An efficient stereoselective synthesis of six stereoisomers of 3, 4-diaminocyclohexane carboxamide as key intermediates for the synthesis of factor Xa inhibitors

Article abstract of DOI:10.1016/j.tet.2017.01.021

An efficient stereoselective route for the preparation of six stereoisomers of tert-butyl ((1R, 2S, 5S)-2-amino-5-(dimethylcarbamoyl)cyclohexyl)carbamate 1 starting from simple 3-cyclohexene-1-carboxylic acid has been described. Stereochemistry of the tit

Full text of DOI:10.1016/j.tet.2017.01.021

Accepted Manuscript
An efficient stereoselective synthesis of six stereoisomers of 3, 4-diaminocyclohexane
carboxamide as key intermediates for the synthesis of factor Xa inhibitors
Xin Wang, Mingliang Ma, A. Gopi Krishna Reddy, Wenhao Hu
PII:
S0040-4020(17)30034-0
10.1016/j.tet.2017.01.021
TET 28391
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 2 December 2016
Revised Date: 6 January 2017
Accepted Date: 9 January 2017
Please cite this article as: Wang X, Ma M, Reddy AGK, Hu W, An efficient stereoselective synthesis of
six stereoisomers of 3, 4-diaminocyclohexane carboxamide as key intermediates for the synthesis of
factor Xa inhibitors, Tetrahedron (2017), doi: 10.1016/j.tet.2017.01.021.
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Graphical Abstract.
An efficient stereoselective synthesis of six stereoisomersLeave this area blank for abstract info.
of 3, 4-diaminocyclohexane carboxamide as key
intermediates for the synthesis of factor Xa inhibitors
Xin Wang, Mingliang Ma, A. Gopi Krishna Reddy and Wenhao Hu
Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, Department of Chemistry, School of Chemistry and
Molecular Engineering, East China Normal University, Shanghai, 200062, China

1
ACCEPTED MANUSCRIPT
Tetrahedron
journal homepage: www.elsevier.com
An efficient stereoselective synthesis of six stereoisomers of 3, 4-diaminocyclohexane
carboxamide as key intermediates for the synthesis of factor Xa inhibitors
Xin Wang, Mingliang Ma, A. Gopi Krishna Reddy and Wenhao Hu
Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, Department of Chemistry, School of Chemistry and
Molecular Engineering, East China Normal University, Shanghai, 200062, China
ARTICLE INFO
ABSTRACT
Article history:
Received
An efficient stereoselective route for the preparation of six stereoisomers of tert-butyl ((1R, 2S,
5S)-2-amino-5-(dimethylcarbamoyl)cyclohexyl)carbamate
1
starting from simple 3-
Received in revised form
Accepted
Available online
cyclohexene-1-carboxylic acid has been described. Stereochemistry of the title compounds was
controlled at C2 center by Mitsunobu reaction and at C5 via a base-catalyzed epimerization.
Only a limited usage of column chromatography has provided a direct and scalable route for the
six stereoisomers.
2016 Elsevier Ltd. All rights reserved
.
Keywords:
Factor Xa inhibitor
Stereoselective synthesis
3,4-diaminocyclohexane carboxamide
Gram scale synthesis
1. Introduction
racemic form. Meanwhile, the control and detection of impurities
is very important for industrial production of pharmaceutical
drugs. Some stereoisomers of compound 1 may be useful
intermediates for the synthesis of impurities of edoxaban, which
are generated in the industrial production process.9 Additionally,
the derivatives of 3, 4-diaminocyclo-hexane carboxylic acid can
be used as chiral organocatalysts for asymmetric direct aldol
reaction with high enantioselectivity.10
Factor Xa (fXa), a serine protease, plays an important role in
the coagulation pathway and forms the prothrombinase complex
via binding to factor Va on activated platelet surface. The
prothrombinase complex converts prothrombin to another serine
protease, thrombin.1 Thrombin is responsible for the conversion
of soluble fibrinogen into insoluble strands of fibrin and also the
formation of blood clots.2 Thus, factor Xa has become an
attractive target for anticoagulant treatment.3 Edoxaban is known
to be an orally and direct factor Xa inhibitor for the prevention
and treatment of venous thromboembolisms, and also anticipated
to exhibit superior oral absorption and a lower risk of bleeding
when compared to other available anticoagulants.4-6
Tert-butyl ((1R,2S,5S)-2-amino-5-(dimethylcarbamoyl)cyclo-
hexyl) carbamate 1 has been reported as a key intermediate in the
synthesis of edoxaban (Fig. 1).7 Similar cycloalkanediamine
derivatives have gained much interest due to their potential as
therapeutic drugs for thrombotic diseases.8 The cis-1, 2-
diaminocyclohexane and a carboxamide substituent on the C5 of
cyclohexane ring which exist in compound 1 makes 7 possible
stereoisomers. Hence, the stereochemistry of the three
substituents on the cyclohexane ring can greatly affect the anti-
fXa activity of edoxaban.8b Nagata and coworkers have reported
the synthesis of four stereoisomers of 3, 4-diaminocyclohexane
carboxylic acid derivatives in order to elucidate the significance
of each substituent stereochemistry for anti-fXa activity.8b
Fig. 1. Structures of edoxaban and its key intermediate.
However, all four compounds they synthesized were only in
———
Fig. 2. Structures of six stereoisomers of compound 1.
Corresponding author.
E-mail address: whu@chem.ecnu.edu.cn (W. Hu).

2
Tetrahedron
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Due to these significant biological activities and structural
compound 1 could be achieved from 8a by the installation of
importance, several processes have been reported for the
preparation of compound 1,8d,11 and its enantiomer, which could
also be easily achieved following the same route from
enantiomeric precursor. However, there were only a few reports
about the synthesis of diastereoisomers of 1.9 Herein we report
our results of stereoselective synthesis of six stereoisomers of
compound 1 starting from 3-cyclohexene-carboxylic acid (Fig. 2)
by using Mitsunobu reaction and a base-catalyzed epimerization
as key steps of the strategy.
amino group via the displacement of tosylated/mesylated
alcoholic group of 8a by azide (N3) followed by reduction. On
the other hand, the other isomer could be resulted from 8a via the
inversion of C2 hydroxyl group under Mitsunobu reaction
conditions12 using a carboxylic acid nucleophile, subsequent
hydrolysis, mesylation or tosylation to form a leaving group
followed by azide substitution and further reduction. The key
intermediate compound 8a which in turn could be obtained by a
literature reported four-step sequence from 5a8b,11a The
stereochemistry at C5 can also be adjusted by racemization of the
ester group of 8a.13 Inversion of amino stereochemistry at C1 is
difficult to achieve by our synthetic route, however, identical
sequences starting from (R)-3-cyclohexene-carboxylic acid 5b
allow access to epimers at C1.
2. Results and discussion
The designed strategy for the synthesis of the six
stereoisomers starting from cyclohexene carboxylic acid 5 is
shown in scheme 1. One of the targeted stereoisomers of
Scheme 1. Retro synthetic approach for the synthesis of 6 stereoisomers.
Keeping our synthetic strategy in mind, we have commenced
with (S)-3-cyclohexene-1-carboxylic acid 5a which has been
prepared from commercially available racemic 3-cyclohexene-1-
carboxylic acid.14 Thus treatment of 5a with KI and I2,15 resulted
4-iodo-6-oxabicyclo[3.2.1]octan-7-one 6a in excellent yield
followed by ethanolysis in the presence of NaOH afforded the
cis-epoxide 7a. Without further purification, the epoxide 7a has
been allowed to react with an excess amount of ammonia in the
next step. Nucleophilic opening of the substituted cis-epoxide 7a
with ammonia gave trans-amino alcohol as a single isomer with
high regio- and stereoselectivity in accordance with Fürst-
Plattner rule.16 Furthermore, the chemo selective protection of the
amino group with Boc2O afforded the key intermediate 8a in
almost quantitative yield with an overall yield of 80% (Scheme
2). The same protocol was applied on (R)-3-cyclohexene-1-
carboxylic acid 5b in order to accomplish the other enantiomer
8b and successfully achieved 8b in comparable yields to that of
8a.
Succeeding the achievement of key intermediates 8a and 8b,
we have turned our interest towards the title compounds. We
have envisioned that, the C2 amino can be introduced by the
conversion of C2 hydroxyl to mesylate followed by nucleophilic
displacement with sodium azide and subsequent hydrogenation.
Hence mesylation of alcohol 8a with MsCl in the presence of
Et3N in dichloromethane gave mesylate 9a. The mesylate 9a
upon treatment with NaN3 in DMF in the presence of catalytic
amount of 15-crown-5 at 75 oC for 48 h furnished the
nucleophilic substitution product 15a in 58% yield with inversion
of configuration at C2. It’s worth mentioning that the epimer 13a
with retention of configuration at C2 was also obtained in 5%
yield, which is due to the neighboring-group participation.17
Advancement of azide 15a to 16a was achieved in a two-step
sequence, i.e., Pd/C catalyzed hydrogenation followed by
protection of amino group with Cbz resulted the cis-
diaminocyclohexane 16a with two different protecting groups
(Scheme 3).
Although a small amount of epimer 13a with retention of
configuration at C2 can be obtained by the above mentioned
method, however, a multigram scale synthesis was hard to
achieve because of low yield. Therefore, the inversion of
configuration at C2 hydroxyl was required before the mesylation.
We have tried initially the Mitsunobu reaction of 8a with PPh3
and DIAD in THF in the presence of (TsO)2Zn, by anticipating
that formation of leaving group -OTs as well as inversion of
configuration of hydroxyl can be achieved in one-step
procedure,18 however, no reaction occurred. We next shifted to
the conventional Mitsunobu condition, the desired alcohol 11a
with inversion of configuration at C2 was achieved in two steps.
Treatment of 8a with DEAD, PPh3 and p-nitrobenzoic acid in
THF, to afford benzoate 10a in 71% yield. Selective hydrolysis
of benzoate 10a was achieved by treatment with K2CO3 in EtOH
to afford the alcohol 11a (Scheme 3).
Sheme 2. Reagents and conditions: (i) KI, I2, NaHCO3,H2O, rt; (ii) 2 N
NaOH, EtOH, rt; (iii) 28% ammonia, EtOH, 45 oC; (iv) Boc2O, EtOH, 0 oC to
rt.

3
Following the same procedures for the synthesis of 16a from
8a as described above, 11a was converted into trans-
diaminocyclohexane 14a in a four-step sequence. Compound 14a
is a common intermediate for the synthesis of both targets 2a and
3a. It is noteworthy that mesylate 12a was treated with NaN3 to
afford 13a with inversion of configuration at C2 as the sole
product in 73% yield without neighboring-group participation
due to the Boc protected amino group and the leaving group
being on the same side. The enantiomers 14b and 16b were
obtained by identical sequences from 8b.
In the final stages of the synthesis of 2a (Scheme 4),
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hydrolysis of ethyl ester 14a with LiOH·H2O in aqueous EtOH
afforded the carboxylic acid 17a in a quantitative yield. Amide
18a was prepared by a conventional condensation of carboxylic
acid 17a with dimethylamine in the presence of EDCI and HOBt
in DMF. The amide 18a was then subjected to Pd-catalyzed
hydrogenation to produce the required monoprotection target
compound trans-diaminocyclohexane carboxamide 2a. Whereas,
the enantiopure 2b was prepared by the application of identical
sequences from 14b.
Sheme 3. Reagents and conditions: (i) CH3SO2Cl, Et3N, CH2Cl2, 0 oC; (ii) NaN3, 15-crown-5, DMF, 75 oC; (iii) 10% Pd/C, H2, EtOH, rt; (iv) CbzCl, NaHCO3,
ethyl acetate/H2O, 0 oC to rt; (v) PPh3, DEAD, p-nitrobenzoic acid, THF, 0 oC to rt; (vi) K2CO3, EtOH, rt; (vii) CH3SO2Cl, Et3N, CH2Cl2, 0 oC; (viii) NaN3, 15-
crown-5, DMF, 75 oC; (ix) 10% Pd/C, H2, EtOH, rt; (x) CbzCl, NaHCO3, ethyl acetate/H2O, 0 oC to rt.
values. The diastereomeric mixtures were then hydrolyzed to
corresponding carboxylic acid in one-pot by addition of water to
the reaction mixtures. Even the diastereomeric mixtures of
carboxylic acid also can’t be separated by column
chromatography.
Sheme 4. Reagents and conditions: (i) LiOH•H2O, EtOH, rt; (ii) EDCI,
HOBt, Me2NH•HCl, Et3N, DMF, 0 oC to rt; (iii) 10% Pd/C, H2, MeOH, rt.
The inversion of stereochemistry at C5 was achieved by a
base-catalyzed epimerization of the ethyl ester 16a via an enolate
intermediate.13 We initially employed LDA or LiHMDS as bases
in THF for deprotonation of the chiral center C5 and subsequent
quenched by water, however, resulted a complex mixture. When
we have treated 14a with a slightly excess amount of sodium
ethoxide9 in anhydrous EtOH at 50 oC for overnight, formation of
a mixture of 14a and 19a was observed with both retention and
1
inversion of configuration at C5 (Scheme 5). H NMR showed
that the ratio of two diastereomers with retention (14a) and
Sheme 5. Reagents and conditions: (i) NaOEt, EtOH, 50 oC; (ii) NaOH,
EtOH/H2O, rt; (iii) EDCI, HOBt, Me2NH•HCl, Et3N, DMF, 0 oC to rt; (iv)
10% Pd/C, H2, MeOH, rt.
inversion (19a) of configuration at C5 was 36:64. However, we
were unable to separate the diastereomeric mixtures by column
chromatography even on a small scale because of closed Rf

4
Tetrahedron
Anhydrous THF was distilled over sodium. HRMS (ESI) Mass
Much to our delight, the required optically pure 20a can be
ACCEPTED MANUSCRIPT
spectra were recorded on Bruker microTOF-Q 10198 mass
easily separated out in 50% yield by simply recrystallization
using EtOH/H2O 10:1 as recrystallization solvents. The using of
column chromatography can be avoided which makes it possible
to prepare the optically pure 20a on a large scale. Subsequent
amidation and deprotection in a good yield to give the required
monoprotection target compound trans-diaminocyclohexane
carboxamide 3a. The enantiomeric 3b was prepared by identical
sequences from 14b.
spectrometer. H NMR, 13C NMR and 2D NMR (1H-13C HSQC,
1
1H-1H COSY, and H-1H NOESY) spectra were recorded on a
1
1
Brucker Ascend-400 MHz spectrometer, 400 MHz for H and
100 MHz for 13C. Optical rotations were recorded on an Autopol
VI polarimeter.
4.2. (S)-3-cyclohexene-1-carboxylic acid (5a)
Optically pure 5a was prepared by resolution of racemic
cyclohex-3-enylcarboxylic acid following the method disclosed
by Schwartz et al.14 Racemic cyclohex-3-enylcarboxylic acid
(100 g, 0.79 mol) was added to acetone (500 mL) and heated to
o
55 C, to the solution, (R)-(+)-α-phenethylamine (95.6 g, 0.79
mol) in acetone (200 mL) was added dropwise over 30 min. After
1 h, the mixture was cooled to room temperature and (R)-(+)-α-
phenethylamine salt of cyclohex-3-enylcarboxylic acid was
formed. The precipitate obtained was filtered off and washed
with acetone. The salt was recrystallized with acetone as solvent.
Recrystallization of the salt was repeated until a required optical
rotation [α]25 D < -40° was achieved.
(R)-(+)-α-phenethylamine salt of (S)-3-cyclohexene-1-
carboxylic (57.6 g, 233 mmol) was dissolved in ethyl acetate
(900 mL) and 2 N HCl (900 mL). The phases were separated, and
the aqueous layer was extracted with ethyl acetate (300 mL). The
organic fractions were combined, washed with water (200 mL)
and saturated brine (200 mL), and dried over anhydrous sodium
sulfate, filtered, and concentrated in vacuo to give optically pure
5a (28.8 g , 29%) as a colorless oil; [α]25D -82.6° (c 1.0, MeOH).
Sheme 6. Reagents and conditions: (i) NaOEt, EtOH, 50 oC; (ii) NaOH,
EtOH/H2O, rt; (iii) EDCI, HOBt, Me2NH•HCl, Et3N, DMF, 0 oC to rt; (iv)
10% Pd/C, H2, MeOH, rt.
For the enantiomer 5b; a colorless oil [α]25 +85.2° (c 1.0,
D
A similar strategy was used for the synthesis of cis-
diaminocyclohexane 4a (Scheme 6). Epimerization of 16a was
performed in anhydrous EtOH with sodium ethoxide at 50 oC for
overnight, subsequent hydrolysis of ethyl ester in one-pot gave
the carboxylic acid as a mixture of two diastereoisomers. It is
noteworthy that the required enantiomerically pure carboxylic
acid 23a with inversion of configuration at C5 was separated out
in 48% yield by simple recrystallization using a mixture of
hexane/ethyl acetate in 5:1 ratio as recrystallization solvents.
Subsequent amidation and deprotection lead to the required
monoprotection target compound cis-diaminocyclohexane
carboxamide 4a in good yield. The enantiomeric 4b was also
obtained in identical sequences from 16b.
MeOH).
4.3. (1S,4S,5S)-4-iodo-6-oxabicyclo [3.2.1] octan-7-one (6a)
Sodium bicarbonate (56 g, 0.67 mol) was added to a solution
of 5a (28 g, 0.22 mol) in water (450 mL). To the solution, iodine
(59.8 g, 0.24 mol) and potassium iodide (220 g, 1.33 mol) were
added successively, followed by stirring at room temperature for
5 h. The reaction mixture was quenched with sodium thiosulfate,
and extracted with ethyl acetate (2 × 200 mL). The combined
organic layers were washed with water (100 mL) and saturated
brine (100 mL), and then dried over anhydrous sodium sulfate.
The solvent was removed under reduced pressure. The obtained
pale yellow solid was added hexane (150 mL) and stirred at
room temperature for 1 h, the solid was collected by filtration and
3. Conclusions
dried to give 6a (50.9 g , 91%) as a white solid; [α]25 -20.4° (c
D
1.0, MeOH); 1H NMR (400 MHz, CDCl3) δ 4.97 – 4.74 (m, 1H),
4.51 (t, J = 4.4 Hz, 1H), 2.79 (d, J = 12.3 Hz, 1H), 2.67 (t, J = 3.9
Hz, 1H), 2.52 – 2.34 (m, 2H), 2.12 (dd, J = 16.5, 5.2 Hz, 1H),
1.98 – 1.77 (m, 2H); 13C NMR (100 MHz, CDCl3) δ 177.74,
80.21, 38.60, 34.51, 29.72, 23.81, 23.12; HRMS (ESI; m/z)
[M+Na]+ calcd for C7H9O2INa 274.9545, found 274.9555.
In conclusion, a highly efficient and stereoselective synthetic
route for the six stereoisomers of tert-butyl ((1R,2S,5S)-2-amino-
5-(dimethylcarbamoyl)cyclo-hexyl)carbamate 1 from 3-cyclo-
hexene-1-carboxylic acid have been accomplished. The
efficiency of our approach derived from Mitsunobu reaction for
fine-tuning of C2 stereochemistry and
a base-catalyzed
For the enantiomer 6b; a white solid ; 93% yield; [α]25
epimerization for amending C5 stereochemistry. Other features
of our synthesis include separation of the diastereomeric mixtures
by simple recrystallization which allows for multigram scale
synthesis of target compounds. Each isomer may be considered a
valuable intermediate for the synthesis of potential fXa inhibitors
for further biological evaluation. The strategy might also be
useful for synthesis of other analogues of trisubstituted
cyclohexane.
D
+26.5° (c 1.0, MeOH); HRMS (ESI; m/z) [M+Na]+ calcd for
C7H9O2INa 274.9545, found 274.9549.
4.4. Ethyl (1S,3R,4R)-3-((tert-butoxycarbonyl)amino)-4-
hydroxycyclohexane-1-carboxylate (8a)
2 N aqueous sodium hydroxide (116 mL, 0.23 mol) was added
to a solution of 6a (48.3 g, 0.193 mol) in EtOH (70 mL) and the
reaction was stirred at room temperature for 3 h. EtOH was
removed under reduced pressure, and the residue was extracted
with dichloromethane (180 mL). The organic layer was washed
with water (35 mL) and saturated brine (35 mL), and then dried
over anhydrous sodium sulfate. The solvent was removed under
reduced pressure to give crude 7a as a yellow oil. The compound
4. Experimental section
4.1. General experimental
All chemicals were of reagent grade quality purchased from
commercial sources and used without further purification.

5
was used for next step without further purification. 28% aqueous
ammonia (315 mL) was added to a solution of crude 7a in EtOH
(150 mL), the reaction was stirred at 45 oC overnight. The
reaction was cooled to room temperature and concentrated in
vacuo to afford the crude amino alcohol as a pale yellow oil. The
oil was dissolved in EtOH (300 mL) and Boc2O (41.3 g, 0.19
mol) was then added in ice-water bath. After 15 min, the reaction
was allowed to warm to room temperature. After 2 h, the solvent
was removed under reduced pressure to give 8a (48.3 g, 88%) as
1.89 – 1.72 (m, 5H), 1.45 (s, 9H), 1.26 (t, J = 7.1 Hz, 3H)ꢀ13C
ACCEPTED MANUSCRIPT
NMR (100 MHz, CDCl3) δ 174.19, 154.97, 79.73, 60.92, 60.66,
48.21, 38.13, 29.36, 28.35, 25.55, 22.41, 14.21; HRMS (ESI; m/z)
[M+Na]+ calcd for C14H24N4O4Na 335.1695, found 335.1706.
For the enantiomer 15b; a white solid; 47% yield; [α]25
-
D
47.0° (c 1.0, MeOH); HRMS (ESI; m/z) [M+Na]+ calcd for
C14H24N4O4Na 335.1695, found 335.1691.
4.7. Ethyl(1S,3R,4S)-4-(((benzyloxy)carbonyl)amino)-3-((tert-
butoxy- carbonyl)amino)cyclohexane-1-carboxylate (16a)
a colorless oil. The crude 8a was used for next step without
1
further purification; [α]25 +4.1° (c 1.0, MeOH); H NMR (400
D
10% palladium on carbon (0.75 g) was added to a solution of
15a (7.54 g, 0.024 mol) in ethanol (50 mL), followed by stirring
at room temperature for 4 h under hydrogen atmosphere. The
reaction mixture was filtered, concentrated in vacuo. The
obtained residue was suspended in a mixture of ethyl acetate (150
mL) and water (30 mL), followed by addition of sodium
bicarbonate (4.04 g, 0.048 mol). Benzyl chloroformate (3.8 mL,
0.026 mol) was added to the reaction mixture at 0 °C over 10
min, and then the reaction was warmed to room temperature.
After 1 h, the mixture was separated and the aqueous layer was
extracted with ethyl acetate (50 mL). The organic fractions were
combined, washed with water (50 mL) and saturated brine (50
mL), and dried over anhydrous sodium sulfate, filtered, and
concentrated in vacuo. The obtained solid was recrystallized
MHz, CDCl3) δ 4.73 (br s, 1H), 4.16 (ddd, J = 10.3, 7.1, 3.5 Hz,
2H), 3.70 – 3.24 (m, 3H), 2.63 (dd, J = 8.8, 4.3 Hz, 1H), 2.41 –
2.25 (m, 1H), 2.16 – 2.07 (m, 1H), 1.95 – 1.79 (m, 1H), 1.52 (dd,
J = 11.0, 8.9 Hz, 2H), 1.45 (s, 10H), 1.27 (t, J = 7.1 Hz, 3H)ꢀ
13C NMR (100 MHz, CDCl3) δ 174.14, 156.75, 79.96, 73.26,
60.61, 52.79, 38.71, 31.20, 29.87, 28.35, 24.64, 14.22; HRMS
(ESI; m/z) [M+Na]+ calcd for C14H25NO5Na 310.1630, found
310.1620.
For the enantiomer 8b; a colorless oil; 83% yield; [α]25 -2.1°
D
(c 1.0, MeOH); HRMS (ESI; m/z) [M+Na]+ calcd for
C14H25NO5Na 310.1630, found 310.1618.
4.5. Ethyl (1S,3R,4R)-3-((tert-butoxycarbonyl)amino)-4-
((methylsulfonyl)oxy) cyclohexane-1-carboxylate (9a)
(with 1/5 EtOAc/hexane as solvents) to give 16a (7.9 g, 78%) as
1
Methanesulfonyl chloride (8.5 mL, 0.11 mol) was added
dropwise to a solution of 8a (21.2 g, 0.074 mol) and
triethylamine (20.5 mL, 0.148 mol) in dichloromethane (200 mL)
at 0 °C over 30 min under argon atmosphere. The reaction was
stirred at the same temperature for 2 h, water (100 mL) was then
added. The mixture was separated and the organic layer was
washed with saturated aqueous solution of sodium bicarbonate
(60 mL) and saturated brine (60 mL) and dried over anhydrous
sodium sulfate. The solvent was removed under reduced pressure,
isopropyl ether (45 mL) and isopropanol (22 mL) were added to
the resultant residue, and the mixture was at room temperature
a white solid; [α]25 -33.6° (c 1.0, MeOH); H NMR (400 MHz,
D
DMSO) δ 7.43 – 7.24 (m, 5H), 6.97 (s, 1H), 6.55 (d, J = 5.2 Hz,
1H), 5.01 (q, J = 11.7 Hz, 2H), 4.04 (q, J = 7.1 Hz, 2H), 3.91 (d,
J = 3.6 Hz, 1H), 3.50 (m, 1H), 2.62 (m, 1H), 1.85 (dd, J = 29.9,
12.2 Hz, 2H), 1.56 (dd, J = 26.1, 12.1 Hz, 3H), 1.46 – 1.30 (m,
10H), 1.17 (t, J = 7.1 Hz, 3H)ꢀ13C NMR (100 MHz, DMSO) δ
174.68, 155.47, 155.27, 137.16, 128.24, 127.64, 127.55, 77.83,
65.07, 59.75, 50.48, 47.77, 36.13, 31.68, 28.19, 26.17, 25.20,
14.04; HRMS (ESI; m/z) [M+Na]+ calcd for C22H32N2O6Na
443.2158, found 443.2154.
For the enantiomer 16b; a white solid; 87% yield; [α]25
D
for 1 h, the solid was collected by filtration and dried to give 9a
+32.0° (c 1.0, MeOH); HRMS (ESI; m/z) [M+Na]+ calcd for
C22H32N2O6Na 443.2158, found 443.2157.
1
(17.3 g , 64%) as a white solid; [α]25 +1.8° (c 1.0, MeOH); H
D
NMR (400 MHz, CDCl3) δ 4.78 (br s, 1H), 4.65 (m, 1H), 4.16 (q,
J = 7.1 Hz, 2H), 3.83 (qd, J = 7.5, 4.6 Hz, 1H), 3.06 (s, 3H), 2.58
(s, 1H), 2.35 – 2.22 (m, 1H), 1.82 – 1.64 (m, 2H), 1.45 (s, 9H),
1.27 (t, J = 7.1 Hz, 3H)ꢀ13C NMR (100 MHz, CDCl3) δ 173.80,
155.09, 80.00, 79.38, 60.79, 49.51, 38.25, 37.90, 30.28, 28.34,
27.52, 23.76, 14.20; HRMS (ESI; m/z) [M+Na]+ calcd for
C15H27NO7SNa 388.1406, found 388.1409.
4.8. (1S,2R,4S)-2-((tert-butoxycarbonyl)amino)-4-(ethoxy-
carbonyl)cyclohexyl 4-nitrobenzoate (10a)
To a stirred solution of 8a (23 g, 0.08 mol) in anhydrous THF
(350 mL) was added triphenylphosphine (31.4 g, 0.12 mol) and
p-nitrobenzoic acid (16 g, 0.096 mol) sequentially. DEAD (20.9
g, 0.12 mol) in anhydrous THF (50 mL) was added dropwise to
the reaction mixture at 0 °C under an argon atmosphere over 30
min. After stirring at 0 °C for another 30 min, the reaction was
allowed to warm to room temperature. After 12 h, the reaction
mixture was concentrated in vacuo and the residue was dissolved
in ethyl acetate (500 mL). The organic layer was washed with
saturated aqueous solution of sodium bicarbonate (150 mL) and
saturated brine (100 mL) and dried over anhydrous sodium
sulfate. The solvent was removed under reduced pressure and the
residue was purified by silica gel column chromatography (with
For the enantiomer 9b; a colorless oil; 76% yield; [α]25 -0.9°
D
(c 1.0, MeOH); HRMS (ESI; m/z) [M+Na]+ calcd for
C15H27NO7SNa 388.1406, found 388.1410.
4.6. Ethyl (1S,3R,4S)-4-azido-3-((tert-butoxycarbonyl)amino)
cyclohexane-1-carboxylate (15a)
To a solution of 9a (17 g, 0.0465 mol) in DMF (100 mL) was
added sodium azide (6 g, 0.093 mol) and 15-crown-5 (five drops)
o
sequentially, and the mixture was stirred at 75 C for 48 h. The
reaction was allowed to cool to room temperature, then water (50
mL) and ethyl acetate (125 mL) were added to the reaction
mixture. The phases were separated, and the aqueous layer was
extracted with ethyl acetate (75 mL). The organic fractions were
combined, washed with water (50 mL) and saturated brine (50
mL), and dried over anhydrous sodium sulfate, filtered, and
concentrated in vacuo and purified by silica gel column
chromatography (with 1/6 EtOAc/hexane as eluent) to give 15a
1/10 EtOAc/hexane as eluent) to give 10a (27.9 g, 71%) as a
1
white solid; [α]25 +26.4° (c 1.0, MeOH); H NMR (400 MHz,
D
CDCl3) δ 8.27 (d, J = 8.6 Hz, 2H), 8.20 (d, J = 8.6 Hz, 2H), 5.20
(d, J = 6.9 Hz, 1H), 4.79 (s, 1H), 4.27 (s, 1H), 4.18 (q, J = 7.1
Hz, 2H), 2.61 (s, 1H), 2.04 (dt, J = 26.7, 11.3 Hz, 4H), 1.92 –
1.71 (m, 2H), 1.39 (s, 9H), 1.28 (t, J = 7.1 Hz, 4H)ꢀ13C NMR
(100 MHz, CDCl3) δ 174.12, 163.85, 155.16, 150.52, 135.80,
130.79, 123.45, 79.77, 73.46, 60.77, 47.34, 37.79, 30.89, 29.66,
28.28, 25.40, 24.36, 14.20; HRMS (ESI; m/z) [M+Na]+ calcd for
C21H28N2O8Na 459.1743, found 459.1745.
(8.4 g, 58%) as a white solid and the epimer 13a (0.75 g, 5%) as
1
a white solid; [α]25 +55.3° (c 1.0, MeOH); H NMR (400 MHz,
D
CDCl3) δ 4.66 (d, J = 7.7 Hz, 1H), 4.15 (q, J = 7.1 Hz, 2H), 3.89
(d, J = 12.9 Hz, 2H), 2.73 – 2.55 (m, 1H), 1.98 – 1.88 (m, 1H),

6
Tetrahedron
For the enantiomer 10b; a white solid; 69% yield; [α]25
-
sulfate, the solvent was removed under reduced pressure. The
ACCEPTED MANUSCRIPT
D
31.5° (c 1.0, MeOH); HRMS (ESI; m/z) [M+Na]+ calcd for
C21H28N2O8Na 459.1743, found 459.1747.
obtained pale yellow solid was added hexane (60 mL) and
stirred at room temperature for 1 h, the solid was collected by
filtration and dried to give 13a (6.9 g , 73%) as a white solid;
[α]25D +21.7° (c 1.0, MeOH); 1H NMR (400 MHz, CDCl3) δ 4.70
(s, 1H), 4.16 (q, J = 7.1 Hz, 2H), 3.66 (ddd, J = 11.9, 7.7, 3.8 Hz,
1H), 3.54 (s, 1H), 2.59 (s, 1H), 2.30 – 2.18 (m, 1H), 2.06 – 1.93
(m, 1H), 1.92 – 1.80 (m, 1H), 1.77 – 1.59 (m, 3H), 1.46 (s, 9H),
1.27 (t, J = 7.1 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 174.03,
155.06, 79.83, 61.33, 60.68, 50.13, 38.22, 30.65, 28.35, 26.14,
24.21, 14.20; HRMS (ESI; m/z) [M+Na]+ calcd for
C14H24N4O4Na 335.1695, found 335.1694.
4.9. Ethyl(1S,3R,4S)-3-((tert-butoxycarbonyl)amino)-4-hydroxy-
cyclohexane-1-carboxylate (11a)
Potassium carbonate (9.1 g, 0.066 mol) was added to a
solution of 10a (26.2 g, 0.06 mol) in ethanol (250 mL). The
reaction was stirred at room temperature overnight. The reaction
mixture was concentrated in vacuo and the residue was dissolved
in ethyl acetate (400 mL). The organic layer was washed with
water (150 mL) and saturated brine (100 mL) and dried over
anhydrous sodium sulfate. The solvent was removed under
reduced pressure and the residue was purified by silica gel
column chromatography (with 1/6 to 1/3 EtOAc/hexane as
eluent) to give 11a (16.4 g, 95%) as a colorless oil; [α]25D +12.2°
(c 1.0, MeOH); 1H NMR (400 MHz, CDCl3) δ 4.93 (s, 1H), 4.14
(q, J = 7.1 Hz, 2H), 3.91 (s, 1H), 3.84 (s, 1H), 3.06 (s, 1H), 2.51
(m, 1H), 2.06 – 1.98 (m, 1H), 1.97 – 1.88 (m, 1H), 1.87 – 1.75
(m, 2H), 1.69 – 1.52 (m, 2H), 1.45 (s, 9H), 1.26 (s, 3H); 13C
NMR (100 MHz, CDCl3) δ 174.87, 156.47, 79.83, 77.38, 77.06,
76.74, 69.51, 60.52, 50.16, 37.86, 30.16, 29.65, 28.36, 24.19,
14.18; HRMS (ESI; m/z) [M+Na]+ calcd for C14H25NO5Na
310.1630, found 310.1635.
For the enantiomer 13b; a white solid; 68% yield; [α]25
-
D
25.9° (c 1.0, MeOH); HRMS (ESI; m/z) [M+Na]+ calcd for
C14H24N4O4Na 335.1695, found 335.1686.
4.12. Ethyl(1S,3R,4R)-4-(((benzyloxy)carbonyl)amino)-3-((tert-
butoxycarbonyl)amino)cyclohexane-1-carboxylate (14a)
10% palladium on carbon (0.68 g) was added to a solution of
13a (6.8 g, 0.021 mol) in ethanol, followed by stirring at room
temperature for 4 h under hydrogen atmosphere. The reaction
mixture was filtered, concentrated in vacuo. The obtained residue
was suspended in a mixture of ethyl acetate (60 mL) and water
(10 mL), followed by addition of sodium bicarbonate (3.67 g,
0.044 mol). Benzyl chloroformate (3.44 mL, 0.024 mol) was
added to the reaction mixture at 0 °C over 10 min, and then the
reaction was warmed to room temperature. After 1 h, the mixture
was separated and the aqueous layer was extracted with ethyl
acetate (30 mL). The organic fractions were combined, washed
with water (450 mL) and saturated brine (45 mL), and dried over
anhydrous sodium sulfate, filtered, and concentrated in vacuo.
The obtained solid was recrystallized (with 1/5 EtOAc/hexane as
solvents) to give 14a (8.36 g, 91%) as a white solid; [α]25D +23.9°
For the enantiomer 11b; a white solid; 92% yield; [α]25
-
D
15.7° (c 1.0, MeOH); HRMS (ESI; m/z) [M+Na]+ calcd for
C14H25NO5Na 310.1630, found 310.1636.
4.10. Ethyl (1S,3R,4S)-3-((tert-butoxycarbonyl)amino)-4-
((methylsulfonyl)oxy)cyclohexane-1-carboxylate (12a)
Methanesulfonyl chloride (6 mL, 0.078 mol) was added
dropwise to a solution of 11a (15 g, 0.052 mol) and triethylamine
(14.5 mL, 0.104 mol) in dichloromethane (150 mL) at 0 °C over
15 min under argon atmosphere. The reaction was stirred at the
same temperature for 2 h, water (75 mL) was then added. The
mixture was separated and the organic layer was washed with
saturated aqueous solution of sodium bicarbonate (50 mL) and
saturated brine (50 mL) and dried over anhydrous sodium sulfate.
The solvent was removed under reduced pressure, isopropyl ether
(30 mL) and isopropanol (15 mL) were added to the resultant
residue, and the mixture was at room temperature for 1 h, the
1
(c 1.0, MeOH); H NMR (400 MHz, DMSO) δ 7.43 – 7.21 (m,
5H), 7.03 (d, J = 6.9 Hz, 1H), 6.67 (d, J = 8.1 Hz, 1H), 5.12 –
4.90 (m, 2H), 4.07 (p, J = 7.2 Hz, 2H), 3.46 (d, J = 5.7 Hz, 1H),
3.32 – 3.24 (m, 1H), 2.77 – 2.65 (m, 1H), 2.03 (d, J = 12.6 Hz,
1H), 1.95 – 1.82 (m, 1H), 1.77 – 1.63 (m, 1H), 1.57 – 1.38 (m,
3H), 1.36 (s, 9H), 1.19 (t, J = 7.1 Hz, 3H); 13C NMR (100 MHz,
DMSO) δ 173.82, 155.74, 155.36, 137.21, 128.23, 127.63,
127.54, 77.50, 65.03, 59.80, 53.15, 49.64, 37.79, 31.36, 28.17,
27.62, 24.83, 14.08; HRMS (ESI; m/z) [M+Na]+ calcd for
C22H32N2O6Na 443.2158, found 443.2136.
solid was collected by filtration and dried to give 12a (12.3 g ,
65%) as a white solid; [α]25 +40.4° (c 1.0, MeOH); H NMR
1
D
For the enantiomer 14b; a white solid; 83% yield; [α]25
-
D
(400 MHz, CDCl3) δ 4.94 (s, 1H), 4.71 (d, J = 7.6 Hz, 1H), 4.17
(tt, J = 7.2, 3.6 Hz, 2H), 3.96 (s, 1H), 3.03 (s, 3H), 2.71 (d, J =
4.0 Hz, 1H), 2.11 – 1.95 (m, 2H), 1.95 – 1.68 (m, 4H), 1.44 (s,
9H), 1.27 (t, J = 7.1 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ
173.91, 154.97, 79.96, 79.72, 60.82, 48.02, 38.10, 37.99, 28.52,
28.34, 26.87, 21.49, 14.21; HRMS (ESI; m/z) [M+Na]+ calcd for
C15H27NO7SNa 388.1406, found 388.1402.
29.3° (c 1.0, MeOH); HRMS (ESI; m/z) [M+Na]+ calcd for
C22H32N2O6Na 443.2158, found 443.2152.
4.13. (1S,3R,4R)-4-(((benzyloxy)carbonyl)amino)-3-((tert-butoxy-
carbonyl)amino)cyclohexane-1-carboxylic acid (17a)
LiOH·H2O (0.84 g, 19.9 mmol) was added to a solution of
14a (2.8 g, 6.64 mmol) in ethanol (30 mL) and water (5 mL) at
room temperature. The reaction was stirred for 6 h, concentrated
in vacuo and the residue was dissolved in water (20 mL). The
reaction mixture was acidified to pH=4-5 by addition of 1 N HCl
and a white precipitate was formed. The solid was collected and
dried to give 17a (2.56 g, 97%) as a white solid; [α]25D +26.7° (c
For the enantiomer 12b; a white solid; 77% yield; [α]25
-
D
45.2° (c 1.0, MeOH); HRMS (ESI; m/z) [M+Na]+ calcd for
C15H27NO7SNa 388.1406, found 388.1404.
4.11. Ethyl(1S,3R,4R)-4-azido-3-((tert-butoxycarbonyl)amino)
cyclohexane-1-carboxylate (13a)
1
1.0, MeOH); H NMR (400 MHz, CDCl3) δ 11.57 (br s, 1H),
To a solution of 12a (11 g, 0.03 mol) in DMF (100 mL) was
added sodium azide (3.9 g, 0.06 mol) and 15-crown-5 (five
drops) sequentially, and the mixture was stirred at 75 oC for 24 h.
The reaction was allowed to cool to room temperature, then
water (50 mL) and ethyl acetate (200 mL) were added to the
reaction mixture. The phases were separated, and the aqueous
layer was extracted with ethyl acetate (50 mL). The organic
fractions were combined, washed with water (80 mL) and
saturated brine (80 mL), and dried over anhydrous sodium
7.40 – 7.24 (m, 5H), 6.41 (d, J = 9.4 Hz, 1H), 5.13 (d, J = 12.4
Hz, 1H), 5.02 (d, J = 12.5 Hz, 1H), 4.85 (d, J = 9.6 Hz, 1H), 3.58
– 3.31 (m, 2H), 2.78 (s, 1H), 2.52 (d, J = 11.2 Hz, 1H), 2.22 (d, J
= 13.3 Hz, 1H), 1.95 – 1.79 (m, 1H), 1.57 (dt, J = 8.4, 7.9 Hz,
1H), 1.37 (s, 9H); 13C NMR (100 MHz, CDCl3) δ 175.95, 157.07,
156.90, 136.96, 128.37, 127.98, 127.83, 80.62, 66.38, 55.72,
51.48, 38.82, 33.86, 29.70, 28.89, 28.27, 25.24; HRMS (ESI; m/z)
[M+Na]+ calcd for C20H28N2O6Na 415.1845, found 415.1841.

7
For the enantiomer 17b; a white solid; 99% yield; [α]25
-
dried to give an offwhite solid. The obtained solid was
ACCEPTE
24.5° (c 1.0, MeOH); HRMS (ESI; m/z) [M+Na]+ calcd for
C20H28N2O6Na 415.1845, found 415.1840.
D
D MANUSCRIPT
recrystallized (with 1/5 EtOAc/hexane as solvents) to give 20a
(2.94 g, 50%) as a white solid; [α]25 -9.8° (c 1.0, MeOH); H
1
D
NMR (400 MHz, CDCl3) δ 7.32 (s, 5H), 5.35 (d, J = 7.9 Hz, 1H),
5.07 (s, 2H), 4.86 (d, J = 8.5 Hz, 1H), 3.51 – 3.28 (m, 2H), 2.49 –
2.33 (m, 1H), 2.28 (dd, J = 12.8, 2.0 Hz, 1H), 2.15 (d, J = 10.3
Hz, 1H), 2.10 – 1.97 (m, 1H), 1.49 (d, J = 13.1 Hz, 1H), 1.39 (s,
9H); 13C NMR (100 MHz, CDCl3) δ 178.78, 156.74, 156.53,
136.48, 128.47, 128.05, 127.96, 79.91, 66.68, 55.30, 53.15, 41.62,
34.38, 31.63, 29.69, 28.30, 27.38; HRMS (ESI; m/z) [M+Na]+
calcd for C20H28N2O6Na 415.1845, found 415.1829.
4.14. Benzyl tert-butyl ((1R,2R,4S)-4-(dimethylcarbamoyl) cyclo-
hexane-1,2-diyl)dicarbamate (18a)
To a solution of 17a (2.36 g, 6 mmol) in DMF (30 mL) was
added triethylamine (4.12 mL, 30 mmol), HOBt (1.62 g, 12
mmol) and dimethylamine hydrochloride (1.47 g, 18 mmol)
sequentially, the mixture was stirred at 0 oC under argon
atmosphere for 10 min, followed by addition of EDCI (2.3 g, 16
mmol). After 30 min, the reaction was allowed to warm to room
temperature and stirred for 2 h. Water (30 mL) and ethyl acetate
(80 mL) were added to the reaction mixture. The phases were
separated, and the aqueous layer was extracted with ethyl acetate
(50 mL). The organic fractions were combined, washed with
saturated aqueous solution of sodium bicarbonate (50 mL) and
saturated brine (50 mL), and dried over anhydrous sodium
sulfate, the solvent was removed under reduced pressure. The
crude residue was purified by silica gel column chromatography
For the enantiomer 20b; a white solid; 43% yield; [α]25D +7.4°
(c 1.0, MeOH); HRMS (ESI; m/z) [M+Na]+ calcd for
C20H28N2O6Na 415.1845, found 415.1834.
4.17. Benzyl tert-butyl((1R,2R,4R)-4-(dimethylcarbamoyl) cyclo-
hexane-1,2-diyl)dicarbamate (21a)
To a solution of 20a (2.68 g, 6.7 mmol) in DMF (35 mL) was
added triethylamine (4.7 mL, 34.2 mmol), HOBt (1.84 g, 13.7
mmol) and dimethylamine hydrochloride (1.67 g, 20.5 mmol)
sequentially, the mixture was stirred at 0 oC under argon
atmosphere for 10 min, followed by addition of EDCI (2.62 g,
13.65 mmol). After 30 min, the reaction was allowed to warm to
room temperature and stirred for 2 h. Water (35 mL) and ethyl
acetate (90 mL) were added to the reaction mixture. The phases
were separated, and the aqueous layer was extracted with ethyl
acetate (50 mL). The organic fractions were combined, washed
with saturated aqueous solution of sodium bicarbonate (50 mL)
and saturated brine (50 mL), and dried over anhydrous sodium
sulfate, the solvent was removed under reduced pressure. The
crude residue was purified by silica gel column chromatography
(with 1/30 MeOH/CH2Cl2 as eluent) to give 18a (2.1 g, 82%) as a
1
white solid; [α]25 +2.2° (c 1.0, MeOH); H NMR (400 MHz,
D
CDCl3) δ 7.31 (dt, J = 6.0, 3.9 Hz, 5H), 5.47 (s, 1H), 5.07 (s, 2H),
4.69 (d, J = 8.0 Hz, 1H), 4.03 (s, 1H), 3.43 (d, J = 6.7 Hz, 1H),
3.01 (d, J = 10.5 Hz, 3H), 2.91 (s, 3H), 2.16 – 2.05 (m, 1H), 1.95
– 1.69 (m, 3H), 1.57 (ddd, J = 17.4, 12.5, 5.5 Hz, 1H), 1.40 (s,
9H); 13C NMR (100 MHz, CDCl3) δ 174.44, 156.53, 155.93,
136.68, 128.42, 127.90, 79.29, 66.46, 54.94, 50.13, 37.42, 35.65,
34.61, 32.80, 31.57, 28.33, 27.98, 25.64, 22.64, 14.11; HRMS
(ESI; m/z) [M+Na]+ calcd for C22H33N3O5Na 442.2318, found
442.2311.
For the enantiomer 18b; a white solid; 73% yield; [α]25D -1.3°
(c 1.0, MeOH); HRMS (ESI; m/z) [M+Na]+ calcd for
C22H33N3O5Na 442.2318, found 442.2319.
(with 1/30 MeOH/CH2Cl2 as eluent) to give 21a (2.0 g, 71%) as a
1
white solid; [α]25 -3.4° (c 1.0, MeOH); H NMR (400 MHz,
D
CDCl3) δ 7.32 (s, 5H), 5.33 (d, J = 7.0 Hz, 1H), 5.08 (s, 2H), 4.98
(d, J = 7.8 Hz, 1H), 3.42 (ddd, J = 18.4, 11.2, 3.3 Hz, 2H), 3.03 (s,
3H), 2.93 (s, 3H), 2.62 (ddd, J = 11.9, 8.7, 3.3 Hz, 1H), 2.20 (dd,
J = 12.9, 3.0 Hz, 1H), 2.06 – 1.96 (m, 1H), 1.77 (d, J = 13.6 Hz,
1H), 1.68 – 1.52 (m, 2H), 1.39 (s, 9H); 13C NMR (100 MHz,
CDCl3) δ 173.87, 156.63, 156.56, 136.60, 128.44, 127.97, 79.64,
66.55, 55.62, 53.36, 39.16, 37.14, 35.67, 34.73, 31.89, 28.30,
27.51; HRMS (ESI; m/z) [M+Na]+ calcd for C22H33N3O5Na
442.2318, found 442.2305.
4.15. tert-Butyl((1R,2R,5S)-2-amino-5-(dimethylcarbamoyl)
cyclohexyl)carbamate (2a)
10% palladium on carbon (0.24 g) was added to a solution of
18a (1.68 g, 4.01 mmol) in ethanol (20 mL), followed by stirring
at room temperature for 6 h under hydrogen atmosphere. The
reaction mixture was filtered, concentrated in vacuo to give 2a
1
(1.11 g, 97%) as a white solid; [α]25 -10.0° (c 1.0, MeOH); H
D
For the enantiomer 21b; a white solid; 78% yield; [α]25D +2.6°
(c 1.0, MeOH); HRMS (ESI; m/z) [M+Na]+ calcd for
C22H33N3O5Na 442.2318, found 442.2326.
NMR (400 MHz, CDCl3) δ 4.78 (d, J = 7.4 Hz, 1H), 3.73 (s, 1H),
3.03 (s, 3H), 2.93 (s, 3H), 2.88 – 2.80 (m, 1H), 2.70 (s, 1H), 2.17
– 2.07 (m, 1H), 1.87 – 1.80 (m, 1H), 1.79 – 1.64 (m, 2H), 1.61 –
1.49 (m, 2H), 1.44 (s, 9H), 1.26 (s, 2H).; 13C NMR (100 MHz,
CDCl3) δ 174.78, 155.55, 79.25, 77.40, 77.09, 76.77, 53.17,
52.25, 37.30, 35.62, 34.97, 29.64, 29.30, 28.38, 24.59; HRMS
(ESI; m/z) [M+H]+ calcd for C14H28N3O3 286.2131, found
286.2121.
4.18. tert-Butyl((1R,2R,5R)-2-amino-5-(dimethylcarbamoyl)
cyclohexyl)carbamate (3a)
10% palladium on carbon (0.19 g) was added to a solution of
21a (1.9 g, 4.53 mmol) in ethanol, followed by stirring at room
temperature for 6 h under hydrogen atmosphere. The reaction
For the enantiomer 2b; a white solid; 93% yield; [α]25D +13.2°
(c 1.0, MeOH); HRMS (ESI; m/z) [M+H]+ calcd for C14H28N3O3
286.2131, found 286.2130.
mixture was filtered, concentrated in vacuo to give 3a (1.2 g,
1
93%) as a white solid; [α]25 -47.1° (c 1.0, MeOH); H NMR
D
(400 MHz, CDCl3) δ 5.07 (d, J = 9.0 Hz, 1H), 3.31 (d, J = 9.0 Hz,
1H), 3.05 (s, 3H), 2.93 (s, 3H), 2.68 (t, J = 11.7 Hz, 1H), 2.52 (s,
3H), 2.13 – 2.05 (m, 1H), 2.03 – 1.94 (m, 1H), 1.80 – 1.71 (m,
1H), 1.64 – 1.48 (m, 2H), 1.44 (s, 9H), 1.27 (d, J = 12.1 Hz, 2H);
13C NMR (100 MHz, CDCl3) δ 174.35, 156.23, 79.37, 56.15,
54.66, 39.23, 37.18, 35.66, 34.91, 29.65, 28.39, 27.72; HRMS
(ESI; m/z) [M+Na]+ calcd for C14H27N3O3Na 308.1950, found
308.1941.
4.16. (1R,3R,4R)-4-(((benzyloxy)carbonyl)amino)-3-((tert-
butoxycarbonyl)amino)cyclohexane-1-carboxylic acid (20a)
Sodium ethoxide (1.22 g, 24.0 mmol) was added to a solution
of 14a (5.46 g, 15.0 mmol) in aqueous ethanol (60 mL), and the
o
mixture was stirred at 45 C under argon atmosphere. After 12 h,
the reaction was allowed to cool to room temperature. To the
reaction mixture was added water (15 mL) and stirred at room
temperature for 3 h. The reaction mixture was concentrated in
vacuo and the residue was dissolved in water (30 mL). The
reaction mixture was acidified to pH=4-5 by addition of 1 N HCl
and a white precipitate was formed. The solid was collected and
For the enantiomer 3b; a white solid; 96% yield; [α]25D +41.9°
(c 1.0, MeOH); HRMS (ESI; m/z) [M+H]+ calcd for C14H28N3O3
286.2131, found 286.2134.

8
Tetrahedron
ACCEPTED MANUSCRIPT
4.19. (1R,3R,4S)-4-(((benzyloxy)carbonyl)amino)-3-((tert-
temperature for 6 h under hydrogen atmosphere. The reaction
butoxycarbonyl)amino)cyclohexane-1-carboxylic acid (23a)
mixture was filtered, concentrated in vacuo to give 4a (1.41 g,
94%) as a white solid; [α]25D +4.4° (c 1.0, MeOH); 1H NMR (400
MHz, CDCl3) δ 5.59 (d, J = 7.6 Hz, 1H), 3.59 (s, 1H), 3.09 (d, J
= 2.1 Hz, 1H), 3.06 (s, 3H), 2.94 (s, 3H), 2.63 (s, 1H), 1.68 (tt, J
= 12.3, 7.3 Hz, 5H), 1.50 (d, J = 12.7 Hz, 2H), 1.43 (s, 10H)ꢀ
13C NMR (100 MHz, CDCl3) δ 174.67, 155.49, 78.93, 51.06,
48.43, 38.86, 37.18, 35.64, 32.17, 29.06, 28.40, 21.68; HRMS
(ESI; m/z) [M+H]+ calcd for C14H28N3O3 286.2131, found
286.2144.
Sodium ethoxide (1.42 g, 20.9 mmol) was added to a solution
of 16a (7.3 g, 17.4 mmol) in aqueous ethanol (70 mL), and the
mixture was stirred at 45 C under argon atmosphere. After 12 h,
o
the reaction was allowed to cool to room temperature. To the
reaction mixture was added water (20 mL) and stirred at room
temperature for 3 h. The reaction mixture was concentrated in
vacuo and the residue was dissolved in water (40 mL). The
reaction mixture was acidified to pH=4-5 by addition of 1 N HCl
and a white precipitate was formed. The solid was collected and
dried to give an offwhite solid. The obtained solid was
For the enantiomer 24b; a white solid; 90% yield; [α]25D -2.9°
(c 1.0, MeOH); HRMS (ESI; m/z) [M+Na]+ calcd for
C14H27N3O3Na 308.1950, found 308.1962.
recrystallized (with 1/10 H2O/EtOH as solvents) to give 23a
(3.3g, 48%) as a white solid; [α]25 +41.8° (c 1.0, MeOH); H
1
D
Acknowledgments
NMR (400 MHz, DMSO) δ 12.05 (s, 1H), 7.48 – 7.25 (m, 5H),
6.89 (d, J = 5.9 Hz, 1H), 6.43 (d, J = 7.5 Hz, 1H), 5.13 – 4.94 (m,
2H), 3.80 (s, 1H), 3.51 (s, 1H), 2.30 (s, 1H), 1.84 (d, J = 7.2 Hz,
1H), 1.72 – 1.51 (m, 3H), 1.47 (t, J = 10.0 Hz, 2H), 1.37 (s, 9H);
13C NMR (100 MHz, DMSO) δ 175.66, 156.11, 154.57, 137.06,
128.28, 127.77, 127.73, 77.85, 65.27, 49.84, 48.81, 40.98, 28.66,
28.16, 21.82; HRMS (ESI; m/z) [M+Na]+ calcd for
C20H28N2O6Na 415.1845, found 415.1845.
Financial supports from NSF of China (21332003) are greatly
acknowledged.
References and notes
1. Mann, K. G.; Nesheim, M. E.; Church, W. R.; Haley, P.;Krishnaswamy,
S. Blood. 1990, 76, 1.
2. Eisenberg, P. R.; Siegel, J. E.; Abendschein, D. R.; Miletich J. P. J.
Clin. Invest. 1993, 91, 1877
For the enantiomer 23b; a white solid; 46% yield; [α]25
-
D
40.6° (c 1.0, MeOH); HRMS (ESI; m/z) [M+Na]+ calcd for
C20H28N2O6Na 415.1845, found 415.1848.
3. Piccini, J. P.; Lopes, R. D.; Mahaffey, K. W. Curr. Opin. Cardiol.
2010, 25, 312
4.20. Benzyl tert-Butyl((1S,2R,4R)-4-(dimethylcarbamoyl) cyclo-
hexane-1,2-diyl)dicarbamate (24a)
4. Samarna, M. M.; WolztM, O.; et al. Am. J. Cardiovasc. Drugs. 2011,
11, 129.
5. Camm, A. J.; Bounameaux, H. Drugs. 2011, 71, 1503.
6. The Hokusai-VTE Investigators. N. Engl. J. Med. 2013, 369, 1406.
7. Yoshino, T.; Nagata, T. et al. Int. Pub. No. WO 01/074774 [P], 2001.
8. (a) Nagata, T.; Yoshino, T.; Haginoya, N.; Yoshikawa, K. Isobe, Y.
Bioorg. Med. Chem. Lett. 2007, 17, 4683; (b) Nagata, T.; Nagamochi,
M.; Kobayashi, S.; Komoriya, S.; et al. Bioorg. Med. Chem. 2008, 18,
4587; (c) Nagata, T.; Yoshino, T.; et al. Bioorg. Med. Chem. 2009, 17,
1193; (d) Yoshikawa, K.; Yokomizo, A.; et al. Bioorg. Med. Chem.
2009, 17, 8206; (e) Yoshikawa, K.; Kobayashi, S.; et al. Bioorg. Med.
Chem. 2009, 17, 8221.
To a solution of 23a (3.14 g, 8 mmol) in DMF (30 mL) was
added triethylamine (5.5 mL, 40 mmol), HOBt (2.16 g, 16 mmol)
and dimethylamine hydrochloride (1.96 g, 24 mmol)
sequentially, the mixture was stirred at 0 oC under argon
atmosphere for 10 min, followed by addition of EDCI (3.07 g, 16
mmol). After 30 min, the reaction was allowed to warm to room
temperature and stirred for 2 h. Water (30 mL) and ethyl acetate
(80 mL) were added to the reaction mixture. The phases were
separated, and the aqueous layer was extracted with ethyl acetate
(50 mL). The organic fractions were combined, washed with
saturated aqueous solution of sodium bicarbonate (50 mL) and
saturated brine (50 mL), and dried over anhydrous sodium
sulfate, the solvent was removed under reduced pressure. The
crude residue was purified by silica gel column chromatography
9. Toshiharu, Y.; Yumi, N.; Tomoyuki, N.; Seishiru, U. Pub. No. US
2012/0053349 A1 [P], 2012.
10. Nakayama, K.; Maruoka, K. J. Am. Chem. Soc. 2008, 130, 17666.
11. (a) Sato, K.; Kawanami, K.; et al. Int. Pub. No. WO 2007/032498 [P],
2007; (b) Kawanami, K.; Ishikawa, H.; Shoji, M. Pub. No. US
2012/0035369 A1 [P], 2012; (c) Takayanagi, Y.; Furuya, Y.; et al. Pub.
No. US 2015/0353577 A1 [P], 2015.
12. Mitsunobu, O., Yamada, M. P. Mukaiyama, T. Bull. Chem. Soc.Jpn.
1967, 40, 935; (b) Mitsunobu, O., Yamada, M. P. Bull. Chem. Soc.Jpn.
1967, 40, 2380; (c) Mitsunobu, O. Synthesis. 1981, 1.
13. (a) Brown, E.; Daugan, A. Tetrahedron Lett. 1985, 26, 3997; (b) Ebbers,
E. J.; Ariaans, G. J. A.; et al. Tetrahedron. 1997, 53, 9417.
14. Schwartz, H. M.; Wu, W. S.; Marr, P.W.; Jones, J. B. J. Am. Chem. Soc.
1978, 100, 5199.
15. Tanyeli, C; Turkut, E.; Tetrahedron: Asymmetry. 2004, 15, 2057.
16. (a) Fürst, A.; Plattner, P. A. Helv. Chim. Acta. 1949, 32, 275; (b)
Chrisman, W.; Camara, J. N.; Marcellini, K.; Singaram, B.; et al.
Tetrahedron Lett. 2001, 42, 5805.
(with 1/30 MeOH/CH2Cl2 as eluent) to give 24a (2.6 g, 78%) as a
1
white solid; [α]25 +39.4° (c 1.0, MeOH); H NMR (400 MHz,
D
CDCl3) δ 7.39 – 7.27 (m, 5H), 5.91 – 5.71 (m, 2H), 5.08 (s, 2H),
4.10 – 3.97 (m, 1H), 3.74 (s, 1H), 2.99 (s, 3H), 2.89 (s, 3H), 2.68
(t, J = 12.5 Hz, 1H), 1.90 (s, 2H), 1.78 (dd, J = 13.7, 7.3 Hz, 2H),
1.59 (dd, J = 18.5, 9.8 Hz, 2H), 1.42 (s, 9H); 13C NMR (100
MHz, CDCl3) δ 174.87, 156.71, 155.58, 136.56, 128.47, 128.15,
128.05, 79.23, 66.70, 50.02, 49.71, 38.24, 37.28, 35.87, 29.69,
28.40, 22.69, 14.11; HRMS (ESI; m/z) [M+Na]+ calcd for
C22H33N3O5Na 442.2318, found 442.2298.
17. Katagiri, N.; Matsuhashi, Y.; Kokufuda, H.; Takebayashi, M.; Kaneko,
C. A. Tetrahedron Lett. 1997, 38, 1961.
18. Galynker, I; Still, W. C. Tetrahedron Lett. 1982, 23, 4461.
For the enantiomer 24b; a white solid; 71% yield; [α]25
-
D
44.2° (c 1.0, MeOH); HRMS (ESI; m/z) [M+Na]+ calcd for
C22H33N3O5Na 442.2318, found 442.2318.
Supplementary Material
4.21. tert-Butyl((1R,2S,5R)-2-amino-5-(dimethylcarbamoyl)
cyclohexyl)carbamate (4a)
1
Supplementary data include H, 13C NMR spectra of all the
products. Supplementary data associated with this article can be
found in the online version, at http://
10% palladium on carbon (0.22 g) was added to a solution of
21a (2.2 g, 5.25 mmol) in ethanol, followed by stirring at room