A practical synthesis of (+)-biotin from L-cysteine

Article abstract of DOI:10.1002/chem.200400733

α-Amino aldehyde 4, which is readily derived from L-cysteine through cyclization and elaboration of the carboxy group, was subjected to the Strecker reaction, which, via sodium bisulfite adduct 16, afforded α-amino nitrile 5 with high diastereose-lectivity (syn/anti = 11:1) and in high yield. Amide 6, derived from 5, was converted to thiolactone 8, a key intermediate in the synthesis of (+)-biotin (1), by a novel S,N-carbonyl migration and cyclization reaction. The Fukuyama coupling reaction of 8 with the zinc reagent 21, which has an ester group, in the presence of a heterogeneous Pd/ C catalyst allowed the efficient installation of the 4-carboxybutyl chain to provide 9. Compound 9 was hydrogenated and the protecting groups removed to furnish 1 in 10 steps and in 34 % overall yield from L-cysteine.

Full text of DOI:10.1002/chem.200400733

FULL PAPER
A Practical Synthesis of (+)-Biotin from l-Cysteine
Masahiko Seki,*[a] Masanori Hatsuda,[b] Yoshikazu Mori,[b] Shin-ichi Yoshida,[b]
Shin-ichi Yamada,[b] and Toshiaki Shimizu[b]
Abstract: a-Amino aldehyde 4, which
is readily derived from l-cysteine
through cyclization and elaboration of
the carboxy group, was subjected to
the Strecker reaction, which, via
sodium bisulfite adduct 16, afforded a-
amino nitrile 5 with high diastereose-
lectivity (syn/anti=11:1) and in high
yield. Amide 6, derived from 5, was
converted to thiolactone 8, a key inter-
mediate in the synthesis of (+)-biotin
(1), by a novel S,N-carbonyl migration
and cyclization reaction. The Fukuya-
ma coupling reaction of 8 with the zinc
reagent 21, which has an ester group,
in the presence of a heterogeneous Pd/
C catalyst allowed the efficient installa-
tion of the 4-carboxybutyl chain to pro-
vide 9. Compound 9 was hydrogenated
and the protecting groups removed to
furnish 1 in 10 steps and in 34% over-
all yield from l-cysteine.
Keywords: amino acids · organo-
zinc compounds · Strecker synthe-
sis · total synthesis · vitamins
Introduction
than 14 steps), 2) the use of toxic reagents and intermediates
is necessary, and 3) it involves theoretically impractical dia-
stereomeric or enzymatic resolution of racemic materials. To
overcome these problems, we initially developed a synthetic
method that involves l-cysteine as the starting material.[5]
Although we attempted to scale up this method for industri-
al large-scale production, it failed because a low tempera-
ture, ꢀ208C, was needed. In addition, from the view point
of atom economy,[6] the use of bulky tert-butyloxycarbonyl
(tBoc) and benzylidene acetal to protect the cysteine deriva-
tives is not satisfactory.
(+)-Biotin (1) has recently induced intense research activity
owing to its important biological role in human nutrition
and animal health.[1] Because 1 cannot be produced effi-
In view of the need to eliminate the use of bulky protect-
ing groups and to decrease the number of steps required for
the protection-deprotection sequence, we sought to develop
a novel protecting group for cysteine derivatives. We envi-
sioned the possible use of 2-thiazolidinone derivatives 2 for
protecting cysteine derivatives (Scheme 1). Compound 2,
ciently by a fermentation approach,[2] the vast amount of 1
required throughout the world, that is, more than 80 ton per
year, is said to be produced by a totally synthetic method.
Of the synthetic approaches to 1,[3] the Goldberg and Stern-
bach approach,[4] which was established about 50 years ago,
is considered to be the most efficient one hitherto accom-
plished. While the Goldberg and Sternbach approach has
been thoroughly optimized for many years, it has some fun-
damental drawbacks: 1) it is a multistep synthesis (more
Scheme 1. A novel protecting group for l-cysteine derivatives.
[a] Dr. M. Seki
Export & Import Group, Purchasing Department
Logistics Division, Tanabe Seiyaku Co., Ltd.
3-2-10, Dosho-Machi, Chuo-Ku, Osaka 541–8505 (Japan)
Fax : (+81)6-6205-5178
which has a thiocarbamate group within the molecule, might
be sufficiently stable to allow transformations at the C-4
substituent. After the transformations, if the relative hard-
ness[7] of the carbonyl group is closer to the X atom (N, O,
etc) than to the sulfur atom, S,X-carbonyl migration should
E-mail: m-seki@tanabe.co.jp
[b] M. Hatsuda, Y. Mori, Dr. S.-i. Yoshida, Dr. S.-i. Yamada, T. Shimizu
Process Chemistry Research Laboratories, Tanabe Seiyaku Co., Ltd.
3–16–89, Kashima, Yodogawa-Ku, Osaka 532-8505 (Japan)
6102
ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/chem.200400733
Chem. Eur. J. 2004, 10, 6102 – 6110

6102 – 6110
Table 1. Synthesis of (R)-2-oxothiazolidine-4-carboxylic acid 10 from l-
cysteine.
take place upon heating to readily liberate the thiol group
(2!3). We therefore considered a route to biotin that in-
volves this novel protecting surrogate.[8]
It was planned that the stereogenic centers of 1 would be
established by the Strecker reaction of a-amino aldehyde 4
derived from l-cysteine (Scheme 2). Then, upon heating,
Entry ClCO2R
(equiv)
Base
(equiv)
Addition
T
Yield[b]
[%]
time[a] [h] [8C]
1
2
3
4
5
6
7
ClCO2Et (2.2)
NaOH (5.0)
ClCO2Ph (2.2) NaHCO3 (5.0)
ClCO2Ph (2.2) Na2CO3 (2.5)
ClCO2Ph (2.2) NaOH (5.0)
ClCO2Ph (1.2) NaOH (3.5)
ClCO2Ph (1.2) NaOH (3.5)
ClCO2Ph (1.4) NaOH (3.5)
1
1
1
1
1
2
2
5–20
5–20 14
5–20 32
20–30 96
40 94
5
40 69
40 98
[a] Time for the addition of ClCO2R. After the addition, the mixture was
further stirred at the indicated temperature for 1 h. [b] Assay yield.
the amount of phenyl chloroformate from 2.2 to 1.2 equiva-
lents and a decrease in the amount of NaOH from 5.0 to
3.5 equivalents combined with an increase in the reaction
temperature from 20–30 to 408C had little effect on the re-
action yield (Table 1, entry 5). However, when the time for
the addition of the chloride was changed from 1 to 2 h, as
might be required in a large-scale synthesis, the yield unex-
pectedly dropped to 69% (Table 1, entry 6). In this case the
reaction was accompanied by the formation of diphenyl car-
bonate ((PhO)2CO) by the reaction between phenyl chloro-
formate and the phenol generated by cyclization. A slight
increase in the amount of phenyl chloroformate from 1.2 to
1.4 equiv was found to improve the yield dramatically
(Table 1, entry 7).
With (R)-2-oxothiazolidine-4-carboxylic acid 10 in hand,
we next tried to synthesize the N-benzyl derivative 12 by
benzylation of the ester derivative 11. Although the benzyla-
tion proceeded in high yield with benzyl bromide and
K2CO3 in DMA (Table 2, entry 1), the use of corrosive
benzyl bromide proved to be commercially unviable for the
large-scale production of 12 and an alternative method,
which employed benzyl chloride, had to be investigated. The
use of benzyl chloride for the benzylation of 11, however,
resulted in some racemization (Table 2, entry 2). It was
eventually found that the use of benzyl chloride in aqueous
DMSO smoothly underwent selective N-benzylation of 10
Scheme 2. Synthetic scheme for (+)-biotin from l-cysteine.
amide 6, derived from 4, should undergo S,N-carbonyl mi-
gration, and subsequent acid hydrolysis might provide the
thiol carboxylic acid 7. Thiolactone 8 obtained from 7 would
then be subjected to Fukuyama coupling[9] with the zinc re-
agent, ethoxycarbonylbutylzinc iodide (21), which has an
ester group, to give 9, a precursor to 1, in a highly efficient
manner.
Results and Discussion
Synthesis of a-amino aldehyde 4: In our initial study, the
synthesis of a-amino aldehyde 4 from l-cysteine was investi-
gated. Treatment of l-cysteine
hydrochloride with ethyl chlo-
roformate in the presence of
NaOH only led to a trace of
(R)-2-oxothiazolidine-4-carbox-
ylic acid 10 (Table 1, entry 1).
The more reactive phenyl chlo-
roformate was thus employed
to effect the cyclization, which
provided 10 in 96% yield, al-
though the use of a weak base
such as NaHCO3 and Na2CO3
Table 2. Synthesis of N-benzyl-2-oxothiazolidine-4-carboxylic acid 12.
Entry
R
BnX
Base
Solvent
T [8C]
t [h]
Yield[a] [%]
ee [%]
1
2
3
4
5
Et
Et
H
H
H
BnBr
BnCl
BnCl
BnCl
BnCl
K2CO3
K2CO3
NaOH
NaOH
NaOH
DMA
DMSO
CH3CN/H2O
DMF/H2O
DMSO/H2O
25
25
25
25
25
14
2
21
20
15
89
60
trace
trace
94
99
81
–
[b]
[b]
gave
much
lower
yields
–
>99
(Table 1, entry 4 versus en-
tries 2 and 3). A reduction in [a] Assay yield. [b] Not determined.
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M. Seki et al.
FULL PAPER
Table 3. Synthesis of 2-oxothiazolidine-4-carbaldehyde 4.[a]
without converting to the ester derivative 11 (Table 2,
entry 5). Note that the use of DMSO is essential and that
the desired product was not obtained when either CH3CN
or DMF was used as the solvent (Table 2, entry 5 versus en-
tries 3 and 4). The synthesis of 12 from l-cysteine was con-
veniently conducted in a one-pot procedure as shown in
Scheme 3: compound 12 was synthesized in 83% yield by
Entry Reagent
(equiv)
Solvent
T
[8C]
t
Yield[b] ee
[h] [%] [%]
1
(COCl)2 (2.2)
DMSO/
CH2Cl2
ꢀ20 to ꢀ10
ꢀ30 to ꢀ20
1
93
97
Et3N(5)
2
Cl2 (2.2)
DMS (4.8)
Et3N (5)
CH2Cl2
1
93
>99
[c]
3
CH2Cl2/H2O
0
1
33
–
Scheme 3. One-pot synthesis of 12 from l-cysteine. Reagents and condi-
tions: a) ClCO2Ph, NaOH, H2O, toluene, 258C, 2 h; b) to the aqueous
phase were added BnCl, NaOH, DMSO, H2O, 25 8C, 15 h.
4
5
DCC (1.5)
H3PO4 (0.25)
DMSO
DCC (1.2)
TFA (0.2)
pyridine (0.2)
DMSO
toluene
AcOEt
50
50
3
3
74
95
99
simple addition of benzyl chloride and NaOH to an aqueous
solution of sodium (R)-2-oxothiazolidine-4-carboxylate 14,
which was prepared by the treatment of l-cysteine with
phenyl chloroformate and NaOH in a mixture of water and
toluene.
The synthesis of a-amino aldehyde 4 from 12 was then in-
vestigated. Because of the ready racemization of 4, a syn-
thetic scheme that involves the reduction of 12 followed by
oxidation was examined. Although the reduction of the
ester derivative 13 took place in high yield on treatment
with NaBH4 in EtOH, it was accompanied by considerable
racemization (93% yield, 69% ee). Instead, the reduction of
12 with borane, generated in situ by treatment of NaBH4
with H2SO4,[10] suppressed this racemization to give the de-
sired alcohol 15 in 91% yield (Scheme 4).
>99
[a] DMS=dimethyl
DMSO= dimethyl sulfoxide, TFA=trifluoroacetic acid. [b] Assay yield.
[c] Not determined.
sulfide,
DCC=1,3-dicyclohexylcarbodiimide,
tivity largely depends on the nature of the solvent: the high-
est syn selectivity (syn/anti=28:1) was achieved when tolu-
ene was used as the solvent (Table 4, entry 3).
Table 4. Synthesis[a] of a-amino nitrile 5.
Scheme 4. Reduction of 12 to 15.
Entry
Method
Solvent
Yield [%][b]
syn/anti[c]
The Swern or Corey–Kim oxidation of 15 was then con-
ducted to give a-amino aldehyde 4 in high yields (Table 3,
entries 1 and 2). However, as a temperature as low as ꢀ20
and ꢀ308C cannot be applied in large-scale production, we
investigated an alternative method and finally found that
Moffatt oxidation,[11] which employs DCC in the presence of
TFA, pyridine, and DMSO, provided 4 in 95% yield under
industrially viable conditions, such as at 508C (Table 3,
entry 5). The oxidation of 15 by using the HO-TEMPO free
radical,[12] which can be conducted under mild conditions,
gave only a poor yield (Table 3, entry 3).
1
2
3
4
5
6
7
A
A
A
A
B
B
B
AcOEt
CH2Cl2
toluene
toluene/DMSO
AcOEt
98
95
96
16:1
20:1
28:1
7:1
11:1
11:1
11:1
94
quant.
quant.
quant.
CH2Cl2
toluene
[a] Reagents and conditions: a) 1) BnNH2 (1.0 equiv), MgSO4, 5–258C,
3 h; 2) TMSCN (2 equiv), solvent, 0–258C, 15 h; b) NaHSO3 (1.1 equiv),
AcOEt, H2O, 20 8C, 18 h; c) 1) BnNH2 (1.7 equiv), CH2Cl2, 208C, 2 h; 2)
NaCN (1.2 equiv), 8–208C, 20 h; 3) NaHSO3 (0.3 equiv), NaCN
(0.3 equiv), 208C, 1.5 h. [b] Assay yield. [c] Determined by HPLC.
Construction of contiguous stereogenic centers: The amino
aldehyde 4 was then treated with benzylamine followed by
TMSCN to afford the syn isomer of a-amino nitrile 5 in
high yield (Method A) (Table 4, entries 1–4). The syn selec-
To avoid using the expensive TMSCN, we initially at-
tempted to use HCN which was generated by the treatment
of NaCN with acetic acid. However, the reaction was diffi-
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Chem. Eur. J. 2004, 10, 6102 – 6110

Synthesis of (+)-Biotin from l-Cysteine
6102 – 6110
cult to perform even in a laboratory-scale experiment owing
to the difficulties of handling toxic and low-boiling HCN. In
addition, there are serious drawbacks due to the chemical
properties of 4. The attempted purification of 4 by silica gel
column chromatography resulted in considerable decompo-
sition and racemization of the product. Taylor and Hauser
reported that the Strecker reaction takes place with sodium
bisulfite adducts of achiral aldehydes and inexpensive and
easy-to-handle NaCN.[13a] We envisioned a possible use of
this protocol for our diastereoselective synthesis of 5 by em-
ploying the chiral a-amino aldehyde 4 (Method B).[14] The
solution of 4 in AcOEt obtained from the Moffatt oxidation
of 15 was treated with aqueous sodium bisulfite (1.1 equiv)
to give the water-soluble sodium bisulfite adduct 16 in 99%
conversion and, as expected, a simple work up involving ex-
traction and separation provided 16 which was pure enough
to be used in the next step. The aqueous solution of 16 was
then treated with benzylamine at 208C for 2 h followed by
NaCN (1.2 equiv) at 88C and this mixture was stirred at am-
bient temperature for 20 h to provide a-amino nitrile 5 in
high yield (syn/anti=11:1, 95% yield based on 15) (Table 4,
entry 5). Although the diastereoselectivity of the reaction
was unaffected by a change of solvent and poorer than was
observed in the reactions that employed TMSCN, both syn-
5 and anti-5 could be used for the subsequent transforma-
tion to (+)-biotin (vide infra). The ee value of 5 was con-
firmed to be >99% ee by HPLC analysis. Note that during
the reaction the mixture was always basic and evolution of
HCN gas in the reaction flask was much less than that ob-
served in the reaction employing NaCN/AcOH.[15] The syn
selectivity of the Strecker reaction may be accounted for by
the Houk model shown in Figure 1.[16] Coordination of the
hypervalent silicon or hydrogen atom to the imine nitrogen
atom enables internal delivery of the cyanide to the imine
from the opposite side of the bulky benzylamide group to
provide syn-a-amino nitrile syn-5 stereoselectively.
Scheme 5. Amidation of 5. Reagents and conditions: a) 1) H2O2, K2CO3,
DMSO/CH2Cl2, 208C, 2.5 h; 2) H2O, filtration; 3) aq. HCl was added to
the filtrate to obtain anti-6·HCl.
1 h to give thiol amide 18 (Scheme 6). The resulting so-
lution, which contained 18, was directly treated with hydro-
chloric acid to afford thiol carboxylic acid 7 in 95% yield
based on syn-6.
Scheme 6. S,N-Carbonyl migration of amide syn-6.
When the hydrochloride anti-6·HCl was heated at a
higher temperature (1208C) for 5 h under a N2 atmosphere,
S,N-carbonyl migration took place to directly give thiolac-
tone 8 in 91% yield (Scheme 7).
A CH2Cl2 solution of 5 was directly amidated by using
Figure 1. Proposed mechanism for the Strecker reaction of 4.
Katritzkyꢁs protocol,[17] which involves the use of H2O2,
K2CO3, and DMSO (Scheme 5). The reaction proceeded
smoothly, even in a mixture of DMSO and CH2Cl2, to afford
the corresponding amide 6 in quantitative yield. Amide syn-
6 was obtained as a solid in 93% yield by just adding water
to the reaction mixture followed by filtration and anti-6 was
isolated from the mother liquor as the hydrochloride salt in
7% yield (Scheme 5).
Scheme 7. S,N-Carbonyl migration of amide hydrochloride anti-6·HCl.
S,N-Carbonyl migration: S,N-Carbonyl migration of amide 6
was the next subject of our investigation. As expected, when
amide syn-6 was heated to 908C in DMF under a N2 atmos-
phere,[18] S,N-carbonyl migration occurred over a period of
The conversion of thiol carboxylic acid 7, derived from
amide syn-6 (Scheme 6), to thiolactone 8 was then investi-
gated. Although Merckꢁs group, by employing DCC in the
Chem. Eur. J. 2004, 10, 6102 – 6110
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M. Seki et al.
FULL PAPER
presence of p-toluenesulfonic acid (PTSA) in pyridine, have
accomplished this transformation,[19] we only obtained a
moderate yield (57%) by following their protocol (Table 5,
for the introduction of the carbon chain at the C-4 position
(Scheme 8). If zinc reagent 21 reacts with thiolactone 8, a
cyclic thiol ester, ketone 22, would be formed. After treat-
Table 5. Cyclization and epimerization of 7 to 8.[a]
Entry
Additive
(equiv)
Solvent
T
[8C]
t
Yield[b]
[%]
[h]
1
PTSA·H2O (0.05)
pyridine (26)
DMAP·HCl (2)
pyridine (2)
PPTS (2)
pyridine (3)
TFA (0.4)
pyridine (1.4)
none
THF
THF
CHCl3
25
65
65
7
3
3
57
2
63
3
87
4[c]
10
60
1
6
93 (80)[d]
[a] PTSA=p-toluenesulfonic acid, DMAP=4-(dimethylamino)pyridine,
PPTS=pyridinium p-toluenesulfonate. [b] Assay yield. [c] DCC
(1.0 equiv) was employed. [d] Yield of product isolated by crystallization
from MeOH.
Scheme 8. Introduction of the chain at C-4 by the Fukuyama coupling re-
action.
entry 1). We then thoroughly investigated the reaction inter-
mediates and found that the reaction took place through an
initial cyclization to trans-8 followed by epimerization to the
desired thiolactone 8.[20] We then tested the reaction by
using DCC in the presence of various acid-base catalysts.
While the use of Bodenꢁs catalyst,[21] DMAP·HCl, provided
8 in 63% yield, the use of the more acidic pyridinium p-tol-
uenesulfonate (PPTS) resulted in a much better yield
(Table 5, entries 2 and 3). Finally, when TFA and pyridine
were employed as additives and a two-step procedure in-
volving initial cyclization to trans-8 at 108C followed by epi-
merization at 608C was conducted, compound 8 was ob-
tained in 93% yield (Table 5, entry 4). Practically, com-
pound 8 was isolated in 80% yield based on 7 by crystalliza-
tion of the crude product from MeOH. Compound 8 is a
well-established key intermediate in the synthesis of (+)-
biotin.[3] Product 8 was identical to an authentic sample with
respect to IR, NMR, and mass spectra and optical rotation.
ment of 22 with acid, cyclization of 22 to 23 followed by de-
hydration should provide the desired compound 9 with the
required C-4 chain.
The reaction was initially tested by using the homogene-
ous catalyst [PdCl2(PPh3)2].[9] Although six equivalents of
iodide 24 was required for the reaction to go to completion,
the desired product 9 was obtained in 80% yield (Table 6,
entry 1).[23] Although the use of inexpensive [Ni(acac)2][24]
was tested with a view to reducing the cost of raw materials,
it gave a moderate yield of 9 (78%, Table 6, entry 2). The
use of easily recoverable heterogeneous Pd/C catalysts was
then examined. While the use of standard conditions involv-
ing THF and toluene as the solvent resulted in a moderate
yield (50%, Table 6, entry 3), the addition of DMF to the
reaction mixture considerably improved the reaction to pro-
vide 9 in 94% yield (Table 6, entry 4).[25] Nonpyrophoric
Pearlmanꢁs catalyst, Pd(OH)2/C, was found to give 9 in ex-
cellent yield with a catalyst loading as low as 0.65 mol%
(Table 6, entry 5).[26] While, in our previous studies, zinc dust
was activated by the addition of 1,2-dibromoethane
(0.026 equiv relative to Zn) followed by TMSCl (0.018 equiv
relative to Zn),[26] here this approach allowed us to address
the serious issues of poor reproducibility and the require-
ment to use an excess of iodide 24 (2.5 equiv relative to 8)
to complete the reaction. As the Fukuyama coupling reac-
tion has been reported not to proceed with dialkylzinc
(R2Zn), the Schlenk equilibrium of the zinc reagents should
lie to the left for maximum utilization of the reduced iodide
(Scheme 9). We envisioned that addition of a ZnII salt
(ZnX2) might shift the equilibrium toward the desired
RZnX, thereby reducing the amount of iodide 24 required.
When the suspension of zinc dust was treated with bromine
(0.25 equiv relative to Zn dust) before the addition of iodide
Introduction of a carbon chain at C-4: The introduction of a
carbon chain at the C-4 position of thiolactone 8 was previ-
ously carried out by using Grignard reagents.[3] Although
the yields are high, this reaction suffers from such draw-
backs as multisteps, the use of hazardous reagents (Na
metal, HBr, and NaCN) and a low reaction temperature.[22]
Development of a better procedure is thus highly desirable.
Fukuyama and co-workers have recently developed a highly
efficient synthetic approach to functionalized ketones.[9] The
treatment of thiol esters with zinc reagents in the presence
of palladium catalyst [PdCl2(PPh3)2] provides a variety of
functionalized ketones in excellent yields. The reaction is
characterized by unusually high chemoselectivity, mild reac-
tion conditions and the use of nontoxic reagents. We envi-
sioned the possible use of the Fukuyama coupling reaction
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Chem. Eur. J. 2004, 10, 6102 – 6110

Synthesis of (+)-Biotin from l-Cysteine
6102 – 6110
Table 6. Introduction of the chain at C-4 by the Fukuyama coupling reac-
tion.
The use of Pearlmanꢁs catalyst [Pd(OH)2/C] in aqueous
MeOH was found to lower the required H2 pressure to
0.9MPa and provided 25 in 90% yield after hydrolysis. Re-
moval of the benzyl groups from 25 to give 1 was best con-
ducted by using methanesulfonic acid.[29] The pure target
compound 1, which was identical to an authentic sample
with respect to IR, NMR, and MS spectra and optical rota-
tion, was obtained by simple crystallization from water.
Conclusion
Entry[a] DMF
[% (v/v)] (mol%[b]
Catalyst
24
Conditions
Yield
)
(equiv) T [8C] t [h] [%][c]
As described above, a practical synthetic approach to (+)-
biotin (1) from l-cysteine has been accomplished through 1)
the formation of contiguous stereogenic centers by the
highly diastereoselective Strecker reaction (4!5), 2) the
novel ring transformation and deblocking by S,N-carbonyl
migration (syn-6!7 and anti-6·HCl!8), and 3) the intro-
duction of the carbon chain at C-4 by the Fukuyama cou-
pling reaction (8!9). The use of 2-thiazolidinone deriva-
tives as a protecting surrogate for cysteine derivatives has
considerably decreased the number of steps in the synthesis
of (+)-biotin, which is now accessible in 10 steps and in
34% overall yield from readily available l-cysteine. The
high yield, ease of operation and mild reaction conditions of
this approach permit ready access to (+)-biotin,[30] a com-
pound of great biological significance.
1
2
3
4
none
4
none
4
4
4
[PdCl2(PPh3)2] (10) 6.0
20
24
80
78
50
[Ni(acac)2] (10)
2.5
6.0
2.5
25–30 15
20
20
25–30
28–40
Pd/C[d] (5)
24
18
2
Pd/C[d] (5)
94[e]
92[e]
94[e]
5
Pd(OH)2/C[f] (0.65) 2.5
6[g]
Pd/C D1[h] (0.86)
1.4
5
[a] Zinc dust was activated by the treatment with 1,2-dibromoethane
(0.026 equiv relative to Zn dust) followed by TMSCl (0.018 equiv).[27]
[b] mol% relative to 8. [c] Yield of isolated product. [d] Purchased from
Kawaken Fine Chemicals; Pd distribution: uniform; reduction degree:
25–99%; Pd dispersion: 36%; water content: 1.8%. [e] Recovery of Pd:
>95%. [f] Purchased from Kawaken Fine Chemicals. [g] Br2 (0.26 equiv
relative to Zn dust) was used to activate the Zn dust (1.9 equiv relative
to 24). [h] Purchased from Degussa Japan Co., Ltd.; Pd distribution: egg
shell; impregnation depth: 50–150 nm; reduction degree: 0–25%; Pd dis-
persion: 29%; water content: 3%.
Experimental Section
Scheme 9. The Schlenk equilibrium of zinc reagents.
General: Melting points were measured on a Büchi melting point appara-
tus (B-450) and are uncorrected. 1H and 13C NMR spectra (400 and
100 MHz, respectively) were recorded on a Bruker Avance 400 spectrom-
eter with tetramethylsilane as the internal standard. Optical rotations
were measured on a Perkin–Elmer 243 automatic polarimeter at the indi-
cated temperature by using a sodium lamp (D line, 589 nm); [a]D values
are given in units of 10ꢀ1 degcm2 gꢀ1. Mass spectra were obtained on a
Hitachi M-2000A double-focusing mass spectrometer and on a Finnigan
MAT LC-Q instrument. Silica gel column chromatography was per-
formed using Kieselgel 60 (E. Merck). Thin-layer chromatography (TLC)
was carried out on E. Merck 0.25 mm precoated glass-backed plates (60
F254). Development of the plates was accomplished by using 5% phos-
phomolybdic acid in ethanol-heat or they were visualized by UV light
where feasible. All solvents and reagents were used as received.
24, zinc reagent 21 was formed with high reproducibility,
and, as expected, the amount of 24 needed was reduced
from 2.5 to 1.4 equiv and provided 9 in high yield as well
(Table 6, entry 6).[28]
Conversion to (+)-biotin (1): Hydrogenation of 9 to 25 in-
herently requires the use of high H2 pressure because of the
catalytic poison caused by the presence of the sulfide moiety
in the substrate 9 (Scheme 10).
(R)-3-Benzyl-2-oxothiazolidine-4-carboxylic acid (12): Whilst cooling
with ice water, l-cysteine hydrochloride monohydrate (176 g, 1 mol) was
added to a solution of NaOH (184 g, 4.6 mol) in water (0.88 L). A so-
lution of phenyl chloroformate (313 g, 2 mol) in toluene (0.35 L) was
added dropwise to this mixture at <308C. After the mixture had been
stirred at 258C for 2 h, the aqueous layer was separated and washed with
toluene (0.35 L) to afford the sodium salt of (R)-2-oxothiazolidine-4-car-
boxylic acid 14 (Net: 246 g) as an aqueous solution that was used in the
next step without further purification. The purified sample of 10 was ob-
tained as follows: The aqueous solution of 14 was acidified (pH 1) by
adding concentrated HCl and then the solvent was evaporated in vacuo.
The residue was extracted with AcOEt. The extracts were evaporated
and the solids that formed were collected and recrystallized from water
to afford 10 as colorless crystals. M.p. 168–1708C; [a]2D5 =ꢀ62.8 (c=1.0 in
H2O); 1H NMR (400 MHz, [D6]DMSO): d=13.22 (brs, 1H), 8.45 (s,
1H), 4.40 (ddd, J=1.3, 3.4, 8.6 Hz, 1H), 3.72 (dd, J=8.6, 11.4 Hz, 1H),
3.46 ppm (dd, J=3.4, 11.4 Hz, 1H); 13C NMR (100 MHz, [D6]DMSO):
d=173.5 (s), 172.8 (s), 55.7 (d), 32.1 ppm (t); IR (KBr): n˜max =3280, 1738,
1627, 1231 cmꢀ1; MS (70 eV, SI): m/z: 148 [M+H]+; elemental analysis
Scheme 10. Hydrogenation and deblocking of 9. Reagents and condi-
tions: a) 1) H2, Pd(OH)2/C (0.9 MPa), MeOH, H2O; 2) NaOH;
b) MeSO3H, mesitylene.
Chem. Eur. J. 2004, 10, 6102 – 6110
www.chemeurj.org
ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
6107

M. Seki et al.
FULL PAPER
calcd (%) for C4H5NO3S: C 32.65, H 3.42, N 9.52; found: C 32.04, H
3.26, N 9.39. The aqueous solution of 14 (Net: 162 g, 0.95 mol) obtained
above was evaporated. Whilst cooling with ice water, a solution of
NaOH (57 g, 1.4 mol) in water (143 mL) and DMSO (418 mL) were
added to the residue. Benzyl chloride (219 mL, 1.9 mol) was then added
at 258C and the mixture was stirred for 15 h. The mixture was acidified
(pH 1) with concentrated HCl and extracted with AcOEt. The organic
layer was washed with water and brine, dried over MgSO4 and the sol-
vent evaporated to afford 12 (213 g, 83%) as colorless crystals. M.p. 95–
ysis calcd (%) for C19H19N3OS: C 67.67, H 5.81, N 12.45; found: C 67.35,
H 5.81, N 12.41.
(2S)-2-[(4R)-3-Benzyl-2-oxothiazolidin-4-yl]-2-benzylaminoacetonitrile
(anti-5): M.p. 1348C; [a]2D5 =ꢀ183.8 (c=0.24 in MeOH); 1H NMR
(400 MHz, CDCl3): d=7.42–7.23 (m, 8H), 7.15–7.07 (m, 2H), 5.03 (d, J=
15.4 Hz, 1H), 4.05 (d, J=13.0 Hz, 1H), 3.96 (d, J=15.4 Hz, 1H), 3.78–
3.68 (m, 2H), 3.52 ppm (m, 2H); 13C NMR (100 MHz, CDCl3): d=172.4,
137.8, 135.8, 118.8 (4s), 129.5, 129.3, 129.2, 129.1, 129.0, 128.8, 128.7,
128.6, 128.43, 128.37, 128.3, 128.1, 59.0, 50.3 (14d), 51.7, 47.9, 28.5 ppm
(3t); IR (film): n˜max =2220, 1674 cmꢀ1; MS (70 eV, SI): m/z: 338 [M+H]+;
elemental analysis calcd (%) for C19H19N3OS: C 67.63, H 5.68, N 12.45, S
9.50; found: C 67.59, H 5.63, N 12.47, S 9.24.
1
978C; [a]2D5 =ꢀ102.2 (c=1.0 in CHCl3); H NMR (400 MHz, CDCl3): d=
7.39–7.32 (m, 3H), 7.27–7.25 (m, 2H), 5.23 (d, J=15.1 Hz, 1H), 5.21 (dd,
J=2.4, 8.6 Hz, 1H), 4.06 (d, J=15.1 Hz, 1H), 3.57 (dd, J=8.6, 15.1 Hz,
1H), 3.43 ppm (dd, J=2.4, 11.5 Hz, 1H); 13C NMR (100 MHz,
[D6]DMSO): d=171.8 (s), 171.4 (s), 136.8 (s), 128.9 (d), 128.1 (d), 127.8
(d), 60.0 (d), 47.5 (t), 29.2 ppm (t); IR (KBr): n˜max =3029, 1729,
1619 cmꢀ1; MS (70 eV, SI): m/z: 238 [M+H]+; elemental analysis calcd
(%) for C11H11NO3S: C 55.68, H 4.67, N 5.90; found: C 55.97, H 4.82, N
5.77.
Preparation of 2-[(4R)-3-benzyl-2-oxothiazolidin-4-yl]-2-benzylaminoace-
tonitrile (5) via sodium bisulfite adduct 16: Pyridine (2.92 mL,
0.036 mol), TFA (2.78 mL, 0.036 mol) and DCC (44.4 g, 0.22 mol) were
successively added to a solution of 15 (40 g, 0.18 mol) in a mixture of
AcOEt (90 mL) and DMSO (90 mL) at <438C. After the mixture had
been stirred at 508C for 3 h, AcOEt (200 mL) was added and the mixture
was cooled in an ice bath. The precipitated DCU 1,3-dicyclohexylurea
(DCU) was filtered and the filtrate was washed with 12% aq. NaCl
(200 mL). The aqueous layer was extracted with AcOEt (100 mL) and
the combined organic phases were washed with 12% aq. NaCl (200 mL).
(R)-3-Benzyl-4-hydroxymethyl-2-oxothiazolidine (15): H2SO4 (2 g,
19.4 mmol) was added dropwise to a suspension of 12 (8 g, 33.7 mmol)
and NaBH4 (1.53 g, 40.4 mmol) in THF (32 mL) at 40–508C and the mix-
ture was stirred at the same temperature for 3 h. Whilst cooling with ice
water, the mixture was carefully acidified to pH 1 with 2N aq. HCl and
then extracted with AcOEt. The extracts were washed twice with water,
dried over MgSO4, and the solvent evaporated. The residue was crystal-
lized by adding isopropyl ether to give 15 (6.82 g, 91%) as colorless crys-
tals. M.p. 87–908C; [a]2D5 =ꢀ26.7 (c=1.0 in MeOH); optical purity:
>99.9% ee [HPLC: Chiralcel AD (Daicel), EtOH/hexane=10:90,
0.8 mLminꢀ1, 408C, 225 nm]; 1H NMR (400 MHz, CDCl3): d=7.37–7.26
(m, 5H), 4.85 (d, J=15.2 Hz, 1H), 4.27 (d, J=15.2 Hz, 1H), 4.13–3.76
(m, 2H), 3.66–3.64 (m, 1H), 3.34–3.27 (m, 2H), 1.90 ppm (brs, 1H); 13C
NMR (100 MHz, CDCl3): d=173.1, 136.2 (2s), 128.9, 128.1, 128.0 (3d),
The AcOEt solution contained a-amino aldehyde
4 (35.9 g, 90%)
[HPLC; Capcell Pak C18 SG 120A (Shiseido), 15 cm”4.6 mm, 15mm
Na2HPO4/CH3CN=5:1, 1 mLminꢀ1, 408C, 220 nm]. Water (80 mL) and
sodium bisulfite (18.6 g, 0.178 mol) were added to compound 4 (35.9 g,
0.162 mol) in AcOEt and the mixture was stirred at 208C for 30 min.
After the solution was concentrated under reduced pressure, AcOEt
(80 mL) was added to the residue. The mixture was stirred at 208C for
17 h and the aqueous layer containing bisulfite adduct 16 (35.4 g,
0.16 mol) was suspended in CH2Cl2 (106 mL). Benzylamine (23.2 g,
0.27 mol) was added to this suspension and the mixture was stirred at
208C for 2 h. The mixture was then cooled to 88C and NaCN (9.4 g,
0.19 mol) was added. After the mixture had been stirred at 208C for
20 h, NaHSO3 (5.0 g, 0.048 mol) and NaCN (2.35 g, 0.048 mol) were
added and the mixture was stirred for 1.5 h. Aq. NaOH (10%, 40 mL)
was added to the mixture. The organic phase was separated and washed
with water (40 mL). The aqueous layer was extracted with CH2Cl2
(40 mL) and the combined extracts were dried over anhydrous MgSO4
and filtered to afford a-amino nitrile 5 (51.1 g, 95%) in CH2Cl2 as a mix-
ture of syn and anti isomers [syn/anti=11:1, HPLC; L-Column ODS
61.0 (t), 59.5 (d), 47.1, 28.0 ppm (2t); IR (KBr): n˜max =3446, 1645 cmꢀ1
;
MS (70 eV, SI): m/z: 224 [M+H]+; elemental analysis calcd (%) for
C11H13NO2S: C 59.17, H 5.87, N 6.27; found: C 58.75, H 5.68, N 6.09.
(R)-3-Benzyl-2-oxothiazolidine-4-carbaldehyde (4): Pyridine (1.45 mL,
17.9 mol), TFA (1.38 mL, 17.9 mol) and DCC (22.2 g, 0.107 mol) in tolu-
ene (40 mL) were successively added to a solution of 15 (20 g, 0.084 mol)
in DMSO (45 mL) at 258C and the mixture was stirred at 458C for 4.5 h.
Toluene (200 mL) was added to the mixture, which was then cooled in an
ice bath and filtered. The filtrate was washed with brine and water while
the aqueous layer was extracted with AcOEt. The extracts were com-
bined, washed with brine and water, dried over MgSO4 and the solvent
(Shimadzu), 0.01m KH2PO4 buffer (pH 3)/CH3CN=55:45, 1 mLminꢀ1
408C, 225 nm].
,
evaporated to afford
4 (16.6 g, 90%) as a
viscous oil. 1H NMR
(2R)-2-[(4R)-3-Benzyl-2-oxothiazolidin-4-yl]-2-benzylaminoacetamide
(400 MHz, CDCl3): d=9.55 (d, J=1.8 Hz, 1H), 7.41–7.24 (m, 5H), 5.00
(d, J=14.9 Hz, 1H), 4.30 (d, J=14.9 Hz, 1H), 4.07 (ddd, J=1.8, 3.3,
8.8 Hz, 1H), 3.52 (dd, J=8.8, 11.5 Hz, 1H), 3.34 ppm (dd, J=3.3,
11.5 Hz, 1H); IR (KBr): n˜max =1649 cmꢀ1; HRMS: m/z for [MꢀH]ꢀ:
calcd for C11H11NO2S: 221.0501; found: 221.0502.
(syn-6): DMSO (140 mL), K2CO3 (fine powder, 2.7 g, 0.019 mol), and
30% H2O2 (46.3 g) were added to a CH2Cl2 solution of 5 (vide supra)
(Net 46.9 g, 0.14 mol). After the mixture had been stirred at 208C for 6 h,
water was added and the crystals that formed were collected and washed
with CH2Cl2 and water to afford syn-6 (46 g, 93%) as colorless crystals.
M.p. 194–1958C; [a]2D5 =ꢀ38.8 (c=0.45 in DMF); 1H NMR (400 MHz,
[D6]DMSO): d=7.64 (s, 1H), 7.41 (s, 1H), 7.36–7.14 (m, 10H), 4.91 (d,
J=16.0 Hz, 1H), 4.33 (d, J=16.0 Hz, 1H), 3.87–3.82 (m, 1H), 3.78 (d,
J=16.0 Hz, 1H), 3.53 (d, J=16.0 Hz, 1H), 3.41–3.25 ppm (m, 2H); 13C
NMR ([D6]DMSO): d=173.4, 171.5, 140.5, 137.0 (4s), 129.0, 128.6, 128.2,
127.9, 127.7, 127.1, 62.1, 59.5 (8d), 51.5, 47.2, 27.7 ppm (3t); IR (KBr):
n˜max =3397, 1660 cmꢀ1; MS (70 eV, SI): m/z: 356 [M+H]+; elemental anal-
ysis calcd (%) for C19H21N3O2S: C 64.20, H 5.95, N 11.82; found: C 63.99,
H 5.84, N 11.79.
2-[(4R)-3-Benzyl-2-oxothiazolidin-4-yl]-2-benzylaminoacetonitrile
(5):
The crude 4 (30 g, 0.13 mol) obtained above was dissolved in toluene
(150 mL) and MgSO4 (15 g) was added at 258C followed by benzylamine
(14.7 mL, 0.13 mol) at <58C. After the mixture had been stirred at 258C
for 2 h, TMSCN (35.8 mL, 0.27 mol) was added at ꢀ58C and the mixture
was stirred at 208C for 15 h. The mixture was concentrated under re-
duced pressure and the solids that formed were collected and washed
with water and hexane to give 5 (42.1 g, 96%, syn/anti=28:1) as a color-
less solid [HPLC; L-Column ODS (Daicel), 0.01m KH2PO4 (pH 3)
buffer/CH3CN=50:50, 0.5 mLminꢀ1, 408C, 225 nm]. Compounds syn-5
and anti-5 were purified by silica gel column chromatography (hexane/
CHCl3/AcOEt=5:5:1).
(2S)-2-[(4R)-3-Benzyl-2-oxothiazolidin-4-yl]-2-benzylaminoacetamide hy-
drochloride (anti-6·HCl): Na2S2O3·5H2O (48.5 g) in H2O (100 mL) was
added to the mother liquor of syn-6 (vide supra). The organic phase was
washed successively with brine (twice), 4% aq. citric acid and water, and
the solvent evaporated. Acetone (36 g) and concentrated HCl (5 g) were
added to the residue and the solids that formed were collected and
washed with acetone to afford anti-6·HCl (3.8 g, 7%) as colorless crystals.
M.p. 200–2078C; [a]2D5 =ꢀ29.3 (c=1.0 in MeOH); IR (KBr): n˜max =1702,
(2R)-2-[(4R)-3-Benzyl-2-oxothiazolidin-4-yl]-2-benzylaminoacetonitrile
(syn-5): M.p. 124–1258C; [a]2D5 =+46.1 (c=1.0 in CHCl3); optical purity:
>99% ee [HPLC: Chiralcel AD-H (Daicel), EtOH/hexane=10:90,
0.8 mLminꢀ1, 408C, 225 nm]; 1H NMR (400 MHz, CDCl3): d=7.36–7.25
(m, 8H), 7.12 (dd, J=3.4, 7.4 Hz, 2H), 5.04 (d, J=15.3 Hz, 1H), 4.30 (d,
J=15.3 Hz, 1H), 4.06 (d, J=13.1 Hz, 1H), 3.86–3.76 (m, 3H), 3.40 (dd,
J=8.2, 11.5 Hz, 1H), 3.23 ppm (dd, J=4.5, 11.5 Hz, 1H); 13C NMR
(100 MHz, CDCl3): d=172.6, 137.6, 135.8, 117.8 (4s), 129.6, 129.5, 129.3,
128.8, 128.6, 128.4, 59.3, 52.13 (8d), 52.07, 48.5, 28.8 ppm (3t); IR (KBr):
n˜max =2220, 1648 cmꢀ1; MS (70 eV, SI): m/z: 338 [M+H]+; elemental anal-
1679 cmꢀ1 1H NMR (400 MHz, CDCl3): d=10.01 (brs, 1H), 9.58 (brs,
;
1H), 8.67 (s, 1H), 8.06 (s, 1H), 7.61–7.26 (m, 10H), 4.78 (d, J=15.9 Hz,
1H), 4.38–4.35 (m, 1H), 4.27 (s, 1H), 4.10 (d, J=15.6 Hz, 1H), 3.99 (s,
2H), 3.77 (dd, J=12.0, 3.2 Hz, 1H), 3.52 ppm (dd, J=12.1, 8.4 Hz, 1H);
13C NMR (100 MHz, [D6]DMSO): d=171.1, 136.3 (4s), 130.5, 129.0,
6108
ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2004, 10, 6102 – 6110

Synthesis of (+)-Biotin from l-Cysteine
6102 – 6110
128.5, 128.4, 127.4, 127.4, 58.8, 57.8 (8d), 49.7, 46.5, 27.3 ppm (3t); MS
lized from AcOEt to afford trans-8 (40.0 g, 42%) as colorless crystals.
M.p. 115–1168C; [a]2D6 =+10.6 (c=1.0 in CHCl3); 1H NMR (400 MHz,
CDCl3): d=7.37–7.29 (m, 8H), 4.95 (d, J=7.3 Hz, 1H), 4.61 (d, J=
7.3 Hz, 1H), 4.31 (d, J=5.5 Hz, 1H), 4.27 (d, J=5.5 Hz, 1H), 3.49 (m,
1H), 3.38 (d, J=7.0 Hz, 1H), 2.95 (dd, J=4.8, 5.2 Hz, 1H), 2.81 ppm (dd,
J=4.6, 4.8 Hz, 1H); 13C NMR (100 MHz, [D6]DMSO): d=170.9, 140.9,
136.8 (3s), 128.5, 128.4, 128.0, 127.9, 127.4, 127.3, 126.5, 57.9 (8d), 52.8,
48.4, 46.0, 28.7 ppm (4t); IR (KBr): n˜max =2944, 1741, 1710 cmꢀ1; MS
(70 eV, SI): m/z: 339 [M+H]+; elemental analysis calcd (%) for
C19H18N2O2S: C, 67.43; H, 5.36; N, 8.28; S, 9.48; found: C 67.27, H 5.31,
N 8.30, S 9.49.
(70 eV, SI): m/z: 356 [M+H]+.
(4R,5R)-1,3-Dibenzyl-5-mercaptomethyl-2-oxothiazolidine-4-carboxylic
acid (7): A solution of syn-6 (100 g, 0.28 mol) in DMF (200 mL) was de-
gassed by bubbling with N2 gas and then stirred at 908C for 3 h under a
N2 atmosphere. Concentrated HCl (200 mL, 1.9 mol) was added dropwise
to the mixture at 908C over 1.75 h. After the mixture had been stirred at
the same temperature for a further 1.25 h, water (100 mL) was added
dropwise at 858C over 30 min. The mixture was cooled to 08C and the
solids that formed were collected to afford 7 (95.1 g, 95%) as colorless
crystals. M.p. 159–1608C; [a]2D0 =+48.8 (c=0.62 in DMF); optical purity:
>99% ee [HPLC: Chiralcel AD (Daicel), EtOH/hexane/THF=
10:90:0.1, 0.8 mLminꢀ1, 408C, 225 nm]; 1H NMR (400 MHz, DMSO-d6):
d=7.58 (s, 1H), 7.37–7.22 (m, 10H), 4.83 (d, J=16.0 Hz, 1H), 4.54 (d,
J=16.0 Hz, 1H), 4.13 (d, J=16.0 Hz, 1H), 4.06 (d, J=16.0 Hz, 1H), 3.82
(d, J=4.0 Hz, 1H), 3.61–3.58 (m, 1H), 2.75–2.65 (m, 2H), 2.13–2.11 ppm
(m, 1H); 13C NMR (100 MHz, [D6]DMSO): d=170.6, 160.7, 136.9, 136.4
(4s), 128.8–127.5, 58.3, 58.0 (8d), 46.5, 46.3, 23.4 ppm (3t); IR (KBr):
n˜max =1735, 1625 cmꢀ1; MS (70 eV, SI): m/z: 357 [M+H]+; elemental anal-
ysis calcd (%) for C19H20N2O2S: C 64.02, H 5.66, N 7.86; found: C 63.83,
H 5.38, N 7.96.
Synthesis of 8 from trans-8: Pyridine (0.5 mL, 6 mmol) was added to a
solution of trans-8 (100 mg, 0.296 mmol) in CHCl3 (1 mL) and the mix-
ture was stirred at 258C for 23 h. The mixture was washed successively
with 2n aq. HCl, water, sat. aq. NaHCO3, and brine, dried over MgSO4
and the solvent evaporated. The residue was crystallized from isopropyl
ether to afford 8 (75.1 mg, 75%) as colorless crystals. The spectral prop-
erties of the product were identical to those of 8 obtained from 7.
Ethyl
(3aS,4Z,6aR)-5-(1,3-dibenzyl-2,3,3a,4,6,6a-hexahydro-2-oxo-1H-
(9): Bromine (5.8 g,
thieno[3,4-d]imidazol-5-ylidene)pentanoate
36 mmol) was added to a suspension of zinc dust (9.3 g, 0.14 mol) in THF
(18 mL) and toluene (12 mL) at 10–408C over 15 min and the mixture
was heated to 508C. Ethyl 5-iodopentanoate (18.6 g, 72.8 mmol) was then
added dropwise to the mixture at 50–608C over 1 h. After stirring the
mixture for 1 h, the mixture was cooled to 308C. Compound 8 (17.6 g,
52 mmol), toluene (36 mL), DMF (4.4 mL), and 10% Pd/C D1 (0.5 g,
0.45 mmol) were added to the resulting mixture and the mixture was stir-
red at 28–408C for 5 h. The mixture was treated with 18% HCl (34 mL)
at 10–308C. After the mixture had been stirred at 208C for 1 h, the mix-
ture was filtered. The organic phase of the filtrate was washed successive-
ly with water, saturated aq. sodium sulfite, and water, dried over MgSO4
Bis{[(4R,5R)-4-carbamoyl-1,3-dibenzyl-2-oxothiazolidin-5-yl]methyl} di-
sulfide (26): A mixture of syn-6 (14 g, 0.039 mol) and NaHCO3 (3.96 g,
0.047 mol) in DMF was stirred at 80–858C for 17 h. The mixture was
evaporated and water (20 mL) was added and the mixture was stirred at
58C for 1 h. The crystals that formed were collected and washed with a
mixture of MeOH (80 mL) and water (40 mL), and dried at 508C for
17 h to afford 26 (12.1 g, 87%) as colorless crystals. M.p. 208–2118C;
[a]2D0 =+55.4 (c=0.29 in DMF); 1H NMR (400 MHz, [D6]DMSO): d=
7.60 (s, 1H), 7.12–7.42 (m, 11H), 4.80 (d, J=16 Hz, 1H), 4.69 (d, J=
16 Hz, 1H), 4.09 (d, J=16 Hz, 1H), 3.84 (d, J=16 Hz, 1H), 3.67 (d, J=
4 Hz, 1H), 3.51–3.55 (m, 1H), 2.86–2.98 ppm (m, 2H); 13C NMR
(100 MHz, [D6]DMSO): d=169.2, 157.2, 135.2, 135.1 (4s), 126.63, 126.6,
125.9, 125.8, 125.4, 125.3, 57.4, 53.7 (8d), 43.9, 42.8, 39.0 ppm (3t); IR
(KBr): n˜max =3356, 1682 cmꢀ1; MS (70 eV, SI): m/z: 709 [M+H]+.
and the solvent evaporated to give 9 (22 g, 94%) as a viscous oil. [a]D25
=
+190.9 (c=0.95 in MeOH); 1H NMR (400 MHz, CDCl3): d=7.08–6.95
(m, 10H), 5.13 (t, J=8.0 Hz, 1H), 4.59 (m, 2H), 3.99–3.72 (m, 6H), 2.71–
2.62 (m, 2H), 1.99–1.95 (m, 2H), 1.88–1.72 (m, 2H), 1.45–1.35 (m, 2H),
0.96 ppm (t, J=8.0 Hz, 3H); 13C NMR (400 MHz, CDCl3): d=173.3,
159.0, 137.9, 137.1 (4s), 129.0–127.3, 125.7, 64.6, 59.0 (13d), 60.3, 46.5,
44.9, 37.1, 33.6, 31.1, 24.2 (7t), 14.3 ppm (1q); IR (KBr): n˜max =2932,
1691 cmꢀ1; HRMS: m/z for [MꢀH]ꢀ: calcd for C26H30N2O3S: 450.1977;
found: 450.1966.
(4S,5R)-1,3-Dibenzyl-3,3a,6,6a-tetrahydro-1H-thieno[3,4-d]imidazole-2,4-
dione (8): Pyridine (32 mL, 0.39 mol) and TFA (8.7 mL, 0.11 mol) were
added to a solution of 7 (100 g, 0.28 mol) in CHCl3 (400 mL) at 08C. A
solution of DCC (86.8 g, 0.42 mol) in CHCl3 (136 mL) was then added to
this mixture at 258C, which was then stirred at 08C for 1 h and refluxed
for 6 h. The mixture was cooled to 258C and the solids that formed were
collected. The filtrate was evaporated and the residue was purified by
(3aS,4S,6aR)-5-(1,3-Dibenzyl-2,3,3a,4,6,6a-hexahydro-2-oxo-1H-
thieno[3,4-d]imidazol-5-yl)pentanoic acid (25): A mixture of 9 (100 g,
0.22 mol) and 20% Pd(OH)2/C (50% wet) (7.3 g, 6.9 mmol) in MeOH
(730 mL) and H2O (200 mL) was stirred under H2 (0.9mPa) at 1108C for
12 h. The mixture was cooled to 258C and filtered. Water (2 mL) and
31% aqueous NaOH [86 g: NaOH (27 g) and H2O (59 mL)] were added
to the filtrate and the mixture was stirred at 408C for 2 h and the solvent
evaporated. The residue was diluted with AcOEt and acidified to pH 1
with 10% aq. HCl. The organic phase was separated and washed twice
with H2O and the solvent evaporated. Hexane was added to the residue
and the solid that formed was collected to afford 25 (85 g, 90%) as color-
less crystals. M.p. 948C; [a]2D0 =ꢀ28.0 (c=0.5 in MeOH); 1H NMR
(400 MHz, CDCl3): d=10.58 (brs, 1H), 7.34–7.23 (m, 10H), 5.07 (d, J=
15.0 Hz, 1H), 4.75 (d, J=15.0 Hz, 1H), 4.15 (d, J=15.0 Hz, 1H), 3.99–
3.83 (m, 3H), 3.10–3.05 (m, 1H), 2.76–2.64 (m, 2H), 2.36–2.32 (m, 2H),
1.68–1.45 (m, 5H), 1.37–1.23 ppm (m, 1H); 13C NMR (100 MHz, CDCl3):
d=178.6, 161.1, 136.9, 136.7 (4s), 128.7–127.7, 62.7, 61.2, 54.2 (13d), 48.0,
46.6, 34.7, 33.9, 28.6, 28.5, 24.4 ppm (7t); IR (ATR): n˜max =1725,
1660 cmꢀ1; MS (70 eV, SI): m/z: 425 [M+H]+; elemental analysis calcd
(%) for C24H28N2O3S: C 67.90, H 6.65, N 6.60, S 7.55; found: C 67.69, H
6.69, N 6.56, S 7.47.
silica gel column chromatography (hexane/AcOEt=2:1) to afford
8
(88.1 g, 93%) as colorless crystals. Pure 8 was obtained in 80% yield by
recrystallization of the crude residue from MeOH. M.p. 122–1238C
(Lit.:[4c] 125.5–1278C); [a]D25 =+90.5 (c=1.0 in CHCl3) {Lit.:[4c] [a]2D0
=
+91.3ꢁ0.9 (c=1.0 in CHCl3)}; 1H NMR (400 MHz, CDCl3): d=7.39–
7.25 (m, 10H), 5.04 (d, J=15.0 Hz, 1H), 4.69 (d, J=15.0 Hz, 1H), 4.37
(d, J=15.0 Hz, 1H), 4.36 (d, J=15.0 Hz, 1H), 4.16–4.09 (m, 1H), 3.81(d,
J=7.8 Hz, 1H), 3.38 (dd, J=13.0, 5.6 Hz, 1H), 3.29 ppm (dd, J=13.0,
2.2 Hz, 1H); 13C NMR (100 MHz, [D6]DMSO): d=205.6, 158.1, 137.1,
136.7 (4s), 128.5–127.3, 62.4, 56.0 (12d), 45.2, 44.6, 32.5 ppm (3t); IR
(KBr): n˜max =1697, 1686 cmꢀ1; MS (70 eV, SI): m/z: 339 [M+H]+.
(4S,5R)-1,3-Dibenzyl-3,3a,6,6a-tetrahydro-1H-thieno[3,4-d]imidazol-2,4-
dione (8): A solution of anti-6·HCl (3.8 g, 9.7 mmol) in DMF (18 g) was
degassed by bubbling with N2 gas and stirred at 1208C for 5 h. AcOEt
(50 mL) and water (50 mL) was added to the mixture and the aqueous
phase was extracted with AcOEt. The combined extracts were collected
and washed twice with water, and the solvent evaporated. The residue
was purified by silica gel column chromatography (hexane/AcOEt=2:1)
to afford 8 (2.99 g, 91%) as colorless crystals. The spectral properties of
the product were identical to those of 8 obtained from syn-6.
(+)-Biotin (1): MeSO3H (15.5 g, 0.16 mol) was added to a solution of 25
(6.36 g, 0.015 mol) in mesitylene (16 mL) at 258C. After the mixture had
been stirred at 1358C for 3 h, it was cooled to 858C. The lower phase was
separated and poured into water (100 mL). After the mixture had been
stirred at 108C for 1 h, the crystals that formed were collected and
washed with water and acetone to give the crude product. NaOH (0.54 g,
0.014 mol) was added to a stirred suspension of the crude solid in water
(45 mL) at 258C, and the pH value of the mixture was adjusted to 7.5–8.0
at 908C by adding concentrated HCl. Activated carbon (2.5 g) was added
to the mixture at the same temperature and the mixture was filtered. The
(4R,5R)-1,3-Dibenzyl-3,3a,6,6a-tetrahydro-1H-thieno[3,4-d]imidazol-2,4-
dione (trans-8): Pyridine (32 mL, 0.39 mol) and TFA (8.7 mL, 0.11 mol)
were added to a solution of 7 (100 g, 0.28 mol) in CHCl3 (400 mL) at
08C. A solution of DCC (63.5 g, 0.31 mol) in CHCl3 (200 mL) was then
added to the mixture at <158C, which was then stirred at 258C for 1 h.
The mixture was diluted with AcOEt and filtered. The filtrate was
washed successively with 2N aq. HCl, water, sat. aq. NaHCO3, and brine,
dried over MgSO4 and the solvent evaporated. The residue was crystal-
Chem. Eur. J. 2004, 10, 6102 – 6110
www.chemeurj.org
ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
6109

M. Seki et al.
FULL PAPER
filtrate was acidified to pH 1.6–1.8 with concentrated HCl at 958C. After
the mixture had been stirred at 108C for 1 h, the crystals that formed
were collected and washed with water to give 1 (2.71 g, 74%) as colorless
crystals. M.p. 231–2328C (Lit.[31] 229.5–2308C): [a]2D4 =+91.0 (c=1.0 in 0.1
N NaOH) {Lit.:[31] [a]2D5 =+91.3 (c=1.0 in 0.1N NaOH)}; IR (neat):
[13] a) H. M. Taylor, C. R. Hauser, Org. Synth. 1973, Coll. Vol. 5, 437–
439; b) J.-P. Leblanc, H. W. Gibson, J. Org. Chem. 1994, 59, 1072–
1077.
[14] M. Seki, M. Hatsuda, S. Yoshida, Tetrahedron Lett. 2004, 45, 6579.
[15] After the reaction, the concentration of HCN gas in the reaction
flask was 50 ppm. Nonetheless, the reaction should be conducted in
a well-ventilated draft.
[16] a) K. N. Houk, M. N. Paddon-Row, N. G. Rondan, Y.-D. Wu, F. K.
Brown, D. C. Spellmeyer, J. T. Metz, Y. Li, R. J. Loncharich, Science
1986, 231, 1108–1117; b) P. Merino, A. Lanaspa, F. L. Merchan, T.
Tejero, J. Org. Chem. 1996, 61, 9028–9032.
[17] A. R. Katritzky, B. Pilarski, L. Urogdi, Synthesis 1989, 949–950.
[18] When the reaction was conducted in the presence of a base and
oxygen, disulfide 26 was exclusively obtained.
n˜max =3299, 2920, 1686 cmꢀ1 1H NMR (400 MHz, [D6]DMSO): d=12.02
;
(brs, 1H), 6.49 (brs, 1H), 6.40 (brs, 1H), 4.31 (dd, J=5.2, 7.6 Hz, 1H),
4.16–4.13 (m, 1H), 3.12–3.10 (m, 1H), 2.81 (dd, J=5.1, 12 Hz, 1H), 2.58
(d, J=12 Hz, 1H), 2.21 (t, J=7.3 Hz, 2H), 1.54–1.36 (m, 4H), 1.36–
1.32 ppm (m, 2H); 13C NMR (100 MHz, [D6]DMSO): d=174.8, 163.1
(2s), 61.4, 59.5, 55.7 (3d), 40.0, 33.8, 28.44, 28.36, 24.9 ppm (5t); MS
(70 eV, SI): m/z: 245 [M+H]+; elemental analysis calcd (%) for
C10H16N2O3S: C 49.16, H 6.60, N 11.47, S 13.13; found: C 49.28, H 6.63,
N 11.54, S 13.09.
Acknowledgement
The authors wish to thank Degussa Japan Co., Ltd. for disclosing the
chemical properties of the Pd/C catalysts.
[19] E. Poetsch, M. Casutt, Chimia 1987, 41, 148–150.
[20] Compound trans-8 was isolated under the conditions described in
the Experimental Section, and then converted to 8 by treatment
with pyridine.
[1] For example, see: a) P. S. Mistry, K. Dakshinamurti, Vitam. Horm.
1964, 22, 1–55; b) C. C. Whitehead, Ann. N. Y. Acad. Sci. 1985, 447,
86–95; c) Y. Izumi, H. Yamada, Biotechnology of Vitamins, Pig-
ments and Growth Factors (Ed.: E. J. Vandamme), Elsevier Applied
Science, New York, 1989; d) M. Maebashi, Y. Makino, Y. Furukawa,
K. Ohinata, S. Kimura, T. Sato, J. Clin. Biochem. Nutr. 1993, 14,
211–218.
[2] For example, see: a) N. Sakurai, Y. Imai, M. Masuda, S. Komatsu-
bara, T. Tosa, Appl. Environ. Microbiol. 1993, 59, 2857–2863; b) N.
Sakurai, Y. Imai, M. Masuda, S. Komatsubara, T. Tosa, Appl. Envi-
ron. Microbiol. 1993, 59, 3225–3232; c) N. Sakurai, Y. Imai, M.
Masuda, S. Komatsubara, T. Tosa, J. Biotechnol. 1994, 36, 63–73;
d) N. Sakurai, Y. Imai, S. Komatsubara, T. Tosa, J. Ferment. Bioeng.
1993, 77, 610–616.
[3] For a review, see: P. J. De Clercq, Chem. Rev. 1997, 97, 1755–1792.
[4] a) M. W. Goldberg, L. H. Sternbach, USA 2489232, 1949; [Chem.
Abstr. 1951, 45, 184b]; b) M. W. Goldberg, L. H. Sternbach, USA
2489235, 1949; [Chem. Abstr. 1951, 45, 186a]; c) M. Gerecke, J. P.
Zimmermann, W. Ashwanden, Helv. Chim. Acta 1970, 53, 991–999.
[5] a) M. Seki, M. Hatsuda, Y. Mori, S. Yamada, Tetrahedron Lett. 2002,
43, 3269–3272; b) M. Seki, Y. Mori, M. Hatsuda, S. Yamada, J. Org.
Chem. 2002, 67, 5527–5536.
[21] E. P. Boden, G. E. Keck, J. Org. Chem. 1985, 50, 2394–2395.
[22] I. Isaka, K. Kubo, M. Takashima, M. Murakami, Yakugaku Zasshi
1968, 88, 964—970; [Chem. Abstr. 1969, 70, 19984r).
[23] a) T. Shimizu, M. Seki, Tetrahedron Lett. 2000, 41, 5099–5101; b) M.
Seki, T. Shimizu, Jp. Pat. Appl. JP 1998374672, 1998 [Chem. Abstr.
1998, 133, 73893].
[24] T. Shimizu, M. Seki, Tetrahedron Lett. 2002, 43, 1039–1042.
[25] T. Shimizu, M. Seki, Tetrahedron Lett. 2001, 42, 429–432.
[26] a) Y. Mori, M. Seki, Heterocycles 2002, 58, 125–126; b) Y. Mori, M.
Seki, J. Org. Chem. 2003, 68, 1571–1574.
[6] R. A. Sheldon, Environ. Chem. 1992, 99–119.
[7] J. March, Marchꢀs Advanced Organic Chemistry, Wiley, New York,
1999, pp. 338–342.
[27] P. Knochel, M. C. P. Yeh, S. C. Beck, J. Talbert, J. Org. Chem. 1988,
53, 2390–2392.
[8] For a preliminary result, see: a) M. Seki, M. Kimura, M. Hatsuda, S.
Yoshida, T. Shimizu, Tetrahedron Lett. 2003, 44, 8905–8907; b) M.
Seki, T. Shimizu, S. Yoshida, M. Hatsuda, PCT Pat. WO 2002 JP
12694, 2002 [Chem. Abstr. 2002, 139, 36521].
[9] H. Tokuyama, S. Yokoshima, T. Yamashita, T. Fukuyama, Tetrahe-
dron Lett. 1998, 39, 3189–3192.
[10] A. Abiko, S. Masamune, Tetrahedron Lett. 1992, 33, 5517–5518.
[11] a) K. E. Pfitzner, J. G. Moffatt, J. Am. Chem. Soc. 1963, 85, 3027–
3028; b) J. G. Moffatt, Org. Synth. 1973, Coll. Vol. 5, 242–245.
[12] J. Jurczak, D. Gryko, E. Kobrzycka, H. Gruza, P. Prokopowicz, Tet-
rahedron 1998, 54, 6051–6064.
[28] M. Kimura, M. Seki, Tetrahedron Lett. 2004, 45, 1635–1637.
[29] T. Takahashi, K. Shimago, K. Maeshima, Eur. Pat. Appl. EP 36030,
1981; [Chem. Abstr. 1982, 96, 85557s.
[30] Of the methods starting from l-cysteine, the Poetsch approach[19]
provides (+)-biotin in the shortest number of steps (9 steps), howev-
er, it requires expensive or hazardous reagents such as BnNCO and
CDI.
[31] R. A. Volkmann, J. T. Davis, C. N. Meltz, J. Am. Chem. Soc. 1983,
105, 5946–5948.
Received: July 18, 2004
Published online: October 29, 2004
6110
ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2004, 10, 6102 – 6110