73–
1.85 (2H, m, CH2), 1.44–1.54 (2H, m, CH2), 1.21 (3H, t,
J=7.7 Hz, CH3), 1.03 (6H, s, CH3); 19F NMR (CDCl3)
d ꢀ24.19; 13C NMR (CDCl3) d 157.18, 136.53, 135.62
(t, JCF=1.8 Hz), 130.28, 130.21 (t, JCF=6.4 Hz), 128.70,
125.86 (t, JCF=6.0 Hz), 122.81, 120.15, 114.65, 82.99,
63.38, 34.85, 34.52, 28.00, 23.95, 23.64, 15.72. MS m/z
(relative intensity) 504 (28), 205 (59), 122 (100), 107 (65),
97 (29), 83 (25), 55 (52). HRMS calcd for
C22H27O4F2S1Br1 504.0782, found 504.0774.
1
oil). H NMR (CDCl3) d 1.00 (s, 9H), 4.11 (s, 2H), 7.36
(t, J=7.8 Hz, 1H), 7.62 (d, J=7.8 Hz, 1H), 7.71 (d,
J=7.8 Hz, 1H), 7.81 (s, 1H); 13C NMR (CDCl3) d
25.91, 32.23, 84.81, 122.83 (t, J=283.5 Hz), 123.90,
125.93 (t, J=6.1 Hz), 130.05 (t, J=22.7 Hz), 130.22 (t,
J=6.7 Hz), 130.39, 135.70; 19F NMR (CDCl3) d
ꢀ24.74. LR-EIMS m/z (relative intensity) 357 (1), 356
(3), 358 (18), 207 (93), 205 (100). HR-EIMS calcd for
C12H15SO3BrF2, 355.9893, found 355.9895.
Neopentyl-3-(5-acetyl-2-thienyl)methanesulfonate (82).
To a solution of 81 (0.476 g, 1.33 mmol) in deox-
ygenated DMF (20 mL), was added 5-acetyl-2-thie-
nylboronic acid (0.339 g, 1.99 mmol), K2CO3 (0.55 g,
4 mmol), Pd(OAc)2 (30 mg, 0.13 mmol) and H2O
(0.27 mL, 15 mmol). The reaction was stirred at room
temperature under nitrogen for 2 h. The reaction was
diluted with ether, washed with saturated NH4Cl, water
and brine, dried (MgSO4) and concentrated to give a
light-yellow solid. Flash chromatography of the crude
product (5:1 hexane/EtOAc) gave pure 82 in 87% yield
(white solid): mp 88–89 ꢁC. 1H NMR (CDCl3) d 1.00 (s,
9H), 2.56 (s, 3H), 4.13 (s, 2H), 7.36 (d, J=3.9 Hz, 1H),
7.54 (t, J=7.9 Hz, 1H), 7.65 (m, 2H), 7.82 (d, J=7.9 Hz,
1H), 7.91 (s, 1H); 13C NMR (CDCl3) d 25.911, 26.67,
32.22, 84.77, 120.73 (t, J=283.9 Hz), 124.72 (t,
J=6.0 Hz), 125.11, 127.37 (t, J=5.5 Hz), 129.16 (t,
J=22.2 Hz), 129.76, 130.14, 133.46, 134.22, 144.23,
150.32, 190.59; 19F NMR (CDCl3) d ꢀ24.74. EIMS m/z
402 (30), 332 (29), 251 (100). HREIMS calcd for
C18H20SO4F2, 402.0771, found 402.0785.
Kinetic studies with PTP1B
Rates of PTP1B-catalyzed dephosphorylation in the
presence or absence of inhibitors were determined using
fluorescein diphosphate (FDP at Km concentration
ꢀ20 mM) as substrate in assay buffer containing 50 mM
Bis-Tris (pH 6.5), 2 mM EDTA, 5 mM N,N0-dimethyl-
N,N0-bis(mercaptoacetyl)hydrazine (DMH) or dithio-
threitol (DTT), 0.01% triton X-100 and 5% DMSO.
For peptides 7–9 and compounds 50–73, assays were
carried out at 25 ꢁC in 96-well plates with total volume
of 200 mL per well. Reactions were initiated by the
addition of PTP1B (final concentration 0.2 mg/mL). The
phosphatase activity was followed by monitoring the
production of the fluorescent product fluorescein
monophosphate (FMP) continuously for 10 min using
the Cytofluor II plate reader (PerSeptive Biosystems),
with excitation at 440 nm (slit width 20 nm) and emis-
sion 530 nm (slit width 25 nm), or the SPECTRAmax
GEMINI XS (Molecular Devices) dual-scanning
microplate spectrofluorometer, with excitation at
485 nm and emission at 538 nm. For compounds 28–40,
assays were carried out in 1 mL cuvettes with total
volumes of 700 mL. The phosphatase activity was fol-
lowed by monitoring the production of FMP at 450 nm
using a Varian Cary 1 spectrophotometer. IC50’s were
determined using at least nine different inhibitor con-
centrations. For Ki determinations (peptides 7–9),
substrate concentrations of 15, 20, 25, 35, and 50 mM
were used. 1/v versus 1/[S] plots were obtained which
exhibited competitive inhibition patterns for all three
peptides. The slopes of these plots were determined
using Microsoft Excel. These slopes were replotted
against the concentration of the inhibitor using
Microsoft Excel and the Ki was obtained from the x-
intercept of this replot.
3 - (5 - Acetyl - 2 - thienyl)difluoromethanesulfonic acid,
ammonium salt (71). Prepared in 98% yield from 82
using the same procedure as thatꢁused for preparing 65
1
from 79 (white solid): dec. at 122 C. H NMR (D2O) d
2.21 (s, 3H), 6.97 (d, J=4.0 Hz, 1H), 7.18 (t, J=7.8 Hz,
1H), 7.32 (m, 2H), 7.40 (d, J=7.8 Hz, 1H), 7.52 (s, 1H);
13C NMR (D2O) d 25.54, 119.73 (t, J=277.2 Hz),
123.66 (t, J=6.5 Hz), 125.36, 127.06 (t, J=5.9 Hz),
128.55, 129.23, 131.00 (t, J=23.3 Hz), 132.47, 136.54,
141.53, 151.86, 195.19; 19F NMR (D2O) d ꢀ28.27. LR-
ESMS m/z (relative intensity) 331 (100). HR-ESMS
calcd for C13H9F2S2O4 330.9910, found 330.9916.
HPLC retention time=11.8 min.
[{5 - (4 - Ethylphenoxy) - 2,2 - dimethylpentyl}(3-bromo-
phenyl)]difluoromethane-sulfonate (83). To a solution of
4-ethylphenol (0.101 g, 0.83 mmol, 1 equiv) in 1:1 anhyd
THF/CH2Cl2 (45 mL) was added TMAD (0.287 g,
1.66 mmol, 2 equiv). Once the TMAD was completely
dissolved, a solution of 42 (0.665 g, 1.66 mmol, 2 equiv)
in 1:1 anhyd THF/CH2Cl2 (25 mL) was added. Tribu-
tylphosphine (0.427 mL, 0.35 g, 1.66 mmol, 2 equiv) was
then added dropwise to the reaction mixture over a
period of 5 min. The reaction was stirred at room tem-
perature for 3 h and then concentrated by rotary eva-
poration. Column chromatography (1:1, CH2Cl2/
hexane) of the crude residue yielded pure 83 as a white
Acknowledgements
We thank Sunia Afzaal, Gary Kruppa and Paul Speir at
BrukerDaltonics for obtaining the high-resolution
FTICR-ES mass spectra.
References and Notes
solid in 96% yield: mp 36–37 ꢁC. H NMR (CDCl3) d
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been reported to be an effective phenylphosphate mimetic for
obtaining PTP1B inhibitors when incorporated into small
molecule inhibitors. This functionality has not been incorpo-
rated into a peptidyl scaffold, therefore, we are unable to
compare this group with those listed in Table 2. See: Andersen
H. S., Iversen L. F., Jeppesen, C. B., Branner, S., Norris, K.,
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22. Sodium (3-bromophenyl)methanesulfonate was prepared
by reacting 3-bromobenzyl bromide with Na2SO3 in refluxing
acetone/water for 48 h.
23. 5-{[1-(tert-Butyl)-1,1-dimethylsilyl]oxy}-2,2-dimethyl-1-
pentanol was prepared by reaction of 2,2-dimethyl-1-pentanol24
with TBDMSCl in the presence of 2 equiv imidazole in DMF.
24. Lambert, J. B.; Vagenas, A. R. Org. Magn. Reson. 1981,
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8. Burke, T. R.; Yao, Z.-J.; Liu, D.-G.; Voight, J.; Gao, Y.
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