Inversion of secondary chiral alcohols in toluene with the tunable complex of R3N{single bond}R′COOH

Article abstract of DOI:10.1016/j.tetasy.2009.12.028

The S_N2 reaction of enantiomerically pure sulfonates with the tunable complex of R₃N-R′COOH in toluene has been extensively studied. It was revealed that the molar ratio of the tertiary amines and carboxylic acids in the complex of R₃NR′COOH is crucial for the S_N2 reaction, and should be tuned for each sulfonate to give the best yield. Fifteen sulfonates 1 and 3-13 (Scheme 2) were prepared and transformed into 22 corresponding inverted esters 2 and 14-24 (Scheme 2) in good to high yields.

Full text of DOI:10.1016/j.tetasy.2009.12.028

Tetrahedron: Asymmetry 21 (2010) 277–284
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Tetrahedron: Asymmetry
journal homepage: www.elsevier.com/locate/tetasy
Inversion of secondary chiral alcohols in toluene with the tunable complex
of R3NAR0COOH
*
Xiao-Xin Shi , Chun-Li Shen, Jian-Zhong Yao, Liang-Deng Nie, Na Quan
Department of Pharmaceutical Engineering, School of Pharmacy, East China University of Science and Technology, PO Box 363, 130 Mei-Long Road, Shanghai 200237, PR China
a r t i c l e i n f o
a b s t r a c t
The SN2 reaction of enantiomerically pure sulfonates with the tunable complex of R3N–R0COOH in toluene
has been extensively studied. It was revealed that the molar ratio of the tertiary amines and carboxylic
acids in the complex of R3NR0COOH is crucial for the SN2 reaction, and should be tuned for each sulfonate
to give the best yield. Fifteen sulfonates 1 and 3–13 (Scheme 2) were prepared and transformed into 22
corresponding inverted esters 2 and 14–24 (Scheme 2) in good to high yields.
Article history:
Received 27 August 2009
Revised 14 December 2009
Accepted 18 December 2009
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
need of a higher reaction temperature, and the use of basic nucle-
ophiles. The removal of DMF or DMSO can be difficult, and b-elim-
Inversion of chiral alcohols is a fundamental task in asymmetric
syntheses.1–5 Two principal methods are often used for this purpose
(Scheme 1). The first one is a direct method (Method A), in which
chiral alcohols are inverted via the Mitsunobu reaction;6–13 the sec-
ond one is an indirect method (Method B), in which chiral alcohols
are first converted to their sulfonates which are then subject to SN2
replacement by oxygen nucleophiles with the sulfonyloxy moieties
as leaving groups.14–31
ination of sulfonates could take place to produce alkenes as by-
products due to the higher reaction temperature and basicity of
the nucleophiles used, hence the use of this traditional method
for inversion of configuration of chiral alcohols is somewhat lim-
ited. The reaction of sulfonates with cesium carboxylates in ben-
zene or toluene in the presence of 18-crown-622,25 or DMAP23
gave satisfactory results in some cases, but it is obviously restricted
by the expense of the reagents and the scope of applications.
Recently, we became interested in the development of a practi-
cal method for the inversion of chiral alcohols during the course of
our pharmaceutical programs. After an extensive study, we have
developed a simple and versatile procedure for the inversion of
chiral secondary alcohols which is based on the SN2 reactions of
sulfonates with tunable complex of R3NAR0COOH (Eq. 1). This
new process allows the conversion of various chiral sulfonates to
inverted carboxylates in the low polar solvent toluene in good to
excellent yields and without observable racemization.
Mitsunobu
R1
R2
R1
R2
OOCR3
OH
hydrolysis
reaction
Method A
H
H
R1
R2
OH
hydrolysis
H
R1
R1
R2
OOCR'
OSO2R
R'COO
R2
H
Method B
H
Scheme 1. Two principal methods for chiral alcohol inversion.
R1
R2
R1
R2
Although the Mitsunobu reaction has been widely used for alco-
hol inversion, the separation of the product from two by-products,
hydrazinedicarboxylate and phosphane oxide, is usually problem-
atic,11,32–36 hence the inversion of chiral alcohols via the Mitsun-
obu reaction may be not suitable for large-scale preparations and
potential industrial syntheses.
The SN2 reaction of the secondary sulfonates with oxygen
nucleophiles has also been widely used for alcohol inversion,14–31
and the alkali metal salts of carboxylic acids are frequently used
as oxygen nucleophiles.14–25 However, this reaction suffered from
several drawbacks such as using DMF or DMSO as a solvent, the
R3N
H
OOCR'
OOCR'
OSO2R
ð1Þ
H
Toluene
H
2. Results and discussion
At first, (S)-1-phenylpropan-2-yl p-toluenesulfonate 137 was
treated with various acetate salts to obtain (R)-1-phenylpropan-
2-yl acetate 2,38,39 and the results are summarized in Table 1.
The reaction of sulfonate 1 with MOAc (M = Na, K and Cs) in
strong polar solvents such as DMF and DMSO gave ester 2 in poor
yields (Table 1, entries 1–5), but afforded b-methyl-styrene as the
major product in 80–85% yields. It was found that both compound
1 and compound 2 easily underwent b-elimination in strong polar
* Corresponding author.
E-mail address: xxshi@ecust.edu.cn (X.-X. Shi).
0957-4166/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2009.12.028

278
X.-X. Shi et al. / Tetrahedron: Asymmetry 21 (2010) 277–284
Table 1
SN2 reaction of sulfonate 1 with various acetate salts to form acetate 2
Entry
Nucleophile (equiv)
Solvent
Temp. (°C)
Time (h)
Yielda (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
NaOAc (5)
KOAc (5)
KOAc (5)
CsOAc (5)
DMF
DMF
90
95
95
95
95
80
110
95
95
95
95
95
80
80
80
90
80
80
80
80
82
78
82
78
80
95
95
2
2
3
3
3
32
6
5
5
3
3
3
6
6
6
5
4
4
4
4
6
8
4
7
5
5
4
8b
6b
DMSO
DMF
DMSO
Benzene
Toluene
DMF
DMF
AcOH
AcOH
AcOH
Benzene
Benzene
Benzene
Toluene
Benzene
Benzene
Benzene
Toluene
CH3CN
EtOAc
CH3CN
EtOAc
Toluene
Toluene
Toluene
5b
3b
CsOAc (5)
2b
CsOAc (5)18-crown-6 (0.5)
CsOAc (5)DMAPc (0.5)
NaOAc–AcOH (5:10)
KOAc–AcOH (5:10)
NaOAc (5)
12b
5b
45d
42d
62d
63d
60d
17b
45
85
86
9b
KOAc (5)
CsOAc (5)
TEAe–AcOH (6:3)
TEA–AcOH (3:3)
TEA–AcOH (3:6)
TEA–AcOH (3:6)
DBUf–AcOH (4:2)
DBU–AcOH (2:2)
DBU–AcOH (2:4)
DBU–AcOH (2:4)
TEA–AcOH (3:6)
TEA–AcOH (3:6)
DBU–AcOH (2:4)
DBU–AcOH (2:4)
DBNg–AcOH (2:4)
TBAh–AcOH (3:6)
DMAP–AcOH (3:6)
41
90
91
75
67
80
74
89
83
78
a
b
c
Isolated yield.
b-Methylstyrene was identified as the major product in 80–85% yields.
p-Dimethylaminopyridine.
1-Phenyl-2-propanol (20–25%) and b-methylstyrene (10–15%) were also formed.
Triethylamine.
1,8-Diazabicyclo[5,4,0]undec-7-ene.
1,5-Diazabicyclo[4,3,0]non-5-ene.
d
e
f
g
h
Tributylamine.
solvents DMF and DMSO with heating, hence we turned our atten-
tion to the reaction of sulfonate 1 with CsOAc in less polar solvents
such as benzene and toluene in the presence of 0.5 equiv of 18-
crown-625 or DMAP23 (Table 1, entries 6 and 7); however un-
wanted b-methylstyrene remained as the major product.
Basic conditions (Table 1, entries 1–7) caused b-elimination as a
major side reaction, hence we attempted the reaction of sulfonate
1 with MOAc (M = Na, K and Cs) under acidic conditions (Table 1,
entries 8–12). Unfortunately, the desired product 2 was obtained
in moderate yields. Meanwhile, 1-phenyl-2-propanol was formed
in 20–25% yields and with 90% ee, while b-methylstyrene was also
formed in 10–15% yields.
At this stage, we attempted the reaction of sulfonate 1 with the
equimolar mixture of triethylamine TEA (or DBU) and acetic acid,
which has been successfully used by Ono et al.40 for the transfor-
mation of alkyl halides to esters. When compound 1 was treated
with the equal molar mixture of TEA (or DBU) and acetic acid
(1:1) in benzene, the desired product 2 was obtained in moderate
yields (Table 1, entries 14 and 18), while the by-product b-methyl-
styrene was also formed in a notable amount (40–50%) from b-
elimination; suppression of the unwanted b-elimination is the
key point for this reaction. Fortunately, we could obtain ester 2
in a good to high yield just by tuning the molar ratio of tertiary
amine (TEA or DBU) and acetic acid. As can be seen from Table 1,
when the molar ratio of the tertiary amine (TEA or DBU) and acetic
acid was changed from 2:1 to 1:2 (Table 1, entries 13–15 and 17–
19), the yield of the desired product 2 increased dramatically,
while the b-elimination was efficiently reduced by changing the
reaction conditions from weakly basic conditions to weakly acidic
conditions. Four solvents were tested, and the reactions gave the
best yields in toluene (Table 1, entries 16 and 20). Other tertiary
amines such as 1,5-diazabicyclo[4,3,0]non-5-ene (DBN), tributyl-
amine (TBA), and p-dimethylaminopyridine (DMAP) have also
been examined; the complex of R3NAAcOH (1:2) of these three ter-
tiary amines could also give compound 2 in good yields (Table 1,
entries 25–27), but from all five amines used, 1,8-diazabicy-
clo[5,4,0]undec-7-ene (DBU) gave the best yield.
To investigate the scope of this reaction, we then attempted to
explore the generality of the tunable complex of R3NAR0COOH as
versatile oxygen nucleophiles for the SN2 reactions of optically ac-
tive secondary sulfonates. Four p-toluenesulfonates 3, 4, 5a,41,42
and 7a (Scheme 2) and ten methanesulfonates 5b,43 6, 7b, 8,44
9,45 10,45,46 11, 12, 13a, and 13b (Scheme 2) of chiral alcohols were
prepared; these fourteen sulfonates were treated with complex of
R3NAR0COOH at heating in toluene. The results are summarized in
Table 2.
As shown in Table 2, although acetate 14a47 and benzoate 14b
were obtained in moderate yields (Table 2, entries 1 and 2) because
of the easy decomposition of both 14a and 14b while heating un-
der either acidic or basic conditions, another nineteen carboxylates
15, 16a, 16b,48 16c,48 17a, 17b, 18a–c, 19a, 19b, 20a,49,50 20b,51
21a,52 21b,52 22, 23, 24a, and 24b (Scheme 2) were obtained in
good to excellent yields (Table 2, entries 3–25). The molar ratio
of tertiary amine (TEA and DBU) and carboxylic acid should be
tuned for each sulfonate to afford the corresponding ester in the
best yield. Heating was required for all the reactions, the reaction
temperature ranged from 85 °C to 110 °C in most cases (Table 2,
entries 1–13 and 18–25), while replacement of the OMs group at
the C-3 position of bismethanesulfonate 8 with the complex of
R3N–R0COOH occurred at relatively low temperatures (Table 2, en-
tries 14–17). Compounds 19a and 19b were obtained in good
yields and with very high regioselectivities, no substitution at the

X.-X. Shi et al. / Tetrahedron: Asymmetry 21 (2010) 277–284
279
Y
X
X
Y
CO2Et
X
Y
5a X=H, Y=OTs
5b X=H, Y=OMs
16a X=OCHO, Y=H
16b X=OAc, Y=H
16c X=OBz, Y=H
X
TsO
3
X=H, Y=OTs
14a X=OAc, Y=H
14b X=OBz, Y=H
Y
H
1 X=H, Y=OTs
2 X=OAc, Y=H
4 X=H, Y=OTs
15 X=OAc, Y=H
NO2
O
2
5
X
1
CO2Et
Y
3
4
F
Y
X
MsO
X
Y
F
OBz
H
H
Y
7a X=H, Y=OTs
7b X=H, Y=OMs
X
6
X=H, Y=OMs
18a X=OCHO, Y=H
18b X=OAc, Y=H
18c X=OBz, Y=H
8
X=H, Y=OMs
9
X=H, Y=OMs
17a X=OAc, Y=H
17b X=OBz, Y=H
19a X=OAc, Y=H
19b X=OBz, Y=H
20a X=OAc, Y=H
20b X=OBz, Y=H
O
Y
OAc
X
OBz
NH
OAc
X
Y
O
H
Z
H
O
X
Y
OAc
N
O
O
O
H
H
H
H
Y
OBz
OAc
OAc
MsO
X
H
13a X=H, Y=OMs, Z=OAc
13b X=H, Y=OMs, Z=OBz
24a X=OBz, Y=H, Z=OAc
24b X=OBz, Y=H, Z=OBz
10 X=H, Y=OMs
21a X=OAc, Y=H
21b X=OBz, Y=H
11 X=H, Y=OMs
22 X=OBz, Y=H
12 X=H, Y=OMs
23 X=OAc, Y=H
Scheme 2. Sulfonates and the corresponding inverted carboxylates.
Table 2
Reaction of sulfonates with R3N–R0COOH in toluene
Entry
Sulfonate
Amine-acid (equiv)
Temp. (°C)
Time (h)
Ester
Yielda (%)
ee (or de) (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
3
3
4
5a
5a
5a
5b
6
TEA–AcOH (3:6)
DBU–BzOH (2:4)
DBU–AcOH (2:4)
TEA–HCO2H (3:6)
TEA–AcOH (3:6)
DBU–BzOH (2:4)
DBU–BzOH (2:4)
DBU–AcOH (2:4)
DBU–BzOH (2:4)
TEA–HCO2H (3:6)
TEA–AcOH (3:6)
DBU–BzOH (3:9)
DBU–BzOH (3:9)
TEA–AcOH (3:6)
DBU–AcOH (3:9)
TEA–BzOH (3:6)
DBU–BzOH (3:9)
DBU–AcOH (3:6)
DBU–BzOH (3:6)
DBU–AcOH (3:6)
DBU–AcOH (3:6)
DBU–BzOH (3:6)
DBU–AcOH (2:4)
DBU–BzOH (2:4)
DBU–BzOH (2:4)
85
85
110
100
110
95
95
95
95
100
110
95
95
65
50
65
50
110
95
3
3
2
5
5
6
4
4
4
6
6
7
6
6
4
7
6
4
5
6
7
9
12
5
5
14a
14b
15
67
66
92
81
84
86
85
82
89
95
96
92
95
83
85
86
89
93
91
90
92
83
85
82
81
98.2b
98.6b
98.0b
16a
16b
16c
16c
17a
17b
18a
18b
18c
18c
19a
19a
19b
19b
20a
20b
21a
21b
22
>98c
>98c
>98c
>98c
>98c
>98c
6
7a
7a
7a
7b
8
8
8
8
9
98.4b
98.4b
98.2b
98.2b
>98c
>98c
>98c
>98c
>98c
>98c
>98c
>98c
>98c
>98c
>98c
>98c
9
10
10
11
12
13a
13b
95
95
110
95
95
23
24a
24b
95
a
b
c
Isolated yield.
The ee values were determined by HPLC with a chiral column (see Section 4).
The de values were estimated according to high-resolution 1H NMR (500 MHz).
C-4 position was observed, because the OMs group at the allylic
position (C-3) of compound 8 is much more active and less hin-
dered than the other OMs group, thus it could be more easily at-
tacked by nucleophiles.
Some points about our novel method are worthy to be discussed
herein. Firstly, the reactions of enantiomerically pure sulfonates
with the complex of R3NAR0COOH follow a typical SN2 mechanism,
and these SN2 reactions convert the sulfonates into the inverted es-

280
X.-X. Shi et al. / Tetrahedron: Asymmetry 21 (2010) 277–284
ters with high stereoselectivities. We tried to detect the enantio-
meric purities of seven esters 2, 14a, 14b, 15, and 18a–c (Scheme 2)
by HPLC analyses with a chiral column, and it was found that the
ee values for these seven esters were greater than 98.0%. We also
tried to observe the diastereomerical purities of fifteen esters
(16a–c, 17a, 17b, and 1–4 in Scheme 2) from the high-resolution
1H NMR spectra of the crude products, but we could not observe
any peak for other diastereomers (de >98%). Secondly, the complex
of R3N–R0COOH is soluble in many organic solvents of a wide range
of polarity such as the non-polar solvent benzene and dipolar apro-
tic solvent DMF or DMSO so that the reaction can be performed in
various solvents. Toluene was chosen as the solvent here, because
the azeotropic removal of moisture during the heating of reaction
solutions in toluene would suppress the hydrolysis of esters as well
as other side reactions, and therefore increase the yields (see also
Table 1, entries 8–12 and 21–24). Thirdly, the molar ratio of ter-
tiary amines (TEA and DBU) and carboxylic acids of the complex
of R3NAR0COOH is crucial for the reactions, an excess of acids over
amines is necessary, because acidic conditions will effectively re-
duce the b-elimination. Fourthly, the separation of product esters
from the reaction mixture is very simple, and the tertiary amines
and carboxylic acids can be readily removed by washing the organ-
ic phase successively with aqueous HCl solution and aqueous
K2CO3 solution during the extraction, so that our procedure can
be suitable for large-scale preparations. Fifthly, the complex of
R3NAR0COOH has obvious advantages over quaternary ammonium
carboxylate53,54 for the alcohol inversion, as the former is more
inexpensive and can be easily prepared.
collected on a Buchner funnel through suction and washed twice
with water. The crude product was dried in warm air and then
purified by recrystallization in a mixed solvent of ethyl acetate
and cyclohexane (1:9) to afford compound 1 (9.01 g, 31.03 mmol)
in 88% yield, mp 75–76 °C (lit.37 72–74 °C), ½a D20
¼ þ28:5 (c 4.0,
ꢀ
benzene) {lit.37
½
a 2D5
ꢀ
¼ þ28 (c 2, CHCl3)}. 1H NMR (CDCl3) d 1.30
(d, J = 6.3 Hz, 3H), 2.41 (s, 3H), 2.77 (dd, J1 = 6.5 Hz; J2 = 13.8 Hz,
1H), 2.91 (dd, J1 = 6.6 Hz; J2 = 13.8 Hz, 1H), 4.70–4.78 (m, 1H),
7.01–7.06 (m, 2H), 7.16–7.23 (m, 5H), 7.61 (d, J = 8.3 Hz, 2H). MS
m/z 290 (M+), 153, 131, 84, 53. IR (KBr) 2985, 1598, 1340, 1180,
915, 895 cmꢁ1. Anal. Calcd for C16H18O3S: C, 66.18; H, 6.25. Found:
C, 65.90; H, 6.12.
4.2.2. (S)-Ethyl 3-tosyloxy-butanoate (3)
85% yield, mp 72–73 °C. ½a D20
ꢀ
¼ ꢁ26:6 (c 1.5, CHCl3). 1H NMR
(CDCl3) d 1.21 (t, J = 7.2 Hz, 3H), 1.35 (d, J = 6.3 Hz, 3H), 2.45 (s,
3H), 2.51 (dd, J1 = 6.7 Hz, J2 = 15.7 Hz, 1H), 2.72 (dd, J1 = 6.4 Hz,
J2 = 15.8 Hz, 1H), 3.97–4.13 (m, 2H), 4.93–5.02 (m, 1H), 7.35 (d,
J = 8.1 Hz, 2H), 7.79 (d, J = 8.3 Hz, 2H). MS m/z 286 (M+), 83, 52.
4.2.3. (S)-4-(4-Tosyloxyphenyl)-butan-2-yl p-toluenesulfonate (4)
92% yield from (S)-4-(4-hydroxyphenyl)-butan-2-ol with
2.5 equiv of TsCl. Mp 88–89 °C, ½a D20
ꢀ
¼ ꢁ7:5 (c 7.7, acetone). 1H
NMR (CDCl3) d 1.26 (d, J = 6.3 Hz, 3H), 1.73–1.81 (m, 1H), 1.85–
1.93 (m, 1H), 2.450 (s, 3H), 2.455 (s, 3H), 2.46–2.53 (m, 1H),
2.55–2.63 (m, 1H), 4.57–4.64 (m, 1H), 6.86 (d, J = 8.4 Hz, 2H),
6.98 (d, J = 8.4 Hz, 2H), 7.33 (t, J = 7.8 Hz, 4H), 7.70 (d, J = 8.2 Hz,
2H), 7.77 (d, J = 8.1 Hz, 2H). 13C NMR (CDCl3) d 148.55, 145.99,
145.29, 140.53, 135.10, 133.14, 130.47, 130.41, 130.04, 129.16,
128.35, 122.98, 80.12, 38.59, 31.14, 30.35, 22.37. 22.29, 21.42. IR
(KBr film) 2940, 2895, 1600, 1505, 1360, 1195, 1185, 1080, 1050,
910, 850, 640, 560 cmꢁ1. HRMS (EI) m/z calcd for C24H28O6S2:
474.1171; found: 474.1175.
3. Conclusion
In conclusion, we have extensively studied the SN2 reaction of
enantiomerically pure sulfonates with the tunable complex of
R3N–R0COOH. The SN2 reaction is the key step of a novel method
for the inversion of secondary chiral alcohols. This method would
become quite useful for the preparations of a variety of chiral alco-
hols because of the wide scope of the above-mentioned SN2 reac-
tion, the simple procedure for experiments, the easy separation
of product esters from other reagents, and the low cost of all the
materials.
4.2.4. (1R,2S,5R)-2-Isopropyl-5-methylcyclohexyl p-toluenesul-
fonate (5a)
98% yield, mp 95–96 °C (lit.41 mp 95–97 °C). ½a 2D0
¼ ꢁ69:5 (c 3.1,
ꢀ
EtOH) {lit.42
[a
]
D = ꢁ74 (c 0.2, ethanol)}. 1H NMR (CDCl3) d 0.53 (d,
J = 6.9 Hz, 3H), 0.78–0.87 (m, 1H), 0.83 (d, J = 7.2 Hz, 3H), 0.88 (d,
J = 6.6 Hz, 3H), 0.92–1.02 (m, 1H), 1.14–1.22 (m, 1H), 1.33–1.47
(m, 2H), 1.61–1.69 (m, 2H), 1.85–1.94 (m, 1H), 2.11–2.17 (m,
1H), 2.44 (s, 3H), 4.36–4.43 (m, 1H), 7.33 (d, J = 8.1 Hz, 2H), 7.80
(d, J = 8.2 Hz, 2H). MS m/z 310 (M+).
4. Experimental
4.1. General
4.2.5. (S)-1-(2,3-Difluro-6-nitrophenoxy)propan-2-yl p-toluene-
Melting points are uncorrected. 1H NMR spectra were acquired
on Bruker AM-500, chemical shifts were given on the delta scale as
parts per million (ppm) with tetramethylsilane (TMS) as the inter-
nal standard. IR spectra were recorded on Nicolet Magna IR-550.
Mass spectra were recorded on HP5989A. Optical rotations were
measured on WZZ-1S automatic polarimeter at room temperature.
HPLC analysis was performed with an Agilent/HP 1100 series
equipped with an Alltech ELSD 2000ES detector. Column chroma-
tography was performed on silica gel (Qingdao Ocean Chemical
Corp.). All chemicals were analytically pure.
sulfonate 7a
95% yield, mp 97–98 °C. ½a D20
ꢀ
¼ ꢁ13:0 (c 3.5, CHCl3). 1H NMR
(CDCl3) d 1.44 (d, J = 6.5 Hz, 3H), 2.42 (s, 3H), 4.21 (dd, J1 = 4.4 Hz,
J2 = 10.2 Hz, 1H), 4.31 (dd, J1 = 5.3 Hz, J2 = 11.3 Hz, 1H), 4.88–5.00
(m, 1H), 6.96–7.05 (m, 1H), 7.30 (d, J = 8.2 Hz, 2H), 7.61–7.68 (m,
1H), 7.80 (d, J = 8.3 Hz, 2H). MS m/z 387 (M+), 216, 213, 199, 170,
158, 155, 91, 65. IR (KBr) 3100, 2940, 1630, 1600, 1540, 1470, 1360,
1290, 1170, 990, 915, 820, 760 cmꢁ1. Anal. Calcd for C16H15F2NO6S:
C, 49.61; H, 3.90; N, 3.62. Found: C, 49.63; H, 3.88; N, 3.61.
4.3. General procedure for preparation of mesylates56
4.2. General procedure for the preparation of tosylates55
4.3.1. (1R,2S,5R)-2-Isopropyl-5-methylcyclohexyl methanesul-
fonate (5b)
4.2.1. (S)-1-Phenylpropan-2-yl p-toluenesulfonate (1)
A solution of (S)-1-phenylpropan-2-ol (4.80 g, 35.24 mmol) and
p-dimethylaminopyridine (0.22 g, 1.80 mmol) in pyridine (25 mL)
was cooled to 0 °C with an ice-bath, p-toluenesulfonyl chloride
(8.74 g, 45.84 mmol) was then added in portions over 30 min. After
the addition was finished, the ice-bath was moved away, and the
mixture was stirred at room temperature for 5 h. Water (80 mL)
was slowly added, and a white solid precipitated. Solid was then
A solution of (1R,2S,5R)-menthol (4.69 g, 30.01 mmol) and tri-
ethylamine (6.07 g, 59.99 mmol) in dichloromethane (60 mL) was
cooled to 0 °C with an ice-bath, after which methanesulfonyl chlo-
ride (5.16 g, 45.05 mmol) was added dropwise within 20 min. After
the addition was finished, the ice-bath was removed, and the mix-
ture was stirred at room temperature for 2 h. The reaction was
quenched with aqueous HCl solution (2 M, 50 mL), and the organic

X.-X. Shi et al. / Tetrahedron: Asymmetry 21 (2010) 277–284
281
phase was separated and washed with aqueous K2CO3 solution
(10% w/v, 50 mL). After the organic solution was dried over anhy-
drous MgSO4, the solvent was removed off by a rotavapor to give a
crude product, which was purified by flash chromatography to fur-
nish compound 5b (6.61 g, 28.20 mmol) as a colorless oil in 94%
940, 860, 750 cmꢁ1. Anal. Calcd for C28H50O3S: C, 72.05; H, 10.80.
Found: C, 72.11; H, 10.80.
4.3.7. 17b-Estra-3,17-diyl bismethanesulfonate (11)
91% yield from 17b-estra-3,17-diol with 3.5 equiv of MsCl.
yield. ½a 2D0
ꢀ
¼ ꢁ68:0 (c 2.0, ethanol) {lit.43
½
a 1D5
ꢀ
¼ ꢁ63:5 (c 1.0, eth-
½
a 2D0
ꢀ
¼ þ35:8 (c 0.5, acetone). 1H NMR (CDCl3) d 0.88 (s, 3H),
anol)}. 1H NMR (CDCl3) d 0.84 (d, J = 6.9 Hz, 3H), 0.85–0.90 (m,
1H), 0.93 (d, J = 6.7 Hz, 3H), 0.95 (d, J = 6.5 Hz, 3H), 1.02–1.11 (m,
1H), 1.23–1.30 (m, 1H), 1.39–1.50 (m, 2H), 1.67–1.75 (m, 2H),
2.06–2.09 (m, 1H), 2.24–2.28 (m, 1H), 3.01 (s, 3H), 4.51–4.57 (m,
1H). MS m/z 234 (M+), 132, 78. IR (neat) 2960, 2875, 1460, 1350,
1.24–1.29 (m, 1H), 1.32–1.53 (m, 5H), 1.75–1.94 (m, 3H), 2.02–
2.09 (m, 1H), 2.21–2.28 (m, 2H), 2.31–2.36 (m, 1H), 2.89 (dd,
J1 = 4.1 Hz, J2 = 8.8 Hz, 2H), 3.02 (s, 3H), 3.13 (s, 3H), 4.58 (t,
J = 8.4 Hz, 1H), 7.01 (d, J = 2.3 Hz, 1H), 7.04 (dd, J1 = 2.5 Hz,
J2 = 8.5 Hz, 1H), 7.30 (t, J = 8.5 Hz, 1H). 13C NMR (CDCl3) d 147.76,
139.88, 139.49, 127.56, 122.55, 119.55, 89.86, 49.69, 44.44, 43.85,
38.86, 38.66, 37.89, 36.88, 30.00, 28.53, 27.32, 26.42, 23.65. IR
(KBr) 2950, 2870, 1605, 1490, 1360, 1280, 1180, 1160, 980, 925,
1175, 920, 865, 750, 536 cmꢁ1
.
4.3.2. (1S,2S,5R)-2-Isopropyl-5-methylcyclohexyl methanesul-
fonate (6)
820, 700, 540 cmꢁ1
. HRMS (EI) m/z calcd for C20H28O6S2:
428.1327; found: 428.1328.
91% yield, ½a 2D0
ꢀ
¼ þ16:8 (c 3.0, CHCl3). 1H NMR (CDCl3) d 0.83–
1.20 (m, 11H), 1.24–1.38 (m, 1H), 1.46–1.58 (m, 1H), 1.62–1.86
(m, 4H), 2.16–2.26 (m, 1H), 3.01 (s, 3H), 5.15 (br s, 1H). MS m/z
234 (M+), 138, 123, 95, 81, 67. IR (neat) 2960, 2880, 1465, 1355,
4.3.8. ((2S,3S,4R,5R)-3,4-Diacetoxy-2-((2R,3R,4S,5R,6R)-3,4-
diacetoxy-6acetoxy-methyl-5-methylsulfonyloxy-tetrahydro-
2H-pyran-2-yloxy)-tetrahydrofuran-2,5-diyl)bis(methylene)
dibenzoate (12)
1178, 945, 925, 840, 540 cmꢁ1
.
4.3.3. (S)-1-(2,3-Difluro-6-nitrophenoxy)propan-2-yl methane-
94% yield, ½a 2D0
ꢀ
¼ þ42:1 (c 1.1, acetone). 1H NMR (CDCl3) d 1.96
sulfonate (7b)
(s, 3H), 2.10 (s, 3H), 2.11 (s, 3H), 2.12 (s, 3H), 2.16 (s, 3H), 2.91 (s,
3H), 4.22 (d, J = 11.3 Hz, 1H), 4.32–4.40 (m, 3H), 4.46 (d, J = 12.4 Hz,
1H), 4.52–4.60 (m, 3H), 4.79–4.84 (m, 2H), 5.44 (t, J = 4.2 Hz, 1H),
5.58 (d, J = 10.1 Hz, 1H), 5.59 (d, J = 12.0 Hz, 1H), 5.74 (d,
J = 3.5 Hz, 1H), 7.47 (t, J = 7.2 Hz, 2H), 7.48 (t, J = 7.1 Hz, 2H), 7.60
(t, J = 7.3 Hz, 2H), 8.09 (d, J = 6.0 Hz, 4H). IR (KBr) 3020, 2980,
1750–1720, 1600, 1380, 1360, 1230, 1180, 1105, 1020, 960, 810,
720 cmꢁ1. HRMS(EI) m/z calcd for C37H42O20S: 838.1990; found:
838.1994.
87% yield, mp 65–66 °C. ½a D20
ꢀ
¼ ꢁ15:5 (c 4.0, CHCl3). 1H NMR
(CDCl3) d 1.46 (d, J = 6.5 Hz, 3H), 3.00 (s, 3H), 4.25 (dd, J1 = 3.0 Hz,
J2 = 10.4 Hz, 1H), 4.32 (dd, J1 = 5.7 Hz, J2 = 11.1 Hz, 1H), 5.00–5.08
(m, 1H), 6.98–7.05 (m, 1H), 7.63–7.69 (m, 1H). MS m/z 311 (M+),
281, 185, 159, 158, 137, 123, 100, 96, 79, 59. IR (KBr) 3100, 2860,
1630, 1600, 1540, 1495, 1365, 1305, 1180, 1060, 920, 810,
700 cmꢁ1. Anal. Calcd for C10H11F2NO6S: C, 38.59; H, 3.56; N,
4.50. Found: C, 38.24; H, 3.57; N, 4.67.
4.3.4. Ethyl (3R,4S,5R)-5-O-benzoyl-3,4-O-bismethanesulfonyl
shikimate (8)
4.3.9. ((2R,3S,5R)-5-(5-Methyl-2,4-dioxo-3,4-dihydropyrimidin-
1(2H)-yl)-3-(methylsulfonyloxy)-tetrahydrofuran-2-yl)methyl
acetate (13a)
96% yield from ethyl (3R,4R,5R)-5-O-benzoyl shikimate with
3.5 equiv of MsCl.
½
a 2D5
ꢀ
¼ ꢁ135:0 (c 1.5, EtOAc) {lit.44
91% yield, ½a 2D0
ꢀ
¼ þ5:6 (c 3.3, acetone). 1H NMR (acetone-d6) d
½
a 2D5
ꢀ
¼ ꢁ135:2 (c 1.9, EtOAc)}. 1H NMR (CDCl3) d 1.31 (t, J = 7.1 Hz,
1.83 (s, 3H), 2.09 (s, 3H), 2.61–2.65 (m, 2H), 3.22 (s, 3H), 4.28–
4.41 (m, 3H), 5.36 (dd, J1 = 4.6 Hz, J2 = 7.6 Hz, 1H), 6.29 (t,
J = 7.1 Hz, 1H), 7.50 (d, J = 1.0 Hz, 1H), 10.08 (s, 1H). 13C NMR
(DMSO-d6) d 170.08, 163.63, 150.36, 135.91, 109.94, 83.98, 80.79,
79.78, 62.98, 37.65, 36.08, 20.55, 12.12. IR (KBr) 3200, 3050,
2950, 2840, 1750, 1710, 1670, 1480, 1380, 1360, 1160, 1100,
1050, 980, 940, 820, 610, 530 cmꢁ1. HRMS(EI) m/z calcd for
C13H18N2O8S: 362.0784; found: 362.0787.
3H), 2.60 (dd, J1 = 19.0 Hz; J2 = 6.6 Hz, 1H), 3.09 (s, 3H), 3.18 (s, 3H),
3.22 (dd, J1 = 19.1 Hz; J2 = 6.7 Hz, 1H), 4.25 (q, J = 7.1 Hz, 2H), 5.16
(dd, J1 = 8.9 Hz; J2 = 4.0 Hz, 1H), 5.52–5.72 (m, 2H), 6.83–6.98 (m,
1H), 7.47 (dd, J1 = J2 = 7.7 Hz, 2H), 7.58–7.63 (m, 1H), 8.03 (d,
J = 7.5 Hz, 2H). 13C NMR (CDCl3) d 165.80, 165.24, 134.34, 134.21,
130.65, 130.40, 129.59, 129.26, 75.36, 73.40, 67.36, 62.29, 39.51,
39.35, 29.99, 14.72. MS (EI) m/z calcd for C18H22O10S2: 462.0654.
Found: 462.0654. IR (KBr) 3031, 2979, 2944, 1722, 1658, 1600,
1453, 1180, 1110, 1032, 1174, 910, 716, 530 cmꢁ1
.
4.3.10. ((2R,3S,5R)-5-(5-Methyl-2,4-dioxo-3,4-dihydropyrimi-
din-1(2H)-yl)-3-(methylsulfonyloxy)-tetrahydrofuran-2-yl)me-
thyl benzoate (13b)
4.3.5. Cholest-5-en-3b-yl methanesulfonate (9)
95% yield, mp 120–121 °C (lit.45 mp 118–119 °C). ½a 2D0
ꢀ
¼ ꢁ33:0
89% yield, ½a 2D0
ꢀ
¼ ꢁ12:9 (c 1.8, acetone). 1H NMR (acetone-d6) d
(c 5.0, CHCl3). 1H NMR (CDCl3) d 0.68 (s, 3H), 0.86 (d, J = 6.7 Hz, 3H),
0.87 (d, J = 6.6 Hz, 3H), 0.91 (d, J = 6.6 Hz, 3H), 0.93–1.01 (m, 2H),
1.02 (s, 3H), 1.03–1.19 (m, 7H), 1.21–1.39 (m, 4H), 1.40–1.68 (m,
7H), 1.72–1.94 (m, 3H), 1.95–2.07 (m, 3H), 2.45–2.57 (m, 2H),
3.01 (s, 3H), 4.48–4.56 (m, 1H), 5.42 (t, J = 2.7 Hz, 1H). MS m/z
464 (M+), 368, 353, 255, 247, 145, 95. IR (KBr) 3025, 2945, 2905,
2860, 1470, 1360, 1335, 1175, 935, 865, 760 cmꢁ1. Anal. Calcd for
C28H48O3S: C, 72.36; H, 10.41. Found: C, 72.20; H, 10.39.
1.60 (s, 3H), 2.66–2.72 (m, 2H), 3.25 (s, 3H), 4.56–4.63 (m, 2H),
4.66–4.70 (m, 1H), 5.54–5.59 (m, 1H), 6.34 (t, J = 7.1 Hz, 1H), 7.43
(d, J = 0.8 Hz, 1H), 7.54 (t, J = 7.8 Hz, 2H), 7.67 (t, J = 7.3 Hz, 1H),
8.09 (t, J = 7.1 Hz, 2H), 10.05 (s, 1H). 13C NMR (acetone-d6) d
206.56, 166.20, 163.96, 150.84, 135.96, 133.93, 130.14, 129.94,
129.19, 111.02, 85.48, 82.41, 80.52, 64.13, 37.96, 37.73, 11.84. IR
(KBr) 3400, 3180, 3025, 2940, 2835, 1720, 1665, 1490, 1380,
1360, 1270, 1180, 1120, 940, 720, 610 cmꢁ1. HRMS(EI) m/z calcd
for C18H20N2O8S: 424.0940; found: 424.0942.
4.3.6. 5a-Cholestan-3b-yl methanesulfonate (10)
92% yield, mp 114–115 °C (lit.45 mp 113–114 °C) ½a 2D0
ꢀ
¼ þ13:5
4.4. General procedure for the SN2 reaction of sulfonates with
complex of R3N–R0COOH in toluene
(c 5.0, CHCl3) {lit.46
½
a 2D2
ꢀ
¼ þ14:1 (c 1.0, CHCl3)}. 1H NMR (CDCl3)
d 0.64 (s, 3H), 0.82 (s, 3H), 0.859 (d, J = 6.6 Hz, 3H), 0.864 (d,
J = 6.6 Hz, 3H), 0.90 (d, J = 6.5 Hz, 3H), 0.92–1.40 (m, 20H), 1.41–
1.82 (m, 9H), 1.93–2.01 (m, 2H), 3.00 (s, 3H), 4.57–4.65 (m, 1H).
MS m/z 466 (M+), 414, 370, 355, 316, 301, 275, 257, 215, 161,
147, 107, 81. IR (KBr) 2950, 2935, 2860, 1470, 1350, 1335, 1170,
4.4.1. (R)-1-Phenylpropan-2-yl acetate (2)
To a solution of DBU (3.04 g, 19.97 mmol) in toluene (5 mL) was
added acetic acid (2.40 g, 39.97 mmol). The solution was then stir-

282
X.-X. Shi et al. / Tetrahedron: Asymmetry 21 (2010) 277–284
red at room temperature for half an hour, and compound 1 (2.90 g,
9.99 mmol) was added. The mixture was heated to 80 °C, and stir-
ring was then continued at this temperature for 4 h. After being
cooled down to room temperature, the reaction mixture was di-
luted with toluene (45 mL). The solution was transferred into a
separatory funnel, and was washed successively with aqueous
HCl solution (2 M, 25 mL), aqueous K2CO3 solution (10% w/v,
30 mL), and brine (10 mL). After the organic solution was dried
over anhydrous Na2SO4, the solvent was removed by distillation
in vacuo to give the crude product which was purified by flash
chromatography to afford acetate 2 (1.63 g, 9.14 mmol) as a color-
4.4.6. (1S,2S,5R)-Isopropyl-5-methylcyclohexyl acetate (16b)
½
a 2D0
ꢀ
¼ þ35:6 (c 2.4, EtOH) {lit.48
½
a 2D0
ꢀ
¼ þ42 (c 1.12, CHCl3)}. 1H
NMR (CDCl3) d 0.84–1.03 (m, 11H), 1.25–1.49 (m, 3H), 1.54–1.69
(m, 1H), 1.70–1.79 (m, 2H), 1.80–1.96 (m, 1H), 2.03 (s, 3H), 5.19
(br s, 1H). IR (neat) 2965, 2830, 1715, 1460, 1385, 1190, 1140,
1015, 820 cmꢁ1. MS m/z 198 (M+), 183, 138, 81, 43.
4.4.7. (1S,2S,5R)-Isopropyl-5-methylcyclohexyl benzoate (16c)
½
a 2D0
ꢀ
¼ þ13:0 (c 2.4, EtOH) {lit.48
½
a 2D0
ꢀ
¼ þ26 (c 2.49, CHCl3)}. 1H
NMR (CDCl3) d 0.78 (d, J = 6.6 Hz, 3H), 0.82 (d, J = 6.7 Hz, 3H), 0.84
(d, J = 6.7 Hz, 3H), 0.86–0.96 (m, 1H), 0.99–1.10 (m, 2H), 1.41–1.52
(m, 2H), 1.58–1.68 (m, 1H), 1.72–1.80 (m, 2H), 1.97–2.04 (m, 1H),
5.38 (d, J = 1.7 Hz, 1H), 7.37 (t, J = 7.6 Hz, 2H), 7.48 (t, J = 7.4 Hz,
1H), 7.98 (d, J = 7.3 Hz, 2H). HRMS (EI) m/z calcd for C17H24O2:
260.1776; found: 260.1778.
less oil in 91% yield.
½
a 2D0
ꢀ
¼ ꢁ10:2 (c 4.5, benzene) {lit.38
½
a 2D7
ꢀ
¼ ꢁ5:6 (c 1.0, CHCl3); lit.39
½
a 2D5
ꢀ
¼ ꢁ10:9 (c 1.0, ether)}. HPLC
analysis: Column: OD-3; mobile phase: 5% IPA (isopropanol) in
CO2; wavelength: 220 nm; flow rate: 2.5 mL/min; tR (retention
time): 1.31 min for (S)-isomer, 1.45 min for (R)-isomer; purity:
98.9% for (R), 1.1% for (S). 1H NMR (CDCl3) d 1.21 (d, J = 6.3 Hz,
3H), 1.98 (s, 3H), 2.74 (dd, J1 = 6.5 Hz; J2 = 13.6 Hz, 1H), 2.92 (dd,
J1 = 6.7 Hz; J2 = 13.6 Hz, 1H), 5.08–5.14 (m, 1H), 7.16–7.24 (m,
3H), 7.25–7.31 (m, 2H). MS m/z 178 (M+). IR (neat) 2980, 2920,
4.4.8. (1R,2S,5R)-Isopropyl-5-methylcyclohexyl acetate (17a)
½
a 2D0
ꢀ
¼ ꢁ80:4 (c 2.1, CHCl3). 1H NMR (CDCl3) d 0.76 (d, J = 7.0 Hz,
3H), 0.82–0.93 (m, 7H), 0.94–1.01 (m, 1H), 1.02–1.12 (m, 1H),
1.33–1.40 (m, 1H), 1.42–1.54 (m, 1H), 1.63–1.72 (m, 2H), 1.82–
1.91 (m, 1H), 1.95–2.02 (m, 1H), 2.03 (s, 3H), 4.64–4.72 (m, 1H).
13C NMR (CDCl3) d 171.27, 74.74, 47.62, 41.55, 34.88, 31.99,
26.92, 24.10, 22.64, 21.94, 21.36, 16.99. MS m/z 198 (M+), 138,
123, 95, 81, 43. IR (neat) 2980, 2955, 1730, 1465, 1385, 1245,
1025 cmꢁ1. HRMS (EI) m/z calcd for C17H24O2: 260.1776; found:
260.1759.
1735, 1465, 1375, 1245, 1065, 965, 750, 700 cmꢁ1
.
4.4.2. (R)-Ethyl 3-acetoxy-butanoate (14a)
½
a 2D0
ꢀ
¼ þ4:0 (c 3.5, CHCl3) {lit.47
½
a 2D5
ꢀ
¼ þ2:9 (c 1.0, CHCl3)}.
HPLC analysis: Column: AS-RH; mobile phase: water/acetoni-
trile = 80/20; wavelength: 205 nm; flow rate: 0.5 mL/min; tR
(retention time): 13.99 min for (S)-isomer, 14.49 min for (R)-iso-
mer; purity: 99.1% for (R), 0.9% for (S). 1H NMR (CDCl3) d 1.26 (t,
J = 7.1 Hz, 3H), 1.30 (d, J = 6.3 Hz, 3H), 2.02 (s, 3H), 2.50 (dd,
J1 = 5.7 Hz, J2 = 15.4 Hz, 1H), 2.63 (dd, J1 = 7.5 Hz, J2 = 15.4 Hz, 1H),
4.15 (q, J = 7.1 Hz, 2H), 5.23–5.32 (m, 1H). MS m/z 174 (M+), 131,
115, 86, 43.
4.4.9. (1R,2S,5R)-Isopropyl-5-methylcyclohexyl benzoate (17b)
½
a 2D0
ꢀ
¼ ꢁ91:2 (c 1.3, CHCl3). 1H NMR (CDCl3) d 0.80 (d, J = 6.9 Hz,
3H), 0.86–0.98 (m, 7H), 1.06–18 (m, 2H), 1.51–1.62 (m, 2H), 1.67–
1.78 (m, 2H), 1.91–2.02 (m, 1H), 2.10–2.18 (m, 1H), 4.90–4.98 (m,
1H), 7.43 (t, J = 7.6 Hz, 2H), 7.54 (t, J = 7.4 Hz, 1H), 8.05 (d,
J = 7.4 Hz, 2H). 13C NMR (CDCl3) d 166.67, 133.30, 131.48, 130.17,
128.90, 75.39, 47.89, 41.60, 34.95, 32.06, 27.11, 24.25, 22.68,
21.40, 17.14. IR (KBr) 2985, 2955, 1715, 1600, 1465, 1285, 1110,
4.4.3. (R)-Ethyl 3-benzoyloxy-butanoate (14b)
½
a 2D0
ꢀ
¼ ꢁ16:0 (c 1.4, CHCl3). HPLC analysis: Column: AS-RH; mo-
975, 710 cmꢁ1
.
bile phase: water/acetonitrile = 80/20; wavelength: 220 nm; flow
rate: 0.5 mL/min; tR (retention time): 15.68 min for (S)-isomer,
16.29 min for (R)-isomer; purity: 99.3% for (R), 0.7% for (S). 1H
NMR (CDCl3) d 1.13 (t, J = 7.1 Hz, 3H), 1.36 (d, J = 6.3 Hz, 3H), 2.56
(dd, J1 = 5.8 Hz, J2 = 15.3 Hz, 1H), 2.72 (dd, J1 = 7.5 Hz, J2 = 15.3 Hz,
1H), 4.06 (q, J = 7.1 Hz, 2H), 5.41–5.49 (m, 1H), 7.36 (t, J = 7.7 Hz,
2H), 7.47 (t, J = 7.4 Hz, 1H), 7.95 (d, J = 7.3 Hz, 2H). MS m/z 236
(M+), 131, 105, 79, 53, 42. Anal. calcd for C13H16O4: C, 66.09; H,
6.83; found: C,66.39; H, 6.80.
4.4.10. (R)-1-(2,3-Difluoro-6-nitrophenoxy)propan-2-yl
formate (18a)
Mp 67–68 °C, ½a 2D0
¼ þ22:0 (c 4.5, CHCl3). HPLC analysis: Col-
ꢀ
umn: AD-3; mobile phase: 5% IPA in CO2; wavelength: 220 nm;
flow rate: 2.5 mL/min; tR (retention time): 8.76 min for (R)-isomer,
9.12 min for (S)-isomer; purity: 99.2% for (R), 0.8% for (S). 1H NMR
(CDCl3) d 1.42 (d, J = 6.6 Hz, 3H), 4.31 (dd, J1 = 6.1 Hz, J2 = 10.2 Hz,
1H), 4.37 (dd, J1 = 3.3 Hz, J2 = 10.2 Hz, 1H), 5.36–5.45 (m, 1H),
7.02–7.09 (m, 1H), 7.67–7.73 (m, 1H), 8.09 (s, 1H). MS m/z 261
(M+), 231, 175, 159, 145, 129, 101, 87, 59. IR (KBr) 3100, 2980,
2940, 1725, 1630, 1600, 1540, 1490, 1350, 1300, 1185, 1060, 980,
810, 700 cmꢁ1. HRMS (EI) m/z calcd for C10H9F2NO5: 261.0449;
found: 261.0444. Anal. Calcd for C10H9F2NO5: C, 45.99; H, 3.47;
N, 5.36. Found: C, 45.97; H, 3.57; N, 5.65.
4.4.4. (R)-4-(4-Tosyloxyphenyl)-butan-2-yl acetate (15)
Mp 77–78 °C, ½a 2D0
¼ þ3:3 (c 4.2, acetone). HPLC analysis: Col-
ꢀ
umn: AD-3; mobile phase: 5% IPA in CO2; wavelength: 220 nm;
flow rate: 2.5 mL/min; tR (retention time): 5.23 min for (S)-isomer,
5.36 min for (R)-isomer; purity: 99.0% for (R), 1.0% for (S). 1H NMR
(CDCl3) d 1.23 (d, J = 6.4 Hz, 3H), 1.72–1.80 (m, 1H), 1.83–1.92 (m,
1H), 2.01 (s, 3H), 2.45 (s, 3H), 2.54–2.68 (m, 2H), 4.85–4.93 (m, 1H),
6.88 (d, J = 8.5 Hz, 2H), 7.07 (d, J = 8.5 Hz, 2H), 7.31 (d, J = 8.1 Hz,
2H), 7.70 (d, J = 8.3 Hz, 2H). 13C NMR (CDCl3) d 171.26, 148.39,
145.89, 141.18, 133.04, 130.33, 129.97, 129.08, 122.85, 70.90,
37.87, 31.75, 22.29, 21.88, 20.59. IR (KBr) 3020, 2980, 2940,
1720, 1600, 1510, 1450, 1380, 1240, 1190, 1080, 960, 860, 700,
640, 560 cmꢁ1. HRMS (EI) m/z calcd for C19H22O5S: 362.1188;
found: 362.1182.
4.4.11. (R)-1-(2,3-Difluoro-6-nitrophenoxy)propan-2-yl acetate
(18b)
Mp 72–73 °C, ½a 2D0
¼ þ35:0 (c 6.7, CHCl3). HPLC analysis: Col-
ꢀ
umn: AD-3; mobile phase: 5% IPA in CO2; wavelength: 220 nm;
flow rate: 2.5 mL/min; tR (retention time): 8.98 min for (R)-isomer,
9.28 min for (S)-isomer; purity: 99.2% for (R), 0.8% for (S). 1H NMR
(CDCl3) d 1.27 (d, J = 6.6 Hz, 3H), 1.97 (s, 3H), 4.18 (dd, J1 = 6.0 Hz,
J2 = 10.3 Hz, 1H), 4.28 (dd, J1 = 3.3 Hz, J2 = 10.3 Hz, 1H), 5.12–5.23
(m, 1H), 6.91–7.01 (m, 1H), 7.54–7.64 (m, 1H). MS m/z 275 (M+),
260, 186, 159, 145, 99, 87, 43. IR (KBr) 3100, 2985, 2845, 1740,
1625, 1590, 1540, 1495, 1350, 1300, 1235, 1120, 1060, 950, 800,
700 cmꢁ1. Anal. Calcd for C11H11F2NO5: C, 48.01; H, 4.03; N, 5.09.
Found: C, 48.22; H, 3.94; N, 5.23.
4.4.5. (1S,2S,5R)-Isopropyl-5-methylcyclohexyl formate (16a)
½
a 2D0
ꢀ
¼ þ24:0 (c 2.4, EtOH). 1H NMR (CDCl3) d 0.84–0.95 (m,
10H), 0.96–1.12 (m, 2H), 1.25–1.49 (m, 2H), 1.58–1.69 (m, 1H),
1.70–1.81 (m, 2H), 1.92–2.02 (m, 1H), 5.34 (br s, 1H), 6.47 (s,
1H). IR (neat) 2960, 2840, 1730, 1460, 1380, 1190, 1140, 1010,
910, 810 cmꢁ1. MS m/z 184 (M+), 139, 124, 79, 68.

X.-X. Shi et al. / Tetrahedron: Asymmetry 21 (2010) 277–284
283
4.4.12. (R)-1-(2,3-Difluoro-6-nitrophenoxy)propan-2-yl benzo-
0.861 (d, J = 6.7 Hz, 3H), 0.866 (d, J = 6.7 Hz, 3H), 0.88–1.41 (m,
20H), 1.43–1.85 (m, 12H), 1.92–1.99 (m, 1H), 2.05 (s, 3H), 5.00
(d, J = 2.6 Hz, 1H). MS m/z 430 (M+), 415, 371, 370, 355, 316, 257,
215, 201, 173, 161, 147, 107, 79, 67. IR (KBr) 2940–2840, 1735,
1465, 1375, 1235, 1160, 1020, 975, 850, 730 cmꢁ1. Anal. Calcd for
C29H50O2: C, 80.87; H, 11.70. Found: C, 80.70; H, 11.51.
ate (18c)
Mp 101–102 °C, ½a D20
¼ ꢁ21:0 (c 4.1, CHCl3). HPLC analysis: Col-
ꢀ
umn: AD-3; mobile phase: 5% IPA in CO2; wavelength: 220 nm;
flow rate: 2.5 mL/min; tR (retention time): 10.16 min for (R)-iso-
mer, 10.32 min for (S)-isomer; purity: 99.1% for (R), 0.9% for (S).
1H NMR (CDCl3) d 1.50 (d, J = 6.7 Hz, 3H), 4.41–4.50 (m, 2H),
5.46–5.55 (m, 1H), 6.94–7.03 (m, 1H), 7.43 (t, J = 7.9 Hz, 2H), 7.56
(t, J = 7.9 Hz, 1H), 7.62–7.70 (m, 1H), 8.02 (d, J = 8.3 Hz, 2H). IR
(KBr) 3085, 2980, 2835, 1725, 1625, 1590, 1535, 1490, 1350,
1270, 1115, 1060, 970, 815, 715 cmꢁ1. HRMS (EI) m/z calcd for
C16H13NO5F2: 337.0762; found: 337.0763.
4.4.18. 5a-Cholestan-3a-yl benzoate (21b)
Mp 101–102 °C (lit.52 mp 100–101 °C), ½a 2D0
¼ þ25:6 (c 1.5,
ꢀ
CHCl3). 1H NMR (CDCl3) d 0.64 (s, 3H), 0.779 (d, J = 6.5 Hz, 3H),
0.783 (d, J = 6.6 Hz, 3H), 0.82–1.32 (m, 26H), 1.35–1.56 (m, 6H),
1.66–1.80 (m, 3H), 1.83–1.89 (m, 1H), 1.91–1.98 (m, 1H), 4.68 (t,
J = 2.5 Hz, 1H), 7.37 (t, J = 7.8 Hz, 2H), 7.47 (t, J = 7.4 Hz, 1H), 8.00
(d, J = 7.5 Hz, 2H). IR (KBr) 2945–2855, 1720, 1605, 1450, 1385,
4.4.13. (3S,4S,5R)-Ethyl 3-acetoxy-5-benzoyloxy-4-(methylsul-
fonyloxy)cyclohex-1-ene carboxylate (19a)
1275, 1120, 1050, 970, 710 cmꢁ1
C34H52O2: 492.3967; found: 492.3969.
. HRMS (EI) m/z calcd for
Mp 98–99 °C, ½a 2D0
ꢀ
¼ ꢁ36:8 (c 2.1, EtOAc). 1H NMR (CDCl3) d
1.30 (t, J = 7.1 Hz, 3H), 2.14 (s, 3H), 2.53–2.62 (m, 1H), 2.94 (s,
3H), 3.21 (dd, J1 = 6.0 Hz, J2 = 17.9 Hz, 1H), 4.24 (q, J = 7.0 Hz, 2H),
5.14 (dd, J1 = 7.5 Hz, J2 = 10.1 Hz, 1H), 5.45–5.52 (m, 1H), 5.79
(dd, J1 = 1.0 Hz, J2 = 7.3 Hz, 1H), 6.71 (t, J = 2.2 Hz, 1H), 7.47 (t,
J = 7.8 Hz, 2H), 7.60 (t, J = 7.4 Hz, 1H), 8.11 (d, J = 7.2 Hz, 2H). 13C
NMR (CDCl3) d 170.61, 165.94, 165.34, 134.19, 133.76, 130.63,
130.48, 129.74, 129.17, 78.74, 71.05, 68.86, 62.03, 39.37, 30.26,
21.37, 14.73. IR (KBr) 2985, 2920, 1750, 1720, 1665, 1345, 1260,
4.4.19. 17a-Estra-3-methanesulfonyloxy-17-yl benzoate (22)
Mp 72–73 °C, ½a 2D0
ꢀ
¼ ꢁ9:2 (c 2.1, acetone). 1H NMR (CDCl3) d
0.87 (s, 3H), 1.32–1.61 (m, 4H), 1.67–1.82 (m, 4H), 1.90–2.01 (m,
2H), 2.26–2.45 (m, 3H), 2.85–2.95 (m, 2H), 3.13 (s, 3H), 5.12 (d,
J = 6.1 Hz, 1H), 7.01 (s, 1H), 7.03 (d, J = 8.7 Hz, 1H), 7.31 (d,
J = 8.5 Hz, 1H), 7.46 (dd, J1 = 7.7 Hz, J2 = 7.6 Hz, 2H), 7.57 (dd,
J1 = 7.4 Hz, J2 = 7.3 Hz, 1H), 8.06 (d, J = 7.6 Hz, 2H). 13C NMR (CDCl3)
d 166.10, 147.10, 139.70, 139.07, 132.83, 130.80, 129.52, 128.38,
126.97, 121.91, 118.86, 82.49, 49.53, 45.31, 43.83, 38.61, 37.29,
32.08, 30.23, 29.64, 27.70, 25.98, 24.45, 16.73. IR (KBr) 2950,
2870, 1720, 1600, 1490, 1380, 1280, 1180, 1120, 1020, 980, 925,
1220, 1115, 1035, 970, 710 cmꢁ1
C19H22O9S: 426.0985; found: 426.0984.
. HRMS (EI) m/z calcd for
4.4.14. (3S,4S,5R)-Ethyl 3,5-dibenzoyloxy-4-(methylsulfonyl
oxy)cyclohex-1-ene carboxylate (19b)
820, 720, 540 cmꢁ1
. HRMS (EI) m/z calcd for C26H30O5S:
454.1814; found: 454.1819.
Mp 134–135 °C, ½a D20
ꢀ
¼ þ15:1 (c 1.5, EtOAc). 1H NMR (CDCl3) d
1.30 (t, J = 7.1 Hz, 3H), 2.61–2.71 (m, 1H), 2.90 (s, 3H), 2.61 (dd,
J1 = 5.9 Hz, J2 = 17.9 Hz, 1H), 4.24 (q, J = 7.1 Hz, 2H), 5.35 (dd,
J1 = 7.3 Hz, J2 = 9.7 Hz, 1H), 5.52–5.60 (m, 1H), 6.00 (dd,
J1 = 1.1 Hz, J2 = 7.1 Hz, 1H), 6.85 (t, J = 2.1 Hz, 1H), 7.42–7.49 (m,
4H), 7.59 (t, J = 7.4 Hz, 2H), 8.07 (d, J = 7.4 Hz, 2H), 8.12 (d,
J = 7.3 Hz, 2H). 13C NMR (CDCl3) d 166.19, 166.07, 165.44, 134.32,
134.17, 133.50, 130.99, 130.59, 130.56, 129.81, 129.51, 129.21,
129.16, 78.75, 71.80, 68.88, 62.10, 39.52, 30.24, 14.76. IR (KBr)
2985, 2925, 1725, 1600, 1460, 1365, 1250, 1180, 1100, 965,
715 cmꢁ1. HRMS (EI) m/z calcd for C24H24O9S: 488.1141; found:
488.1163.
4.4.20. ((2S,3S,4R,5R)-3,4-Diacetoxy-2-((2R,3R,4S,5S,6R)-3,4,5-
triacetoxy-6-acetoxymethyl-tetrahydro-2H-pyran-2-yloxy)-tet-
rahydrofuran-2,5-diyl) bis(methylene) dibenzoate (23)
½
a 2D0
ꢀ
¼ þ52:5 (c 0.5, acetone). 1H NMR (CDCl3) d 2.00 (s, 3H),
2.02 (s, 3H), 2.05 (s, 3H), 2.08 (s, 3H), 2.13 (s, 3H), 2.14 (s, 3H),
4.07 (dd, J1 = 4.5 Hz, J2 = 11.3 Hz, 1H), 4.13 (dd, J1 = 5.0 Hz,
J2 = 11.3 Hz, 1H), 4.36–4.42 (m, 2H), 4.47 (d, J = 12.1 Hz, 1H),
4.54–4.61 (m, 2H), 4.64 (dd, J1 = 6.3 Hz, J2 = 12.1 Hz, 1H), 5.16
(dd, J1 = 3.6 Hz, J2 = 10.9 Hz, 1H), 5.40 (dd, J1 = 3.2 Hz, J2 = 10.9 Hz,
1H), 5.46 (d, J = 2.3 Hz, 1H), 5.54 (t, J = 6.1 Hz, 1H), 5.64 (d,
J = 6.0 Hz, 1H), 5.82 (d, J = 3.6 Hz, 1H), 7.43–7.50 (m, 4H), 7.55–
7.62 (m, 2H), 8.04–8.10 (m, 4H). IR (KBr) 2980, 2940, 1750–1720,
1605, 1445, 1380, 1230, 1080, 720 cmꢁ1. HRMS(EI) m/z calcd for
C38H42O19: 802.2320; found: 802.2325.
4.4.15. Cholest-5-en-3a-yl acetate (20a)
Mp 86–87 °C (lit.49 mp 85.6 °C), ½a 2D0
¼ ꢁ12:0 (c 1.5, CHCl3)
ꢀ
{lit.50
½
a 2D2
ꢀ
¼ ꢁ11:4 (c 1.54, CHCl3)}. 1H NMR (CDCl3) d 0.68 (s,
3H), 0.86 (d, J = 6.6 Hz, 3H), 0.87 (d, J = 6.5 Hz, 3H), 0.91 (d,
J = 6.5 Hz, 3H), 0.92–1.19 (m, 13H), 1.21–1.63 (m, 12H), 1.80–
1.89 (m, 3H), 1.91–2.02 (m, 1H), 2.03 (s, 3H), 2.26–2.33 (m, 2H),
4.56–4.65 (m, 1H), 5.38 (d, J = 4.9 Hz, 1H). MS m/z 428 (M+), 386,
368, 353, 255, 213,,159, 145, 134, 105, 81. IR (KBr) 2945–2840,
1730, 1470, 1370, 1240, 1150, 1020, 950, 810, 735 cmꢁ1. Anal.
Calcd for C29H48O2: C, 81.25; H, 11.29. Found: C, 81.07; H, 11.29.
4.4.21. (2R,3R,5R)-2-(Acetoxymethyl)-5-(5-methyl-2,4-dioxo-
3,4-dihydro-pyrimidin-1(2H)-yl)-tetrahydrofuran-3-yl benzo-
ate (24a)
Mp 105–106 °C, ½a D20
ꢀ
¼ þ74:5 (c 1.5, acetone). 1H NMR (ace-
tone-d6)
d 1.79 (s, 3H), 1.96 (s, 3H), 2.40 (dd, J1 = 2.3 Hz,
J2 = 15.7 Hz, 1H), 2.97–3.05 (m, 1H), 4.50–4.54 (m, 3H), 5.75 (dd,
J1 = 1.2 Hz, J2 = 5.5 Hz, 1H), 6.29 (dd, J1 = 2.8 Hz, J2 = 8.0 Hz, 1H),
7.55 (t, J = 7.7 Hz, 2H), 7.68 (t, J = 7.4 Hz, 1H), 7.74 (d, J = 0.9 Hz,
1H), 8.05 (t, J = 7.4 Hz, 2H), 10.00 (s, 1H). 13C NMR (CDCl3) d
171.10, 165.75, 164.65, 151.18, 135.82, 134.54, 130.06, 129.45,
129.37, 111.40, 85.10, 81.15, 73.17, 62.32, 40.22, 21.25, 13.17. IR
(KBr) 3400, 3200, 3060, 2920, 1720, 1690, 1470, 1380, 1280,
1110, 1050, 720 cmꢁ1. HRMS (EI) m/z calcd for C19H20N2O7:
388.1271; found: 388.1275.
4.4.16. Cholest-5-en-3a-yl benzoate (20b)
Mp 103–104 °C (lit.51 mp 101–103 °C). ½a 2D0
¼ ꢁ18:9 (c 1.5,
ꢀ
CHCl3). 1H NMR (CDCl3) d 0.69 (s, 3H), 0.866 (d, J = 6.6 Hz, 3H),
0.869 (d, J = 6.7 Hz, 3H), 0.92 (d, J = 6.5 Hz, 3H), 0.98–1.37 (m,
16H), 1.41–1.65 (m, 7H), 1.69–2.06 (m, 6H), 2.47 (d, J = 7.8 Hz,
2H), 4.82–4.91 (m, 1H), 5.42 (d, J = 4.1 Hz, 1H), 7.43 (t, J = 7.8 Hz,
2H), 7.55 (t, J = 7.3 Hz, 1H), 8.05 (d, J = 7.3 Hz, 2H). IR (KBr) 2950–
2870, 1720, 1600, 1450, 1310, 1280, 1110, 1035, 810, 710 cmꢁ1
.
HRMS (EI) m/z calcd for C34H50O2: 490.3811; found: 490.3812.
4.4.22. (2R,3R,5R)-2-(Benzoyloxymethyl)-5-(5-methyl-2,4-dio-
xo-3,4-dihydro-pyrimidin-1(2H)-yl)-tetrahydrofuran-3-yl ben-
zoate (24b)
4.4.17. 5a-Cholestan-3a-yl acetate (21a)
Mp 95–96 °C (lit.52 mp 94–95 °C). ½a 2D0
ꢀ
¼ þ24:8 (c 1.6, CHCl3).
Mp 149–150 °C, ½a D20
ꢀ
¼ þ66:0 (c 1.3, acetone). 1H NMR (ace-
1H NMR (CDCl3) d 0.65 (s, 3H), 0.69–0.77 (m, 1H), 0.79 (s, 3H),
tone-d6)
d
1.75 (d, J = 0.8 Hz, 3H), 2.44 (dd, J1 = 2.9 Hz,

284
X.-X. Shi et al. / Tetrahedron: Asymmetry 21 (2010) 277–284
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135.03, 134.35, 130.45, 130.12, 129.94, 129.62, 129.42, 129.23,
112.38, 85.53, 83.27, 75.66, 64.98, 38.62, 12.78. IR (KBr) 3405,
3190, 3040, 2940, 1725, 1680, 1450, 1380, 1280, 1110, 720 cmꢁ1
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Acknowledgments
We are grateful to the National Natural Science Foundation of
China (No. 20972048) and the Shanghai Educational Development
Foundation (The Dawn Program: 03SG27) for the financial support
of this work.
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