Rapid and efficient synthesis of stable isotope labeled [ 13C4, D4]-5-(hydroxymethyl)thiazole: Versatile building block for biologically interesting compounds

Article abstract of DOI:10.1002/jlcr.1576

5-(Hydroxymethyl)thiazole is a versatile building block for many biologically active compounds. A rapid and efficient four- step synthesis of its stable isotope labeled counterpart with four ¹³C and four deuterium atoms in 32% total yield is reported. Condensation of [¹³C ₂]-chloro acetic acid with [¹³C]-thiourea gave [ ¹³C₃]-2,4-thiazolidinedione. Reaction of [ ¹³C₃]-2,4-thiazolidinedione with phosphorus oxybromide and [¹³C, D]-DMF (Me₂N¹³CDO) produced [ ¹³C₄ D]-2,4-dibromo- thiazole-5-carboxaldehyde. The resultant aldehyde was then reduced by sodium borodeuteride to [ ¹³C₄, D₂]-(2,4-dibromo- thiazol-5-yl)-methanol. Catalytic deuteration of [¹³C₄, D₂]-(2,4- dibromo-thiazol-5-yl)-methanol by palladium black with deuterium gas at 1 atm pressure and room temperature produced completely de-brominated [ ¹³C₄, D₄]-5-(hydro- xymethyl)thiazole. De-bromination of the 2,4-dibromothiazole by the catalysis of palladium black provides a simple and convenient synthetic method for the stable isotope labeled and potentially radioactive isotope labeled thiazole compounds. Copyright

Full text of DOI:10.1002/jlcr.1576

Research Article
Received 5 October 2008,
Revised 20 November 2008,
Accepted 8 December 2008
Published online 13 March 2009 in Wiley Interscience
(
www.interscience.wiley.com) DOI: 10.1002/jlcr.1576
Rapid and efficient synthesis of stable isotope
4
1
labeled [ C D ]-5-(hydroxymethyl)thiazole:
3
, 4
versatile building block for biologically
interesting compounds
Ã
Ronghui Lin, Rhys Salter, and Yong Gong
5
step synthesis of its stable isotope labeled counterpart with four C and four deuterium atoms in 32% total yield is
-(Hydroxymethyl)thiazole is a versatile building block for many biologically active compounds. A rapid and efficient four-
13
1
reported. Condensation of [ C ]-chloro acetic acid with [ C]-thiourea gave [ C ]-2,4-thiazolidinedione. Reaction of
3
13
13
2
3
1
3
13
]-2,4-thiazolidinedione with phosphorus oxybromide and [ C, D]-DMF (Me
13
13
[
thiazole-5-carboxaldehyde. The resultant aldehyde was then reduced by sodium borodeuteride to [
C
3
2
N CDO) produced [ C4, D]-2,4-dibromo-
1
3
C
4,
D
D ]-(2,4-dibromo-thiazol-5-yl)-methanol by palladium black with
2
]-(2,4-dibromo-
1
thiazol-5-yl)-methanol. Catalytic deuteration of [ C4,
3
2
1
deuterium gas at 1 atm pressure and room temperature produced completely de-brominated [ C4, D ]-5-(hydro-
3
4
xymethyl)thiazole. De-bromination of the 2,4-dibromothiazole by the catalysis of palladium black provides a simple and
convenient synthetic method for the stable isotope labeled and potentially radioactive isotope labeled thiazole
compounds.
Keywords: stable isotope label; synthesis; 5-(hydroxymethyl)thiazole; catalytic de-bromination; palladium black
Introduction
possess a difference of at least 3 amu’s compared with the
unlabeled parent molecules.
Several methods for the synthesis of 5-(hydroxymethyl)thia-
5-(Hydroxymethyl)thiazole (1, Figure 1) is a versatile and
important building block for many biologically active com- zole from small molecules have been reported in literature; for
pounds. For example, it was built into anti-viral protease example, multiple-step synthesis from chloro-acetic acid ethyl
1
–4
5
anti-diabetes agents, and anti-cancer agents. In
6
8
ester, ethyl formate, and thioformate, from 1,3-dichloropro-
inhibitors,
particular, thiazol-5-ylmethyl carbamate commonly resides in
9
penes and sodium thiocyanate, from 3-oxo-propionic acid ethyl
1
10
many anti-viral agents, such as anti-HIV drug Ritonavir (2). To ester and thioformate, as well as from 2,4-thiazolidinedione
support our drug development efforts stable isotope-labeled and DMF. However, none of these methods were suitable to
1
1
5-(hydroxymethyl)thiazole with at least six isotope atoms is
required.
be directly used for the stable isotope-labeled synthesis due to
various reasons such as not commercially available starting
Stable isotope-labeled compounds are powerful tools as materials, poor yields, or drastic reaction conditions. Herein, we
internal standards for liquid chromatography–mass spectro-
report a rapid and efficient synthesis of the stable isotope-
metry (LC–MS–MS) quantitative analysis. In order to better labeled 5-(hydroxymethyl)thiazole (3).
evaluate biological behavior of drug candidates, accurate
7
analysis is required to establish their exposure in both animal
and human subjects. LC–MS has been widely used to quantify
the low levels of drug compounds found in biological samples The synthesis of stable-labeled [ C4,
Results and discussion
1
3
D ]-5-(hydroxymethyl)thia-
4
1
3
13
2
such as blood, plasma, serum, urine, or tissues. The nature of the zole starting from [ C ]-chloro acetic acid (4) and [ C]-thiourea
internal standard is an important aspect of any quantitative was outlined in Scheme 1.
analytical procedure. For LC–MS analysis, the optimum internal
standard is a pure, stable, isotopically labeled counterpart of the
drug compound, with a sufficiently large mass difference to
nullify the effect of naturally abundant heavy isotopes in
Global Preclinical Development, Johnson & Johnson Pharmaceutical Research
the drug molecule. This mass difference depends upon the and Development L.L.C., 1000 Route 202, Raritan, NJ 08869, USA
molecular weight and elements of the analyte. The stable
*
Correspondence to: Ronghui Lin, Global Preclinical Development, Johnson and
isotopes should be incorporated at non-exchangeable positions.
The stable isotope-labeled compounds should be chemically
Johnson Pharmaceutical Research and Development LLC, 1000 Route 202,
Raritan, NJ 08869, USA.
pure, free or less than 0.1% of unlabeled compound, and usually E-mail: Ronghui.Lin@yahoo.com
J. Label Compd. Radiopharm 2009, 52 110–113
Copyright r 2009 John Wiley & Sons, Ltd.

R. Lin et al.
1
First at all, commercially available [ C ]-chloro acetic acid (4) found that, at 1 atm pressure, 10% palladium on charcoal
3
2
1
3
was condensed with [ C]-thiourea upon heating to give catalyzed hydrogenation of 2,4-dibromo-thiazol-5-yl-methanol
compound 5 in 92% yield. in the presence of sodium acetate in methanol, produced only
Next, reaction of compound 5 with excess of phosphorus the mono-de-brominated product, (4-bromo-thiazol-5-yl)-
1
3
oxybromide and N,N-dimethyl(formyl- C, D)amide produced methanol, but none of the desired 5-(hydroxymethyl)thiazole.
compound 6 in 43% isolated yield. Slight H/D exchange on the Under the same conditions, the catalytic hydrogenation of
formyl group was observed in a trial reaction. To avoid the H/D (2,4-dibromo-thiazol-5-yl)-methanol with Adam’s catalyst (plati-
exchange exchangeable proton was exchanged to deuterium num oxide) also produced only quantitative (4-bromo-thiazol-5-
with deuterated methanol prior to its reaction with phosphorus yl)-methanol. It is known that the 4-bromo substituent on the
1
3
11,12
oxybromide and N,N-dimethyl(formyl- C, D)amide. In addition, thiazole is much less reactive than the 2-bromo substituent.
worthy of mention is that some 2,4-dibromo-thiazole-5-carbox- Remarkably, when much more reactive palladium black was
aldehyde was converted to its corresponding dimethyl acetal used as catalyst for the hydrogenation (2,4-dibromo-thiazol-
when methanol-containing solvent system was used at the 5-yl)-methanol was converted to completely de-brominated
isolation and purification process. Thus, the crude product was 5-(hydroxymethyl)thiazole at 1 atm pressure. Similarly, under the
purified by chromatography with gradient 0–5% ethyl acetate/ same conditions, (4-bromo-thiazol-5-yl)-methanol was comple-
heptane on silica gel.
tely de-brominated to 5-(hydroxymethyl)thiazole quantitatively.
Then, the resultant aldehyde was reduced readily by sodium Thus, the catalytic hydro-de-bromination of the 2,4-dibromo
borodeuteride in deuterated methanol to the corresponding thiazole could be achieved stepwise, first at 2-position, then at
alcohol 7 in 81% yield.
4-position. In addition, the catalytic reaction in the absence of
Catalytic hydrogenation of (2,4-dibromo-thiazol-5-yl)-metha- the base (sodium acetate) failed to produce desired product due
nol utilizing 10% palladium on charcoal, in a Parr hydrogenation to formation of un-identified by-products. Replacement of
reactor at 4 atm pressure, has been reported by Kerdesky and sodium acetate with other bases such as triethyl amine
1
1,12
13
Seif.
sphere pressure is preferred for the small-scale reaction and D ]-5-(hydroxymethyl)thiazole (3), catalytic deuteration of [ C
For the catalytic reduction, deuteration at near atmo- produced comparable yield. Finally, toward the desired [ C4,
1
3
4
4,
convenience. An exploratory model on hydrogenation of (2,4-
2
D ]-(2,4-dibromo-thiazol-5-yl)-methanol (7), at 1 atm pressure
dibromo-thiazol-5-yl)-methanol was first investigated. It was and room temperature, by palladium black with deuterium gas
in the presence of sodium acetate in deuterated methanol
produced targeted compound 3 in near quantitative yield.
D
13C
D
13C
D
Experimental
13C
S
OH
OH
N
N
1
[
3
13
2
C ]-chloro acetic acid, [ C]-thiourea, and N,N-dimethyl(for-
13C
D
S
13
myl- C,D)amide were purchased from Isotec (a division of
Sigma-Aldrich, St. Louis, MO). Phosphorus oxybromide, sodium
acetate, and palladium black were purchased from Sigma-
Aldrich and were used as received. Other reagents and solvents
were obtained from VWR International.
H NMR spectra were acquired on a Bruker 300-Avance
spectrometer operated at 300.13 MHz with TMS as an internal
13
standard. C NMR spectra were acquired at 75.47 MHz in
1
3
S
Ph
N
S
i-Pr
1
OH
Ph
O
N
H
N
H
N
O
N
N
H
Me
O
i-Pr O
deuterated chloroform unless stated otherwise. Chemical shifts
are expressed in parts per million (ppm, d scale). LC–MS analysis
was performed on an Agilent 1100 series LC/MSD with an
2
Ritonavir
s
Agilent Zorbax SB C18 column (3 mm, 2.1 Â 50 mm), gradient
Figure 1. 5-(Hydroxymethyl)thiazole (1), Ritonavir (2), and the stable isotope
labeled 5-(hydroxymethyl) thiazole (3).
10–100% CH
3
CN-H
2
O, 0.05% TFA or 0.05% NH
4
OAc over 3.5 min,
O
D
13C
O
N 13
Br
13C
N
13C
Br
D
13C
Br
13C
D
C
13C
O
D
H N
13C
2
13CH
S
13C
S
NaBD , CD OD
13C
S
13C
heat
2%
CD
3
OD
O
4
3
OH
Cl
2
POBr
3
HN
13C
N
HO
13C
H2
+
S
81%
9
43%
13C
Br
H N
2
O
7
4
5
6
D , Pd black
2
AcONa, CD OD
3
9
9%
D
13C
D
13C
D
13C
OH
N
13C
D
S
3
Scheme 1. Synthesis of stable isotope labeled 5-(hydroxymethyl)thiazole (3).
J. Label Compd. Radiopharm 2009, 52 110–113
Copyright r 2009 John Wiley & Sons, Ltd.
www.jlcr.org

R. Lin et al.
1
3
13
hold at 100% CH CN for 2.5 min, flow rate 0.5 mL/min, detection 2.2 (s, br, 1H). C NMR (CDCl ) d 138.5–136.7 (m, C-5), 135.8
3
3
1
3
13
13
2
at 214 and 254 nm, mass scan range 120–1500 amu. Flash (s, C-2), 121.6 (d, C-4, J = 75.5 Hz), 58.0–56.7 (m, CD OH). MS
1
chromatography was performed using a Teledyne Isco Combi- m/z 279 (MH) .
s
Flash Companion system and a RediSep silica gel column.
1
[
3
C
4,
D
4
]-5-(hydroxymethyl)thiazole (3)
1
[
3
C
3
]-2,4-thiazolidinedione (5)
1
Into a flask under nitrogen with a mixture of [ C D ]-(2,4-
3
4
,
2
This was prepared by modifying a reported literature proce- dibromo-thiazol-5-yl)-methanol (7, 2.875 g, 10.34 mmol) and
1
3
dure. sodium acetate (1.790g, 21.72 mmol, 2.1 eq) was added palla-
To a solution of [ C]-thiourea (1.611 g, 21.16 mmol) in water dium black (1.437g) and anhydrous deuterated methanol (83 mL).
2 mL) in a flask under nitrogen was added dropwise a solution Deuterium gas was slowly bubbled into the suspension under
1
3
(
1
3
of [ C
The reaction mixture was stirred at room temperature for agitation was connected to a balloon filled with deuterium
0 min, then at 1051C overnight. The mixture was then cooled to overnight. The reaction was followed by TLC analysis with 5%
room temperature, and a white solid was collected by MeOH/CH Cl . The palladium black was filtered off and rinsed
2
]-chloro acetic acid (4, 2.0 g, 21.16 mmol) in water (2 mL). stirring for 5 h, and then the reaction flask under vigorous
3
2
2
suction–filtration, rinsed with water, and dried at 451C under with deuterated methanol. The filtrate was concentrated; and re-
vacuum to give 2.178 g of the desired product. The filtrate was charged with CH Cl (50 mL) and sonicated. The remaining white
2
2
concentrated to dryness and re-dissolved in methanol and solid (presumably sodium bromide) was filtered and rinsed with
water, loaded with silica gel, evaporated to dryness, and CH Cl (50 mL). The filtrate was again concentrated to give the
subjected to column chromatography separation with 0–5% crude desired product as oil (1.50 g). Distillation of the crude
2
2
1
2
MeOH/CH Cl to give a second batch of the desired compound product under vacuum at 138–1401C/10 mmHg (lit. 140–1421C/
2
2
as white solid (1.268 g). The two batches of desired compound 10mmHg) gave the pure product as pale yellowish oil (1.27 g,
13
1
were combined to give 3.446 g (92% yield). H NMR (DMSO-d
6
)
99%). The product [ C4,
D
4
]-5-(hydroxymethyl)thiazole was
1
3
1
13
d 12.0 (s, br, 1H), 4.40 and 3.90 (each m, 2H). C NMR (DMSO-d6) confirmed by H and C NMR in CDCl and CD OD in comparison
3
3
1
3
13
13
d 174.1–172.9 (m, C-2, and C-4), 36.2 (d, CH
MS m/z 121 (MH) .
2
, J = 45.3 Hz). with authentic non-labeled compound, 5-(hydroxymethyl)thia-
zole (1), and by LCMS analysis, and HPLC analysis. For compound
1
1
13
13
3
, H NMR (CDCl ) d 2.2 (s, br, 1H). C NMR (CDCl ) d 153.5 (t, C-
3 3
13 13
1
[
3
C
4, D]-2,4-dibromo-thiazole-5-carboxaldehyde (6)
2, J = 30.9 Hz), 141.4–137.7 (m, C-5 and C-4), 57.4–55.8 (m,
1
3
13
13
CD
2
3
OH). C NMR (CD OD) d 155.6 (t, C-2, J = 32.4Hz),
13 13
1
[
3
C
3
]-2,4-thiazolidinedione (5, 1.268 g, 10.57 mmol) was first
13
1
m/z 124.2 (MH , 100% relative intensity), 123.2 (M-1)H , 13%
13
relative intensity. For non-labeled compound 1, C NMR (CD
41.5–140.7 (m, C-5 and C-4), 57.6–56.0 (m, CD OD). MS
2
dissolved in deuterated methanol (5 mL). The resultant solution
was stirred for 5 min at room temperature and then evaporated
to dryness under vacuum. This process was repeated one more
time. The resultant dry residue was then thoroughly mixed with
phosphorus oxybromide (15.15 g, 52.83 mmol, 5 eq) under
nitrogen. To the well-mixed reaction mixture at 01C under
1
1
3
OD)
1
55.5 (s, C-2), 141.6 (s, C-5), 141.1 (s, C-4), 57.3 (s, CH OD).
2
Conclusion
1
3
nitrogen was added N,N-dimethyl(formyl- C, D)amide (0.942 ml,
889 mg, 10.84 mmol, 1.12 eq). The reaction mixture was stirred at
A rapid and efficient four-step synthesis for stable isotope
1
3
labeled [ C4,
D
C and four deuterium atoms in 32% total yield is reported.
4
]-5-(hydroxymethyl)thiazole (3) with four
1
3
room temperature for 1 h, then at 70–801C for another hour, and
then at 1051C for 4 h. The mixture was then cooled to 01C; and
quenched with 100 ml of ice water; and then extracted with
1
3
13
[
to give [ C
C ]-chloro acetic acid (4) was condensed with [ C]-thiourea
2
1
3
3
]-2,4-thiazolidinedione (5). Reaction of compound 5
1
with excess phosphorus oxybromide and [ CD]-DMF
3
CH
with saturated NaHCO
2
Cl
2
(total ꢀ600 mL). The extracts were combined, washed
, dried over Na SO , filtered, and
1
3
13
3
2
4
(Me N CDO) produced [ C D]-2,4-dibromo-thiazole-5-carbox-
2 4,
aldehyde (6). Facile reduction of the resultant aldehyde 6 by
concentrated. The residue was then loaded with silica gel and
evaporated to dryness. The mixture loaded on silica gel was
purified by column chromatography with gradient 0–5%
EtOAc/heptane on silica gel to give the desired compound as
1
3
sodium borodeuteride provided [ C4,
-yl)-methanol (7). Remarkably, catalytic deuteration of com-
pound 7 by palladium black with deuterium gas at 1 atm
2
D ]-(2,4-dibromo-thiazol-
5
1
3
1
3
a pale yellow solid (1.32 g, 43%). C NMR (CDCl
1
3
) d 182.1–180.6
m, C(O)D), 145.2–145.1 (m, C-2), 137.4–135.5 (m, C-5),
pressure produced completely de-brominated [ C4,
D
4
]-5-
hydroxymethyl)thiazole (3). The stable isotope labeled 5-
hydroxymethyl)thiazole (3) may be utilized as a valuable
3
13
13
(
(
(
1
3
1
33.2–132.2 (m, C-4). MS m/z 274 (MH) .
1
building block in synthesis of isotope labeled biologically
interesting compounds and pharmaceutical compounds. Cata-
lytic hydrogenation of the 2,4-dibromothiazole with palladium
black at 1 atm pressure and room temperature provides
simplicity and convenience for the stable isotope labeling
synthesis and potential for radioactive isotope labeling synthesis
of thiazole compounds.
1
3
[
4, 2
C D ]-(2,4-dibromo-thiazol-5-yl)-methanol (7)
1
3
To a solution of [ C4, D]-2,4-dibromo-thiazole-5-carboxaldehyde
6, 3.315 g, 12.77 mmol) in dry CH Cl (4 mL) was added
anhydrous deuterated methanol (60 mL). To the resultant
(
2
2
solution at 01C was added sodium borodeuteride (507 mg,
12.11 mmol). The reaction mixture was stirred at 01C for 2 h, then
at room temperature for another 2 h. The mixture was then
loaded with silica gel, and evaporated to dryness. This mixture Acknowledgement
was further purified by column chromatography separation on
silica gel with gradient 0–5% MeOH/CH
product as yellowish solid (2.875 g, 81% yield). H NMR (CDCl ) d discussion and David C. Evans for reviewing the manuscript.
2 2
Cl to give the desired We wish to thank Maarten Vliegen and Luc Moens for helpful
1
3
www.jlcr.org
Copyright r 2009 John Wiley & Sons, Ltd.
J. Label Compd. Radiopharm 2009, 52 110–113

R. Lin et al.
References
Mass Spectrom. 2005, 19, 401–407; (d) E. Stokvis, H. Rosing,
L. Lopez-Lazaro, J. H. M. Schellens, J. H. Beijnen, Biomed.
Chromatogr. 2004, 18, 400–402.
[
1] D. J. Kempf, J. B. Taylor, D. J. Triggle (Eds.), Comprehensive
Medicinal Chemistry II, Vol. 8, 2006, pp. 187–197, Elsevier Ltd.,
Oxford, UK, and the relevant references therein cited.
[
8] G. N. Kumar, T. R. Herrin, D. J. Kempf, D. A. Betebenner, X. Chen,
D. W. Norbeck, H. L. Sham, K. M. Patel, J.-H. Liu, J.-H. J. Tien,
E. J. Stoner, P. J. Stengel, D. J. Plata, P. A. Oliver, L. Kolaczkowski,
S. M. Hannick, D. A. Dickman, A. J. Cooper, S. L. Condon, Aust Pat
Appl AU 2004201149 A1 20040422, 2004.
9] G. F. Hillstrom, M. A. Hackman, R. Murugan, E. F. V. Scriven,
J. R. Stout, J. Yang, ARKIVOC (Gainesville, FL, United States) [online
computer file] 2001, 6, 94–99. Can be found under http://
www.arkatusa.org/ark/journal/Volume2/Part3/Abramovitch/RA-
[
2] L. L. Klein, H.-J. Chen, M. C. Yeung, C. A. Flentge, J. T. Randolph,
P. P. Huang, D. K. Hutchinson, D. J. Kempf, PCT Int Appl WO
2
008027932 A2 20080306, 2008.
3] M. C. Desai, A. Y. Hong, H. Liu, L. Xu, R. W. Vivian, PCT Int Appl WO
008010921 A2 20080124, 2008.
4] G. A. E. Van’t Klooster, H. A. De Kock, P. J.-M. B. Raboisson,
C. F. E. Van den Eynde, PCT Int Appl WO 2008046860 A2 20080424,
[
[
[
2
241/RA-241.pdf
2
008.
[
10] D. J. Kempf, D. W. Norbeck, J. W. Erickson, L. M. Codacovi,
H. L. Sham, J. J. Plattner, Eur Pat Appl EP 402646 A1 19901219,
1990.
[11] F. A. Kerdesky, L. S. Seif, Synth. Commun. 1995, 25,
2639–2645.
[
5] D. Stenkamp, S. G. Mueller, T. Lehmann-Lintz, G. J. Roth, J. Kley,
K. Rudolf, A. Heckel, M. Schindler, R. Lotz, PCT Int Appl WO
2008022979 A1 20080228, 2008.
6] J. W. Brown, Q. Dong, B. R. Paraselli, J. A. Stafford, M. B. Wallace,
H. Wijesekera, PCT Int Appl WO 2008054956 A2 20080508, 2008.
[
[
7] (a) D. Hesk, P. McNamar, J. Labelled Compd. Radiopharm. 2007, 50, [12] F. A. Kerdesky, L. S. Seif, Synth. Commun. 1995, 25, 4081–4086.
8
1
75–887; (b) H. H. Maurer, Anal. Bioanal. Chem. 2007, 388, [13] S. R. Pattan, C. Suresh, V. D. Pujar, V. V. K. Reddy, V. P. Pasal,
315–1325; (c) E. Stokvis, H. Rosing, J. H. Beijnen, Rapid Commun.
B. C. Koti, Indian J. Chem. 2005, 44B, 2404–2408.
J. Label Compd. Radiopharm 2009, 52 110–113
Copyright r 2009 John Wiley & Sons, Ltd.
www.jlcr.org