Design and synthesis of novel fluoropeptidomimetics as potential mimics of the transition state during peptide hydrolysis

Article abstract of DOI:10.1021/jo026310c

α-Fluoroamino acids were targeted in our ongoing efforts to design novel fluoropeptidomimetics (1) as potential protease inhibitors. α-Fluoroglycine derivative (2) and α-fluoro-β-aminoethanethiol derivatives (3-9) were synthesized for the first time en ro

Full text of DOI:10.1021/jo026310c

Design a n d Syn th esis of Novel F lu or op ep tid om im etics a s P oten tia l
Mim ics of th e Tr a n sition Sta te d u r in g P ep tid e Hyd r olysis
Subhash C. Annedi,† Weiyong Li,† Sheeba Samson,† and Lakshmi P. Kotra*,†,‡
Faculty of Pharmacy, Molecular Design and Information Technology Center, and
Department of Chemistry, University of Toronto, 19 Russell Street, Toronto, Ontario, M5S 2S2, Canada
p.kotra@utoronto.ca
Received August 12, 2002
R-Fluoroamino acids were targeted in our ongoing efforts to design novel fluoropeptidomimetics
(1) as potential protease inhibitors. R-Fluoroglycine derivative (2) and R-fluoro-â-aminoethanethiol
derivatives (3-9) were synthesized for the first time en route to obtain the peptidomimetic moiety
1. The stability of 2-9 was investigated under organic as well as aqueous conditions. The stability
of 3-9 under acidic and basic conditions, the effect of substitution at C-2 position, and potential
biological activities are discussed.
In tr od u ction
Peptidomimetics have been a focus of investigation for
several years and some transition-state analogues that
mimic the transition state during the hydrolysis of a
peptide bond have been successful therapeutic agents.1
The transition-state analogue strategy is based on the
hypothesis that enzymes bind tighter to their transition
states than to their corresponding substrate or the
products.2 Such strategies involving peptidomimetics
include the hydroxyethylene moiety, where the tetrahe-
dral oxyanion species during peptide hydrolysis is sub-
stituted with a hydroxyethylene moiety, and the latter
is more stable than the oxyanion species under physi-
ological conditions for therapeutic development.3,4
The mechanism of hydrolysis of a peptide bond by a
serine protease involves an oxyanion species (Figure 1).4
This species is formed two times during the hydrolysis
of one peptide bond, once during the acylation of the
protease and then again during the deacylation of the
acyl-enzyme species by a water molecule. Fluoropepti-
domimetics, such as the derivatives of R-fluoroethylamine
or R-fluoroethanethiol or R-fluoroethanol (Figure 1), are
designed to mimic the oxyanion by a fluorine atom and
the -NH- in the peptide bond by a -S- or -O-. In
these compounds the sp2-hybridized carbonyl group
(Scheme 1) in the peptide moiety such as in 10 (planar)
is substituted by an sp3-tetrahedral carbon with a
F IGURE 1.
fluorine atom generating a peptidomimetic such as 1. The
latter tetrahedral carbon with a fluorine substitution may
mimic the transition state during the hydrolysis of
peptide bond by proteases. The design of the peptidomi-
metic moiety 1 is based on the hypothesis that the
fluorine atom will occupy the position of the oxyanion in
the active site of serine proteases and interact with the
oxyanion hole via hydrogen bonds. This interaction may
result in the elimination of fluorine facilitated by the lone
pair electrons on the heteroatom (X ) NH, S, O). This
would generate a reactive species such as 11 in the active
site of the protease, leading to the formation of a covalent
bond between the species 11 and a nucleophilic residue
in the vicinity such as a serine. Key moiety 12 was
designed as the prototype moiety with X ) NH or S,
which may be derivatized to obtain the intended com-
pounds such as 1. R-Fluoroglycine derivatives (13) and
2-amino-R-fluoroethanethiol derivatives (14) are good
starting points to prepare target compounds such as 1
(X ) NH, S). Preparation of compounds such as 13 and
14 has been of interest to some research groups in the
* Corresponding author: Tel. (416) 978-2882. Fax. (416) 978-8511.
† Faculty of Pharmacy, Molecular Design and Information Technol-
ogy Center.
‡ Department of Chemistry.
(1) Radzicka, A.; Wolfenden, R. Methods Enzymol. 1995, 249, 284-
312.
(2) Schramm, V. L. Annu. Rev. Biochem. 1998, 67, 693-720.
(3) (a) Mobashery, S.; Kotra, L. P. Encyclopedia of life sciences;
Macmillan Publishers Ltd., Nature Publishing Group: New York, 2002
(www.els.net) and references cited therein. (b) Powers, J . C.; Harper,
J . W. Proteinase Inhib. 1986, 55-152. (c) Babine, R. E.; Bender, S. L.
Chem. Rev. 1997, 97, 1359-1472.
(4) Leung, D.; Abbenante, G.; Fairlie, D. P. J . Med. Chem. 2000,
43, 305-341.
10.1021/jo026310c CCC: $25.00 © 2003 American Chemical Society
Published on Web 01/11/2003
J . Org. Chem. 2003, 68, 1043-1049
1043

Annedi et al.
SCHEME 1
F IGURE 2. 1H NMR spectra during the reaction between
benzylamine and ethyl bromofluoroacetate at t ) 0 (a), 5 (b),
10 (c), 20 (e), 60 (f), and 120 min (g). The reaction was carried
out in deuterated dimethyl formatminde. The methylene peak
is shown by an arrow.
SCHEME 2
past.5 Several attempts were reported in the literature
to obtain both R-fluoro amino acids as well as R-fluoro-
â-aminoethanethiol derivatives.6 Many attempts failed
due to the chemical instability of the “-NH-CHF-”
moiety. Recently, Bailey et al. reported the synthesis of
trimethylammonium R-fluoroglycine; however, no success
has been reported so far in preparing R-fluoroglycine
without a quaternary amine.7 This report describes our
successful synthesis of R-fluoroglycine (2) containing the
-NH-CHF- moiety, several R-fluoro-â-aminoethaneth-
iol derivatives 3-9, and their chemistry. Some insight
into the stability of these compounds and their biological
compatibility and potential biological activities are re-
vealed for the first time.
gave R-fluoro-N-benzyl ethyl glycine 2 in 21% yield
(Scheme 2). The same reaction in other solvents such as
THF, DMSO, and CHCl3 did not yield an isolable product,
but a complex mixture was obtained as observed on TLC.
In our experiments, a prolonged reaction time either
reduced the yield or resulted in no product isolation.
Compound 2 was characterized using 1H, 13C, and 19F
NMR and mass spectral analyses. This reaction was
monitored by conducting the experiment in an NMR tube
using DMF-d7 as the solvent and recording 1H NMR
spectra at various time points. A characteristic peak at
4.85 ppm for the methylene protons of benzyl moiety were
observed as the reaction progressed (Figure 2). A gradual
appearance of this characteristic peak at 4.85 ppm up to
120 min was noted, implying the formation of the R-fluoro
analogue 2 in situ. On the basis of the TLC and isolated
yields (21%), the reaction did not appear to go to
completion; thus, in the NMR experiments, we did not
observe completion of the reaction, even up to 120 min.
We attempted the reduction of ethyl ester 2 to obtain
the alcohol en route to the amino derivative 12. Reduction
of ethyl ester 2 using NaBH4 or DIBAL-H at 0 °C did
not yield the desired product. Conceivably, these reaction
conditions are causing the fluoride elimination leading
toward decomposed products. Following the synthesis of
2, we were interested in exploring R,R-difluoroglycine
derivatives. Ethyl bromodifluoroacetate was treated with
benzylamine to obtain compound 15 as the only product
Resu lts a n d Discu ssion
We first started investigating the synthesis of R-fluoro-
R-amino acids, particularly glycine derivatives, because
these compounds could serve as precursors to synthesize
target intermediates such as 1. Many unsuccessful at-
tempts were made, which included the fluorination of
N-diprotected R-amino acids, conversion of the amide
ketone into difluoro derivative, or reduction of the amide
ketone in to the corresponding alcohol. In the course of
these investigations, treatment of benzylamine with ethyl
bromofluoroacetate in anhydrous DMF at 0 °C for 15 min
(5) (a) Takeuchi, Y.; Kirihara, K.; Kirk, K. L.; Shibata, N. J . Chem.
Soc. Chem. Commun. 2000, 785-786. (b) Takeuchi, Y. J . Fluorine
Chem. 2000, 105, 215-217 and references cited therein. (c) Takeuchi,
Y.; Kamezaki, M.; Kirihara, K.; Haufe, G.; Laue, K. W. Chem. Pharm.
Bull. 1998, 46, 1062-1064.
(6) (a) Takeuchi, Y.; Takagi, K.; Nagata, K.; Koizumi, T. Chem.
Pharm. Bull. 1991, 39, 3120-3122. (b) Takeuchi, Y.; Takagi, K.;
Yamaba, T.; Nabetani, M.; Koizumi, T. J . Fluorine Chem. 1994, 68,
149-154. (c) Huang, X.; Blackburn, B. J .; Au-Yeung, S. C. F.; J anzen,
A. F. Can. J . Chem. 1990, 68, 477-479.
(7) Bailey, P. D.; Baker, S. R.; Boa, A. N.; Clayson, J .; Rosair, G. M.
Tetrahedron Lett. 1998, 39, 7755-7758.
1044 J . Org. Chem., Vol. 68, No. 3, 2003

Novel Fluoropeptidomimetics
SCHEME 3a
SCHEME 4a
a
Reagents: (a) NaBH4, MeOH; (b) BzCl, Et3N, CH2Cl2 or DHP,
PTSA, Et2O; (c) NaN3, DMSO, 50 °C.
(Scheme 2), but not a difluoro derivative of 2. No further
attempts were made in this direction. Thus, compound
2 could not be utilized in further reactions due to its poor
stability (vide infra).
a
Reagents: (a) (i) (Boc)2O, Et3N, Dioxane:H2O; (ii) (Boc)2O,
DMAP, CH3CN; (b) Selectfluor, Et3N, CH3CN.
The stability of compound 2 was investigated to better
understand its utility in subsequent reactions. During
the purification of compound 2, column chromatography
appeared to decrease the yields of the isolated product.
Compound 2 was relatively stable in CDCl3 at room
temperature, when the 1H NMR spectrum of 2 was
SCHEME 5a
1
monitored for up to 5 h. The H peaks characteristic for
compound 2 were consistent, although some noise peaks
were observed in the region between 2 and 5 ppm, as
the time elapsed to 5 h. In the 1H NMR experiments
1
using CDCl3/D2O (9:1) as the solvent, we did not see H
peaks characteristic of compound 2 and the compound
appeared to have decomposed.
a
Due to the observed instability of compound 2 contain-
ing a secondary amine, we were interested in studying
its derivatives containing various groups on the amino
moiety of R-fluoroglycine. Thus, the synthesis of R-fluo-
roglycine analogues was investigated using several pri-
mary and secondary amines such as benzyl carbamate,
N-benzyl methylamine, and N-(CBz)benzylamine, and
fully protected R-fluoroglycine derivatives were the an-
ticipated products. When ethyl bromodifluoroacetate was
treated with N-benzyl methylamine, amide 16 was
isolated as a major product (Scheme 2), where as in the
cases with benzyl carbamate or N-CBz-benzylamine,
starting material was recovered. In cases where a
relatively strong base (such as NaOH) was used to
activate the amine, decomposition of the starting mate-
rial was observed.
An alternate approach to compound 12 was considered
by reducing ethyl bromofluoroacetate and then condens-
ing with an amine. Ethyl bromofluoroacetate was sub-
jected to reduction at room temperature to give the
corresponding alcohol, and the alcohol was protected with
either a benzoyl or a THP moiety to obtain compound 17
or 18 (Scheme 3).8 Substitution of the bromo moiety in
compound 17 or 18 with various primary and secondary
amines [BnNH2, (CBz)2NH, CBzNHMe] under various
conditions [(i-Pr)2EtN, DMAP, NaOH, K2CO3, NaH and
NaOEt] resulted in either the recovery or decomposition
of starting material. Treatment of compounds 17 and 18
with NaN3 in DMSO at 50 °C, however, gave the
corresponding azides 19 and 20, respectively, in good
yields. Reduction of the azido moiety in compounds 19
and 20 was not successful under several conditions (Pd-
C/H2; Pd-C/H2/Boc2O; TPP/THF/H2O; SnCl2/MeOH; Raney
nickel; SmI2/MeOH/THF), and no product could be iso-
lated. These observations did not bode well for us to
Reagents: (a) Selectfluor, Et3N, CH3CN; (b) (i) TPP, THF:H2O,
rt, (ii) BocHN-L-Ala-OH, EDAC, HOBt, CH2Cl2.
introduce the substituents to stabilize the R-fluoroglycine
template to synthesize biologically suitable, oxyanion-
mimicking peptidomimetics.
Then we turned our attention to the synthesis
of R-fluoro-â-aminoethanethiol derivatives such as 1
(X ) S). Thus, 2-bromoethylamine was first converted
to S-phenyl derivative 21 (Scheme 4).9 Compound 21
upon reaction with (Boc)2O followed by fluorination
with Selectfluor at room temperature gave the required
R-fluorothio derivative 23 in 20% yield and a cyclic
product 24 in 44% yield.10 To avoid the cyclic byproduct,
the target fluoro peptide was obtained through an azide
intermediate (26) as well as N-phthaloyl derivative (28).
Accordingly, the azide 25 upon fluorination with Select-
fluor gave the R-fluoro derivative 26 (Scheme 5).11 Reduc-
tion of the azide 26 to an amine was conveniently carried
out by TPP and the amine was coupled to BocNH-L-Ala-
OH to give the dipeptide 3 in 41% overall yield from 26.
The deprotection of the Boc group in 3 could not be
achieved using standard CF3CO2H conditions and the
1
fluorine signature was not found in the H NMR spec-
trum of the product. This indicated that the R-fluorothio
moiety was not stable in acidic media. Due to the acid
labile nature of this R-fluorothio moiety, methyl carbam-
ate or phthaloyl group was used as a protecting group
for the amine in the subsequent dipeptide synthesis.
Compound 27 upon treatment with Selectfluor (Scheme
6) gave the fluoro derivative 28.12 The phthaloyl group
(9) Katritzky, A. R.; Xu, Y.-J .; He, H.-Y.; Mehta, S. J . Org. Chem.
2001, 66, 5590-5594.
(10) (a) Gunnarsson, K.; Ragnarsson, U. Acta Chem. Scand. 1990,
44, 944-951. (b) Banks, R. E. J . Fluorine Chem. 1998, 87, 1-17 and
references sited there in; (c) Curran, T. P.; Pollastri, M. P.; Abelleira,
S. M.; Messier, R. J .; McCollum, T. A.; Rowe, C. G. Tetrahedron Lett.
1994, 35, 5409.
(8) (a) Sekine, M.; Peshakova, L. S.; Hata, T.; Yokoyama, S.;
Miyazawa, T. J . Org. Chem. 1987, 52, 5061-5063. (b) Derek, H. R. B.;
Franck, L. Tetrahedron 1997, 53, 14565-14578.
(11) Carboni, B.; Vaultier, M.; Carrie, R. Tetrahedron 1987, 43,
1799-810.
J . Org. Chem, Vol. 68, No. 3, 2003 1045

Annedi et al.
SCHEME 6a
SCHEME 7a
a
Reagents: (a) Selectfluor, Et3N, CH3CN; (b) NH2-NH2-H2O,
MeOH; (c) MeCO2HN-L-Ala-OH or PhthN-L-Ala-OH, EDAC, HOBt,
CH2Cl2.
was removed by hydrazine monohydrate in methanol at
room temperature to obtain compound 29.13 The R-fluoro
monomer 29 was coupled with MeCO2NH-L-Ala-OH and
PhthN-L-Ala-OH to give the dipeptides 4 and 5, respec-
tively. Deprotection of the methyl carbamate in 4 was
not successful,14 whereas the phthaloyl deprotection of 5
was conveniently achieved by hydrazine monohydrate to
give compound 6.
Various alkyl substitutions at the C-2 position of
compound 3 were investigated. Several amino alcohols
were prepared (Scheme 7) and converted into the ap-
propriate substrates (compounds 30-32) for the fluorina-
tion.15 Compounds 30-32 upon treatment with diphenyl
disulfide and Bu3P yielded 33-35, respectively.16 The
monomers 33-35 were fluorinated with Selectfluor to
give the R-fluoro-â-aminothio derivatives 36-38, respec-
tively. Deprotection of the phthaloyl groups in 36-38
followed by coupling of the amines 39-41 with MeCO2-
NH-L-Ala-OH gave the desired dipeptides 7-9, respec-
tively. Compounds 42 and 43 were isolated as byproducts
during the transformation of 37 and 38 into 8 and 9,
respectively, due to the incomplete cleavage of the
phthaloyl moiety.
The stability of these dipeptides 3-9 was studied in
organic and aqueous media using 1H NMR spectroscopy.
The 1H NMR spectra of the compounds 3-9 were
recorded in CDCl3 as solvent, and no changes in the NMR
spectra were observed even after several days. When the
1H NMR spectra were recorded in CD3OD/D2O (1:1), a
decrease of 10-40% of the peak intensities was observed
after 24 h (Table 1). Compounds without any substitution
at C-2, such as in compounds 3-6 (for atom numbering,
see Figure 1), or with benzyl substitution (8) showed a
loss of peak intensity of up to 40%. Whereas for those
with alkyl substitutions (compounds 7 and 9), the de-
composition was slow (ca. 12%), as characterized by the
a
Reagents: (a) PhSSPh, Bu3P, DMF; (b) Selectfluor, Et3N,
CH3CN; (c) NH2-NH2-H2O, MeOH; (d) MeCO2HN-L-Ala-OH,
EDAC, HOBt, CH2Cl2.
TABLE 1. Th e 1H NMR Sta bility Stu d y in
Meth a n ol-d 4:D2O (1:1) a fter 22 h a t Room Tem p er a tu r ea
compd no.
% dec obsd
compd no.
% dec obsd
3
4
5
6
31
35
38
a
7
8
9
11
36
12
a
a ) not determined.
1
decrease in H NMR peak intensity. Alkyl substitutions
at the C-2 carbon provided more stability (7 and 9) than
without any substitution or with benzyl substitution
(Table 1).
In preliminary biological evaluations, compound 8 was
studied for its inhibitory activity against chymotrypsin
in a time-dependent enzyme inhibition assay.17 Com-
(17) Li, Z.-H.; Bulychev, A.; Kotra, L. P.; Massova, I.; Mobashery,
S. Hydrogen Bonding and Attenuation of the Rate of Enzymatic
Catalysis. J . Am. Chem. Soc. 1998, 120, 13003-13007. The activity of
chymotrypsin was measured using the “Kinetics” module on a Shi-
madzu UV-2401 PC spectrophotometer. The absorbance of the enzymic
reaction mixture was measured at 410 nm using the UV probe
(photometric module) in the UV-2401 PC spectrophotometer. The
standard curves were obtained by plotting the concentration of
substrate N-Succ-Ala-Ala-Pro-Phe-p-nitroanilide vs absorbance at 315
nm; the standard curve showed linearity till 150 µmol concentration.
Stock solution of substrate and R-chymotrypsin were prepared in Tris
buffer pH 7.8 (0.10 mol Tris/HCl, 0.01 mol CaCl2, pH 7.8) and stock
solution of the inhibitor (compound 8) prepared in MeOH. To study
the time dependent loss of activity of chymotrypsin, the enzyme and
the inhibitor were incubated for different time periods (0, 1, 4, 6, 8,
and 16 h) at 25 °C, and then the substrate was added and the time
course curve plotted for 5 min at 410 nm. Another set of reactions was
incubated for the same time periods but no inhibitor was present in
reaction mixtures, which was used a control set. After plotting the
Lineweaver-Burk plot, the KM and Vmax for chymotrypsin were
calculated as 27.1989 µmol and 0.3718 mAbs/min.
(12) (a) Takano, S.; Iida, H.; Inomata, K.; Ogasawara, K. Heterocycles
1993, 35, 47-52. (b) Nair, M. D.; David, J .; Nagarajan, K. Ind. J . Chem.
Sec (B) 1985, 24B (9), 940-947.
(13) Khan, M. N. J . Org. Chem. 1995, 60, 4536.
(14) Shono, T.; Matsumura, Y.; Uchida, K.; Tsubata, K.; Makino,
A. J . Org. Chem. 1984, 49, 300-304.
(15) (a) McKennon, M. J .; Meyers, A. I. J . Org. Chem. 1993, 58,
3568-3571. (b) Torsten, H.; Walter, S. A.; David, M. B. Can. J . Chem.
1988, 66, 779-782.
(16) (a) Nakagawa, I.; Hata, T. Tetrahedron Lett. 1975, 1409-1412.
(b) Siedlecka, R.; Skarzewsi, J . Synlett 1996, 757-758.
1046 J . Org. Chem., Vol. 68, No. 3, 2003

Novel Fluoropeptidomimetics
127.41, 135.08, 161.51; 19F NMR (282 MHz, CDCl3) δ -70.45
(d, J ) 51.0 Hz); MS-EI m/z 191 (17), 166 (62), 117 (42), 91
(100), 65 (23).
(2-(P h en ylsu lfa n yl)eth yl)ca r ba m ic Acid Di-ter t-bu tyl
Ester (22). A solution of compound 21 (0.5 g, 0.32 mmol) and
Et3N (1.04 mL, 0.75 mmol) in dioxane:H2O (2.0 mL, 4:1) was
treated with Boc2O (0.71 g, 0.32 mmol) at 0 °C. After 10 min,
more Et3N (0.4 mL) was added and the mixture was stirred
for another 2.5 h at room temperature. The reaction mixture
was concentrated; dissolved into ethyl acetate; washed with
10% citric acid solution, 10% NaHCO3 solution, and brine; and
dried (Na2SO4). The combined organic layers were concen-
trated to obtain the monoprotected amino derivative as a syrup
(0.692 g, 84%).
A solution of the above crude amino derivative (0.475 g, 1.87
mmol) in anhydrous CH3CN (3.0 mL) was treated with DMAP
(0.02 g, 0.18 mmol) and Boc2O (0.4 g, 1.87 mmol) at 0 °C. The
reaction mixture was stirred overnight at room temperature,
concentrated, dissolved into ether, washed with water and
brine, and dried (Na2SO4). The combined organic layers were
concentrated, and the crude product was purified by column
chromatography (EtOAc:Hex, 5:95) to obtain compound 22 as
a syrup (0.6 g, 91%): 1H NMR (300 MHz, CDCl3) δ 1.47 (s,
18H), 3.05-3.10 (m, 2H), 3.76-3.81 (m, 2H), 7.13-7.38 (m,
5H).
F IGURE 3. Plot of time vs percent inhibition of the activity
of chymotrypsin, in a time-dependent assay. Three different
concentrations of the inhibitor 8 were tested, as indicated in
the graph above.
pound 8 was selected because it has a benzyl group at
the pseudo-P1 position that was anticipated to fit into
the S1 hydrophobic pocket of chymotrypsin. This site on
chymotrypsin is the specificity-determining site and
contributes toward the binding of the inhibitor.18 In this
assay, chymotrypsin lost 30% of enzyme activity at 2 h
after incubation with compound 8 at 100 and 250 µM
concentrations (Figure 3), and this activity was not
recovered even after 24 h. These results are encouraging,
and the inhibition of chymotrypsin may be due to the
formation of proposed reactive species in the active site
of chymotrypsin, as proposed earlier. However, further
proof of these inhibition studies are needed and mecha-
nistic investigations are in progress, to confirm the exact
mode of inhibition.
(2-F lu or o-2-(p h en ylsu lfa n yl)eth yl)ca r ba m ic Acid Di-
ter t-bu tyl Ester (23). A suspension of Selectfluor (0.05 g, 0.14
mmol) in anhydrous CH3CN (2.0 mL) was treated with
compound 22 (0.05 g, 0.14 mmol) in anhydrous CH3CN (1.0
mL). After stirring for 15 min, Et3N (0.019 mL, 0.14 mmol)
was added and the mixture was stirred for another 10 min.
The reaction mixture was then treated with water and
extracted into ether. The organic layer was washed with
saturated NaHCO3 solution and brine and dried (Na2SO4). The
concentrated organic layer was purified by column chroma-
tography (EtOAc:Hex, 5:95) to obtain compound 23 (0.01 g,
20%) with a cyclic byproduct 24 (0.018 g, 44%). 23: solid; mp
59-61 °C; 1H NMR (300 MHz, CDCl3) δ 1.48 (s, 18H), 3.92
(ddd, 1H, J ) 4.5 Hz), 4.07, 4.12 (dt, 1H, J ) 8.4 Hz), 5.93
(ddd, 1H, J ) 4.2, 55.0 Hz), 7.30-7.32 (m, 3H), 7.49-7.52 (m,
2H); 13C NMR (75 MHz, CDCl3) δ 28.37, 49.38 (d, J ) 27.0
Hz), 83.17, 99.29 (d, J ) 219.5 Hz), 128.42, 129.13, 131.65,
132.97, 152.05; 19F NMR (282 MHz, CDCl3) δ -77.08 (ddd, J
) 8.1, 54.8 Hz); EI-MS m/z 371 (M+, 21), 353 (M - F, 6), 215
Exp er im en ta l Section
Gen er a l. All anhydrous reactions were performed under
an argon atmosphere. All solvents and reagents were obtained
from commercial sources and were used as received. Chro-
matographic purification was performed using silica gel (60
Å, 70-230 mesh). NMR spectra were recorded at 200 or 300
MHz for 1H, 75 MHz for 13C, and 282 MHz for 19F. Chemical
1
(33), 195 (58), 154 (100), 57 (72). 24: solid; mp 83-85 °C; H
NMR (300 MHz, CDCl3) δ 1.49 (s, 9H), 3.80 (dd, 1H, J ) 5.7,
11.2 Hz), 4.24 (dd, 1H, J ) 8.7, 11.2 Hz), 5.72 (dd, 1H, J )
5.7, 8.7 Hz), 7.32-7.37 (m, 3H), 7.52-7.56 (m, 2H); 13C NMR
(75 MHz, CDCl3) δ 28.22, 48.89, 79.68, 84.31, 129.21, 129.34,
129.86, 133.70, 148.59, 150.46; EI-MS m/z 295 (M+, 25), 178
(23), 135 (29), 110 (100), 57 (81).
1
shifts were reported in δ ppm using TMS standard for H and
13C NMR spectra and external CF3CO2H standard for 19F NMR
spectra. In some of the 13C NMR spectra, due to the diaster-
eomeric mixtures, the spectral values were reported in a range
of chemical shifts (particularly for aromatic carbons) rather
than a particular value. Mass spectra were obtained at the
Department of Chemistry Mass Spectrometry facility at the
University of Toronto.
(2-Azid o-1-flu or oeth ylsu lfa n yl)ben zen e (26). A suspen-
sion of Selectfluor (5.44 g, 15.36 mmol) in anhydrous CH3CN
(30 mL) was treated with compound 25 (2.5 g, 13.96 mmol) in
anhydrous CH3CN (20 mL). After stirring for 30 min. Et3N
(1.94 mL, 13.96 mmol) was added and stirred for another 10
min. The reaction mixture was purified as described for 23 to
obtain compound 26 as a syrup (1.32 g, 48%): 1H NMR (300
MHz, CDCl3) δ 3.49-3.58 (m, 2H), 5.80 (ddd, 1H, J ) 4.5, 53.0
Hz), 7.30-7.34 (m, 3H), 7.49-7.52 (m, 2H); 13C NMR (75 MHz,
CDCl3) δ 54.04 (d, J ) 52.6 Hz), 99.65 (d, J ) 220.4 Hz), 128.82,
129.28, 130.64, 133.19, 133.21; 19F NMR (282 MHz, CDCl3) δ
-73.07 (ddd, J ) 15.7, 19.1, 54.8 Hz).
[1-((2-Flu or o-2-(ph en ylsu lfan yl)eth yl)car bam oyl)eth yl]-
ca r ba m ic Acid ter t-Bu tyl Ester (3). A solution of compound
26 (0.83 g, 4.22 mmol) in THF:H2O (5:1, 5 mL) was treated
with TPP (1.10 g, 4.22 mmol). The reaction mixture was stirred
for 3 h at room temperature, dissolved in ethyl acetate, washed
with water and brine, and dried (Na2SO4). The combined
organic layers were concentrated to obtain the crude amine.
(Ben zyla m in o)flu or oa cetic Acid Eth yl Ester (2). A
solution of BnNH2 (0.05 g, 0.46 mmol) in anhydrous DMF (1.0
mL) was treated with ethyl bromofluoroacetate (0.05 mL, 0.46
mmol) at 0 °C. After stirring for 15 min at 0 °C, the reaction
mixture was treated with water and was extracted into ethyl
acetate. The organic layer was washed with brine and dried
(Na2SO4). The concentrated organic layer was purified by
column chromatography (EtOAc:Hex, 1:4) to yield compound
2 as a syrup (0.02 g, 21%): 1H NMR (300 MHz, CDCl3) δ 1.35
(t, 3H), 4.34 (q, 2H), 4.86 (s, 2H), 6.65 (d, 1H, J ) 51.0 Hz),
7.26-7.37 (m, 5H), 7.72 (s, 1H); 1H NMR (300 MHz, DMF-d7)
δ 1.28 (t, 3H), 4.26 (q, 2H), 4.85 (d, 2H, J ) 1.5 Hz), 7.17 (d,
1H, J ) 49.5 Hz), 7.24-7.37 (m, 5H), 7.93 (t, 1H, J ) 0.75, 1.5
Hz); 13C NMR (75 MHz, CDCl3) δ 13.06, 42.43, 60.62, 83.28
(d, J ) 264.8 Hz), 126.17, 126.34, 126.52, 127.08, 127.23,
A solution of BocHN-L-Ala-OH (0.79 g, 4.22 mmol) in
anhydrous CH2Cl2 (10 mL) was treated with EDAC (0.8 g, 4.22
(18) Scheidig, A. J .; Hynes, T. R.; Pelletier, L. A.; Wells, J . A.;
Kossiakoff, A. A. Protein Sci. 1997, 6, 1806-1824.
J . Org. Chem, Vol. 68, No. 3, 2003 1047

Annedi et al.
mmol), HOBt (0.57 g, 4.22 mmol), and the above prepared
crude amine at 0 °C. The reaction mixture was stirred at room
temperature for 4 h; concentrated; dissolved into ethyl acetate;
washed with 10% citric acid solution, 10% NaHCO3 solution,
water, and brine; and dried (Na2SO4). The organic layers were
concentrated and purified by column chromatography (EtOAc:
Hex, 1:9) to obtain compound 3 as a syrup (0.65 g, 45%): 1H
NMR (300 MHz, CDCl3) δ 1.35 (dd, 3H, J ) 0.9, 7.0 Hz), 1.44
(s, 9H), 3.51-3.83 (m, 2H), 4.15 (brt, 1H), 4.91 (brs, 1H), 5.78
(ddd, 1H, J ) 4.8, 53.9 Hz), 6.60 (brs, 1H), 7.29-7.34 (m, 3H),
7.46-7.51 (m, 2H); 13C NMR (75 MHz, CDCl3) δ 18.64, 18.74,
28.63, 43.20 (dd, J ) 25.9 Hz), 50.25, 80.36, 99.32 (dd, J )
217.8 Hz), 128.46-132.91 (aromatic), 155.43, 173.05.
2-(2-F lu or o-2-(p h en ylsu lfa n yl)et h yl)isoin d ole-1,3-d i-
on e (28). A suspension of Selectfluor (1.35 g, 3.81 mmol) in
anhydrous CH3CN (5 mL) was treated with compound 27 (0.9
g, 3.18 mmol) in anhydrous CH3CN (5 mL). After stirring for
30 min, Et3N (0.44 mL, 3.18 mmol) was added and the mixture
was stirred for another 10 min. The reaction mixture was
purified as described for 23 to obtain compound 28 as a syrup
(0.3 g, 32%): 1H NMR (300 MHz, CDCl3) δ 3.97-4.22 (m, 2H),
6.05 (ddd, 1H, J ) 5.1, 54.0 Hz), 7.29-7.32 (m, 3H), 7.48-
7.51 (m, 2H), 7.69-7.72 (m, 2H), 7.82-7.85 (m, 2H); 13C NMR
(75 MHz, CDCl3) δ 41.17 (d, J ) 28.5 Hz), 97.42 (d, J ) 220.6
Hz), 123.42, 123.49, 128.52, 129.13, 130.94, 131.70, 131.72,
132.82, 134.11, 134.16, 167.35, 167.54.
2-F lu or o-2-(p h en ylsu lfa n yl)eth yla m in e (29). A solution
of compound 28 (0.05 g, 0.16 mmol) in anhydrous MeOH (2.0
mL) was treated with hydrazine monohydrate (0.02 mL, 0.16
mmol) and stirred overnight at room temperature. The reac-
tion mixture was concentrated and the crude product was
purified by column chromatography (EtOAc) to obtain com-
pound 29 as a syrup (0.01 g, 36%): 1H NMR (300 MHz, CDCl3)
δ 1.48 (brs, 2H), 3.12 (brd, 2H, J ) 14.4 Hz), 5.71 (dt, 1H, J )
5.7, 54.6 Hz), 7.29-7.34 (m, 3H), 7.49-7.52 (m, 2H); 13C NMR
(75 MHz, CDCl3) δ 46.34 (d, J ) 25.9 Hz), 103.39 (d, J ) 213.8
Hz), 128.16, 129.13, 132.18, 132.42, 132.44; 19F NMR (CDCl3)
δ -74.66 (dt, J ) 16.0, 54.1 Hz).
[1-((2-Flu or o-2-(ph en ylsu lfan yl)eth yl)car bam oyl)eth yl]-
ca r ba m ic Acid Meth yl Ester (4). A solution of MeCO2NH-
L-Ala-OH (0.03 g, 0.20 mmol) in anhydrous CH2Cl2 (3.0 mL)
was treated with EDAC (0.047 g, 0.24 mmol), HOBt (0.027 g,
0.20 mmol), and compound 29 (0.035 g, 0.20 mmol) at 0 °C.
The same procedure as that for compound 3 was used to finally
obtain compound 4 as a white solid (0.037 g, 61%): mp 89-92
°C; 1H NMR (300 MHz, CDCl3) δ 1.37 (dd, 3H, J ) 2.4, 2.7
Hz), 3.50-3.85 (m, 5H), 4.26 (m, 1H), 5.41 (brt, 1H, J ) 5.7,
6.3 Hz), 5.70, 5.88 (2m, 1H), 6.79 (brs, 1H), 7.30-7.33 (m, 3H),
7.47-7.50 (m, 2H); 13C NMR (75 MHz, CDCl3) δ 18.86, 19.03,
43.23 (dd, J ) 25.9 Hz), 50.77, 52.75, 99.40 (dd, J ) 217.5 Hz),
128.59, 129.20, 131.07, 132.96, 133.00, 133.02, 156.61, 172.67;
19F NMR (CDCl3) δ -74.72 to -74.41 (m).
compound 6 as a syrup (0.03 g, 94%): 1H NMR (300 MHz,
CDCl3) δ 1.34 (dd, 3H, J ) 2.1 Hz), 1.72 (brs, 2H), 3.48-3.85
(m, 3H), 5.73, 5.91 (2m, 1H, J ) 2.7, 54.3 Hz), 7.30-7.34 (m,
3H), 7.49-7.53 (m, 2H), 7.72 (brs, 1H); 13C NMR (75 MHz,
CDCl3) δ 21.84, 21.86, 42.69 (dd, J ) 25.6 Hz), 50.84, 50.89,
99.68 (dd, J ) 218.4 Hz), 128.66, 129.36, 131.49, 133.09,
133.09, 176.19; 19F NMR (CDCl3) δ -75.15 (ddd, J ) 13.8, 54.1
Hz).
2-(1-Met h yl-2-(p h en ylsu lfa n yl)et h yl)isoin d ole-1,3-d i-
on e (33). A solution of compound 30 (1.25 g, 6.09 mmol) in
anhydrous DMF (3.0 mL) was treated with Bu3P (2.27 mL,
9.14 mmol) and diphenyl disulfide (1.99 g, 9.14 mmol). The
reaction mixture was stirred for 1 h at room temperature and
diluted with ether. The organic layer was washed with 1 N
NaOH solution and brine and dried (Na2SO4). The combined
organic layers were concentrated and purified by column
chromatography (EtOAC:Hex, 1:9) to obtain compound 33 as
a syrup (1.49 g, 83%): 1H NMR (300 MHz, CDCl3) δ 1.53 (d,
3H, J ) 6.9 Hz), 3.18 (dd, 1H, J ) 5.4, 13.9 Hz), 3.68 (dd, 1H,
J ) 9.9, 13.9 Hz), 4.44-4.56 (m, 1H), 7.03-7.09 (m, 1H), 7.13-
7.18 (m, 2H), 7.29-7.33 (m, 2H), 7.63-7.68 (m, 2H), 7.71-
7.76 (m, 2H).
2-(1-Ben zyl-2-(p h en ylsu lfa n yl)et h yl)isoin d ole-1,3-d i-
on e (34). A solution of compound 31 (0.2 g, 0.71 mmol) in
anhydrous DMF (2.0 mL) was treated with Bu3P (0.26 mL,
1.06 mmol) and diphenyl disulfide (0.23 g, 1.06 mmol). Same
procedure as that for compound 33 was used to obtain
compound 34 as a syrup (0.23 g, 84%): 1H NMR (300 MHz,
CDCl3) δ 3.08-3.33 (m, 3H), 3.74 (dd, 1H, J ) 10.2, 14.1 Hz),
4.60-4.70 (m, 1H), 6.99-7.26 (m, 10H), 7.59-7.68 (m, 4H).
2-(2-Meth yl-1-((ph en ylsu lfan yl)m eth yl)pr opyl)isoin dole-
1,3-d ion e (35). A solution of compound 32 (1.05 g, 4.50 mmol)
in anhydrous DMF (3.0 mL) was treated with Bu3P (3.3 mL,
6.75 mmol) and diphenyl disulfide (1.47 g, 6.75 mmol). The
same procedure as explained for compound 33 was used to
obtain compound 35 as a solid (1.23 g, 84%): mp 89-91 °C;
1H NMR (300 MHz, CDCl3) δ 0.84 (d, 3H, J ) 6.6 Hz), 1.04 (d,
3H, J ) 6.9 Hz), 2.34-2.46 (m, 1H), 3.32 (dd, 1H, J ) 3.3,
13.8 Hz), 3.72 (dd, 1H, J ) 11.7, 13.8 Hz), 3.96-4.05 (m, 1H),
6.99-7.14 (m, 3H), 7.24-7.28 (m, 2H), 7.64-7.68 (m, 2H),
7.71-7.75 (m, 2H).
2-(2-Flu or o-1-m eth yl-2-(ph en ylsu lfan yl)eth yl)isoin dole-
1,3-d ion e (36). A suspension of Selectfluor (0.71 g, 2.02 mmol)
in anhydrous CH3CN (5 mL) was treated with compound 33
(0.5 g, 1.68 mmol) in anhydrous CH3CN (5 mL). After stirring
for 30 min at room temperature, Et3N (0.23 mL, 1.68 mmol)
was added and the mixture was stirred for another 10 min.
The reaction mixture was purified as described for 23 to obtain
compound 36 as a syrup (0.22 g, 42%): 1H NMR (300 MHz,
CDCl3) δ 1.62 (d, 3H, J ) 6.9 Hz), 4.53-4.65 (m, 1H), 6.31
(ddd, 1H, J ) 9.9, 52.5 Hz), 7.24-7.28 (m, 2H), 7.32-7.35 (m,
2H), 7.52-7.55 (m, 1H), 7.67-7.75 (m, 2H), 7.77-7.88 (m, 2H);
13C NMR (75 MHz, CDCl3) δ 15.91, 16.09, 49.18 (dd, J ) 21.0,
32.4 Hz), 100.99 (dd, J ) 221.8 Hz), 123.37-134.78 (aromatic),
167.40, 167.75; 19F NMR (282 MHz, CDCl3) δ -74.15 (ddd, J
) 5.3, 53.1 Hz).
2-(1-Ben zyl-2-flu or o-2-(ph en ylsu lfa n yl)eth yl)isoin d ole-
1,3-d ion e (37). A suspension of Selectfluor (0.2 g, 0.56 mmol)
in anhydrous CH3CN (3 mL) was treated with compound 34
(0.2 g, 0.51 mmol) in anhydrous CH3CN (2 mL). After stirring
for 30 min at room temperature, Et3N (0.07 mL, 0.51 mmol)
was added and the mixture was stirred for another 10 min.
The reaction mixture was purified as described for 23 to obtain
compound 37 as a syrup (0.13 g, 65%): 1H NMR (300 MHz,
CDCl3) δ 3.36-3.49 (m, 2H), 4.69-4.81 (m, 1H), 6.40 (ddd, 1H,
J ) 9.3, 52.8 Hz), 6.99-7.74 (m, 14H); 13C NMR (75 MHz,
CDCl3) δ 34.83, 35.16, 54.93 (dd, J ) 20.4, 30.8 Hz), 100.41
(dd, J ) 222.9 Hz), 123.27-136.61 (aromatic), 167.43, 167.71;
19F NMR (282 MHz, CDCl3) δ -74.91 to -74.64 and -72.49
to -72.22 (2m).
2-(1,3-Dioxo-1,3-d ih yd r oisoin d ol-2-yl)-N-(2-flu or o-2-
(p h en ylsu lfa n yl)eth yl)p r op ion a m id e (5). A solution of
PhthN-L-Ala-OH (0.057 g, 0.26 mmol) in anhydrous CH2Cl2
(3.0 mL) was treated with EDAC (0.06 g, 0.31 mmol), HOBt
(0.035 g, 0.26 mmol), and compound 29 (0.045 g, 0.26 mmol)
at 0 °C. The same procedure as that for compound 3 was used
to finally isolate compound 5 as a foam (0.069 g, 71%): 1H
NMR (300 MHz, CDCl3) δ 1.69 (d, 3H, J ) 6.9 Hz), 3.47-3.91
(m, 2H), 4.93 (q, 1H), 5.72, 5.90 (2m, 1H, J ) 54.3 Hz), 6.53
(m, 1H), 7.30-7.33 (m, 3H), 7.45-7.50 (m, 2H), 7.70-7.74 (m,
2H), 7.80-7.85 (m, 2H); 13C NMR (75 MHz, CDCl3) δ 15.36,
15.41, 43.32 (dd, J ) 25.9 Hz), 49.48, 99.23 (d, J ) 218.6 Hz),
123.64-134.49 (aromatic), 167.89, 169.65, 169.68; 19F NMR
(CDCl3) δ -75.76 to -75.13 (m).
2-Am in o-N-(2-flu or o-2-(ph en ylsu lfan yl)eth yl)pr opion a-
m id e (6). A solution of compound 5 (0.05 g, 0.13 mmol) in
anhydrous MeOH (2.0 mL) was treated with hydrazine mono-
hydrate (0.006 mL) and was stirred overnight at room tem-
perature. The reaction mixture was concentrated and purified
by column chromatography (MeOH:CHCl3 5:95) to obtain
2-[1-(F lu or o(p h en ylsu lfa n yl)m eth yl)-2-m eth ylp r op yl]-
isoin d ole-1,3-d ion e (38). A suspension of Selectfluor (1.3 g,
1048 J . Org. Chem., Vol. 68, No. 3, 2003

Novel Fluoropeptidomimetics
3.69 mmol) in anhydrous CH3CN (15 mL) was treated with
compound 35 (1.0 g, 3.07 mmol) in anhydrous CH3CN (20 mL).
After stirring for 30 min at room temperature, Et3N (0.42 mL,
3.07 mmol) was added and the mixture was stirred for another
10 min. The reaction mixture was purified as described for 23
to obtain compound 38 as a syrup (0.31 g, 30%): 1H NMR (300
MHz, CDCl3) δ 0.95 (dd, 3H, J ) 3.6 Hz), 1.04-1.08 (m, 3H),
2.54-2.83 (m, 1H), 4.30-4.40 (m, 1H), 6.44 (ddd, 1H, J ) 6.6,
53.7 Hz), 7.26-7.31 (m, 3H), 7.40-7.43 (m, 1H), 7.49-7.52 (m,
1H), 7.69-7.76 (m, 2H), 7.82-7.87 (m, 2H); 13C NMR (75 MHz,
CDCl3) δ 19.47, 19.68, 20.76, 20.84, 28.57, 29.84, 59.34 (dd, J
) 20.5, 28.2 Hz), 100.64 (dd, J ) 225.2 Hz), 123.45, 123.50,
128.40, 128.44, 129.06, 129.14, 131.47, 131.56, 132.60, 132.62,
133.01, 133.03, 134.09, 134.16, 168.14; 19F NMR (282 MHz,
CDCl3) δ -73.95 (ddd, J ) 5.9, 15.7, 53.0 Hz).
2-F lu or o-1-m eth yl-2-(p h en ylsu lfa n yl)eth yla m in e (39).
A solution of compound 36 (0.175 g, 0.55 mmol) in anhydrous
MeOH (2.0 mL) was treated with hydrazine monohydrate (0.02
mL, 0.55 mmol) and stirred for overnight at room temperature.
The reaction mixture was concentrated and purified as de-
scribed for 29 to obtain compound 39 as a syrup (0.095 g,
93%): 1H NMR (300 MHz, CDCl3) δ 1.17-1.25 (m, 3H), 1.52
(brs, 2H), 3.22-3.36 (m, 1H), 5.54 (ddd, 1H, J ) 5.1, 54.4 Hz),
7.24-7.33 (m, 3H), 7.46-7.51 (m, 2H); 13C NMR (75 MHz,
CDCl3) δ 19.13, 20.14, 50.79 (dd, J ) 23.3 Hz), 107.61 (dd, J
) 219.0 Hz), 127.49-133.43 (aromatic); 19F NMR (282 MHz,
CDCl3) δ -77.32 to -76.98 and -72.96 to -72.63 (2m).
[1-((2-Flu or o-1-m eth yl-2-(ph en ylsu lfan yl)eth yl)car bam -
oyl)eth yl]ca r ba m ic Acid Meth yl Ester (7). A solution of
MeCO2NH-L-Ala-OH (0.043 g, 0.29 mmol) in anhydrous CH2-
Cl2 (2.0 mL) was treated with HOBt (0.036 g, 0.27 mmol),
EDAC (0.062 g, 0.32 mmol), and compound 39 (0.05 g, 0.27
mmol) in anhydrous CH2Cl2 (1.0 mL) at 0 °C and was purified
as described for 3 to obtain compound 7 as a solid (0.065 g,
77%): mp 89-91 °C; 1H NMR (300 MHz, CDCl3) δ 1.29-1.43
(m, 6H), 3.66 (s, 3H), 4.32-4.60 (m, 2H), 5.60-5.69, 5.86-
5.88 (2m, 2H), 6.84 (m, 1H), 7.28-7.31 (m, 3H), 7.44-7.50 (m,
2H); 13C NMR (75 MHz, CDCl3) δ 16.97, 19.37, 19.64, 48.61
(dd, J ) 24.2 Hz), 50.05, 50.76, 52.65, 104.30 (dd, J ) 221.5
Hz), 128.12-132.82 (aromatic), 156.49, 171.85, 172.16; 19F
NMR (282 MHz, CDCl3) δ -81.27 (ddd, J ) 15.7, 20.5, 53.7
Hz).
[1-((1-Ben zyl-2-flu or o-2-(p h en ylsu lfa n yl)eth yl)ca r ba m -
oyl)eth yl]ca r ba m ic Acid Meth yl Ester (8). A solution of
compound 37 (0.53 g, 1.35 mmol) in anhydrous MeOH (5.0 mL)
was treated with hydrazine monohydrate (0.06 mL, 1.35 mmol)
and stirred overnight at room temperature. The solvent was
evaporated and the crude product was purified to obtain a
nonseparable mixture of compounds 40 and the partially
deprotected compound 42, using the same procedure as
described for 29.
A solution of MeCO2NH-L-Ala-OH (0.21 g, 1.45 mmol) in
anhydrous CH2Cl2 (4.0 mL) was treated with HOBt (0.178 g,
1.32 mmol), EDAC (0.3 g, 1.58 mmol), and the mixture of
compounds 40 and 42 (0.36 g, 1.32 mmol) in anhydrous CH2-
Cl2 (1.0 mL) at 0 °C. The same procedure as described for 3
was used and after chromatographic separation, compounds
8 (0.017 g, 8%) and 42 (0.21 g, 36%) were obtained. Compound
8: solid; mp 108-110 °C; 1H NMR (300 MHz, CDCl3) δ 1.26-
1.40 (m, 3H), 2.88-3.16 (m, 2H), 3.66, 3.68 (2s, 3H), 4.15-
4.27 (m, 1H), 4.61-4.75 (m, 1H), 5.16 (brdd, 1H), 5.78 (ddd,
1H, J ) 2.7, 54.4 Hz), 6.52 (brdd, 1H), 7.19-7.52 (m, 10H);
13C NMR (75 MHz, CDCl3) δ 19.10, 35.71, 37.78, 50.83, 52.74,
53.92 (dd, J ) 22.5 Hz), 103.01 (dd, J ) 220.9 Hz), 126.89-
136.39 (aromatic), 156.35, 172.02; 19F NMR (282 MHz, CDCl3)
δ -80.51 (ddd, J ) 16.9, 18.8, 55.2 Hz); Compound 42: 1H
NMR (300 MHz, CDCl3) δ 2.96-3.21 (m, 2H), 3.95 (brs, 2H),
4.77-4.93 (m, 1H), 5.88 (ddd, 1H, J ) 3.6, 54.3 Hz), 7.05 (d,
1H, J ) 8.7 Hz), 7.14-7.51 (m, 14H), 8.06 (s, 1H); 13C NMR
(75 MHz, CDCl3) δ 35.57, 37.57, 54.61 (dd, J ) 22.5 Hz), 102.86
(dd, J ) 220.9 Hz), 126.87-136.59 (aromatic), 168.30, 168.42,
169.31; 19F NMR (282 MHz, CDCl3) δ -80.39 (ddd, J ) 17.4,
20.5, 54.4 Hz).
{1-[(1-(Flu or o(ph en ylsu lfan yl)m eth yl)-2-m eth ylpr opyl)-
ca r ba m oyl]eth yl}ca r ba m ic Acid Meth yl Ester (9). A
solution of compound 38 (0.3 g, 0.87 mmol) in anhydrous
MeOH (2.0 mL) was treated with hydrazine monohydrate (0.04
mL, 0.87 mmol) and was stirred overnight at room tempera-
ture. The reaction mixture was concentrated and the crude
product was purified as described for 29 to give compound 41
and the partially deprotected compound 43 as a nonseparable
mixture.
A solution of MeCO2NH-L-Ala-OH (0.15 g, 1.03 mmol) in
anhydrous CH2Cl2 (4.0 mL) was treated with HOBt (0.126 g,
0.938 mmol), EDAC (0.216 g, 1.12 mmol), and mixture of
compounds 41 and 43 (0.2 g, 0.93 mmol) in anhydrous CH2-
Cl2 (1.0 mL) at 0 °C. The same procedure as described for 3
was used to finally obtain compound 9 (0.015 g, 8%) and
1
compound 43 (0.12 g, 37%). 9: solid; mp 92-94 °C; H NMR
(300 MHz, CDCl3) δ 0.95-1.03 (m, 6H), 1.42 (dd, 3H, J ) 6.9,
7.2 Hz), 1.88-2.19 (m, 1H), 3.68 (s, 3H), 4.16-4.39 (m, 2H),
5.33 (m, 1H), 5.86 (ddd, 1H, J ) 2.1, 5.1, 54.6 Hz), 6.37 (brs,
1H), 7.30-7.32 (m, 3H), 7.46-7.51 (m, 2H); 19F NMR (282
MHz, CDCl3) δ -78.86 (ddd, J ) 15.2, 24.5, 54.1 Hz). 43: 1H
NMR (300 MHz, CDCl3) δ 1.02-1.07 (m, 6H), 1.95-2.23 (m,
1H), 4.06 (brs, 2H), 4.30-4.56 (m, 1H), 5.94 (ddd, 1H, J ) 2.1,
4.8, 54.4 Hz), 6.85 (t, 1H, J ) 8.4 Hz), 7.30-7.68 (m, 9H), 8.01
(d, 1H, J ) 18.6 Hz); 13C NMR (75 MHz, CDCl3) δ 17.95, 19.46,
19.97, 20.57, 29.42, 31.03, 58.18 (dd, J ) 20.4 Hz), 103.35 (d,
J
) 221.5 Hz), 128.25-134.55 (aromatic), 168.61, 168.76,
169.49, 169.59; 19F NMR (282 MHz, CDCl3) δ -78.75 (ddd, J
) 14.3, 23.4, 54.4 Hz).
Ack n ow led gm en t. S.C.A. is a recipient of a Rx&D
Health Research Foundation-Canadian Institutes of
Health Research (Rx&D HRF-CIHR) postdoctoral fel-
lowship. L.P.K. is a recipient of a Rx&D HRF-CIHR
research career award. This work is supported by grants
from CIHR (# MOP49414), Canadian Foundation for
Innovation, and Ontario Innovation Trust.
Su p p or tin g In for m a tion Ava ila ble: Experimental pro-
cedures to synthesize compounds 15-20 and the NMR spectra
for compounds 2-9. This material is available free of charge
via the Internet at http://pubs.acs.org.
J O026310C
J . Org. Chem, Vol. 68, No. 3, 2003 1049