Practical Synthesis of (+)-Biotin Key Intermediate by Calcium Borohydride Reduction and Temperature-Dependent Purity Upgrade during Crystallization

Article abstract of DOI:10.1021/acs.oprd.1c00196

An expedient synthesis of a key intermediate for (+)-biotin has been accomplished through high-yielding reduction of chiral imide with calcium borohydride and efficient isolation of the desired isomer by crystallization at a specific temperature where only undesired isomer was converted to soluble anhydrate while the desired isomer kept unchanged as a less soluble monohydrate.

Full text of DOI:10.1021/acs.oprd.1c00196

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Article
Practical Synthesis of (+)-Biotin Key Intermediate by Calcium
Borohydride Reduction and Temperature-Dependent Purity
Upgrade during Crystallization
Masahiko Seki* and Yusuke Takahashi
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ABSTRACT: An expedient synthesis of a key intermediate for (+)-biotin has been accomplished through high-yielding reduction of
chiral imide with calcium borohydride and efficient isolation of the desired isomer by crystallization at a specific temperature where
only undesired isomer was converted to soluble anhydrate while the desired isomer kept unchanged as a less soluble monohydrate.
KEYWORDS: (+)-biotin, calcium borohydride, preferential solvation, crystallization, solubility, van’t Hoff equation
INTRODUCTION
explored. On the other hand, in 1975, synthesis of 2 based on
sodium borohydride reduction of chiral imide 3 to amide
alcohol 4a was reported. In sharp contrast to the above
method, it employed very cheap (R)-1-methylbenzylamine (R-
PEA, ca. $10/kg) as a chiral source to introduce chirality.
However, selectivity and yield of the reduction of 3 to 4a were
not good enough to be applied for commercial production of
■
Over the past few decades, (+)-biotin (1) has received
increasing interest due to the significance in human nutrition
7
1
and animal health. It has a highly functionalized hetero-
bicyclic scaffold with properly oriented nitrogen, oxygen, and
sulfur atoms in the molecule. It carries a 4-carboxybutyl side
chain at 4 position along with three contiguous asymmetric
centers, all being set up as cis-configuration. Unlike other
vitamins, as much as 200 MTN of 1 is currently being
produced using the total synthetic method due to lack of an
2
. Nonetheless, fascinated by the exceptionally low price and
ready availability of R-PEA used as a chiral source, we decided
to reconsider the possibility of the synthetic method as a
practical approach to 2. Herein, we report a much improved
synthesis of 2 based on calcium borohydride reduction of
chiral imide 3 and subsequent isolation of the desired isomer
2
efficient fermentation technology. Among a number of
synthetic approaches hitherto developed for 1, synthesis
using thiolactone (2) as a key intermediate has been
considered the most efficient and viable method for large
4
a by controlled crystallization.
3
scale production of 1.
For the synthesis of 2, considerable efforts have long been
made to meet the ever growing demand of 1. Among them, a
RESULTS AND DISCUSSION
■
3
7
To begin with, the synthesis of chiral imide 3, a substrate for
reduction, was investigated. The starting material cyclic
carboxylic acid 5 was produced commercially from fumaric
acid via dibromination, amination with benzylamine, and
method based on optical resolution employing cinchonidine as
the resolving agent has been considered one of the most
4
practical approaches to obtain 2. However, lack of alkaloids
from natural resources has inevitably forced the supplier to
change the route of synthesis. In the meantime, as an
alternative method, synthesis based on desymmetrization of
meso-cyclic acid anhydride by (S)-1,1-diphenyl-1,2-propanediol
3,14
subsequent ureido formation. For preparation of 3 from 5, a
sequential procedure was first tested that involved anhydride
5
Received: May 28, 2021
has been reported. It can produce required chiral centers with
excellent selectivity and yield and has been considered the
6
most reliable approach to obtain 2. Nonetheless, considering
the price of the chiral alcohol, we thought that the method was
not cheap enough and a more economical synthetic method
that can cut manufacturing cost and reduce waste had to be
©
XXXX American Chemical Society
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A

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Scheme 1. Synthesis of Chiral Imide 3 Using a Sequential Procedure
formation, amidation with R-PEA, and final dehydration to 3
Scheme 1). Owing to the poor solubility of the anhydride 6,
dimethylacetamide (DMA, 1.5 v/w) to provide 3 in 93.9%
yield and 99.23% purity. As expected, in all reactions
employing polar solvents, heterogeneous nucleation was not
observed during the reaction, which made the operation quite
easy.
(
the reaction was required to be carried out at a high
temperature (>190 °C) in mesitylene to avoid any
crystallization during the reaction. Although the procedure
provided 3 in 92.0% yield and 98.2% purity, it was difficult to
scale up because very careful operation of the reaction was
required. To overcome the drawback, the reactions in which 5
and R-PEA were blended in the beginning and heated in polar
solvents were examined (Table 1).
Then, we moved to the synthesis of amide alcohol 4a by
reduction of chiral imide 3. In our initial study, reduction of 3
7
was tested using a previously reported procedure employing
NaBH as a reductant (Scheme 2). When NaBH reduction of
4
4
3
was run at 40 °C for 10 h, the reaction was completed, and
upon simple addition of water, the desired isomer 4a
monohydrate, vide infra, 4a/4b = >99:1 after crystallization)
a
(
Table 1. Screening of the Solvent for Imidation of 5 to 3
was isolated as a white crystal. However, the yield (40.8%) was
not high enough to be applied for commercial production.
As a solution to resolve the problem, we came up with an
1
0
2+
idea to employ Ca(BH4)2 as a reductant because Ca
cations are much more Lewis acidic and sterically demanding
+
9
2+
than Na . Considering these favorable features of Ca
cations, use of Ca(BH ) might induce stronger and more
4
2
selective coordination to one of the diastereomeric imide
carbonyl groups of 3 to enhance selectivity of the reaction. To
our delight, use of Ca(BH ) gave a higher selectivity (4a/4b =
b
c
entry
solvent
time (h)
yield (%)
purity (%)
4
2
1
2
3
NMP
DMSO
DMA
2.5
3.5
2
92.4
86.0
93.9
98.85
97.30
99.23
70:30) than with NaBH (4a/4b = 61:39, Table 2, entry 1 vs
4
entry 2). Other borohydrides carrying different metal cations
(K, Mg, and Al) were tested (Table 2, entries 3−5). However,
they gave much lower selectivities (4a/4b = 59:41 to 66:34)
and yields (0−20%). Screening of the solvent was then
conducted (Table 2, entries 6−11). Although use of 1-PrOH
gave a similar result (92% conversion, 4a/4b = 71:29, Table 2,
entry 6), considerably decreased conversions were observed for
other alcoholic solvents (Table 2, entries 7−10). Furthermore,
use of a well-employed ether-type solvent (diglyme) was found
to be much less effective than EtOH (31% conversion, 4a/4b
= 61:39, Table 2, entry 11). Consequently, the reduction of 3
was found to proceed well with Ca(BH ) , especially in EtOH.
a
The reaction was conducted using 5 (50 g, 0.141 mol) and R-PEA
17.1 g, 0.141 mol). Isolated yield. Area (%) of 3 in high-
performance liquid chromatography (HPLC).
b
c
(
Use of 1-methyl-2-pyrrolidone (NMP, 1.5 v/w) as a solvent
and heating at 170 °C for 2.5 h produced 3 in 92.4% yield and
8.85% purity (Table 1, entry 1). However, NMP is a potential
hazard and needs to be avoided for scale up. The use of
DMSO (1.5 v/w) finished the reaction in 3.5 h, and it was
accompanied by considerable sulfur odor and the yield was
diminished (86.0%, Table 1, entry 2). Finally, to our delight,
the reaction was found to go well using cheap N, N-
9
8
4
2
A possible mechanism of the reduction of 3 by Ca(BH ) is
4
2
shown in Figure 1. A phenyl group of 3 attached to the chiral
Scheme 2. Reduction of 3 with NaBH4
B
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a
Table 2. Screening of the Reductant and Solvent for Reduction of 3 to 4a/4b
b
c
entry
reductant
solvent
conversion (%)
4a/4b (%)
1
2
3
4
5
6
7
8
9
Ca(BH4)2
NaBH4
KBH4
EtOH
EtOH
EtOH
EtOH
EtOH
1-PrOH
IPA
1-BuOH
2-BuOH
t-BuOH
diglyme
100
100
20
6
0
92
2
8
8
0
31
70:30
61:39
59:41
66:34
65:35
71:29
68:32
69:31
65:35
-
Mg(BH4)2
Al(BH4)3
Ca(BH4)2
Ca(BH4)2
Ca(BH4)2
Ca(BH4)2
Ca(BH4)2
Ca(BH4)2
1
1
0
1
61:39
a
b
The reaction was conducted using 3 (2.0 g, 4.6 mmol) and reductant (4.6 × 2 mmol based on [BH ] count). Based on the ratio of area (%) of 3
4
n
c
consumed in HPLC. Based on the ratio of area (%) of 4a and 4b in HPLC.
Scheme 3. Preparation of Undesired Isomer 4b
Monohydrate
Figure 1. Possible mechanism of Ca(BH ) reduction of 3.
4
2
center was assumed to orient to the concave side of the bicyclic
ring due to a steric repulsion by two ureide benzyl groups.
Ca(BH ) would preferentially attack to the left-hand side of
4
2
the imide carbonyl group to avoid steric repulsion by the
neighboring methyl group. Both higher coordination ability
and steric bulkiness of Ca2 are presumably the reasons for the
better selectivity. It is worth noting that Ca(BH ) has never
been used for reduction of imide to amide alcohol and
represents the first example.
+
of these compounds, which showed the water content of 4a
and 4b to be 4.18 and 4.19%, respectively (calculated value for
monohydrate: 3.90%). Monohydrates of 4a and 4b lost water
on drying under a reduced pressure (1 mmHg) at 90 °C for 60
min and at 60 °C for 30 min, respectively, to produce
4
2
Although a better protocol for reduction of 3 was obtained
using Ca(BH ) , the regioselectivity was moderate (4a/4b =
11
corresponding anhydrates of 4a and 4b. The X-ray diffraction
data on hydrates and anhydrates of 4a and 4b showed different
patterns, which substantiated that the water included was not
adhering water but crystalline water (Figures 2 and 3).
Literature precedent showed that monohydrates are
4
2
7
0:30). To compensate this, we explored effective purification
of 4a. It was quite difficult to obtain enough amount of
undesired isomer 4b of high quality by means of recrystalliza-
tion and/or chromatographic purification. Hence, an alter-
native synthesis of 4b was devised (Scheme 3). Starting from
cyclic carboxylic acid 5, coupling with (S)-1-methylbenzyl-
amine (S-PEA) gave chiral imide 7 with S-configuration. Then,
12
generally less soluble than anhydrates. We have imagined,
under certain conditions, that preferential crystallization of 4a
should be achieved if selective monohydration with 4a rather
than with 4b is possible.
7
was subjected to Ca(BH ) reduction to provide amide
4 2
alcohol 8, which upon treatment with HCl gave lactone 9.
In the meantime, thermogravimetry−differential thermal
analysis (TG−DTA) of monohydrates of 4a and 4b gave
information on their structural changes by temperature. For 4a
monohydrate, 3.87% decrease of weight, close to the calculated
value of one water loss (3.90%), was observed by heating at
72.1−85.0 °C (Figure 4), while a similar trend of weight loss
(3.13%) was found for 4b monohydrate, though at a much
lower temperature (42.5−56.4 °C) (Figure 5). Consequently,
Finally, ring opening of 9 with R-PEA and Me Al followed by
3
recrystallization from aqueous EtOH afforded desired 4b as a
monohydrate (vide infra).
Elemental analysis of 4a and 4b conducted under usual
drying conditions (50 °C for 17 h in a tray dryer) revealed that
both 4a and 4b existed as an monohydrate rather than as an
anhydrate. This was further confirmed by Karl Fischer titration
C
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Figure 2. PXRD patterns of monohydrate and anhydrate of 4a.
selective crystallization of 4a over 4b might be possible by
crystallization within the temperature range of 42.5 and 72.1
χ = mole fraction of molecule; ΔH = enthalpy; and R
ideal gas constant.
=
°C.
To demonstrate the feasibility of our prediction, solubilities
To gain a further insight into the crystal structures of 4a and
b during the heating process, the van’t Hoff plot on the basis
of the solubility data shown in Table 3 and Figure 6 was
of monohydrates of 4a and 4b have been determined at
different temperatures. As shown in Table 3 and Figure 6,
solubility of 4b monohydrate was found to increase
dramatically at 303−313 K (30−40 °C), while that of 4a
monohydrate did not change significantly at the same
temperature.
4
plotted (Figure 7). For 4a monohydrate, one linear regression
2
line (R = 0.975) was observed at 283−343 K (10−70 °C),
2
while 4b monohydrate showed two linear regression lines (R
=
0.9541 and 0.9521) whose transition was detected at 303−
3
13 K (30−40 °C). This might suggest that 4a and 4b behave
For dissolution of molecules, the van’t Hoff equation shown
differently toward temperature: the crystal structure of 4b
altered from a monohydrate to an anhydrate at 303−313 K
13
in eq 1 is considered. If linearity of the van’t Hoff plot is
observed, it can be concluded that there is no change in the
crystal structure within the temperature.
(
30−40 °C) while that of 4a kept unchanged as a
monohydrate over the same temperature range.
On the basis of the thermodynamic properties of 4a and 4b
mentioned above, selective isolation of 4a monohydrate might
Ln χ = −ΔH/RT + const
(1)
D
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Figure 3. PXRD patterns of monohydrate and anhydrate of 4b.
be possible by crystallization within the range of 42.5 and 72.1
of 4a monohydrate actually worked well to enable efficient
isolation of 4a monohydrate by simple adjustment of the
crystallization temperature.
°
C where increase of solubility is possible only for 4b by a
structural change from monohydrate to anhydrate. Isolation of
a monohydrate from a mixture of monohydrates of 4a and 4b
4
Taking account of the operational advantage as well as the
fundamental insights on crystallization mentioned above into
consideration, we conducted direct isolation of 4a mono-
hydrate from the reaction mixture by adding concentrated HCl
(c-HCl) and water and concomitant crystallization at a specific
temperature (40−60 °C, Scheme 4). Expectedly, to our
delight, by implementing the elaborated procedure, diaster-
eomerically pure 4a was isolated in a good yield (63% based on
3). As a consequence, the enabling process met the objective of
increasing the yield of 4a by more than 50% of the initial
protocol based on the literature precedent (40.8%, Scheme
by crystallization was thus tested by changing the crystal-
lization temperature (Table 4). When a mixture of
monohydrates of 4a and 4b (4a/4b = 73:27) was crystallized
from toluene (50 v/w) at 25−29 °C, incomplete isolation of
4
4
a resulted to afford an 80.1:19.9 mixture of monohydrates of
a and 4b (Table 4, entry 1). In contrast, when it was carried
out at 52−55 °C, complete separation of isomers was achieved
to provide virtually pure 4a monohydrate (4a/4b = 99.2:0.8,
Table 4, entry 2). When a mixture of EtOH and H O (7:3)
2
was employed as the solvent, a similar temperature dependence
7
of the crystallization was noticed (4a/4b = 98.5:1.5 at 52−55
2). Conceptually, recovery of 4b would be possible by
°
C vs 95.8:4.2 at 25−29 °C, Table 4, entry 4 vs entry 3). It was
oxidation of 4b and cyclization to 3. However, due to the
possibly high recovery cost, it was not considered.
thus concluded that our assumption on selective crystallization
E
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Figure 4. TG−DTA of 4a monohydrate.
Figure 5. TG−DTA of 4b monohydrate.
Table 3. Measured Solubility Expressed in Mole Fraction
(
χ) of Monohydrates of 4a And 4b in a Mixture of EtOH
and H O (6:4 (v/v))
2
T (K)
4a·H O/χ
4b·H O/χ
2
2
2
2
3
3
3
3
3
83
93
03
13
23
33
43
0.00001921
0.00003202
0.00004484
0.00014754
0.00025701
0.00036682
0.00053545
0.00019901
0.00025701
0.00043806
0.00178659
0.00196904
0.00205044
0.00235050
Figure 6. Solubility of monohydrates of 4a and 4b at various
temperatures.
Amide alcohol 4a thus obtained underwent further
conversion to 2 as illustrated in Scheme 5. Treatment of 4a
with c-HCl in 1-methoxy-2-propanol at 100 °C for 15 min
followed by crystallization by simple addition of water gave
lactone 10 in 98.0% yield. Finally, 10 was converted to 2 in
hydrogenation, and subsequent removal of benzyl protecting
3
,15
groups.
14
CONCLUSIONS
8
6.9% yield using the reported procedure. Thiolactone 2 was
■
Practical synthesis of a key intermediate 2 for (+)-biotin (1)
converted to (+)-biotin (1) using a well-established method
involving Fukuyama coupling with a side-chain zinc reagent,
has been accomplished through high-yielding reduction of
F
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Scheme 5. Synthesis of 2 from 4a Monohydrate
EXPERIMENTAL SECTION
■
General. Melting points were uncorrected. H and 13C
nuclear magnetic resonance (NMR) spectra (JEOL Reso-
nance, 400 and 100 MHz, respectively) were recorded with
tetramethylsilane as an internal standard. TG−DTA was
conducted using a Rigaku TG−DTA-8120. X-ray diffraction
1
Figure 7. van’t Hoff plot of the solubility of monohydrates of 4a and
4b at various temperatures.
(
XRD) patterns were recorded on a Rigaku SmartLab
diffractometer equipped with a 5-axis goniometer and operated
at 30 kV and 10 mA. The source of radiation was Cu Kα, and
its wavelength was set to be 1.5060 Å. 2θ covered the range
between 4.998° and 39.998° at a speed of 1°/min with a step
size of 0.020°. The solubility measurement was performed
using ChemiStation (EYELA, Japan). An excess quantity of
sample was added to each tube of the instrument followed by
the solvent. While the temperature of the slurry was controlled,
the slurry was stirred for 2 h and then filtrated through a 0.45
μm membrane filter. The concentration of the filtrate was
measured by HPLC to determine the solubility of the sample.
HPLC analyses were performed using an Xbridge C18, 5 μm
Table 4. Recrystallization of a Mixture of Monohydrates of
a and 4b at Different Temperatures
4
b
temp
(°C)
time
(h)
yield
a
c
entry
solvent (v/w)
toluene (50)
toluene (20)
(%)
4a/4b
(
4.6 mm × 150 mm) column at a flow rate of 1 mL/mL,
1
2
3
25−29
52−55
25−29
2
1
2
76.5
64.3
65.3
80.1:19.9
99.2:0.8
95.8:4.2
elution solvent of 40−100% aq. CH CN (0−20 min),
3
detection wavelength of 210 nm, and column temperature of
30 °C. All solvents and reagents were used as received.
[5(R)-cis]-Tetrahydro-5-(1-Phenylethyl)-1,3-Bis-
EtOH/H O = 7:3
2
(
20)
4
EtOH/H O = 7:3
52−55
1
62.3
98.5:1.5
2
(
10)
(
Phenylmethyl)Pyrrolo[3,4-d]Imidazole-2,4,6(5H)-Tri-
a
7
The recrystallization was tested using crude 4a (10 g, 4a/4b =
3:27). Isolated yield. Based on the area (%) of 4a and 4b in
one (3). To a suspension of cyclic carboxylic acid 5 (200 g,
b
c
7
0.564 mol) in DMA (300 mL) was added R-PEA (68.4 g,
HPLC.
0.564 mol) and the mixture was stirred at 150 °C for 2 h. The
mixture was cooled down to 90 °C and water (60 mL) was
added gradually. After precipitation starts, the mixture was
further stirred for 30 min. Then, water (840 mL) was added at
85 °C for over 1 h. The mixture was stirred at 25−30 °C for 2
h. The crystals formed were filtered and washed with water and
dried at 60 °C for 25 h in a tray dryer to provide 3 as a white
chiral imide with Ca(BH4)2 and subsequent efficient
separation of the desired isomer by crystallization. Although
the selectivity of the reduction was moderate, the recovery rate
of the desired isomer was excellent (90%) to afford the product
in a very cost-effective way. Ready availability of raw materials,
ease of operation, and a high overall yield of the current
process would permit ready access to (+)-biotin (1), a
compound of growing interest.
crystal (232 g, 93.9%). HPLC purity: 99.23 A%. Mp: 157−159
1
°C; H NMR (400 MHz, CDCl ) δ =7.28−7.35 (m, 15H),
3
5.33−5.40 (m, 1H), 5.02−5.09 (m, 2H), 4.21−4.29 (m, 2H),
3.88−3.95 (m, 2H), 1.79 (t, J = 7.2 Hz, 3H).
Scheme 4. Synthesis of 4a by Ca(BH ) Reduction of 3 and Subsequent Controlled Crystallization of 4a
4
2
G
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[
at 25 °C for 1 h. Solids formed were filtered, washed with a
(
Phenylmethyl)Pyrrolo[3,4-d]Imidazole-2,4,6(5H)-Tri-
one (7). To a suspension of cyclic carboxylic acid 5 (20 g,
mixture of EtOH and H O (1/1, 5 mL), and dried at 50 °C for
2
3 h in a tray dryer to give a white crystal of 4b monohydrate
(1.44 g, 50.2%). Mp: 93.4−93.9 °C; [α] + 180.8 o (c, 0.5,
25
0
0
.0564 mol) in DMA (30 mL) was added S-PEA (6.84 g,
.0564 mol) and the mixture was stirred at 150 °C for 2 h. The
D
THF); IR (neat): ν = 3468, 3267, 2976, 1680, 1645, 1465,
max
−
1 1
mixture was cooled to 95 °C and water (6 mL) was added
gradually. After precipitation starts, the mixture was further
stirred for 30 min. Then, water (84 mL) was added at 85 °C
for over 1 h. After completion of the addition, the mixture was
stirred at 50 °C for 1 h. The crystals formed were filtered and
washed with water and dried at 60 °C for 12 h in a tray dryer
to provide 7 as a white crystal (24.2 g, 97.6%). HPLC purity:
1452, 1055 cm ; H NMR (400 MHz, CDCl ) δ = 7.12−7.36
3
(m, 15H), 6.67−6.69 (m, 1H), 5.14−5.18 (m, 1H), 4.96 (d, J
= 14.8 Hz, 1H), 4.75 (d, J = 15.2 Hz, 1H), 4.19 (d, J = 15.2
Hz, 1H), 3.94 (d, J = 9.6 Hz, 1H), 3.84 (d, J = 14.8 Hz, 1H),
3.63−3.69 (m, 2H), 3.47−3.53 (m, 1H), 3.05 (dd, J = 4.8, 9.6
1
3
1
Hz, 1H), 1.50 (d, J = 7.2 Hz, 3H). C{ H} NMR (100 MHz,
CDCl ) δ = 168.5, 161.1, 142.1, 136.5, 135.8, 129.1, 128.9,
128.8, 128.3, 128.1, 128.0, 127.8, 126.1, 60.1, 59.4, 57.3, 49.2,
47.7, 46.4, 21.3. Anal. calcd for C H N O ; C, 70.26; H,
6.77; N, 9.10. Found: C, 69.70; H, 6.70; 8.90. PXRD (2θ in
3
2
5
9
9.40 A%. Mp: 159.1−159.4 °C; [α]D −76.3° (c, 0.5, THF);
IR (neat): ν = 3033, 2940, 1713, 1685, 1449, 1358, 1233
max
2
7
31
3
4
−
1 1
cm ; H NMR (400 MHz, CDCl ) δ = 7.26−7.34 (m, 15H),
3
5
3
(
.34−5.40 (m, 1H), 5.03−5.06 (m, 2H), 4.24−4.30 (m, 2H),
degrees): 5.325, 7.770, 9.822, 11.458, 13.920, 14.638, 17.307,
13 1
.89−3.95 (m, 2H), 1.80 (t, J = 7.2 Hz, 3H). C{ H} NMR
1
7.522, 18.599, 19.991, 21.156, 22.398, 23.506, 24.686, 26.959,
28.651, 33.328, 39.218.
4R,5S)-5-(Hydroxymethyl)-2-Oxo-N-[(1R)-1-Phenyl-
ethyl]-1,3-Bis(Phenylmethyl)-4-Imidazolidinecarboxa-
mide Anhydrate (4b Anhydrate). 4b monohydrate
obtained above was dried at 60 °C for 30 min under vacuum
100 MHz, CDCl ) δ = 172.9, 172.8, 157.6, 138.6, 135.8,
3
1
4
35.7, 128.9, 128.7, 128.3, 128.1, 127.5, 53.1, 53.0, 50.8, 46.43,
6.39, 16.4. HRMS (ESI-TOF): [M + H] calcd for
(
+
C H N O , 440.1929; found, 440.1947.
2
7
25
3
3
(
3aR,6aS)-Tetrahydro-1,3-Bis(Phenylmethyl)-1H-
16
Furo[3,4-d]Imidazole-2,4-Dione (9). Calcium chloride
4.77 g, 0.0430 mol) was added to ethanol (126 mL) and the
(
9
3
1 mmHg) to give 4b anhydrate as a white crystal. Mp: 93.1−
(
25
+ 181.3 o (c, 0.5, THF); IR (neat): ν
3.7 °C; [α]
=
D
max
−1
mixture was stirred at 25 °C for 30 min. The mixture was
1
398, 3324, 2933, 1672, 1651, 1471, 1451, 1060 cm ; H
cooled down to 10 °C and NaBH (3.41 g, 0.0902 mol) was
4
NMR (400 MHz, CDCl ) δ = 7.12−7.36 (m, 15H), 6.64 (d, J
3
added, and the mixture was stirred at 10 °C for 5 min. To the
suspension was added portionwise 7 (18 g, 0.0410 mol) below
=
4
=
3
8.4 Hz, 1H), 5.14−5.18 (m, 1H), 4.96 (d, J = 14.8 Hz, 1H),
.75 (d, J = 15.2 Hz, 1H), 4.19 (d, J = 15.6 Hz, 1H), 3.94 (d, J
10.0 Hz, 1H), 3.84 (d, J = 14.8 Hz, 1H), 3.63−3.69 (m, 2H),
.47−3.53 (m, 1H), 3.05 (dd, J = 4.8 Hz, 9.6 Hz, 1H), 1.50 (d,
J = 7.2 Hz, 3H). PXRD (2θ in degrees): 5.446, 6.498, 8.104,
1
0 °C for over 15 min and the mixture was stirred below 5−15
C for 1 h and at 20−25 °C for 22 h. Then, c-HCl (9.12 g) was
added for over 15 min, and the mixture was warmed up to 60
C and H O (43 mL) was added at 25−35 °C for over 30 min.
°
°
2
1
2
1.081, 12.018, 14.606, 16.447, 17.726, 18.401, 19.950, 20.789,
2.453, 23.002, 25.328.
4S,5R)-5-(Hydroxymethyl)-2-Oxo-N-[(1R)-1-Phenyl-
ethyl]-1,3-Bis(Phenylmethyl)-4-Imidazolidinecarboxa-
mide Monohydrate (4a Monohydrate). Calcium chloride
The mixture was stirred at 60 °C for 2 h followed by at 40 °C
for 2 h. The solids formed were filtered and washed with a
mixture of MeOH (14.4 mL) and water (20 mL) to give the 8
monohydrate (wet, 20.24 g). Into the monohydrate 8 (wet,
(
7
2
0.24 g) was added DMA (10.8 mL) and c-HCl (5.4 g) for
(
46.4 g, 0.418 mol) was added to ethanol (1225 mL) and the
over 10 min. The mixture was stirred at 100 °C for 2 h. After
completion of the reaction, the mixture was cooled down to 30
mixture was stirred at 25−30 °C. After dissolution was
confirmed, the mixture was cooled down to 10 °C and NaBH
4
°
C and CH Cl (43.2 mL) and 10% aq. NaCl (43 g) were
2 2
(
33.1 g, 0.876 mol) was added and the mixture was stirred
added. The organic layer was washed with H O (43.2 mL × 3)
2
below 10 °C for 5 min. To the suspension was added
portionwise 3 (175 g, 0.398 mol) below 10 °C for over 15 min
and the mixture was stirred below 5−15 °C for 1 h and at 20−
and evaporated to give 9 as a white crystal (57.2% based on 7).
HPLC purity: 99.33 A%. Mp: 115.8−116.8 °C; [α] −162.9°
(
1
(
25
D
c, 0.5, THF); IR (neat): ν = 3034, 2921, 1777, 1698, 1445,
max
−
1
1
25 °C for 26 h. Then, dil. aq. HCl (c-HCl (88.7 g) + H O
2
416, 1211 cm ; H NMR (400 MHz, CDCl ) δ = 7.25−7.38
m, 10H), 5.06 (d, J = 15.2 Hz, 1H), 4.64 (d, J = 15.2 Hz, 1H),
3
(
420 mL)) was added at 25−35 °C for over 1 h. The mixture
was stirred at 60 °C for 2 h followed by at 40 °C for 2 h, and
the solids formed were filtered and washed with a mixture of
MeOH (140 mL) and water (210 mL) and dried at 70 °C for
4
1
.38−4.40 (m, 2H), 4.10−4.17 (m, 3H), 3.92 (d, J = 8.4 Hz,
H).
(
4R,5S)-5-(Hydroxymethyl)-2-Oxo-N-[(1R)-1-Phenyl-
1
8 h in a tray dryer to provide 4a monohydrate as a white
crystal (113.2 g, 63%). 4a/4b = 99.1:0.9. HPLC purity: 98.90
ethyl]-1,3-Bis(Phenylmethyl)-4-Imidazolidinecarboxa-
mide Monohydrate (4b Monohydrate). To a solution of
R-PEA (0.66 g, 5.45 mmol) in CH Cl (8 mL) was added
2
5
A%. Mp: 155.5−156.1 °C; [α] + 93.0 ° (c, 0.5, THF); IR
D
2
2
−
1
(
neat): ν = 3429, 3271, 1682, 1652, 1453, 1240, 1064 cm ;
max
Me Al (2.8 mL, 2.0 M in toluene) at −76 °C under a N
3
2
1
H NMR (400 MHz, CDCl ) δ = 7.24−7.32 (m, 15H), 6.55
atmosphere and the mixture was stirred at 20−30 °C for 30
min. To the solution was added dropwise 9 (2.0 g, 6.21 mmol)
in CH Cl (8 mL) for over 4 min. After the mixture was stirred
3
(
1
=
d, J = 8.0 Hz, 1H), 5.07−5.11 (m, 1H), 4.81 (d, J = 15.2 Hz,
H), 4.64 (d, J = 15.6 Hz, 1H), 4.10−4.21 (m, 2H), 3.99 (d, J
2
2
9.6 Hz, 1H), 3.60−3.70 (m, 1H), 3.45−3.55 (m, 1H), 3.20−
at 25 °C for 3 h and at 40 °C for 2 h, a mixture of c-HCl (0.59
3
.30 (m, 1H), 2.91−2.95 (m, 1H), 1.34 (d, J = 7.2 Hz, 3H).
g) and H O (6 mL) was carefully added for over 20 min. The
2
1
3
1
organic phase was separated and washed with H O (6 mL ×
C{ H} NMR δ = 168.6, 161.3, 142.3, 136.4, 129.1, 128.9,
2
3
). To the mixture was added n-hexane (15 mL) and solids
128.8, 128.5, 128.2, 127.9, 127.8, 127.8, 126.2, 60.1, 59.9, 57.8,
49.1, 48.3, 46.6, 21.3. Anal. Calcd for C H N O ; C, 70.26;
H, 6.77; N, 9.10. Found: C, 70.10; H, 6.60; 8.90. PXRD (2θ in
formed were filtered and washed with AcOEt (10 mL). The
crude 4b thus obtained was dissolved in EtOH (15 mL) at 60
2
7
31
3
4
°
C and H O (15 mL) was added, and the mixture was stirred
degrees): 5.279, 6.060, 7.658, 9.734, 11.424, 12.304, 14.513,
2
H
https://doi.org/10.1021/acs.oprd.1c00196
Org. Process Res. Dev. XXXX, XXX, XXX−XXX

Organic Process Research & Development
pubs.acs.org/OPRD
Article
1
2
5.450, 16.986, 17.524, 19.668, 21.382, 22.012, 23.146, 24.945,
8.302, 32.107.
orcid.org/0000-0002-9942-377X; Email: ma-seki@
tokuyama.co.jp
(
4S,5R)-5-(Hydroxymethyl)-2-Oxo-N-[(1R)-1-Phenyl-
Author
ethyl]-1,3-Bis(Phenylmethyl)-4-Imidazolidinecarboxa-
mide Anhydrate (4a Anhydrate). 4a monohydrate
obtained above was dried at 90 °C for 60 min under vacuum
Yusuke Takahashi − New Business Promotion Department,
Tokuyama Corporation, Ibaraki 300-4247, Japan
(
1
3
1 mmHg) to give 4a anhydrate as a white crystal. Mp: 155.4−
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.oprd.1c00196
2
5
55.9 °C; [α]D + 94.0° (c, 0.5, THF); IR (neat): ν = 3480,
max
1 1
−
276, 1685, 1651, 1453, 1237, 1041 cm ; H NMR (400
MHz, CDCl ) δ = 7.23−7.33 (m, 15H), 6.53 (d, J = 8.0 Hz,
Notes
3
1
H), 5.07−5.10 (m, 1H), 4.81 (d, J = 15.2 Hz, 1H), 4.64 (d, J
The authors declare no competing financial interest.
=
15.6 Hz, 1H), 4.12−4.21 (m, 2H), 4.00 (d, J = 9.6 Hz, 1H),
3
2
.63−3.70 (m, 1H), 3.45−3.54 (m, 1H), 3.20−3.27 (m, 1H),
.87 (dd, J = 4.4 Hz, 9.6 Hz, 1H), 1.33 (d, J = 6.8 Hz, 3H).
REFERENCES
■
(
1) For example, see: (a) Mistry, P. S.; Dakshinamurti, K.
PXRD (2θ in degrees): 7.252, 8.506, 9.697, 11.188, 11.940,
Biochemistry of Biotin. Vitam. Horm. 1964, 22, 1−55. (b) Payne,
C. G.; Gilchrist, P.; Pearson, J. A.; Hemsley, L. A. Involvement of
Biotin in the Fatty Liver and Kidney Syndrome of Broilers. Brit. Poult.
Sci. 1974, 15, 489−498. (c) Whitehead, C. C.; Blair, R.; Bannister, D.
W.; Evans, A. J.; Jones, R. M. The Involvement of Biotin in Preventing
the Fatty Liver and Kidney Syndrome in Chicks. Res. Vet. Sci. 1976,
1
2
2.854, 13.804, 14.642, 15.592, 18.329, 19.600, 20.676, 21.459,
2.544, 23.937, 24.736, 25.395, 26.516, 27.669, 31.945.
(
3aS,6aR)-Tetrahydro-1,3-Bis(Phenylmethyl)-1H-
7,14
Furo[3,4-d]Imidazole-2,4-Dione (10).
4a monohydrate
(
4.15 g, 9.0 mmol) was added to a mixture of 1-methoxy-2-
2
0, 180−184. (d) Hood, R. L.; Johnson, A. R.; Fogarty, A. C.;
propanol (8.3 mL) and c-HCl (2.1 g) at 25−30 °C and the
mixture was stirred at 100 °C for 15 min. After completion of
the reaction, the mixture was cooled down to 25−30 °C and
water (83 mL) was added. The mixture was stirred at 25−30
Pearson, J. A. Fatty Liver and Kidney Syndrome in Chicks. II.
Biochemical Role of Biotin. Aust. J. Biol. Sci. 1976, 29, 429−441.
(
e) Whitehead, C. C.; Ann, N. Y. Crystallographic Investigations of
Biotin and Carboxybiotin Derivatives. Acad. Sci. 1985, 447, 86−95.
(c) Maebashi, M.; Makino, Y.; Furukawa, Y.; Ohinata, K.; Kimura, S.;
Sato, T. Therapeutic Evaluation of the Effect of Biotin on
Hyperglycemia in Patients with Non-Insulin Dependent Diabetes
Mellitus. J. Clin. Biochem. Nutr. 1993, 14, 211−218.
°
C for 2 h, and solids formed were filtered and washed with
water and dried for 16 h in a tray dryer to provide 10 as a white
1
crystal (2.84 g, 98.0%). HPLC purity: 98.36 A%. H NMR
(
400 MHz, CDCl ) δ = 7.26−7.38 (m, 10H), 5.06 (d, J = 15.2
3
(2) For example, see: (a) Sakurai, N.; Imai, Y.; Masuda, M.;
Hz, 1H), 4.64 (d, J = 15.2 Hz, 1H), 4.34−4.40 (m, 2H), 4.10−
Komatsubara, S.; Tosa, T. Molecular Breeding of a Biotin-Hyper-
producing Serratia Marcescens Strain. Appl. Environ. Microbiol. 1993,
4
.17 (m, 3H), 3.92 (d, J = 8.4 Hz, 1H); HRMS (ESI-TOF):
+
[M + H] calcd for C H N O , 323.1351; found, 323.1398.
19 18 2 3
5
9, 2857−2863. (b) Sakurai, N.; Imai, Y.; Masuda, M.; Komatsubara,
(
3aS,6aR)-Tetrahydro-1,3-Bis(Phenylmethyl)-1H-
7,14
S.; Tosa, T. Molecular Breeding of a Biotin-Hyperproducing Serratia
Thieno[3,4-d]Imidazole-2,4-Dione (2).
28.0 g, 86.8 mmol) in degassed DMA (42 mL) was added to
S-potassium thioacetate (AcSK) (14.88 g, 130.3 mmol) at 125
A solution of 10
Marcescens Strain. Appl. Environ. Microbiol. 1993, 59, 3225−3232.
(
(
c) Sakurai, N.; Imai, Y.; Masuda, M.; Komatsubara, S.; Tosa, T.
Improvement of a d-Biotin-Hyperproducing Recombinant Strain of
Serratia Marcescens. J. Biotechnol. 1994, 36, 63−73. (d) Sakurai, N.;
Imai, Y.; Komatsubara, S.; Tosa, T. Integration of The Mutated Biotin
Biosynthetic Genes to The Chromosome of a d-Biotin-Producing
Strain of Serratia Marcescens. J. Ferment. Bioeng. 1993, 77, 610−616.
°
C under a N atmosphere and the mixture was stirred at 125
2
°C for 1.5 h. After completion of the reaction, the reaction
mixture was cooled down to 100 °C and water (140 mL) was
added, and the slurry was stirred at 25 °C for 2 h. The solids
formed were filtered to give crude 2 (wet, 40.4 g), which was
dissolved in 2-butanol (196 mL) at 70 °C and treated with
activated carbon (1.4 g) at 70 °C and filtered. The filtrate was
evaporated to 112 g and stirred at −10 to −5 °C for 3 h. The
solids formed were filtered and dried at 60 °C for 12 h in a tray
dryer to give 2 (25.5 g, 86.9%) as a white crystal. HPLC purity:
(3) (a) De Clercq, P. J. Biotin: A Timeless Challenge for Total
Synthesis. Chem. Rev. 1997, 97, 1755−1792. (b) Seki, M. Biological
Significance and Development of Practical Synthesis of Biotin. Med.
Res. Rev. 2006, 26, 434−482.
(4) Senuma, M.; Fujii, T.; Seto, M.; Okamura, K.; Date, T.;
Kinumaki, A. Highly Effective Resolution of 1,3-Dibenzyl-6-hydroxy-
3,3a,6,6a-tetrahydro-1H-furo[3, 4-d]-imidazole- 2,4-dione, an Inter-
mediate for Biotin, with Optically Active Amines and Reutilization of
the Unwanted Epimer. Chem. Pharm. Bull. 1990, 38, 882−887.
2
5
1
9
9.92 A%. Mp: 125−126 °C; [α] + 80.0° (c, 1.0, DMF); H
D
NMR (400 MHz, CDCl ) δ = 7.25−7.36 (m, 10H), 5.02 (d, J
3
(5) Wehrli, C. A. Process for the Stereoselective Synthesis of
=
4
1
14.8 Hz, 1H), 4.68 (d, J = 15.6 Hz, 1H), 4.33−4.38 (m, 2H),
Lactones. WO2004/094367 A2, 2004.
(6) Bettenhausen, C. DSM Prevails in Vitamin Patent Case in China.
.09−4.16 (m, 1H); 3.80 (d, J = 8.0 Hz, 1H), 3.34−3.39 (m,
+
H), 3.29−3.294 (m. 1H); HRMS (ESI-TOF): [M + H]
C&EN 2021, 99, 10.
calcd for C H N O S, 339.1123; found, 339.1181.
1
9
18
2
2
(7) Aoki, Y.; Suzuki, H.; Akiyama, H.; Okano, S. Method for
Synthesis of Optically Active Lactones. US 3,876,656, 1975.
(8) Reisch, M. Solvent Users Look to Replace NMP. C&EN 2008,
86, 32.
ASSOCIATED CONTENT
sı Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.oprd.1c00196.
■
*
(9) For a recent example of use of calcium salt in the stereoselective
organic transformations, see: Ibanez, I.; Kaneko, M.; Kamei, Y.;
Tsutsumi, R.; Yamanaka, M.; Akiyama, T. Enantioselective Friedel-
Crafts Alkylation Reaction of Indoles with α-Trifluoromethylated β-
Nitrostyrenes Catalyzed by Chiral BINOL Metal Phosphate. ACS
Catal. 2019, 9, 6903−6909.
1H- and 13C-NMR spectra of the products (PDF)
AUTHOR INFORMATION
Corresponding Author
Masahiko Seki − New Business Promotion Department,
Tokuyama Corporation, Ibaraki 300-4247, Japan;
■
(
10) Ca(BH ) was prepared in situ from NaBH and CaCl by
4
2
4
2
modification of reported procedure and used as such, see: Brown, H.
C.; Narasimhan, S.; Choi, Y. M. Selective Reductions. 30. Effect of
Cation and Solvent on the Reactivity of Saline Borohydrides for
I
https://doi.org/10.1021/acs.oprd.1c00196
Org. Process Res. Dev. XXXX, XXX, XXX−XXX

Organic Process Research & Development
pubs.acs.org/OPRD
Article
Reduction of Carboxylic Esters. Improved Procedures for the
Conversion of Esters to Alcohols by Metal Borohydrides. J. Org.
Chem. 1982, 47, 4702−4708.
(
11) Anhydrate of 4a and 4b absorbed water when standed under air
(
40%RH). Water content of 4a anhydrate became 0.90% in 10 min
and 2.15% in 17 h while that of 4b anhydrate kept almost unchanged
over the same time span, 0.14% in 10 min and 0.19% in 17 h.
(
12) For an example, see: Roy, S.; Quinones, R.; Matzger, A. J.
̃
Structural and Physicochemical Aspects of Dasatinib Hydrate and
Anhydrate Phases. Cryst. Growth Des. 2012, 12, 2122−2126.
(
13) For an example, see: Waid, O.; Joachim, U. Solid Liquid
Equilibrium, Metastable Zone and Nucleation Parameters of the
Oxalic Acid-Water System. Cryst. Growth Des. 2006, 6, 1927−1930.
(
14) Gerecke, M.; Zimmermann, J.-P.; Aschwanden, W. Versuche
zur Biotinsynthese. Herstellung von (3aS,6aR)-1,3-Dibenzyl-tetrahy-
dro-4H- thieno[3,4-d]imidazol-2,4 (1H)-dion. Helv. Chim. Acta 1970,
5
(
3, 991−999.
15) (a) Shimizu, T.; Seki, M. Facile Synthesis of (+)-Biotin via
Fukuyama Coupling Reaction. Tetrahedron Lett. 2000, 41, 5099−
101. (b) Shimizu, T.; Seki, M. Palladium on Charcoal-catalyzed
Fukuyama Coupling Reaction. Tetrahedron Lett. 2001, 42, 429−432.
c) Shimizu, T.; Seki, M. A Novel Synthesis of Functionalized
5
(
Ketones via A Nickel-Catalyzed Coupling Reaction of Zinc Reagents
with Thiolesters. Tetrahedron Lett. 2002, 43, 1039−1042. (d) Mori,
Y.; Seki, M. A Practical Synthesis of (+)-Biotin through Palladium
Hydroxide on Charcoal-Catalyzed Fukuyama Coupling Reaction.
Heterocycles 2002, 58, 125−127. (e) Mori, Y.; Seki, M. Pd(OH) /C
2
(
Pearlman’s Catalyst): A Highly Active Catalyst for Fukuyama,
Sonogashira, and Suzuki Coupling Reactions. J. Org. Chem. 2003, 68,
571−1574. (f) Seki, M.; Kimura, M.; Hatsuda, M.; Yoshida, S.;
1
Shimizu, T. 2-Thiazolidinone: a Novel Thiol Protective Surrogate of
Complete Atom Efficiency, A Practical Synthesis of (+)-Biotin.
Tetrahedron Lett. 2003, 44, 8905−8907. (g) Kimura, M.; Seki, M. A
Novel Procedure for The Preparation of Zinc Reagents: A Practical
Synthesis of (+)-Biotin. Tetrahedron Lett. 2004, 45, 1635−1637.
(
h) Seki, M.; Hatsuda, M.; Mori, Y.; Yoshida, S.; Yamada, S.; Shimizu,
T. A Practical Synthesis of (+)-Biotin from L-Cysteine. Chem. − Eur.
J. 2004, 10, 6102−6110. (i) Mori, Y.; Seki, M. Highly Efficient
Phosphine-Free Pd(OAc) -Catalyzed Fukuyama Coupling Reaction:
2
Synthesis of a Key Intermediate for (+)-Biotin under Low Catalyst
Loading. Synlett 2005, 2233. (j) Mori, Y.; Seki, M. A Practical
Synthesis of Multifunctional Ketones through the Fukuyama
Coupling Reaction. Adv. Synth. Catal. 2007, 349, 2027−2038.
(
k) Mori, Y.; Seki, M. Synthesis of Multi-Functionalized Ketones
through The Fukuyama Coupling Reaction Catalyzed by Pearlman’s
Catalyst: Preparation of Ethyl 6-Oxotridecanoate. Org. Synth. 2007,
8
(
4, 285−294.
16) Wang, Y.-F.; Sih, C. J. Bifunctional Chiral Synthons via
Biochemical Methods 4. Chiral Precursors to (+)-Biotin and (−)-A-
Factor. Tetrahedron Lett. 1984, 25, 4999−5002.
J
https://doi.org/10.1021/acs.oprd.1c00196
Org. Process Res. Dev. XXXX, XXX, XXX−XXX