Alternative one-pot synthesis of (trifluoromethyl)phenyldiazirines from tosyloxime derivatives: Application for new synthesis of optically pure diazirinylphenylalanines for photoaffinity labeling

Article abstract of DOI:10.1021/ol503630z

Alternative one-pot synthesis of 3-(trifluoromethyl)-3-phenyldiazirine derivatives from corresponding tosyloximes is developed. The deprotonation of intermediate diaziridine by NH₂^- is a new approach for construction of diazirine. Moreover, a novel synthesis of optically pure (trifluoromethyl)diazirinylphenylalanine derivatives was attempted involving these methods.

Full text of DOI:10.1021/ol503630z

Letter
pubs.acs.org/OrgLett
Alternative One-Pot Synthesis of (Trifluoromethyl)phenyldiazirines
from Tosyloxime Derivatives: Application for New Synthesis of
Optically Pure Diazirinylphenylalanines for Photoaffinity Labeling
Lei Wang,† Yuta Murai,†,∥ Takuma Yoshida,† Akiko Ishida,† Katsuyoshi Masuda,‡ Yasuko Sakihama,†
Yasuyuki Hashidoko,† Yasumaru Hatanaka,§ and Makoto Hashimoto*,†
†Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Kita 9, Nishi 9, Kita-ku, Sapporo 060-8589,
Japan
‡Suntory Institute for Bioorganic Research, 1-1-1 Wakayamadai, Shimamoto-cho, Mishima-gun, Osaka 618-8503, Japan
§Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan
S
* Supporting Information
ABSTRACT: Alternative one-pot synthesis of 3-(trifluoro-
methyl)-3-phenyldiazirine derivatives from corresponding
tosyloximes is developed. The deprotonation of intermediate
−
diaziridine by NH2 is a new approach for construction of
diazirine. Moreover, a novel synthesis of optically pure
(trifluoromethyl)diazirinylphenylalanine derivatives was at-
tempted involving these methods.
3-(Trifluoromethyl)-3-phenyldiazirine (TPD)1 has emerged as
the most effective photoreactive group in photoaffinity labeling2
because of its relatively small size, long activation wavelength
(approximately 360 nm), thermal and chemical stability, low
rate of rearrangement, and high reactivity of its intermediate.3
Nevertheless, compared to the other commonly used photo-
reactive groups in photoaffinity labeling (aryl azides2b and
benzophenones4), the tedious synthetic procedure of TPD
derivatives is a major consideration for researchers. In the past
decades, the formation of diaziridines from tosyloxime
derivatives is the crucial step to further construct TPD
(Scheme 1, I). Generally, liquid NH3 was used to construct
prepare TPD derivatives from tosyloximes can not only
decrease the cost and waste but also minimize the synthetic
cycles of TPD-containing probes in photoaffinity labeling.
Optically pure (trifluoromethyl)diazirinylphenylalanine
((Tmd)Phe) has been used as important building block for
investigation of peptides, proteins, and other biomacromole-
cule.7 One widely used method to prepare optically pure
(Tmd)Phe derivatives involved the concatenation of halo-
genated TPD and α-amino acids followed by the enzymatic
resolution of N-acylamino acids7e,8 or the use of amino acid
oxidase to afford the relative configuration.9 Asymmetric
syntheses were achieved through treatment of halogenated
TPD with the chiral Ni complex10 or cinchonidine-based
asymmetric catalyst.7b By combination of p-diodobenzene and
L-serine, Fillion et al. prepared Fmoc-L-(4-Tmd)Phe with a 14%
overall yield via 10 steps.7c However, although the preparation
were successful, all of the above-mentioned methods generally
could not circumvent tedious enzymatic procedure, low yields,
complicated preparation of chiral complex, or a limited
configuration of the desired products. Herein, for the first
time, we developed a one-pot synthesis of TPD derivatives
from the corresponding tosyloximes (Scheme 1, II). For further
application, direct construction of the Tmd group on optically
pure phenylalanines for preparation of (Tmd)Phe derivatives
was first reported.
Scheme 1. Construction of TPD Derivatives from the
Corresponding Tosyloximes
During the synthesis of diaziridines with liquid NH3, we
found that the corresponding TPD derivatives were sometimes
generated in small amounts, possibly derived from diaziridines.
To confirm our hypothesis, initial studies were performed using
diaziridines from tosyloximes (Scheme 1, I, step 1). Despite its
wide use, long reaction time and low yields were reported.5 To
further construct TPD derivatives by oxidation6 (Scheme 1, I,
step 2), the inevitable isolation of diaziridines, preparation of
fresh oxidant,6b and post-treatment after oxidation were also
time-consuming and yield-diminishing. In light of the
importance of TPD derivatives, a convenient method to
Received: December 16, 2014
Published: January 14, 2015
© 2015 American Chemical Society
616
DOI: 10.1021/ol503630z
Org. Lett. 2015, 17, 616−619

Organic Letters
Letter
tosyloxime 1a as the model substrate. It was found that
formation of TPD 3a, at room temperature, was dependent on
reaction time to a great extent (Table 1, entries 1−3).
11). To our delight, reaction at 0 °C provided 3a in 100% yield
within 10 h (Table 1, entry 12). The reaction was completed
within 4 h at room temperature (Table 1, entry 13). Sodium
amide and sodium hydride afforded to no desired product due
to the ammonolysis of ester (Table 1, entries 14 and 15), but
diazirine ring was formed. Further investigation indicated that
both reagents were suitable for synthesis of TPD without
substituent (Table S1, Supporting Information). Compared to
sodium amide, lithium amide displays low solubility in liquid
NH3,13 which has a wide application scope due to its milder
conditions. The highly isolated yield of 3a (96%, Table 1, entry
13) also proved its viability. The amount of lithium amide
should be set as 5 equiv to maintain the efficiency (Table 1,
entries 16 and 17). Solvent optimization was carried out,
although the efficiency was not improved (Table 1, entries 18−
20). Because of the similar efficiency and various advantages,
we outlined the alternative strategies for one-pot construction
of TPD from tosyloxime: one was accomplished with liquid
NH3 at 80 °C without any additive (Table 1, entry 5, method
A), and the other involved lithium amide in liquid NH3 at room
temperature (Table 1, entry 13, method B).
a
Table 1. Optimization of the Reaction Conditions
temp
(°C)
additive
(equiv)
time
(h)
b
entry solvent
yield 2/3a (%)
1
2
3
4
Et2O
Et2O
Et2O
Et2O
Et2O
CH2Cl2
THF
rt
1
12
96
8
100/0
rt
82/18
rt
3/97
c
c
60
80
80
80
80
80
80
−78
0
0/100
5
4
0/100 (97)
0/100
c
6
7
8
9
4.5
5
c
0/100
c
4
0/100
d
4
100/0
c
To clearly present the conversion of the substrates, we
carried out a kinetic investigation of the model reaction by
method A (Figure 1). As shown in the kinetic curve plot,
10
11
12
Et2O
Et2O
Et2O
Et2O
Et2O
Et2O
Et2O
Et2O
CH2Cl2
THF
NH4Cl (5)
LiNH2 (5)
LiNH2 (5)
LiNH2 (5)
NaNH2 (5)
NaH (5)
4
84/16
12
10
4
100/0
0/100
13
14
15
16
17
18
19
20
rt
0/100 (96)
rt
1
rt
1
rt
LiNH2 (10)
LiNH2 (2)
LiNH2 (5)
LiNH2 (5)
LiNH2 (5)
4
0/100
80/20
0/100
0/100
0/100
rt
8
rt
7
rt
6
rt
4.5
a
Reaction conditions: 1a (0.3 mmol), solvent (0.5 mL), liquid NH3 (5
b
mL) in a sealed tube. Yields were determined by 1H NMR
spectroscopy. Isolated yield of 3a in parentheses. Liquid NH3 (10
mL) was used. 1a was directly treated with gaseous NH3 at 80 °C in a
c
d
sealed tube.
Temperature optimization indicated that 80 °C was clearly
ideal for the reaction (Table 1, entries 4 and 5). However,
reaction at 100 °C resulted in decomposition of the diazirine
ring within 1 h (Figure S1, Supporting Information). No
decomposition of diazirine and high isolated yield of 3a (Table
1, entry 5) indicated the viability of this strategy. Other solvents
also worked well, although reactions did not improve (Table 1,
entries 6 and 7). An attempt to perform the reaction in the
absence of solvent was successful (Table 1, entry 8), which was
beneficial for the tosyloximes with low solubility in common
organic solvents. To confirm the species responsible for the
formation of 3a, tosyloxime 1a was directly treated with
gaseous NH3 at 80 °C (Table 1, entry 9). Diaziridine 2 was
detected as the sole product without 3a, indicating liquid NH3
was essential for the formation of 3a. On the basis of these
Figure 1. Kinetic investigation of one-pot synthesis of 3a. Reaction
conditions: 1a (0.3 mmol), Et2O (0.5 mL), liquid NH3 (10 mL) in a
sealed tube at 80 °C. Ratio were determined by 1H NMR spectroscopy
(for details, see Figure S2, Supporting Information).
tosyloxime 1a decreased rapidly and diaziridine 2 was quickly
generated within 10 min. TPD 3a formed gradually with the
consumption of diaziridine 2. After 4 h, diaziridine 2 was
completely converted to TPD 3a. These results also indicated
that diaziridine 2 was the intermediate for formation of 3a in
this reaction.
To highlight the viability of these strategies, gram-scale
reactions were carried out, respectively (Table 2, entries 1 and
2). As expected, TPD 3a was obtained in high yield by these
methods. With the optimal conditions in hand, the scope of the
reaction was explored with commonly used TPD derivatives for
postfunctional synthesis in photoaffinity labeling.14 Both of the
methods readily produced the desired products regardless of
the electronic properties of the substituents (Table 2, entries
3−16). Substrates with both electron-deficient and -rich
−
results, we postulated that the NH2 species generated from
liquid NH311 may be responsible for the formation of TPD 3a,
despite liquid NH3 having a low self-ionization constant (pKa =
27.6 at 25 °C).12 A control experiment with NH4Cl as an ion
counter for inhibiting the self-ionization of liquid NH3 also
confirmed this hypothesis (Table 1, entry 10). Inspired by these
−
results, a series of experiments with alkali amide as NH2
supplier in liquid NH3 were carried out at low temperature.
Initially, lithium amide was tested, but the reaction at −78 °C
afforded 2 in 100% yield without 3a after 12 h (Table 1, entry
617
DOI: 10.1021/ol503630z
Org. Lett. 2015, 17, 616−619

Organic Letters
Letter
a
Using these newly developed methods, a novel strategy for
preparation of optically pure (Tmd)Phe derivatives was
attempted. Commercially available Boc-L-Phe(4-I)-OH 4 was
treated with tert-butyl bromide to form Boc-L-Phe(4-I)-O-t-Bu
5 (Scheme 3). Lithiation of Boc-L-Phe(4-I)-O-t-Bu 5 with t-
Table 2. One-Pot Synthesis of TPD Derivatives
entry
R
method
yield (%), time (h)
Scheme 3. Synthesis of Optically Pure L-(4-Tmd)Phe
b
1
(1a) p-COOtBu
(1a) p-COOtBu
(1b) H
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
(3a) 90 (5)
(3a) 88 (6)
(3b) 97 (7)
(3b) 99 (6)
(3c) 98 (11)
(3c) 97 (12)
(3d) 99 (6)
(3d) 100 (8)
(3e) 94 (13)
(3e) 92 (16)
(3f) 96 (10)
(3f) 99 (9)
(3g) 99 (1)
(3g) 98 (1)
(3h) 93 (10)
(3h) 91 (9)
b
2
3
4
(1b) H
5
(1c) p-CH3
6
(1c) p-CH3
7
(1d) m-CH3
(1d) m-CH3
(1e) p-OCH3
(1e) p-OCH3
(1f) m-OCH3
(1f) m-OCH3
(1g) m-NO2
(1g) m-NO2
(1h) m-NHBoc
(1h) m-NHBoc
8
9
10
11
12
13
14
15
16
BuLi (2.5 equiv) and MeLi (1.3 equiv) followed by treatment
with ethyl trifluoroacetate afforded 6. However, use of a 1.5
equiv of t-BuLi or less led to the deiodination of 5. Following
further oximation and tosylation, tosyloxime 7 was obtained.
One-pot synthesis of 8 was conducted via methods A and B,
respectively. It was found that method A afforded optically pure
product in 90% yield but method B resulted in the racemization
of phenylalanine. The possible reason could be that, for method
B, deprotonation of the amino group at the aliphatic chain may
result in proton transfer at the adjacent position to form
carbanion. Further deprotection of 8 with trifluoroacetic acid
afforded L-(4-Tmd)Phe 9 in 92% yield. Thus, using method A,
the overall yield of L-(4-Tmd)Phe was calculated as 45% via six
steps. The synthesis of L-(4-Tmd)Phe was significantly
shortened in comparison to previous methods (9 steps in
36% yield from trifluoroacetophenone,7b 10 steps in 14% yield
from p-diodobenzene and L-serine for Fmoc-L-(4-Tmd)Phe,7c
and 12 steps in 47% yield from 4-bromobenzyl alcohol10a).
Inspired by this result, D-(4-Tmd)Phe 11, L-(3-Tmd)Phe 13,
and D-(3-Tmd)Phe 15 were all prepared in moderate yields
(Scheme 4). The use of isotope-labeled compounds for mass
analysis is an effective technique to identify the photolabeled
components in photoaffinity labeling.17 Previously, we reported
the preparation of deuterated L-(4-Tmd)Phe by H/D exchange
with TfOD,18 but the deuteration efficiency was up to 70%.19
Using our new method, we successfully prepared the highly
a
Reaction conditions: 1 (0.3 mmol), Et2O (0.5 mL), isolated yields,
b
NH3 (liquid): 10 mL for method A, 5 mL for method B. 1a (1.0 g)
was used.
substituents afforded to the desired products in high yields, and
the former generally led to completion in shorter time. The
nitro group also survived under these reactions (Table 2,
entries 13 and 14). It should be noted that, for these two
methods, byproducts could be readily removed by washing with
water and a normal purification procedure such as silica gel
column chromatography is not necessary, which averts the
material-consuming and yield-diminishing purification proce-
dure.
A plausible mechanism is outlined in Scheme 2. Initially,
tosyloxime 1a is attacked by NH3 molecule to form the
Scheme 2. Plausible Mechanism
Scheme 4. Comprehensive Synthesis of Optically Pure
(Tmd)Phe Derivatives by Method A
intermediate gem-diamine I.15 With the removal of tosyl group
and proton, diaziridine 2 is formed. At a high temperature
(method A), deprotonation occurs at the diaziridine ring,
−
forming the intermediate II in the presence of NH2 derived
from self-ionization of liquid NH3. The electron pair over
nitrogen can attack the other one to release TPD 3a along with
hydrogen and NH3. When lithium amide is added to the
reaction (method B), deprotonation of 2 was mainly triggered
−
by the NH2 derived from lithium amide. The generated
lithium hydride can further react with liquid NH3 to form
lithium amide.16
618
DOI: 10.1021/ol503630z
Org. Lett. 2015, 17, 616−619

Organic Letters
Letter
(5) (a) Wiegand, M.; Lindhorst, T. K. Eur. J. Org. Chem. 2006, 21,
4841. (b) Kuboe, S.; Yoda, M.; Ogata, A.; Kitade, Y.; Tomari, Y.;
Ueno, Y. Chem. Commun. 2010, 46, 7367. (c) Ismaili, H.; Lee, S.;
Workentin, M. S. Langmuir 2010, 26, 14958. (d) Nakamoto, K.; Ueno,
Y. J. Org. Chem. 2014, 79, 2463.
(6) (a) Bentz, E. L.; Gibson, H.; Hudson, C.; Moloney, M. G.;
Seldon, D. A.; Wearmouth, E. S. Synlett 2006, 2, 247. (b) Lawrence, E.
J.; Wildgoose, G. G.; Aldous, L.; Wu, Y. A.; Warner, J. H.; Compton,
R. G.; McNaughter, P. D. Chem. Mater. 2011, 23, 3740. (c) Sanderson,
J. M.; Findlay, J. B. C.; Fishwick, C. W. G. Tetrahedron 2005, 61,
11244. (d) Baldwin, J. E.; Jesudason, C. D.; Moloney, M. G.; Morgan,
deuterated L-(4-Tmd)Phe 17 from deuterated L-Phe 16. HPLC
spectra indicated that all of the (Tmd)Phe derivatives (9, 11,
13, 15, and 17) retained their optical purity (Figure S3,
Supporting Information). The photoreactive properties of the
L-(Tmd)Phe derivatives (9, 13, and 17) were further
investigated in the presence of CH3OH and CD3OD under
UV irradiation (Figure S4, Supporting Information). The half-
lives (t1/2) were calculated as 1.3, 0.6, and 1.3 min for 9, 13, and
17, respectively, indicating their effective photoreactivity. Then,
the reaction mixtures were subjected to MS analysis for
investigation of the photoreaction products (Figure S5,
Supporting Information).
D. R.; Pratt, A. J. Tetrahedron 1991, 47, 5603. (e) Fernan
́
dez-Gacio, A.;
Mourino, A. Eur. J. Org. Chem. 2002, 15, 2529. (f) Hatanaka, Y.;
̃
Nakayama, H.; Kanaoka, Y. Heterocycles 1993, 35, 997. (g) Halbfinger,
In conclusion, we developed a novel approach to synthesize
TPD derivatives from the corresponding tosyloximes in a one-
́
E.; Gorochesky, K.; Levesque, S. A.; Beaudoin, A. R.; Sheihet, L.;
Margel, S.; Fischer, B. Org. Biomol. Chem. 2003, 1, 2821. (h) Murai, Y.;
Masuda, K.; Ogasawara, Y.; Wang, L.; Hashidoko, Y.; Hatanaka, Y.;
Iwata, S.; Kobayashi, T.; Hashimoto, M. Eur. J. Org. Chem. 2013, 12,
2428.
−
pot reaction. NH2 species generated from liquid NH3 or
lithium amide contribute to the formation of TPD derivatives.
These one-pot methods will significantly shorten the synthetic
route of TPD derivatives in photoaffinity labeling. To
conveniently prepare optically pure (Tmd)Phe derivatives,
these one-pot methods were applied. The result indicated that
liquid NH3 at 80 °C was feasible while reaction with lithium
amide in liquid NH3 led to the racemization of phenylalanine.
(7) (a) Ploug, M.; Østergaard, S.; Hansen, L. B. L.; Holm, A.; Danø,
K. Biochemistry 1998, 37, 3612. (b) Nakashima, H.; Hashimoto, M.;
Sadakane, Y.; Tomohiro, T.; Hatanaka, Y. J. Am. Chem. Soc. 2006, 128,
15092. (c) Fillion, D.; Deraet, M.; Holleran, B. J.; Escher, E. J. Med.
̈
Chem. 2006, 49, 2200. (d) High, S.; Martoglio, B.; Gorlich, D.;
Andersen, S. S. L.; Ashford, A. J.; Giner, A.; Hartmann, E.; Prehn, S.;
Rapoport, T. A.; Dobberstein, B.; Brunner, J. J. Biol. Chem. 1993, 268,
26745. (e) Tippmann, E. M.; Liu, W. S.; Summerer, D.; Mack, A. V.;
Schultz, P. G. ChemBioChem 2007, 8, 2210. (f) Baldini, G.; Martoglio,
B.; Schachenmann, A.; Zugliani, C.; Brunner, J. Biochemistry 1988, 27,
7951.
ASSOCIATED CONTENT
■
S
* Supporting Information
General information, experimental procedures, characterization,
and NMR, HPLC, UV, and mass spectra of corresponding
products. This material is available free of charge via the
Internet at http://pubs.acs.org.
(8) (a) Nassal, M. J. Am. Chem. Soc. 1984, 106, 7540. (b) Shih, L. B.;
Bayley, H. Anal. Biochem. 1985, 144, 132.
(9) Masuda, K.; Koizumi, A.; Misaka, T.; Hatanaka, Y.; Abe, K.;
Tanaka, T.; Ishiguro, M.; Hashimoto, M. Bioorg. Med. Chem. Lett.
2010, 20, 1081.
(10) (a) Fishwick, C. W. G.; Sanderson, J. M.; Findlay, J. B. C.
Tetrahedron Lett. 1994, 35, 4611. (b) Hashimoto, M.; Hatanaka, Y.;
Sadakane, Y.; Nabeta, K. Bioorg. Med. Chem. Lett. 2002, 12, 2507.
(11) Fernelius, W. C.; Bowman, G. B. Chem. Rev. 1940, 26, 3.
(12) Coulter, L. V.; Sinclair, J. R.; Cole, A. G.; Roper, G. C. J. Am.
Chem. Soc. 1959, 81, 2986.
(13) Bergstrom, F. W.; Fernelius, W. C. Chem. Rev. 1933, 12, 43.
(14) (a) Hatanaka, Y.; Hashimoto, M.; Nakayama, H.; Kanaoka, Y.
Chem. Pharm. Bull. 1994, 42, 826. (b) Hatanaka, Y.; Hashimoto, M.;
Kurihara, H.; Nakayama, H.; Kanaoka, Y. J. Org. Chem. 1994, 59, 383.
(15) Smith, R. A. G.; Knowles, J. R. J. Chem. Soc., Perkin Trans. 2
1975, 7, 686.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: hasimoto@abs.agr.hokudai.ac.jp.
Present Address
∥(Y.M.) Faculty of Advanced Life Science, Frontier Research
Center for Post-Genome Science and Technology, Hokkaido
University, Kita 21, Nishi 11, Kita-ku, Sapporo 001-0021, Japan.
Notes
The authors declare no competing financial interest.
(16) Ruff, O.; Geisel, E. Chem. Ber. 1906, 39, 842.
ACKNOWLEDGMENTS
■
(17) (a) Sinz, A. Angew. Chem., Int. Ed. 2007, 46, 660. (b) Song, Z.
Q.; Huang, W. G.; Zhang, Q. S. Chem. Commun. 2012, 48, 3339.
(18) Murai, Y.; Wang, L.; Masuda, K.; Sakihama, Y.; Hashidoko, Y.;
Hatanaka, Y.; Hashimoto, M. Eur. J. Org. Chem. 2013, 23, 5111.
(19) Wang, L.; Murai, Y.; Yoshida, T.; Okamoto, M.; Masuda, K.;
Sakihama, Y.; Hashidoko, Y.; Hatanaka, Y.; Hashimoto, M. Biosci.
Biotechnol. Biochem. 2014, 78, 1129.
M.H. thanks the Suhara Memorial Foundation for financial
support. Part of this work was performed under the
Cooperative Research Program of “Network Joint Research
Center for Materials and Devices”.
REFERENCES
■
(1) Brunner, J.; Senn, H.; Richards, F. M. J. Biol. Chem. 1980, 255,
3313.
(2) (a) Converse, C. A.; Richards, F. F. Biochemistry 1969, 8, 4431.
(b) Fleet, G. W. J.; Porter, R. R.; Knowles, J. R. Nature 1969, 224, 511.
(c) Ruoho, A. E.; Kiefer, H.; Roeder, P. E.; Singer, S. J. Proc. Natl.
Acad. Sci. U.S.A. 1973, 70, 2567.
(3) (a) Das, J. Chem. Rev. 2011, 111, 4405. (b) Smith, R. A. G.;
Knowles, J. R. J. Am. Chem. Soc. 1973, 95, 5072. (c) Hatanaka, Y.;
Yoshida, E.; Nakayama, H.; Kanaoka, Y. Bioorg. Chem. 1989, 17, 482.
(d) Hiramatsu, T.; Guo, Y.; Hosoya, T. Org. Biomol. Chem. 2007, 5,
2916. (e) Qiu, Z. H.; Lu, L. H.; Jian, X.; He, C. J. Am. Chem. Soc. 2008,
130, 14398. (f) Song, Z. Q.; Zhang, Q. S. Org. Lett. 2009, 11, 4882.
(4) Galardy, R. E.; Craig, L. C.; Jamieson, J. D.; Printz, M. P. J. Biol.
Chem. 1974, 249, 3510.
619
DOI: 10.1021/ol503630z
Org. Lett. 2015, 17, 616−619