Development of a scalable process for the synthesis of DNDI-VL-2098: A potential preclinical drug candidate for the treatment of visceral leishmaniasis

Article abstract of DOI:10.1021/acs.oprd.6b00331

A process suitable for kilogram-scale synthesis of (2R)-2-methyl-6-nitro-2-{[4-(trifluoromethoxy)phenoxy]- methyl}-2,3-dihydroimidazo[2,1-b][1,3]oxazole (DNDI-VL-2098, 2), a preclinical drug candidate for the treatment of visceral leishmaniasis, is described. The four-step synthesis of the target compound involves the Sharpless asymmetric epoxidation of 2- methyl-2-propen-1-ol, 8. Identification of a suitable synthetic route using retrosynthetic analysis and development of a scalable process to access several kilograms of 2 are illustrated. The process was simplified by employing in situ synthesis of some intermediates, reducing safety hazards, and eliminating the need for column chromatography. The improved reactions were carried out on the kilogram scale to produce 2 in good yield, high optical purity, and high quality.

Full text of DOI:10.1021/acs.oprd.6b00331

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Full Paper
Development of a Scalable Process for the Synthesis
of DNDI-VL-2098: A Potential Preclinical Drug
Candidate for the Treatment of Visceral Leishmaniasis
Vijay S. Satam, Srinivasa Rao Pedada, Pasumpon Kamraj, Nakita Antao, Apoorva Singh, Rama
Mohan Hindupur, Hari Narayan Pati, Andrew M. Thompson, Delphine Launay, and Denis Martin
Org. Process Res. Dev., Just Accepted Manuscript • DOI: 10.1021/acs.oprd.6b00331 • Publication Date (Web): 06 Dec 2016
Downloaded from http://pubs.acs.org on December 11, 2016
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Organic Process Research & Development
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N
O
O2N
OCF3
O (R)
CH2
O
(R)
H3C
N
OH
O
H3C
CH3
2
DNDI-VL-2098
OCF3
21
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Development of a Scalable Process for the Synthesis of DNDI-VL-2098: A Potential
Preclinical Drug Candidate for the Treatment of Visceral Leishmaniasis
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Vijay S. Satam, Srinivasa Rao Pedada, Pasumpon Kamraj, Nakita Antao, Apoorva Singh, Rama
Mohan Hindupur, Hari N. Pati*
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Process Chemistry Division, Advinus Therapeutics Ltd., 21 & 22 Phase II, Peenya Industrial Area,
Bangalore ꢀ 560058, Karnataka, India.
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Andrew M. Thompson
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Auckland Cancer Society Research Centre, School of Medical Sciences, The University of Auckland,
Private Bag 92019, Auckland 1142, New Zealand.
Delphine Launay, Denis Martin
Drugs for Neglected Diseases initiative (DNDi), 15 Chemin Louis Dunant, 1202 Geneva, Switzerland.
*Corresponding author:
Hari N. Pati
Process Chemistry Division,
Advinus Therapeutics Ltd.,
21 & 22 Phase II, Peenya Industrial Area,
Bangalore ꢀ 560058, Karnataka, India.
eꢀmail: hari.pati@advinus.com
Tel No: (+91)9900212096
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TOC Graphic:
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N
O
O2N
OCF3
O (R)
CH2
O
H3C (R)
N
OH
O
H3C
CH3
OCF3
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2
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DNDI-VL-2098
Keywords:
Leishmaniasis, Sharpless asymmetric epoxidation, scalable process, safety hazards
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ABSTRACT: A process suitable for kilogramꢀscale synthesis of (2R)ꢀ2ꢀmethylꢀ6ꢀnitroꢀ2ꢀ{[4ꢀ
(trifluoromethoxy)phenoxy]methyl}ꢀ2,3ꢀdihydroimidazo[2,1ꢀb][1,3]oxazole (DNDIꢀVLꢀ2098, 2),
a
preclinical drug candidate for the treatment of visceral leishmaniasis, is described. The fourꢀstep synthesis of
the target compound involves Sharpless asymmetric epoxidation of 2ꢀmethylꢀ2ꢀpropenꢀ1ꢀol, 8. Identification
of a suitable synthetic route using retrosynthetic analysis and development of a scalable process to access
several kilograms of 2 are illustrated. The process was simplified by employing in situ synthesis of some
intermediates, reducing safety hazards, and eliminating the need for column chromatography. The improved
reactions were carried out on kilogramꢀscale to produce 2 in good yield, high optical purity, and high
quality.
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INTRODUCTION
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Visceral Leishmaniasis (VL), infamously known as kalaꢀazar (black fever) in the Indian subꢀcontinent, is
the most lethal form of leishmaniasis and is caused by protozoan parasites.1 This deadly disease is the
second largest parasitic killer in the world, surpassed only by malaria, with a worldwide distribution in Asia,
East Africa, South America, and the Mediterranean region.2 In the search for effective treatments for
visceral leishmaniasis, the Drugs for Neglected Diseases initiative (DNDi) recently evaluated fexinidazole
(1, Figure 1), a nitroimidazole being developed as a treatment for Human African Trypanosomiasis.
Fexinidazole 1 showed potential as a safe and effective oral drug for the treatment of visceral leishmaniasis
and is now in clinical trials.3 Earlier, through an agreement with TB Alliance and in association with the
ACSRC at the University of Auckland (NZ), DNDi screened about 70 other nitroimidazole analogs
belonging to four chemical subclasses and investigated them for antiꢀleishmanial activity. Through these
efforts, DNDIꢀVLꢀ2098 (2, Figure 1) was identified as a promising drug candidate for the treatment of
visceral leishmaniasis. To support preclinical studies of this nitroimidazoꢀoxazole based compound 2, the
process chemistry team at Advinus Therapeutics Ltd. initiated the development of a safe and scalable
process to produce it on kilogramꢀscale. In this communication, we wish to report a robust and practical
synthesis suitable for the preparation of multiꢀkilogram quantities of 2.
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O2N
N
N
N
O
CH3
O(R)
O2N
O
S
N
OCF3
CH3
1
CH3
2
Figure 1. Structures of fexinidazole (1) and DNDIꢀVLꢀ2098 (2).
ANTECEDENTS AND RESULTS
Having identified the target compound, DNDi collaborated with Advinus Therapeutics Ltd., India for its
kilogram scale synthesis. The process chemistry team at Advinus began route scouting to develop a scalable
and safe process for the synthesis of 2. The objective was to produce about 10 kg of 2 to support preclinical
and pharmaceutical development studies, within a stringent time frame, utilizing the available resources, and
with due regard for overall process efficiency and cost. During the initial drug discovery stage, the racemic
analog of 2 (DNDIꢀVLꢀ2001) as well as the Rꢀ and Sꢀenantiomers (DNDIꢀVLꢀ2098 = 2 and DNDIꢀVLꢀ
2099, respectively) were evaluated as potential drug candidates to treat visceral leishmaniasis. The Auckland
medicinal chemistry group had synthesized multiꢀgram quantities of the racemate using a route shown in
Scheme 1 that had been employed in initial work at the University of Auckland.4 Pure enantiomers needed
for preliminary efficacy and pharmacokinetic evaluation were prepared at the University of Auckland using
a route similar to that shown in Scheme 2 below, but using 2ꢀchloroꢀ4ꢀnitroimidazole in place of 2ꢀbromoꢀ4ꢀ
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nitroimidazole in step 3. This route was based on methods published by Otsuka Pharmaceuticals5 for the
synthesis of analogs of 2.
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The process chemistry team initially considered Scheme 1 for the synthesis of DNDIꢀVLꢀ2001, which
could then be subjected to chiral resolution to obtain 2 in high optical purity. However, because
nitroimidazoles are insufficiently basic for salt resolution processes, attention was focused on asymmetric
synthetic approaches. After carrying out a detailed literature survey and careful retrosynthetic analysis, two
pathways were designed for the synthesis of 2. Both pathways (Figure 2) used 2ꢀbromoꢀ4ꢀnitroimidazole 3
and 2ꢀmethylꢀ2ꢀpropenꢀ1ꢀol 8 as key starting materials, and employed Sharpless asymmetric epoxidation of
commercially available 2ꢀmethylꢀ2ꢀpropenꢀ1ꢀol 8. At this juncture, we also needed to ensure the availability
of 2ꢀbromoꢀ4ꢀnitroꢀ1Hꢀimidazole 3 in large quantities since it was identified as one of the key starting
materials. Although the reported routes for the synthesis of 3 are relatively straightforward, several
limitations such as poor yield, high cost, and hazardous nitration reactions prevented their use for largeꢀscale
production. Hence, the team undertook process development of 3 in parallel to process development of 2.
An improved, safe, and practical process suitable for the preparation of multiꢀkilogram quantities of 3 has
recently been reported.6
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O2N
O2N
N
N
N
N
O2N
Cl
N
K2CO3
Br
CH3
m-CPBA
DCM, 40 °C
Br
CH3
CH3
Br
DMF, 65 °C
N
H
CH2
O
CH2
4
5
3
6
HO
OCF3
N
O
O2N
OCF3
7
N
O
NaH/DMF
50 °C
CH3
racemic
DNDI-VL-2001
Scheme 1. Synthesis of the racemate DNDIꢀVLꢀ2001
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Figure 2. Retrosynthetic pathways for the synthesis of DNDIꢀVLꢀ2098 (2)
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O
S
Cl
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O
O
S
(S)
Ti(O-i-Pr)4,
D(-)DiPT, TBHP
O
CH2
O
NO2
H3C
(R)
OH
10
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H3C
O
H3C
O2N
DCM
TEA, DCM
NO2
8
9
11
O2N
N
Br
N
HO
OCF3
N
N
H
O2N
OCF3
O
(R)
N
Br
7
N
3
(R)
O
CH3
H3C
NaH/DMF
85-90 °C
O
K2CO3,
DMF, 60 °C
2
12
Scheme 2. Proposed synthetic route for 2 based on retrosynthetic pathway 1
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In the initial Sharpless asymmetric epoxidation step, the team faced several challenges with respect to the
isolation and stability of chiral epoxide 9. Following completion of the epoxidation reaction, the usual
aqueous workꢀup resulted in substantial loss of 9 owing to its high water solubility. Nonꢀaqueous workꢀup
involving vacuum distillation was unsuitable for scaleꢀup due to the viscous nature of the pot residue and the
tendency of epoxide 9 to undergo polymerization. The problems associated with high water solubility and
stability during isolation of 9 prompted us to consider its in situ derivatization with pꢀnitrobenzenesulfonyl
chloride (10), instead of the two step process proposed in Scheme 2. However, in situ reaction of 9 with pꢀ
nitrobenzenesulfonyl chloride (10) to prepare intermediate 11 was extremely tedious for several reasons. In
the first step to prepare epoxide 9, tertꢀbutyl hydroperoxide (TBHP) was used as an epoxidation agent. After
completion of the asymmetric epoxidation reaction, it was essential to reduce the excess TBHP by treatment
with trimethyl phosphite in order to prevent its reaction with pꢀnitrobenzenesulfonyl chloride (10). On a
larger scale, because of the violent and exothermic reaction, it was necessary to quench the excess TBHP
very carefully over a long period of time under cold conditions (below ꢀ20 °C) to avoid any unsafe situation.
Moreover, the necessity for high vacuum distillation to remove excess trimethyl phosphite and trimethyl
phosphate, formed after reduction of TBHP, rendered scaleꢀup even more difficult. In addition, during the
sulfonylation of 9, traces of trimethyl phosphite that remained in the reaction mixture reacted with pꢀ
nitrobenzenesulfonyl chloride (10) to form the corresponding sulfinate as an impurity, which was very
difficult to separate from the reaction mixture. The multiple recrystallizations needed to obtain substantially
pure intermediate 11 inevitably resulted in lower yields of 11. In situ sulfonylation reactions carried out
without quenching TBHP resulted in poor yields and purity of compound 11; this was presumably due to the
reaction of pꢀnitrobenzenesulfonyl chloride (10) with TBHP and alcoholic byꢀproducts.
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Difficulties in the synthesis and scaleꢀup of 11 led us to explore the possibility of making an ester
derivative using benzoyl or pꢀnitrobenzoyl chloride. Synthesis of ester derivative 14 (Scheme 3) by reaction
of the S enantiomer of epoxide 9 with pꢀnitrobenzoyl chloride has been reported in the literature.7 In fact,
DNDIꢀVLꢀ2098 and its analogs were synthesized by Tsubouchi et al8 using ester 14, as described in Scheme
3. However, this route was lengthy and unsuitable for scaleꢀup as purification of compounds 16, 18, and 2
needed column chromatography. In our hands, attempts to purify these compounds by recrystallization
resulted in lower yields. In addition, the problems associated with quenching of TBHP using trimethyl
phosphite, and removal of excess trimethyl phosphite as well as trimethyl phosphate, formed after
quenching, persisted even in the synthesis of (R)ꢀ(2ꢀmethyloxiranyl)methylꢀ4ꢀnitrobenzoate (14).
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O2N
N
N
NO2
O2N
N
N
1
2
Cl
O
(R)
TEA
NO2
K2CO3
Cl
O
H3C
OH
3
4
5
6
ethyl acetate,
60-65 °C, 6 h
O
methanol,
rt, 2 h
O
H
13
14
H3C (R)
15
O
7
8
9
O2N
O2N
N
N
N
N
CH3SO2Cl
pyridine,
DBU
Cl
OH
O2N
Cl
N
ethyl acetate,
rt, 2 h
Cl
10
11
12
13
14
15
16
17
18
19
20
10-15 °C, 2 h
OH
O
S
N
OH
O
CH3
(R) O
H3C (R)
H3C (R)
17
16
O
H3C
18
HO
OCF3
N
O2N
OCF3
O
(R)
7
N
O
CH3
NaH/DMF
50 °C, 2 h
2
Scheme 3. Reported route for the synthesis of 2
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HO
OH
Ti(O-i-Pr)4,
D(-)DiPT, TBHP
OCF3
O
CH2
O
H3C
7
(R)
OH
OH
H3C
(R)
H3C
K2CO3, methanol,
43%
DCM
OCF3
19
9
8
O
Cl
S
O
O2N
O
O
S
NaOH
O
O
H3C
O
(R)
NO2
OH
water/DCM,
92%
10
(S)
21
OCF3
O
TEA, DCM
H3C
20
OCF3
O2N
N
Br
N
H
3
N
Br
N
O2N
OCF3
O(R)
O2N
OCF3
OH
(R)
K2CO3
DMF,
N
N
O
O
CH3
CH3
DIPEA,
110-115 °C,
96%
2
22
90 °C, 51%
Scheme 4. An improved synthesis of DNDIꢀVLꢀ2098 (2)
These difficulties led us to focus our efforts on the second retrosynthetic pathway shown in Figure 2.
The process team had now realized that, on a large scale, it would be difficult to make a suitable derivative
of epoxide 9 in situ while keeping the epoxy ring intact and without quenching all of the TBHP. The team
therefore began to explore the possibility of making a derivative of 9 in situ by opening the epoxy ring,
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which, after isolation, would allow for subsequent reconstruction of this ring. It occurred to us that epoxide 9
could be treated in situ with pꢀtrifluoromethoxyphenol (7) in the presence of a base, causing nucleophilic
opening of the epoxide ring to give (R)ꢀ2ꢀmethylꢀ3ꢀ(4ꢀtrifluoromethoxyphenoxy)propaneꢀ1,2ꢀdiol (19)
directly, following aqueous workꢀup (Scheme 4). The reaction could be carried out under mild anhydrous
conditions and would not be hampered by the presence of TBHP, thus potentially eliminating the tedious
low temperature quenching step (with associated safety issues) and the need for high vacuum distillation.
Furthermore, it was obvious that the sulfonylation of diol 19 with pꢀnitrobenzenesulfonyl chloride (10)
would occur regioselectively at the terminal hydroxyl group to afford compound 20, owing to the steric
hindrance between the pꢀnitrobenzenesulfonyl group of 10 and both the 4ꢀtrifluoromethoxyphenoxy group
and the 2ꢀmethyl substituent adjacent to the tertiary hydroxyl group. Nosylate 20 could then be treated with
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base
to
restore
the
epoxy
ring,
affording
optically
pure
(R)ꢀ2ꢀmethylꢀ2ꢀ(4ꢀ
trifluoromethoxyphenoxymethyl)oxirane (21). Oxirane 21 could subsequently be reacted with 2ꢀbromoꢀ4ꢀ
nitroimidazole (3) to obtain the desired DNDIꢀVLꢀ2098 (2).
To validate the feasibility of this approach (Scheme 4), smallꢀscale reactions (25 g) were initially
performed. Fortunately, the in situ reaction of epoxide 9 with pꢀtrifluoromethoxyphenol (7) proceeded
smoothly to give the diol 19 in 45% yield. In this step, the reaction mixture obtained after Sharpless
asymmetric epoxidation of 8 was added slowly to a mixture of pꢀtrifluoromethoxyphenol (7) and anhydrous
potassium carbonate in dry methanol at ambient temperature, and then stirred at 60 °C for 16 h. After
cooling to ambient temperature, the reaction mixture was extracted with dichloromethane, which was then
thoroughly washed with water, dilute sodium hydroxide, and brine solution. The organic layer was
separated, dried over anhydrous sodium sulfate, and concentrated to provide a pale yellow gummy solid,
which, on purification by column chromatography using silica gel, gave the desired diol 19 as an offꢀwhite
solid in 45% yield. Next, diol 19 was subjected to sulfonylation at the terminal hydroxyl group to obtain the
corresponding nosylate, 20. The subsequent baseꢀcatalyzed ring closure proceeded smoothly to give oxirane
21 in high enantiomeric excess and >95% purity (HPLC a/a). Oxirane 21 was then treated with 2ꢀbromoꢀ4ꢀ
nitroimidazole (3) and N,Nꢀdiisopropylethylamine to afford compound 22, which was further cyclized
(K2CO3/DMF) to provide the desired DNDIꢀVLꢀ2098 (2) in 51% yield. In order to ascertain the exact
configuration, compound 2 thus obtained was subjected to single crystal Xꢀray crystallographic analysis.
The single crystal was obtained by slow evaporation of its saturated solution in acetone. The Xꢀray structure
depicted in Figure 3 unambiguously established the Rꢀconfiguration of 2.
Figure 3. Single crystal Xꢀray structure of (R)ꢀDNDIꢀVLꢀ2098 (2)
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Encouraged by these results, we decided to study the scalability of Scheme 4 to prepare DNDIꢀVLꢀ2098
(2) in kilogram quantities. The chemistry discussed above gave rise to a putative process for the synthesis of
2, but several issues needed to be addressed before proceeding to largeꢀscale synthetic efforts. Especially,
issues such as the preparation of anhydrous TBHP for the moisture sensitive Sharpless asymmetric
epoxidation and quenching of TBHP after in situ synthesis of the diol 19 needed to be resolved. In addition,
molecular sieves, used to maintain anhydrous conditions in the Sharpless asymmetric epoxidation reaction,
and column chromatography, used to isolate pure 19, had to be eliminated for convenient scaleꢀup.
The initial Sharpless asymmetric epoxidation reaction proceeded with excellent conversion (>90% by
GC), however, it was essential to maintain anhydrous conditions throughout the reaction. The main reason
for this is because water destroys the titaniumꢀtartrate complex, leading to a slow reaction rate and poor
enantioselectivity of the desired epoxide.7 In addition, the presence of water, under mildly acidic conditions,
causes the epoxide ring to open, which in turn results in the formation of diol byꢀproducts.
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An even greater challenge was to prepare anhydrous TBHP on a larger scale from commercially available
aqueous TBHP (~70%). Whereas TBHP in 70% aqueous solution is relative safe to handle, its anhydrous
form is highly reactive, flammable, toxic, and prone to violent decomposition by adventitious catalysts and
hence is exceptionally dangerous. Procedures to prepare anhydrous TBHP in dichloromethane or toluene
have been reported earlier.9ꢀ10 However, these procedures involve azeotropic distillation, which needs to be
carried out behind a blast shield in a wellꢀventilated fume hood because of the flammable and explosive
nature of TBHP.11 The safety concerns associated with azeotropic distillation on a large scale led us to
devise a simpler procedure to obtain anhydrous TBHP. The commercially available 70% aqueous TBHP
solution was first stirred with dichloromethane. The organic layer was carefully separated, stirred with
anhydrous sodium sulfate for 30 min and then decanted. The procedure was repeated thrice. The solution of
anhydrous TBHP in DCM was carefully collected in a clean and dry container. The strength of this solution
of TBHP in DCM was determined by iodometric titration.9 To the solution thus obtained were added
activated molecular sieves (4 Å) and the mixture was stirred gently for 30 min. All operations were
performed under a nitrogen blanket. This TBHP solution was then stored in an airtight highꢀdensity
polyethylene (HDPE) container under nitrogen atmosphere at 4 °C. This method to obtain anhydrous TBHP
was effective, simple and safe, as it eliminated safety hazards associated with heating the TBHP solution
during azeotropic distillation. Our team carried out this procedure many times to prepare anhydrous TBHP
and used it in subsequent asymmetric epoxidation reactions to consistently obtain the desired epoxide 9 in
high enantiomeric excess and excellent purity. Anhydrous TBHP in DCM is reported to be unstable at room
temperature and relatively stable when stored at 4 °
C.9 At Advinus, the solution stored at 4 °C under
nitrogen for more than 1 year did not show any appreciable loss in strength as determined by iodometric
titration. It is not feasible to determine the moisture content of the anhydrous TBHP solution at ambient
temperature because of the tendency of TBHP to react with the Karl Fisher reagent. The water content in the
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anhydrous TBHP solution can be measured at lower temperature (~ ꢀ60 °C) in specialized equipment using
Hydranal; however, such equipment was not available at Advinus. Hence to determine the efficacy of the
anhydrous solution of TBHP in dichloromethane, the process team decided to use a performance test by
trialing it in small scale (10 g) asymmetric epoxidation reactions before using it for larger scale work.
Several experiments were carried out attempting to avoid molecular sieves in the asymmetric epoxidation
reaction. However, as reported earlier,9 the reactions that were performed in the absence of molecular sieves
proceeded slowly, achieved lower conversion (~40ꢀ45%), and yielded epoxide 9 in poor enantiomeric
excess. Considering the high moisture sensitivity of this reaction, it was decided to perform further
optimization efforts using freshly activated molecular sieves (4 Å).
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Next, experiments were designed to develop the formation of epoxide 9 and its in situ reaction with phenol
7. In these experiments, the asymmetric epoxidation reaction was carried out using molecular sieves and
anhydrous TBHP, prepared as described above. All reactions were performed under a nitrogen atmosphere.
In a typical reaction, (ꢀ)ꢀdiisopropylꢀDꢀtartrate was added to the solution of 2ꢀmethylꢀ2ꢀpropenꢀ1ꢀol (8) in
dry dichloromethane at ꢀ30 °C. To the reaction mixture was added titanium tetraisopropoxide at ꢀ30 °C
under gentle stirring. After stirring the reaction mixture at ꢀ30 °C for 1.0 h, the solution of anhydrous TBHP
in dichoromethane was added over a period of 1.0 h, maintaining the temperature between ꢀ25 and ꢀ30 °C.
The reaction mixture was then allowed to warm to ꢀ5 °C and stirred for 2.0 h. The progress of the reaction
was monitored by GC. After the epoxidation was complete, this reaction mixture was added slowly into the
mixture of pꢀtrifluoromethoxyphenol (7) and anhydrous potassium carbonate in methanol at room
temperature. The resulting reaction mixture was then stirred at 60 °C for 22 h, after distilling off
dichloromethane. The progress of this reaction was monitored by HPLC. Upon completion, the reaction was
quenched by adding water and the reaction mixture was then extracted with dichloromethane. The twoꢀ
phase mixture appeared translucent and did not give a clear phase separation, presumably due to the
presence of molecular sieves and titanium tetraisopropoxide used in epoxidation reaction. Clear phase
separation, however, was achieved after filtering the reaction mixture through celite. The organic layer was
separated and washed with water. At this stage, as revealed by GC and HPLC analysis, the organic layer
contained the desired diol 19, excess TBHP, unreacted pꢀtrifluoromethoxyphenol (7), and tartrate ester.
It occurred to us that TBHP in the organic layer could be removed if the organic layer was washed with
dilute aqueous sulfuric acid. Sulfuric acid reacts with TBHP to give peroxymonosulfuric acid, which in turn
can be washed away by water. In general, for Sharpless asymmetric epoxidation reactions, the excess TBHP
cannot be destroyed using dilute aqueous sulfuric acid because acid catalyzes nucleophilic attack by water
on the epoxide ring, causing it to open. In our case, however, it was possible to destroy the excess TBHP
using dilute aqueous sulfuric acid since epoxide 9 had been converted to diol 19 by reacting it with pꢀ
trifluoromethoxyphenol (7). Although the peroxymonosulfuric acid formed after reaction of sulfuric acid
with TBHP is a strong oxidant, we considered that its solution in the aqueous layer would be too dilute to
cause any harm to the product. With this rationale in mind, we decided to wash the organic layer, obtained
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after asymmetric epoxidation and subsequent reaction of resulting epoxide 9 with phenol 7, with dilute
aqueous sulfuric acid (15%) under cold conditions and analyze it by GC and HPLC. GC analysis confirmed
that after one wash with dilute sulfuric acid the organic layer was free of TBHP. HPLC analysis further
revealed that the organic layer was free of any unwanted byꢀproducts, suggesting that diol 19 did not
undergo oxidation or decomposition after the dilute sulfuric acid wash. The unreacted phenol 7 and tartrate
ester were easily removed by washing the organic layer with 25% aqueous sodium hydroxide solution. The
organic layer was then washed with 10% brine solution, dried over sodium sulfate, and concentrated to
obtain a pale yellow gummy solid. The crude gummy solid so obtained was stirred in nꢀhexane to afford diol
19 as a white solid in 43% yield. HPLC analysis of 19 revealed that the compound was ~99% pure and could
be used for the next reaction without further purification. After these improvements, the team was confident
of synthesizing epoxide 9 on a large scale and subsequently converting it to diol 19 without prior quenching
of TBHP. We felt that, even on a large scale, this strategy of ignoring TBHP during in situ reaction of 9 with
phenol 7 and later destroying it with dilute sulfuric acid would be both safe and the most convenient option.
Having developed both the epoxidation reaction to make 9 and its in situ reaction with 7, we turned our
attention to regioselective sulfonylation of diol 19 at the terminal hydroxyl group and the subsequent baseꢀ
catalysed intramolecular nucleophilic substitution reaction to reconstruct the epoxy ring. Diol 19 was treated
with pꢀnitrobenzenesulfonyl chloride (10) in the presence of triethylamine in dichloromethane. The reaction
was carried out at room temperature for 2.0 h to obtain sulfonylated compound 20. Upon completion of this
reaction, the reaction mixture was washed with aqueous hydrochloric acid (4.0 N), to remove excess
triethylamine and triethylamine hydrochloride formed during reaction, followed by brine solution (10%).
We envisaged that because the pꢀnitrobenzenesulfonyl group is an excellent leaving group, its
intramolecular displacement to reconstruct the epoxy ring should be possible under mildly basic biphasic
conditions, which could be carried out in situ, removing the need to isolate compound 20. The solution of 20
in dichloromethane obtained after sulfonylation was therefore stirred with aqueous sodium hydroxide
solution at 15ꢀ20 °C and the progress of this reaction was monitored by HPLC. HPLC analysis revealed that
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nosylate
20
was
easily
converted
into
the
desired
(R)ꢀ2ꢀmethylꢀ2ꢀ(4ꢀ
trifluoromethoxyphenoxymethyl)oxirane (21) in 1.0 h. After the reaction was complete, the reaction mixture
was worked up to obtain desired oxirane 21 in >99% enantiomeric excess, ~95% chemical purity, and 92%
yield.
While this development work was underway, our process team had also developed a robust process for the
synthesis of multiꢀkilogram quantities of the required starting material, 2ꢀbromoꢀ4ꢀnitroimidazole (3).6 With
both 3 and 21 in hand, the team proceeded to the coupling reaction. As disclosed in the experimental section,
the reaction was performed by stirring a mixture of imidazole 3 and oxirane 21 in N,Nꢀ
diisopropylethylamine at 110ꢀ115 °C. The reaction selectively produced compound 22 as a major product
along with 5ꢀnitro isomer of 22 as a minor product (~1% a/a by HPLC). The crude solid so obtained was
used for the final cyclization reaction without purification. In the final step, compound 22 was cyclized
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using anhydrous potassium carbonate in DMF at 90 °C to obtain DNDIꢀVLꢀ2098 (2) having >99.5% chiral
purity and >99.5% chemical purity by HPLC (area %) in 51% yield. The safer and reliable largeꢀscale route
for the synthesis of DNDIꢀVLꢀ2098 (2) was thus established. The process chemistry team at Advinus
successfully utilized this improved synthetic protocol to produce 10.2 kilograms of 2 in two batches of 5.6
kg and 4.6 kg. This compound is currently being evaluated as a potential treatment for visceral
leishmaniasis.
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CONCLUSIONS
The new process for the synthesis of DNDIꢀVLꢀ2098 (2) has several key advantages over the reported
routes, such as experimental simplicity in the conversion of epoxide 9 to key intermediate 21 by means of in
situ reactions, greatly simplified isolation procedures, economy due to savings on solvents required for
chromatographic purification, and easy scalability to access kilogram quantities of 2 in high chemical and
chiral purities. Largeꢀscale applicability of this method was successfully demonstrated by producing 10.2 kg
of DNDIꢀVLꢀ2098 API (active pharmaceutical ingredient) in good yield and excellent purity. Future work
on this new process will focus on further improvements in the synthesis of hydroxyl derivative 22 and on
development of a suitable method for recrystallization of crude 2 to obtain final API having suitable crystal
form and habit as well as particle size distribution.
EXPERIMENTAL SECTION
All raw materials were purchased from S.D. Fine Chem Ltd., India, and used without further purification.
1
The H NMR, 13C NMR and 19F NMR spectra were recorded on a VARIAN 400 MHz NMR spectrometer.
The chemical shifts are reported as δ ppm relative to tetramethylsilane. The FTIR spectra were obtained as a
potassium bromide pellet using a Spectrum 100 PerkinꢀElmer FTꢀIR spectrometer. Mass spectra were
recorded on a QꢀTOF Premier spectrometer, using electronꢀspray ionization. Melting points were
determined on a Buchi (Bꢀ545) melting point apparatus and are uncorrected. HPLC chromatographic
purities were determined on a Waters HPLC using a Cosmosil Cꢀ18 column (250 mm × 4.6 mm). Chiral
purities were determined on a Waters HPLC using a CHIRALPAK ADꢀH column (250 mm × 4.6 mm, 5.0
µm) and CHIRALPAK IC column (250 mm × 4.6 mm, 5.0 µm) for compound 21 and compound 2,
respectively. Specific Optical Rotations (SORs) were recorded on a Rudolph Research Analytical
AUTOPOL V automatic polarimeter.
Preparation of anhydrous tert-butyl hydroperoxide (TBHP). In a clean and dry 20 L capacity fourꢀneck
round bottom flask was charged TBHP (70% in water, 10.0 L) at 25ꢀ30 °C. To it was added 10% aqueous
sodium chloride solution (500 mL), followed by dichloromethane (2.0 L). The biphasic mixture was stirred
for 15 min and allowed to settle for 1.0 h. The organic layer was separated and charged into another clean
and dry 20 L capacity fourꢀneck round bottom flask through a bed of anhydrous sodium sulfate. To the clear
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Organic Process Research & Development
solution thus obtained was charged anhydrous sodium sulfate (750 g) and the mixture was stirred gently for
30 min. The solution of TBHP in dichloromethane was decanted and the sodium sulfate was washed with
dichloromethane (2 × 250 mL). This procedure was repeated thrice. The strength of this TBHP solution was
then determined by iodometric titration.9 Finally, activated molecular sieves (4 Å, 1.0 kg) were added into
the TBHP solution. The translucent solution was stirred gently under a nitrogen blanket for 30 min and then
stored in an airtight highꢀdensity polyethylene (HDPE) container at 4 °C. Before proceeding to larger scale
reactions, the efficacy of anhydrous TBHP thus obtained was checked by performing a small scale (10.0 g)
asymmetric epoxidation reaction using this stock solution.
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(R)-2-Methyl-3-(4-trifluoromethoxyphenoxy)propane-1,2-diol (19). In a 50 L capacity AGLR (all glass–
lined reactor) equipped with a temperature probe, a condenser, addition funnel and a mechanical stirrer was
charged dichloromethane (12.0 L) and activated powdered molecular sieves (4 Å, 500 g) at room
temperature under nitrogen atmosphere. 2ꢀMethylꢀ2ꢀpropenꢀ1ꢀol (8) (2.0 kg, 27.78 mol) was added and the
mixture was cooled to ꢀ25 to ꢀ30 °C. To this solution was added (ꢀ)ꢀdiisopropylꢀDꢀtartrate (2.6 kg, 11.11
mol) and titanium(IV) isopropoxide (2.5 kg; 8.8 mol). The reaction mixture was stirred for 1.0 h at ꢀ25 to ꢀ
30 °C. Anhydrous TBHP in dichloromethane (83.2 mol) was then added to the reaction mixture over a
period of 1.0 h, maintaining the temperature between ꢀ25 and ꢀ30 °C. The reaction mixture was allowed to
warm slowly and then stirred for 1.0 h at ꢀ5 °C. The progress of the reaction was monitored by GC. After
completion of reaction, the reaction mixture was allowed to attain room temperature. It was then added into
a 200 L capacity AGLR (all glass–lined reactor) containing the reaction mixture of pꢀ
(trifluoromethoxy)phenol (7) (4.45 kg, 25 mol) and anhydrous potassium carbonate (17.2 kg, 125 mol) in
methanol (22 L) over a period of 2.0 h at room temperature, under a nitrogen atmosphere. During addition,
no exothermicity was noticed. The reaction mixture was heated at 60 °C while simultaneously removing
dichloromethane by distillation. The reaction mixture was then stirred at 60 °C for about 22 h. The progress
of the reaction was monitored by HPLC and GC analysis. After completion of the reaction, water (40 L) and
dichloromethane (30 L) were added to the reaction mixture. The mixture was stirred for 30 min and then
filtered through celite. The organic layer was separated and the aqueous layer was washed with
dichloromethane (10 L) and separated. The combined organic layer was then cooled to 0ꢀ5 °C and washed
with aqueous sulfuric acid (15%, 30 L), aqueous sodium hydroxide (25%, 3 × 20 L) and finally with brine
solution (10%, 2 × 10 L). It was dried over anhydrous sodium sulfate and concentrated to obtain a pale
yellow crude solid, which on stirring in nꢀhexane for 30 min gave (R)ꢀ2ꢀmethylꢀ3ꢀ(4ꢀ
trifluoromethoxyphenoxy)propaneꢀ1,2ꢀdiol (19) as a white solid (3.17 kg; 43%). Mp: 67ꢀ69 °C; HPLC: 99%
1
(a/a); H NMR (400 MHz, CDCl3): δ 7.16–7.14 (d, 2H, J=8.0 Hz), 6.92ꢀ6.90 (d, 2H, J=8.0 Hz), 3.96ꢀ3.89
(m, 2H), 3.74ꢀ3.71 (d, 1H, J=12.0 Hz), 3.61ꢀ3.58 (d, 1H, J=12.0 Hz), 2.60 (br, 1H), 2.08 (br, 1H), 1.30 (s,
3H); 13C NMR (100 MHz, CDCl3): δ 156.9, 143.0, 124.3ꢀ116.7 (q, J=255 Hz, CF3), 122.5, 115.3, 72.6, 72.2,
67.1, 21.7; IR (KBr, cmꢀ1): 3242, 2944, 1508, 1459, 1274, 1158, 918, 835; Mass (m/z): 266.1 (M)+.
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(R)-2-Methyl-2-(4-trifluoromethoxyphenoxymethyl)oxirane (21). In a 100 L capacity AGLR equipped
1
with a temperature probe, a condenser, and a mechanical stirrer was charged dichloromethane (20 L)
followed by diol 19 (4.0 kg, 15.04 mol) at room temperature. The solution was cooled to 0ꢀ5 °C and
triethylamine (2.73 kg, 27.07 mol) was added under stirring. To the reaction mixture was added a solution of
pꢀnitrobenzenesulfonyl chloride (10) (5.98 kg, 27.07 mol) in dichloromethane (12 L) over a period of 1.0 h
at 5–15 °C. The reaction mixture was brought to 25ꢀ30 °C and stirred for 2.0 h. The progress of the reaction
was monitored by HPLC analysis. Upon completion of the reaction, hydrochloric acid (4.0 N, 6.0 L) was
added to the reaction mixture and stirring was continued for 15 min while maintaining the temperature
below 30 °C. The organic layer containing compound 20 was separated, washed with brine solution (10%,
7.5 L), and cooled to 10ꢀ15 °C. A solution of sodium hydroxide (1.8 kg, 45.12 mol) in water (3.6 L) was
then added to this solution of 20 in dichloromethane. The biphasic reaction mixture thus obtained was stirred
for 1.0 h at 15–20 °C. The progress of the reaction was monitored by HPLC analysis. Upon completion of
the reaction, the aqueous layer was separated. The organic layer was washed with water (3 × 20 L) followed
by 10% brine solution (1 × 20 L), dried over anhydrous sodium sulfate, and concentrated to afford the crude
product. This crude product was dissolved in nꢀheptane and stirred for 30 min. The clear solution was then
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filtered
through
celite.
Evaporation
of
the
filtrate
gave
(R)ꢀ2ꢀmethylꢀ2ꢀ(4ꢀ
trifluoromethoxyphenoxymethyl)oxirane (21) as a yellow liquid (3.43 kg, 92%). HPLC: 96.4% (a/a); HPLC
1
(chiral): 99.3% (a/a); H NMR (400 MHz, CDCl3): δ 7.13–7.15 (d, 2H, J=8.8 Hz), 6.92–6.90 (d, 2H, J=8.8
Hz), 4.06–4.03 (d, 1H, J=10.4 Hz), 3.94–3.92 (d, 1H, J=10.0 Hz), 2.86–2.85 (d, 1H, J=4.4 Hz), 2.74–2.72
13
(d, 1H, J=4.8 Hz), 1.48 (s, 3H); C NMR (100 MHz, CDCl3): δ 157.1, 142.9, 124.3, 122.3, 116.7, 115.5,
71.8, 55.3, 51.7, 18.2; IR (KBr, cmꢀ1): 2929, 1505, 1193, 1030, 819; Mass (m/z): 248.2 (M)+.
(R)-1-(2-Bromo-4-nitroimidazol-1-yl)-2-methyl-3-(4-trifluoromethoxyphenoxy)propan-2-ol (22). In a
20 L capacity AGLR equipped with a temperature probe, a condenser, and a mechanical stirrer was charged
N,Nꢀdiisopropylethylamine (2.5 L), (R)ꢀ2ꢀmethylꢀ2ꢀ(4ꢀtrifluoromethoxyphenoxymethyl)oxirane (21) (3.5
kg, 14.11 mol), and 2ꢀbromoꢀ4ꢀnitroꢀ1Hꢀimidazole6 (3) (2.84 kg, 14.81 mol) at room temperature. The
resulting reaction mixture was heated to 110ꢀ115 °C and stirred for 2.0 h. The progress of the reaction was
monitored by HPLC analysis. Upon completion of the reaction, the reaction mixture was cooled to 25ꢀ30 °C.
To the reaction mixture was added dichloromethane (12 L) under stirring. The resulting clear solution was
washed with 3.0 N aqueous hydrochloric acid (2 × 14 L), 10% aqueous sodium bicarbonate solution (1 ×
17.5 L), and water (1 × 17.5 L). The organic layer was dried over anhydrous sodium sulfate and
concentrated to obtain 22 as a light brown gummy solid (5.93 kg, 96%). Mp: 95–97 °C; HPLC: 90% (a/a);
1
HPLC (chiral): 99.8% (a/a); H NMR (400 MHz, DMSO–d6): δ 8.35 (s, 1H), 7.32–7.30 (d, 2H, J=8.8 Hz),
7.04–7.02 (d, 2H, J=8.8 Hz), 5.5 (bs, 1H), 4.26–4.14 (dd, 2H, J=14.4 Hz), 3.87ꢀ3.80 (dd, 2H, J=9.6 Hz),
1.21 (s, 3H); 13C NMR (100 MHz, DMSO–d6): δ 157.0, 146.0, 142.0, 125.1, 124.0, 122.5, 122.0, 121.4,
119.0, 115.8, 72.9, 70.4, 54.6, 22.5; IR (KBr, cmꢀ1): 3354, 3318, 1539, 1508, 1458, 1327, 837; Mass (m/z):
440.5 (M + 1)+.
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1
2
(2R
)-2-Methyl-6-nitro-2-(4-trifluoromethoxyphenoxymethyl)-2,3-dihydroimidazo[2,1-b]oxazole (2). In
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a 100 L capacity AGLR equipped with a temperature probe, a condenser, and a mechanical stirrer was
charged N,Nꢀdimethylformamide (25 L), (R)ꢀ1ꢀ(2ꢀbromoꢀ4ꢀnitroimidazolꢀ1ꢀyl)ꢀ2ꢀmethylꢀ3ꢀ(4ꢀ
trifluoromethoxyphenoxy)propanꢀ2ꢀol (22) (5.0 kg, 11.36 mol), and anhydrous potassium carbonate (7.8 kg,
56.8 mol) at room temperature under a nitrogen blanket. The resulting reaction mixture was heated to 85ꢀ
90 °C and stirred for 6.0 h. The progress of the reaction was monitored by HPLC. After completion of the
reaction, the reaction mixture was poured slowly into an iceꢀwater mixture. The resulting mixture was then
stirred for 1.0 h. The solid precipitate was filtered, washed with water (20 L), followed by nꢀheptane (5 L),
and dried in an air oven at 45 °C for 8.0 h. The crude product thus obtained was dissolved in DCM (35 L) at
room temperature. To the solution was added nꢀheptane (35 L) in a thin stream over a period of 45 min at
room temperature. The resulting mixture was stirred for 45 min, and filtered to separate the solid. This solid
was washed with a mixture of DCM:n-heptane (1:3, 5 L) and dried in an air oven for 4.0 h to obtain
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1
compound 2 (2.08 kg, 51%). Mp: 169–171 °C; HPLC (area%): 99.52%; HPLC (chiral): 99.8% (a/a); H
NMR (400 MHz, CDCl3): δ 7.57 (s, 1H), 7.14–7.16 (d, 2H, J=10.0 Hz), 6.83–6.86 (d, 2H, J=7.2 Hz), 4.48–
4.50 (d, 1H, J=10.0 Hz), 4.22–4.24 (d, 1H, J=10.0 Hz), 4.05–4.10 (t, 2H, J=9.6 & 10.4 Hz), 1.79 (s, 3H);
13C NMR (100 MHz, CDCl3): δ 156.0, 155.8, 147.1, 143.5, 122.6, 115.5, 112.6, 122.6, 121.7 & 119.1 (JCꢀ
F=255.1 Hz), 116.6, 92.9, 71.8, 51.3, 23.0; 19F NMR (CDCl3, 376 MHz): δ ꢀ58.4; IR (KBr, cmꢀ1): 3155,
2996, 1607, 1456, 1281, 1106, 978, 921, 834,783, 708; Mass (m/z): 360.3 (M + 1)+ [α]25 = (+)8.445 (c
;
589
1.00 g/100 mL, CHCl3).
AUTHOR INFORMATION
Corresponding Author
Eꢀmail: hari.pati@advinus.com;
Tel No: (+91)9900212096
ACKNOWLEDGEMENTS
We thank the Drugs for Neglected Disease initiative (DNDi) for financial aid to support this research.
Specific funding was obtained through DNDi from the Bill and Melinda Gates Foundation, U.S.A.; the
Department for International Development (DFID), U.K.; Dutch Ministry of Foreign Affairs (DGIS), The
Netherlands; Federal Ministry of Education and Research (BMBF) through KfW, Germany; and Médecins
Sans Frontières (Doctors without Borders)/International. We also thank Advinus Therapeutics Ltd.,
Bangalore, India, for supporting this research.
Conflict of Interest: The authors declare no competing financial interest.
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REFERENCES
1
(1) (a) "Leishmaniasis". WHO Fact sheet N°375. World Health Organization (Retrieved April 29, 2015). (b)
James, W. D.; Berger, T. G.; Odom, R. B. Andrews' Diseases of the Skin: Clinical Dermatology; W. B.
Saunders Co. 2006. (c) Perry, D.; Dixon, K.; Garlapati, R.; Gendernalik, A.; Poche´, D.; Poche´, R. Am.
J. Trop. Med. Hyg. 2013, 88(4), 778.
2
3
4
5
6
7
8
9
(2) Desjeux, P. Trans. Royal Soc. Trop. Med. Hyg. 2001, 95(3), 239.
(3) Wyllie, S.; Patterson, S.; Fairlamb, A. H. Antimicrob. Agents Chemother. 2013, 57(2), 901.
(4) Thompson, A. M; O’Connor, P. D.; Blaser, A.; Yardley, V.; Maes, L.; Gupta, S.; Launay, D.; Martin, D.;
Franzblau, S. G.; Wan, B.; Wang, Y.; Ma, Z.; Denny, W. A. J. Med. Chem. 2016, 59, 2530−2550.
(5) (a) Tsubouchi, H.; Sasaki, H.; Kuroda, H.; Itotani, M.; Hasegawa, T.; Haraguchi, Y.; Kuroda, T.;
Matsuzaki, T.; Tai, K.; Komatsu, M.; Matsumoto, M.; Hashizume, H.; Tomishige, T.; Seike, Y.;
Kawasaki, M.; Sumida, T.; Miyamura, S. 2,3ꢀDihydroꢀ6ꢀnitroimidazo[2,1ꢀb]oxazoles. Eur. Pat. Appl. EP
1555267, 2005. (b) Goto, F.; Takemura, N.; Otani, T.; Hasegawa, T.; Tsubouchi, H.; Utsumi, N.; Fujita,
S.; Kuroda, H.; Shitsuta, T.; Sasaki, H. 1ꢀSubstituted 4ꢀnitroimidazole compound and process for
producing the same. Eur. Pat. Appl. EP 1553088, 2005.
(6) Srinivasa, R. P.; Satam, V. S.; Tambade, P. J.; Srinivas, K. A.; Hindupur, R. M.; Pati, H. N.; Launay, D.;
Martin, D. Org. Proc. Res. Dev. 2013, 17(9), 1149.
(7) Gao, Y.; Hanson, R. M.; Klunder, J. M.; Ko, S. Y.; Masamune, H.; Sharpless, K. B. J. Am. Chem. Soc.
1987, 109, 5765.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(8) Sasaki, H.; Haraguchi, Y.; Itotani, M.; Kuroda, H.; Hashizume, H.; Tomishige, T.; Kawasaki, M.;
Matsumoto, M.; Komatsu, M.; Tsubouchi, H. J. Med. Chem. 2006, 49, 7854.
(9) Hanson, R. M.; Sharpless, K. B. J. Org. Chem. 1986, 51(10), 1922.
(10) Hill, J. G.; Sharpless, K. B.; Exon, C. M.; Regenye, R. Org. Synth. 1985, 63, 66.
(11) Verhoeff, J. Explosion hazards of Tertiary Butyl Hydroperoxide (TBHP). I. Chem. E. Symposium Series
No. 68, https://www.icheme.org/communities/subject_groups/safety%20and%20loss%20prevention/
resources/ hazards%20archive/~/media/Documents/Subject%20Groups/Safety_Loss_Prevention/
Hazards%20Archive/S068%20ꢀ%20Runaway%20Reactions/S68ꢀ18.pdf (accessed November 22, 2016).
.
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