Asymmetric total synthesis of Tofacitinib

Article abstract of DOI:10.1016/j.tetlet.2013.07.042

A novel stereoselective synthesis of Tofacitinib (CP-690,550), a Janus tyrosine kinase (JAK3) specific inhibitor, has been achieved starting from (5S)-5-hydroxypiperidin-2-one in 10 steps from 2 with a 9.5% overall yield. The potentiality of this synthetic route is the obtention of tert-butyl-(3S,4R)-3- hydroxy-4-methylpiperidine-1-carboxylate (6b) as a new chiral precursor involved in the synthesis of CP690,550, in a three-step reaction, without epimerizations, rather than the 5 or more steps used in described reactions to achieve this compound from analogues of 6b.

Full text of DOI:10.1016/j.tetlet.2013.07.042

Accepted Manuscript
Asymmetric Total Synthesis of Tofacitinib
Adolfo Maricán, Mario J. Simirgiotis, Leonardo S. Santos
PII:
S0040-4039(13)01181-7
DOI:
http://dx.doi.org/10.1016/j.tetlet.2013.07.042
TETL 43240
Reference:
To appear in:
Tetrahedron Letters
Received Date:
Revised Date:
Accepted Date:
20 May 2013
3 July 2013
8 July 2013
Please cite this article as: Maricán, A., Simirgiotis, M.J., Santos, L.S., Asymmetric Total Synthesis of Tofacitinib,
Tetrahedron Letters (2013), doi: http://dx.doi.org/10.1016/j.tetlet.2013.07.042
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Asymmetric Total Synthesis of Tofacitinib
Adolfo Maricán,a Mario J. Simirgiotisb and Leonardo S. Santosa,*
aLaboratory of Asymmetric Synthesis, Chemistry Institute of Natural Resources, University of Talca, Talca, P.O. Box 747, Chile.
bLaboratory of Natural Products, Department of Chemistry, University of Antofagasta, Antofagasta, P.O. Box 170, Chile.

Tetrahedron Letters
1
TETRAHEDRON
LETTERS
Pergamon
Asymmetric Total Synthesis of Tofacitinib
Adolfo Maricán,a Mario J. Simirgiotisb and Leonardo S. Santosa
*
aLaboratory of Asymmetric Synthesis, Chemistry Institute of Natural Resources, University of Talca, Talca, P.O. Box 747, Chile
bLaboratory of Natural Products, Department of Chemistry, University of Antofagasta, Antofagasta, P.O. Box 170, Chile
Abstract— A novel stereoselective synthesis of Tofacitinib (CP-690,550), a Janus tyrosine kinase (JAK3) specific inhibitor, has been
achieved starting from (5S)-5-hydroxypiperidin-2-one in 10 steps from 2 with a 9.5% overall yield. The potentiality of this synthetic route
is the obtention of tert-butyl-(3S,4R)-3-hydroxy-4-methylpiperidine-1-carboxylate (6b) as a new chiral precursor involved in the synthesis
of CP690,550, in a three-step reaction, without epimerizations, rather than the 5 or more steps used in described reactions to achieve this
compound from analogues of 6b.
Keywords: CP-690,550, JAK3 inhibitor, Mitsunobu reaction, alane reduction
© 2013 Elsevier Science. All rights reserved
Numerous immunosuppressants have been employed for
organ transplantation and autoimmune related diseases.
However, there is an unmet medical need for a safe drug.
Major complications have been observed in transplant
patients such as nephrotoxicity, neurotoxicity, diabetes
mellitus, hyperlipidemia, and hypertension with common
immunosuppressive agents cyclosporin A, tacrolimus,
mycophenolate mofetil, and sirolimus.1 Inhibition of Janus
Kinase 3 (JAK3), a hematopoetic cell-restricted tyrosine
pyrrolo[2,3-d]pyrimidin-4-yl)amino)piperidin-1-yl)-3-
oxopropanenitrile) is a small molecule designed by Pfizer,
also known as CP-690,550 with the chemical structure of
substituted piperidine linked to a deazapurine core, as
depicted in Figure 1. It is a promising immunosuppressant
compound, less toxic than predecessors and very effective,
orally active and described as a JAK3 specific inhibitor,
which has demonstrated efficacy against psoriasis,
rheumatoid arthritis, Chron’s disease, kidney transplant
rejection, and ulcerative colitis.2-5
kinase,
represents
an
attractive
target
for
immunosuppression owing to its limited distribution in
tissue and specific role in lymphoid homeostasis. The Janus
protein tyrosine kinases (JAK1, JAK2, JAK3, and TYK2)
mediate intracellular signaling of numerous cytokines,
therefore play a critical role in a variety of biological
processes, including the regulation of hematopoiesis and
immune and inflammatory responses.2 The compound
Tofacitinib,
(3-((3R,4R)-4-methyl-3-(methyl(7H-
———
* Corresponding author. Tel.: +56 71 201575; fax: +56 71 200448.
E-mail address: lssantos@utalca.cl (L.S. Santos).

2
Tetrahedron Letters
Compound 413 was obtained by the addition of
phenylselenide chloride to 3 followed by elimination with
H2O2 (30%) achieving the product in 60% overall yield.
Then, Grignard methylcuprate addition to 4 gave 514 in 62%
yield and >94% de (determined by using ChiralPack-OD
HPLC column). After several problems in the optimization
of this particular reaction by means of diastereoselectivities,
following our proposal, alane reduction of 5 improved the
yields considerably of the piperidine product (78%) when
compared with the use of boranes (45%). Then, TBAF
deprotection afforded free alcohol 6b15 in 75% yield. It is
worth to mention that by using HF, we obtained the amine
and alcohol deprotection, however this compound did not
afforded 1-NH due to problems in the Mitsunobu reaction.
With synthons 6b moiety obtained, we turned our attention
to the exploration of Mitsunobu protocol by addition 7.
Previously, the feasibility of the Mitsunobu route from 7,
generated by functionalizing the corresponding commercial
Figure 1. The chemical structure of CP–690,550 (Tofacitinib).
The synthetic approach of Tofacitinib employed by Pfizer
is a 4-step transformation yielding the precursor (3R,4R)-1-
benzyl-N-4-dimethylpiperidin-3-amine
from
4-
methylpyridin-3-amine, followed by a resolution step with
a di-p-toluoyltartrate salt to achieve enantiopurity. That
synthesis is completed by a reduction of the substituted
pyridine derivative. This route is efficient in the production
of the enantiomerically pure material needed for large scale
production of CP-690,550.3
available
6-amino-7-deazapurine
through
HCHO/
NaBH3CN reaction in MeCN/AcOH conditions, was
evaluated through model studies. Among all protocols
employed for the addition of 7 to 6b, best yields for 1-Boc
o
Despite the published route for the synthesis of this
compound has been published,3,6-7 we proposed an
alternative strategy based on the precursor 3-hydroxy-4-
methylpiperidine 6. According to our retrosynthetic
analysis applied to the target CP-690,550 (Figure 2), 5 is
converted in the free alcohol 6, which under Mitsunobu
were observed by using Ph3P, DIAD, Dioxane, 100 C, 2 h
(68% yield, >94% de), or di-tert-butyl azodicarboxylate
o
(DTBAD),16 n-Bu3P, THF, 0 C to r.t., 18 h (48% yield,
>94% de).
17
Finally, Boc deprotection with ZnBr2 of 1-Boc in CH2Cl2
followed by the coupling of the resulting amine 1-NH18
(95%) with commercial available cyanoacetic acid through
EDC/HOBt catalyzed reaction afforded 13,5-7 in 80% yield
(9.5% overall yield from 2). Furthermore, no
epimerizations were observed during the synthesis of 1.
In summary, a new asymmetric convergent route has been
developed for the total synthesis of CP-690,550, thorough
the optimization of the Mitsunobu conditions for the
reaction between two designed hydroxypiperidine and
pyrrolopirimidine precursor molecules. Our strategy
allowed the synthesis of 1 in a three-step reaction from 6b,
without epimerizations, rather than the 5 or more steps used
in classical reactions through analogues of this compound.
conditions
by
using
4-N-methylaminopyrrolo[2,3-
d]pyrimidine afforded 1-NH that after deprotection and
addition of nitrile-propanamide side-chain achieves CP–
690,550 (Tofacitinib).
CN
OH
HN
N
6
O
N
H
NMe
NMe
N
N
NHMe
N
N
N
N
H
N
7
Acknowledgments
H
1
1-NH
N
N
H
Authors are grateful to the Fondecyt (1110022) and Anillo
ACT 11107 for financial support. A.M. thanks CONICYT
―
Figure 2. Retrosynthetic analysis of CP-690,550
Avanzado‖ (79090038).
The total synthesis employed in this work is depicted in
Scheme 1. Since there is only one approach for the
synthesis described in literature thorough SNAr of a
(3S,4R)-3-NH2-piperidine analogue of 6b,3-7 we propose a
complete new approach for the synthesis of this new
immunosuppressive compound. Following the sequence
depicted in Scheme 1, compound 28 was obtained in
multigram scale through the methodology described by
Herdeis.9 Then, hydroxyl protection with TBDPS-
Cl/imidazole afforded the protected alcohol 2-OTBDPS10
(96%), followed by N-Boc protection by using
BuLi/DABCO/Boc2O11 that gave 312 in 85% yield.
References
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Magnuson, K.S.; Martin, W.H.; Rizzuti, B.J.; Sawyer, P.S.;
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Conklyn, M.J.; Elliott, E.A.; Koslov, E.R.; Fisher, M.B.;
Strelevitz, T.J.; Yoon, K.; Whipple, D.A.; Sun, J.; Munchhof,
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Woodworth, T.G.; Gaweco, A.S.; Beals, C.R.; Littman, B.H.;

Tetrahedron Letters
3
Fisher, D.A.; Smith, J.F.; Zagouras, P.; Magna, H.A.;
Saltarelli, M.J.; Johnson, K.S.; Nelms, L.F.; Des Etages, S.G.;
Hayes, L.S.; Kawabta, T.T.; Finco–Kent, D.; Baker, D.L.;
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2. Kulagowski, J.J; Blair, W; Bull, R.J.; Chang ,C.; Deshmukh,
G.; Dyke, H.J.; Eigenbrot, C.; Ghilardi, N.; Gibbons, P.;
Harrison, T.K.; Hewitt, P.R.; Liimatta, M.; Hurley, C.A.;
Johnson, A.; Johnson, T.; Kenny, J.R.; Bir Kohli, P.; Maxey,
R.J.; Mendonca, R.; Mortara, K.; Murray, J.; Narukulla, R.;
BuLi, DABCO,
1. HMDS
OH
TBDPSCl
O
tBu Boc2O, -78˚C
O
tBu
OTBDPS
BuLi
PhSeCl
-78˚C
THF
2. H2O2
60%
Si
Si
THF
Ph
Ph
Ph
Ph
imidazole
DMF
96%
85%
O
N
H
O
N
H
O
N
O
N
Boc
Boc
2
3
4
NHMe
DIAD-Ph3P
Dioxane
100 oC, 2 h
68%
Boc
N
MeMgBr
CuBr.S(CH3)2
(CH3)3SiCl
Et2O
OTBDPS
OH
a. AlH3, THF, 78%
b. TBAF/THF, 75%
N
NMe
N
N
O
N
N
N
H
Boc
Boc
-78˚C, 62%
5
6b
7
1-Boc
N
N
H
CN
HN
ZnBr2
CH2Cl2
EDC/HOBt
CH2Cl2
N
NMe
N
O
NC
CO2H
80%
95%
NMe
N
N
N
N
H
N
H
1
1-NH
Scheme 1. Proposed synthetic route for the total synthesis of CP-690,550.
1.05 (s, 9H), 1.75-1.95 (m, 2H), 2.23 (ddd, J 17.2, 6.1, 6.1
Hz, 1H), 2.66 (ddd, J 17.2, 9.0, 6.1 Hz, 1H), 3.16-3.23 (m,
2H), 4.03-4.10 (m, 1H), 6.08 (s, 1H, NH), 7.30-7.50 (m, 6H),
7.60-7.70 (m, 2H). 13C NMR (100 MHz, CDCl3), : 19.0,
27.0, 27.6, 28.5, 48.8, 64.5, 127.8 (4xC), 129.9 (4xC), 130.2
(2xC), 135.5 (2xC), 172.3. HRMS (ESI): m/z calc. for
[C21H27NO2Si + H]+ 354.1889; found: 354.1893. Anal. calcd
for C21H27NO2Si: C, 71.34; H, 7.70; N, 3.96; O, 9.05. Found:
C, 71.42; H, 7.68; N, 3.94; O, 9.08.
4. Vijayakrishnan, L.; Venkataramana, R.; Gulati, P. Trends
Pharmacol. Sci. 2011, 32, 25–34.
5. Seavey, M.M.; Dobrzanski, P. Biochem. Pharmacol. 2012,
83, 1136–1145.
6. Matsumura, Y.; Ogino, T.; Libendi, S.S.; Onomura, O. 209th
ECS Meeting, Abstract #952, 2006.
7. Cabello-Sanchez, N.; Jean, L.; Maddaluno, J.; Lasne, M.-C.;
Rouden, J. J. Org. Chem. 2007, 72, 2030–2039.
8. Analytical data for compound 2: []D = -12.9 (c 1.0,
CH3OH). >96% ee determined by HPLC using a Chiralpack
OD column. m.p. 120-121 oC, white solid. 1H NMR (400
MHz, CD3OD), : 1.82-2.01 (m, 2H), 2.28 (ddd, J 16.0, 7.0,
7.0 Hz, 1H), 2.51 (ddd, J 16.0, 7.0, 7.0 Hz, 1H), 3.19 (dd, J
12.0, 5.0, 1H), 3.40 (dd, J 12.0 Hz, 4.0 Hz, 1H), 4.09 (m, 1H).
13C NMR (100 MHz, CD3OD), : 28.0, 28.9, 49.0, 63.5,
172.3. HRMS (ESI): m/z calc. for [C5H10NO2 + H]+ 116.0712;
found: 116.0710. Anal. calcd for C21H27NO2Si: C, 71.34; H,
7.70; N, 3.96; O, 9.05. Found: C, 71.42; H, 7.68; N, 3.94; O,
9.08.
11. Kaiser, E. M.; Yun, H. H. J. Org. Chem. 1970, 35, 1348-
1351.
12. Analytical data for compound 3: []D = -21.9 (c 1.0,
EtOAc). Colourless oil. FT-IR (KBr cell): 1775 and 1720
cm-1. 1H NMR (400 MHz, CDCl3), : 1.05 (s, 9H), 1.47 (s,
9H), 1.80-1-90 (m, 2H), 2.40 (ddd, J 17.0, 6.0, 6.0 Hz, 1H),
2.71 (ddd, J 17.0, 9.0, 6.0 Hz, 1H), 3.39 (dd, J 13.0, 3.0 Hz,
1H), 3.70 (dd, J 13.0, 4.0 Hz, 1H), 4.12-4.18 (m, 1H), 7.30-
7.46 (m, 6H), 7.63-7.70 (m, 4H). 13C NMR (100 MHz,
CDCl3), : 18.5, 26.8, 27.6, 28.1, 30.6, 51.6, 64.9, 82.1,
127.5, 129.6, 133.0, 135.0, 152.1, 170.3. HRMS (ESI): m/z
calc. for [C26H34NO4Si + H]+ 453.2335; found: 453.2333.
Anal. calcd for C26H34NO4Si: C, 68.84; H, 7.78; N, 3.09; O,
14.11. Found: C, 68.88; H, 7.81; N, 3.10; O, 14.13.
9. Herdeis, C. Synthesis 1986, 3, 232–233.
10. Analytical data for compound 2-OTBDPS: []D = -14.9 (c
1.0, EtOAc). m.p. 79-80 oC, colorless crystal. FT-IR (KBr
1
cell): 3210 and 1675 cm-1. H NMR (400 MHz, CDCl3), :

2
Tetrahedron Letters
13. Analytical data for compound 4: []D = +39.0 (c 1.0,
EtOAc). Colorless oil. FT-IR (KBr cell): 1770 and 1722
cm-1. 1H NMR (400 MHz, CDCl3), : 1.07 (s, 9H), 1.48 (s,
9H), 3.65 (dd, J 13.0, 4.0 Hz, 1H), 3.91 (dd, J 13.0, 6.0 Hz,
1H), 4.32-4.41 (m, 1H), 5.88 (d, J 10.0 Hz, 1H), 6.56 (dd, J
10, 4.0 Hz, 1H), 7.30-7.42 (m, 6H), 7.63-7.70 (m, 4H). 13C
NMR (100 MHz, CDCl3), : 18.7, 26.6, 27.6, 50.1, 63.5,
82.5, 126.0, 127.5, 129.6, 132.6, 135.0, 144.0, 151.8, 162.3.
HRMS (ESI): m/z calc. for [C26H33NO4Si + H]+ 452.2257;
found: 452.2260. Anal. calcd for C26H33NO4Si: C, 69.14; H,
7.36; N, 3.10; O, 14.17. Found: C, 69.33; H, 7.37; N, 3.11;
O, 14.18.
14. Analytical data for compound 5: []D = -42.0 (c 1.0,
EtOAc). Colorless oil. FT-IR (KBr cell): 1770 and 1725
1
cm-1. H NMR (400 MHz, CDCl3), : 0.80 (d, J 6.6 Hz,
3H), 1.06 (s, 9H), 1.48 (s, 9H), 2.00-2.20 (dd, J 18.0, 6.0
Hz, 2H), 2.85 (dd, J 18.0, 8.0 Hz, 1H), 3.45 (dd, J 17.0, 3.0
Hz, 1H), 3.61-3.72 (m, 2H), 7.35-7.48 (m, 6H), 7.63-7.70
(m, 4H). 13C NMR (100 MHz, CDCl3), : 17.8, 18.7, 26.5,
27.6, 34.1, 39.0, 49.0, 71.0, 82.0, 127.4, 129.5, 132.6,
135.0, 151.4, 170.0. HRMS (ESI): m/z calc. for
[C27H37NO4Si + H]+ 468.2570; found: 468.2565. Anal.
calcd for C27H37NO4Si: C, 69.34; H, 7.97; N, 2.99; O,
13.68. Found: C, 69.50; H, 8.00; N, 3.00; O, 13.73.
15. Analytical data for compound 6b: []D = +4.0 (c 1.0,
o
EtOAc). M.p. 96-97 C, colorless solid. FTIR (KBr cell):
1
1683 cm-1. H NMR (400 MHz, CDCl3), : 1.05 (d, J 6.0
Hz, 3H), 1.15-1.32 (m, 2H), 1.46 (s, 9H), 1.66 (ddd, J 10.0,
6.0, 3.1 Hz, 1H), 2.00 (br s, 1H, OH), 2.56 (dd, J 12.0, 10.0
Hz, 1H), 2.70 (t, J 12.0, 1H), 3.20 (ddd, J 10.0, 10.0, 4.5
Hz, 1H), 3.97 (d, J 12.0 Hz, 1H), 4.21 (dd, J 12.0, 4.3 Hz,
1H). 13C NMR (100 MHz, CDCl3), : 17.7, 28.5, 32.0,
38.5, 43.5, 50.0, 72.7, 80.0, 155.0. HRMS (ESI): m/z calc.
for [C11H22NO3 + H]+ 216.1600; found: 216.1598. Anal.
calcd for C11H21NO3: C, 61.37; H, 9.83; N, 6.51; O, 22.29.
Found: C, 61.54; H, 9.86; N, 6.53; O, 22.36.
16. Bell, I. M.; Beshore, D. C.; Gallicchio, S. N.; Williams, T.
M. Tetrahedron Lett. 2000, 41, 1141-1145.
17. (a) Shankaraiah, N.; da Silva, W. A.; Andrade, C. K. Z.;
Santos, L. S. Tetrahedron Lett. 2008, 49, 4289-4291. (b)
Nigam, S. C.; Mann, A.; Taddei, M.; Wermuth, C. -G. Synth.
Commun. 1989, 19, 3139–3142.
18. Analytical data for compound 1-NH is in accordance with
1
references 3, 5-7: H NMR (400 MHz, CDCl3), : 1.10 (d, J
7.0 Hz, 3H), 1.58-1.81 (m, 2H), 1.82-1-99 (m, 1H), 2.44-2.59
(m, 1H), 2.78-3-10 (m, 3H), 3.25-3-40 (m, 1H), 3,46 (s, 3H),
4.85-5.00 (m, 1H), 6.59 (d, J 3.5 Hz, 1H), 7.05 (d, J 3.5 Hz,
1H), 8.33 (s, 1H), 10.50 (br s, 1H). HRMS (ESI): m/z calc. for
[C13H19N5 + H]+ 246.1719; found: 246.1721. Anal. calcd for
C13H19N5: C, 63.65; H, 7.81; N, 28.55. Found: C, 63.82; H,
7.84; N, 28.65.