Selective deprotection of silyl ethers with sodium periodate

Article abstract of DOI:10.1055/s-0028-1088062

Highly selective deprotection of silyl ethers by NaIO₄ in THF-H₂O (4:1) is reported. The mild neutral conditions enable efficient applications to complex, polyfunctional, and sensitive substrates. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-0028-1088062

1904
PAPER
Selective Deprotection of Silyl Ethers with Sodium Periodate
Selective
D
u
eprotection
n
of
S
ilyl
E
thers wit
L
h
N
aIO i,a Dirk Menche*b
4
a
Helmholtz-Zentrum für Infektionsforschung, Medizinische Chemie, Inhoffenstr. 7, 38124 Braunschweig, Germany
b
Department of Organic Chemistry, University of Heidelberg, INF 270, 69120 Heidelberg, Germany
Fax +49(6221)544205; E-mail: dirk.menche@oci.uni-heidelberg.de
Received 29 January 2009; revised 2 February 2009
may be used for the selective removal of one silyl group
in the presence of another and whether it may be applica-
ble also to complex and sensitive substrates has not been
addressed.
Abstract: Highly selective deprotection of silyl ethers by NaIO4 in
THF–H2O (4:1) is reported. The mild neutral conditions enable ef-
ficient applications to complex, polyfunctional, and sensitive sub-
strates.
Key words: synthetic methodology, selective deprotection, sodium
periodate, silyl ethers, natural products
Me
OTBS
NaIO4
Me
OH
HO
(6.0 equiv)
OH
O
Me
O
O
Me
THF–H2O (4:1)
25 °C, 2 h
As synthetic targets such as natural products and their an-
alogues have grown more complex, protection/deprotec-
tion methods have assumed prominent roles in synthetic
organic chemistry.1–3 In this respect, the transformation of
alcohols to the corresponding silyl ethers is a very com-
mon way to protect hydroxyl groups. Selective deprotec-
tion of one silyl ether without affecting other silyl ethers
in the same molecule plays an important role and can be a
crucial step in the total synthesis of natural products and
their analogues.4 Generally, silyl ethers may be deprotect-
ed under (1) acidic conditions,5 (2) basic/nucleophilic
conditions,5 and (3) oxidative conditions.6,7
DMPM
DMPM
93%
1a
2a
Scheme 1
We first studied the types of TBS ethers to be attacked by
NaIO4 in THF–H2O. As shown in Table 1, primary allylic
and nonallylic representatives 1b–h are readily cleaved,
while secondary congeners are not affected (entries 2, 6,
7). In all cases the alcohols were obtained in high yields.
These latter examples also demonstrate the usefulness of
this method to more elaborate substrates, such as 1c, 1g,
and 1h.
Selective deprotection of primary TBS ethers in the pres-
ence of secondary TBS ethers is a most widely used strat-
egy in the total synthesis of natural products. Reagents
used for this purpose include AcOH–THF–H2O,8 CSA,9
PPTS,10 TsOH,11 TFA,12 HCl,13 NH4F/MeOH–H2O,14
DDQ/CH2Cl2,7a quinolinium fluorochromate,15 Vilsmeier–
Haack reagent (POCl3–DMF),16 ceric ammonium nitrate
[CAN, (NH4)2Ce(NO3)6],17 CBr4 in alcohol solvents,18
and LiBr with 18-crown-6 in acetone.19 Herein, we report
the selective cleavage of silyl ethers with NaIO4 and the
use of this method to complex polyfunctional and sensi-
tive substrates.
We then investigated the cleavage of TBDPS and TES
ethers. As shown in Scheme 2, treatment of 3 with NaIO4
gave no conversion, indicating primary allylic TBDPS
ethers to be stable under these conditions.
NaIO4
I
OTBDPS
I
OH
THF–H2O (4:1)
25 °C, 72 h
3
4
Scheme 2
TES ethers, on the contrary, are readily removed. As
shown in Table 2, substrates include primary and second-
ary allyl ethers 5a–e (entries 1–5). The last two examples
demonstrate the utility of this mild method to sensitive
and polyfunctional substrates. Entry 5 shows that primary
TBDPS ethers are stable under these conditions, in agree-
ment with substrate 3 (see Scheme 2). In all cases, the re-
sulting alcohols 6a–e were obtained in high yields.
During a total synthesis campaign, we serendipitously re-
alized that oxidative cleavage of diol 1a with NaIO4 in
THF–H2O (4:1)20 was accompanied with concomitant
deprotection of the primary silyl ether to give 2a
(Scheme 1). The high yield, facile experimental proce-
dure, and mild reaction conditions attracted our attention
and prompted us to further evaluate this deprotection re-
agent. Previously, it has been reported that secondary TES
and TBS silyl ethers may be cleaved with NaIO4.7d How-
ever, the full scope and applicability of this method has
not been evaluated. In particular, the question, whether it
Finally, the true applicability of this procedure to complex
polyketide synthesis21 was demonstrated. As shown in
Scheme 3, the primary allylic TBS ether of polyfunctional
macrocyclic polyketide 7 was selectively removed with
NaIO4 giving the desired product 8 in high yield. Notably,
this yield was shown to be superior as compared to the re-
sults obtained with TBAF (72%) and NH4F (70%).
SYNTHESIS 2009, No. 11, pp 1904–1908
x
x.
x
x
.
2
0
0
9
Advanced online publication: 20.04.2009
DOI: 10.1055/s-0028-1088062; Art ID: Z01709SS
© Georg Thieme Verlag Stuttgart · New York

PAPER
Selective Deprotection of Silyl Ethers with NaIO4
1905
Table 1 Selective Deprotection of Primary TBS Ethers20,21
Entrya
1
Substrate
Product
Yield (%)
1b
2b
90
I
OTBS
Me
I
OH
Me
OTBS
OH
2
1c
2c
94
BzO
BzO
O
O
Me
O
O
Me
TBS
TBS
O
O
3
4
5
1d
1e
1f
2d
2e
2f
92
92
92
OTBS
OH
OTBS
OH
OH
O
OTBS
O
MeO
MeO
HO
OTBS
OTBS
6
7
1g
1h
2g
2h
90
85
TBSO
I
I
TBS
O
TBS
O
TBS
O
O
O
OPMB
OH
O
O
OPMB
a Reaction conditions: TBS ether (0.1 M), NaIO4 (6.0 equiv) in THF–H2O (4:1).
20,21
Table 2 Deprotection of TES Ethers with NaIO4
Entrya
Substrate
Product
Yield (%)
91
1
5a
6a
I
OTES
I
OH
2
3
5b
5c
6b
6c
92
92
OTES
OH
OTES
OH
EtO2C
Me
EtO2C
Me
Ph
O
OTES
Ph
O
O
OH
4
5
5d
5e
6d
6e
91
86
O
I
I
N
N
Bn
SO2Mes
Bn
SO2Mes
TBS
TBS
O
TBS
O
OR
O
O
OPMB
OR OH
O
OPMB
R = TBDPS
R = TBDPS
a Reaction conditions: TES ethers (0.1 M), NaIO4 (6.0 equiv) in THF–H2O (4:1).
In summary, we have elaborated NaIO4 in THF–H2O (4:1) tions to acid- and/or base-sensitive as well as complex
as an efficient method for the selective deprotection of si- substrates. Under these conditions, (1) primary and sec-
lyl ethers. The mild, neutral conditions enable applica- ondary TES ethers are deprotected, (2) primary TBS
Synthesis 2009, No. 11, 1904–1908 © Thieme Stuttgart · New York

1906
J. Li, D. Menche
PAPER
Selective Deprotection of Silyl Ethers with NaIO4; General Pro-
cedure
O
OTBS
To a solution of the silyl ether (0.1 M) in THF–H2O (4:1) was added
NaIO4 (6.0 equiv) as solid at r.t. After the completion of the reaction
(TLC control), H2O (10 mL) and CH2Cl2 (10 mL) were added
(workup procedure 1). The organic layer was separated and the
aqueous layer was extracted with CH2Cl2 (3 × 5 mL). The combined
organic phases were dried (MgSO4), filtered, and evaporated in vac-
uo. Alternatively, Et2O (10 mL) and MgSO4 (1 g) were added
(workup procedure 2). The mixture was stirred for 5 min. After fil-
tration, the organic phases were evaporated in vacuo. Silica gel
chromatography (hexanes–EtOAc, gradient elution, 9:1 to 2:1) af-
forded the product alcohols with the indicated yields.
O
O
O
OTBS
O
O
TBS TBS
7
OCH3
NaIO4
THF–H2O (4:1)
25 °C, 15 h
84%
O
OTBS
O
O
(E)-3-Iodo-2-methylprop-2-en-1-ol (2b/6a)
Rf = 0.2 (hexanes–EtOAc. 9:1).
1H NMR (400 MHz, CDCl3): d = 1.58 (m, 1 H), 1.83 (s, 3 H), 4.12
(d, J = 4.1 Hz, 2 H), 6.28 (s, 1 H).
O
OH
O
O
TBS TBS
13C NMR (100 MHz, CDCl3): d = 21.4, 67.2, 77.3, 147.2.
OCH3
8
Spectroscopic data were identical to those previously reported.22
Scheme 3
(2S,4R,5R,6E,8E)-5-(tert-Butyldimethylsilyloxy)-10-hydroxy-
4,7-dimethyl-3-oxodeca-6,8-dien-2-yl Benzoate (2c)
ethers are selectively removed in the presence of second-
ary TBS ethers, (3) TBDPS ethers are stable, (4) primary
TBS ethers are selectively deprotected in the presence of
primary TBDPS ethers, and (5) secondary TES ethers
may be selectively cleaved in the presence of secondary
TBS or TBDPS ethers. It is expected that this method will
be useful in devising successful protective group strate-
gies in the synthesis of complex targets.
Rf = 0.2 (hexanes–EtOAc, 4:1); [a]D20 +12.2 (c 0.32, CHCl3).
1H NMR (400 MHz, CDCl3): d = –0.06 (s, 3 H), –0.04 (s, 3 H), 0.80
(s, 9 H), 0.99 (d, J = 7.1 Hz, 3 H), 1.41 (t, J = 4.8 Hz, 1 H) 1.52 (d,
J = 7.1 Hz, 3 H), 1.79 (s, 3 H), 2.90 (m, 1 H), 4.21 (t, J = 5.1 Hz, 2
H), 4.73 (t, J = 9.4 Hz, 1 H), 5.31 (d, J = 9.2 Hz, 1 H), 5.40 (q,
J = 7.0 Hz, 1 H), 5.81 (dt, J = 15.8, 5.8 Hz, 1 H), 6.24 (d, J = 15.8
Hz, 1 H), 7.44 (tm, J = 7.6 Hz, 2 H), 7.56 (tm, J = 7.4 Hz, 1 H), 8.07
(dm, J = 7.1 Hz, 2 H).
13C NMR (100 MHz, CDCl3): d = –4.9, –4.4, 13.5, 13.9, 15.2, 18.0,
25.8, 49.5, 63.7, 71.5, 75.4, 127.9, 128.4 (2C), 129.8, 133.2, 133.6,
134.4, 135.4, 165.8, 209.2.
HRMS (ESI): m/z [M + Na]+ calcd for C25H38O5Si + Na: 469.2386;
found: 469.2386.
NMR spectra were recorded in CDCl3 on Bruker AM 300, AM 400
and DMX-600 spectrometers. Chemical shifts are reported in parts
per million (ppm, d) with the residual nondeuterated solvent as an
internal standard. TLC analyses were performed on precoated silica
gel 60 F254 (Merck) analytical plates and visualized by fluorescence
quenching under UV light. Mass spectra were obtained on a Finni-
gan MAT 95 spectrometer, high-resolution data were acquired us-
ing peak matching (M/DM = 10000).
4-Hydroxybutan-2-one (2d)
Rf = 0.12 (hexanes–EtOAc, 1:1).
1H NMR (400 MHz, CDCl3): d = 2.18 (s, 3 H), 2.69 (t, J = 5.3 Hz,
2 H), 3.83 (t, J = 5.3 Hz, H).
13C NMR (100 MHz, CDCl3): d = 30.5, 45.3, 57.8, 209.5.
(3R,4R,5E,7E)-4-(3,4-Dimethoxybenzyloxy)-9-hydroxy-3,6-
dimethylnona-5,7-dien-2-one (2a)
To a solution of diol 1a (11.7 mg, 23.0 mmol, 1.0 equiv) in THF–
H2O (200 mL:50 mL) was added NaIO4 (29.5 mg, 138 mmol, 6.0
equiv) at 25 °C. After stirring for 6.5 h, the reaction was quenched
with H2O (4 mL). The organic layer was separated and the aqueous
layer was extracted with CH2Cl2 (3 × 6 mL). The combined organ-
ics were dried (MgSO4), filtered and evaporated in vacuo. Silica gel
chromatography (hexanes–EtOAc, 2:1) afforded the methyl ketone
2a (7.5 mg, 21.5 mmol, 93%) as a colorless oil; Rf = 0.1 (hexanes–
EtOAc, 2:1); [a]D20 –20.4 (c 0.37, CHCl3).
1H NMR (400 MHz, CDCl3): d = 0.90 (d, J = 7.1 Hz, 3 H), 1.41 (t,
J = 5.9 Hz, 1 H), 1.79 (d, J = 1.5 Hz, 3 H), 2.19 (s, 3 H), 2.75 (m, 1
H), 3.85 (s, 3 H), 3.87 (s, 3 H), 4.19 (d, J = 11.2 Hz, 1 H), 4.25 (t,
J = 5.1 Hz, 2 H), 4,33 (t, J = 9.7 Hz, 1 H), 4.40 (d, J = 11.7 Hz, 1
H), 5.32 (d, J = 9.7 Hz, 1 H), 5.87 (dt, J = 15.8, 5.8 Hz, 1 H), 6.33
(d, J = 15.8 Hz, 1 H), 6.75 (m, 3 H).
Spectroscopic data were identical to those previously reported.23
4-Phenylbutan-1-ol (2e/6b)
Rf = 0.1 (hexanes–EtOAc, 9:1).
1H NMR (400 MHz, CDCl3): d = 1.33 (s, 1 H), 1.60 (m, 2 H), 1.69
(m, 2 H), 2.65 (t, J = 7.6 Hz, 2 H), 3.65 (t, J = 6.4 Hz, 2 H), 7.17
(m, 3 H), 7.27 (m, 2 H).
13C NMR (100 MHz, CDCl3): d = 27.5, 32.3, 35.6, 62.8, 125.8,
128.3, 128.4, 142.3.
Spectroscopic data were identical to those previously reported.24
(E)-Methyl 5-Hydroxy-3-methylpent-2-enoate (2f)
Rf = 0.3 (hexanes–EtOAc, 2:1).
1H NMR (300 MHz, CDCl3): d = 2.19 (d, J = 1.3 Hz, 3 H), 2.40 (dt,
J = 6.4, 1.0 Hz, 2 H), 3.68 (s, 3 H), 3.78 (t, J = 6.3 Hz, 2 H), 5.74
(m, 1 H).
13C NMR (75 MHz, CDCl3): d = 18.8, 43.7, 50.9, 60.2, 117.3,
156.3, 166.9.
13C NMR (100 MHz, CDCl3): d = 13.1, 13.5, 30.8, 51.4, 55.8, 55.9,
63.6, 70.3, 110.8, 111.2, 120.2, 128.3, 130.7, 135.2, 138.1, 148.5,
148.9, 211.8.
HRMS (ESI): m/z [M + Na]+ calcd for C20H28O5 + Na: 371.1834;
found: 371.1838.
Spectroscopic data were identical to those previously reported.25
Synthesis 2009, No. 11, 1904–1908 © Thieme Stuttgart · New York

PAPER
Selective Deprotection of Silyl Ethers with NaIO4
1907
(2S,3S,E)-3-(tert-Butyldimethylsilyloxy)-5-iodo-2,4-dimethyl-
pent-4-en-1-ol (2g)
(d, J = 8.6 Hz, 2 H), 7.22 (d, J = 8.1 Hz, 2 H), 7.39 (m, 6 H), 7.67
(m, 4 H).
13C NMR (100 MHz, CDCl3): d = –4.8, –4.5, 10.9, 14.2, 15.2, 18.0,
19.2, 25.9, 26.9, 32.7, 37.2, 48.9, 51.9, 55.3, 65.7, 66.3, 69.9, 72.6,
113.8, 127.7, 129.3, 129.7, 130.7, 133.4, 135.6, 135.7, 159.1, 217.5.
Rf = 0.2 (hexanes–EtOAc, 9:1); [a]D20 –30.2 (c 1.00, CHCl3).
1H NMR (300 MHz, CDCl3): d = –0.01 (s, 3 H), 0.07 (s, 3 H), 0.79
(d, J = 7.0 Hz, 3 H), 0.88 (s, 9 H), 1.77 (s, 3 H), 1.84 (m, 1 H), 2.45
(t, J = 5.6 Hz, 1 H), 3.61 (t, J = 5.2 Hz, 2 H), 4.01 (d, J = 7.9 Hz, 1
H), 6.19 (s, 1 H).
Spectroscopic data were identical to those previously reported.27
13C NMR (75 MHz, CDCl3): d = –5.3, –4.7, 14.0, 18.1, 19.5, 25.8,
(1R,2S,3R,7R,11S,13Z,15E,18S,19R,23S)-7-[(2S,3S, 4R,5E,7E)-
2,4-Bis(tert-butyldimethylsilyloxy)-9-hydroxy-3,6-dimethyl-
nona-5,7-dienyl]-3-(tert-butyldimethylsilyloxy)-11-methoxy-
2,18,21,21,23-pentamethyl-6,20,22-trioxabicyclo[17.3.1]tricosa-
13,15-dien-5-one (8)
38.8, 66.2, 79.3, 82.8, 148.9.
HRMS (ESI): m/z [M + Na]+ calcd for C13H27IO2Si + Na: 393.0723;
found: 393.0728.
Rf = 0.1 (hexanes–EtOAc, 9:1); [a]D20 +12.3 (c 0.85, CHCl3).
(S)-2-{(4R,5S,6R)-6-[(2S,3R)-3-(tert-Butyldimethylsilyloxy)-5-
(4-methoxybenzyloxy)pentan-2-yl]-2,2,5-trimethyl-1,3-dioxan-
4-yl}propan-1-ol (2h)
1H NMR (600 MHz, CDCl3): d = –0.05 (s, 3 H), –0.02 (s, 6 H), 0.02
(s, 3 H), 0.04 (s, 3 H), 0.05 (s, 3 H), 0.69 (d, J = 7.1 Hz, 3 H), 0.85
(s, 9 H), 0.87 (d, J = 6.0 Hz, 3 H), 0.88 (s, 9 H), 0.89 (s, 9 H), 0.90
(d, J = 6.8 Hz, 3 H), 0.99 (d, J = 6.8 Hz, 3 H), 1.35 (s, 3 H), 1.37 (s,
3 H), 1.45–1.57 (m, 6 H), 1.63 (m, 1 H), 1.74–1.83 (m, 5 H), 1.77
(s, 3 H), 2.09 (m, 1 H), 2.18 (m, 3 H), 2.33 (m, 1 H), 2.50 (m, 1 H),
3.31–3.46 (m, 3 H), 3.35 (s, 3 H), 4.17–4.23 (m, 3 H), 4.21 (d,
J = 6.0 Hz, 2 H), 4.80 (m, 1 H), 5.34 (d, J = 8.7 Hz, 1 H), 5.46 (m,
1 H), 5.66 (m, 1 H), 5.79 (dt, J = 15.8, 5.8 Hz, 1 H), 6.00 (t, J = 10.7
Hz, 1 H), 6.25 (d, J = 15.1 Hz, 1 H), 6.43 (dd, J = 14.3, 11.7 Hz, 1
H).
13C NMR (75 MHz, CDCl3): d = –4.9, –4.8, –4.4, –4.3, –4.0, –3.7,
6.0, 9.2, 13.4, 18.0, 18.8, 19.6, 21.0, 25.9, 26.0, 30.1, 31.0, 32.0,
32.3, 33.4, 33.8, 35.0, 40.6, 46.3, 57.1, 63.7, 63.8, 67.7, 71.3, 72.2,
78.8, 80.0, 99.0, 126.0, 126.4, 127.3, 129.9, 132.6, 135.8, 135.9,
172.5.
Rf = 0.5 (hexanes–EtOAc, 4:1); [a] D20 +9.8 (c 1.40, CHCl3).
1H NMR (300 MHz, CDCl3): d = 0.04 (s, 3 H), 0.06 (s, 3 H), 0.87
(s, 9 H), 0.89 (d, J = 6.6 Hz, 3 H), 0.91 (d, J = 6.6 Hz, 3 H), 0.96 (d,
J = 6.6 Hz, 3 H), 1.10 (m, 1 H), 1.35 (s, 3 H), 1.38 (s, 3 H), 1.49–
1.67 (m, 4 H), 1.80 (m, 1 H), 3.28 (m, 2 H), 3.43 (dd, J = 9.7, 1.8
Hz, 1 H), 3.52 (m, 3 H), 3.80 (s, 3 H), 3.93 (m, 1 H), 4.37 (s, 2 H),
6.88 (m, 2 H), 7.24 (m, 2 H).
13C NMR (75 MHz, CDCl3): d = –4.7, –4.0, 5.8, 9.9, 14.1, 18.1,
19.6, 25.9, 30.1, 30.6, 32.0, 36.5, 40.1, 55.4, 63.9, 67.3, 67.4, 72.8,
75.9, 99.2, 113.8, 129.4, 130.8, 159.3.
HRMS (ESI): m/z [M + Na]+ calcd for C29H52O6Si + Na: 547.3431;
found: 547.3433.
(E)-Ethyl 4-Hydroxy-3-methylhexa-2,5-dienoate (6c)
Rf = 0.3 (hexanes–EtOAc, 6:1).
1H NMR (400 MHz, CDCl3): d = 1.26 (t, J = 7.1 Hz, 3 H), 1.99 (d,
J = 4.1 Hz, 1 H), 2.08 (s, 3 H), 4.15 (q, J = 7.1 Hz, 2 H), 4.55 (m, 1
H), 5.23 (dm, J = 10.2 Hz, 1 H), 5.34 (dm, J = 17.3 Hz, 1 H), 5.79
(m, 1 H), 6.00 (s, 1 H).
HRMS (ESI): m/z [M + Na]+ calcd for C55H104O9Si3 + Na:
1015.6886; found: 1015.6880.
Acknowledgment
Generous financial support by the Fonds der Chemischen Industrie
(‘Liebig-Stipendium’ to D.M.), the Deutsche Forschungsgemein-
schaft, Volkswagenstiftung, and the HZI is most gratefully acknow-
ledged. We thank Antje Ritter and Tatjana Arnold for technical
support.
13C NMR (100 MHz, CDCl3): d = 14.3, 15.1, 59.9, 77.6, 115.4,
117.4, 137.6, 157.8, 166.9.
(2R,3S,E)-[(1R,2S)-2-(N-Benzyl-2,4,6-trimethylphenylsulfon-
amido)-1-phenylpropyl]-3-hydroxy-5-iodo-2,4-dimethylpent-4-
enoate (6d)
Rf = 0.4 (hexanes–EtOAc, 8:1).
References
1H NMR (300 MHz, CDCl3): d = 0.95 (d, J = 7.2 Hz, 3 H), 1.17 (d,
J = 7.0 Hz, 3 H), 1.81 (d, J = 1.1 Hz, 3 H), 2.27 (s, 3 H), 2.50 (s, 6
H), 2.54–2.65 (m, 1 H), 2.77 (d, J = 3.8 Hz, 1 H, OH), 4.10 (dq,
J = 4.1, 7.0 Hz, 1 H), 4.24 (dd, J = 3.4 Hz, 1 H), 4.56 (A of ABq,
(1) Jarowicki, K.; Kocienski, P. J. Chem. Soc., Perkin Trans. 1
2000, 2495.
(2) Green, T. W.; Wuts, P. G. M. Protective Groups in Organic
Synthesis, 3rd ed.; Wiley: New York, 1999.
JA,B = 16.6 Hz, 1 H), 4.74 (B of ABq, JA,B = 16.6 Hz, 1 H), 5.85 (d,
(3) Kocienski, P. Protecting Groups; Thieme: Stuttgart, 1994.
(4) Nelson, T. D.; Crouch, R. D. Synthesis 1996, 1031.
(5) Crouch, R. D. Tetrahedron 2004, 60, 5833.
(6) For a review, see: Muzart, J. Synthesis 1993, 11.
(7) (a) Tanemura, K.; Suzuki, T.; Horaguchi, T. J. Chem. Soc.,
Perkin Trans. 1 1992, 2997. (b) Vaino, A. R.; Szarek, W. A.
Chem. Commun. 1996, 2351. (c)Paterson, I.; Cowden, C. J.;
Rahn, V. S. Synlett 1998, 915. (d) Wang, M.; Li, C.; Yin,
D.; Liang, X.-T. Tetrahedron Lett. 2002, 43, 8727.
(e) Karimi, B.; Rajabi, J. Org. Lett. 2004, 6, 2841.
(f) Iranpoor, N.; Firouzabadi, H.; Pourali, A. R. Synth.
Commun. 2005, 35, 1527. (g) Raghuvanshi, R. S.; Singh, K.
N. Synth. Commun. 2007, 37, 1371.
J = 4.1 Hz, 1 H), 6.29 (s, 1 H), 6.82–6.85 (m, 2 H), 6.87 (s, 2 H),
7.13–7.35 (m, 8 H).
13C NMR (75 MHz, CDCl3): d = 13.4, 14.1, 18.9, 20.9, 23.0, 43.3,
48.3, 56.8, 78.6, 78.7, 81.2, 125.9, 127.2, 127.6, 128.0, 128.4 128.5,
132.2, 133.4, 138.1, 138.6, 140.3, 142.6, 146.9, 174.1.
Spectroscopic data were identical to those previously reported.26
(5R,6R,8S,9S,10S)-9-Hydroxy-5-(2-(4-methoxybenzyloxy)eth-
yl)-2,2,3,3,6,8,10,14,14-nonamethyl-13,13-diphenyl-4,12-dioxa-
3,13-disilapentadecan-7-one (6e)
Rf = 0.3 (hexanes–EtOAc, 9:1).
1H NMR (400 MHz, CDCl3): d = 0.08 (s, 3 H), 0.02 (s, 3 H), 0.84
(s, 9 H), 0.98 (d, J = 7.1 Hz, 3 H), 1.04 (s, 9 H), 1.04 (d, J = 7.0 Hz,
3 H), 1.05 (d, J = 6.8 Hz, 3 H), 1.70 (m, 2 H), 1.84 (m, 1 H), 2.96
(m, 2 H), 3.31 (d, J = 6.1 Hz, 1 H, OH), 3.50 (m, 2 H), 3.59 (m, 1
H), 3.71 (m, 2 H), 3.77 (s, 3 H), 4.17 (m, 1 H), 4.39 (s, 2 H), 6.83
(8) Ali, S. M.; Georg, G. I. Tetrahedron Lett. 1997, 38, 1703.
(9) Mori, Y.; Yaegashi, K.; Furukawa, H. J. Am. Chem. Soc.
1997, 119, 4557.
(10) Shimano, K.; Ge, Y.; Sakaguchi, K.; Isoe, S. Tetrahedron
Lett. 1996, 37, 2253.
Synthesis 2009, No. 11, 1904–1908 © Thieme Stuttgart · New York

1908
J. Li, D. Menche
PAPER
(11) Shahid, K. A.; Mursheda, J.; Okazaki, M.; Shuto, Y.; Goto,
F.; Kiyooka, S. Tetrahedron Lett. 2002, 43, 6377.
(12) Ichikawa, S.; Shuto, S.; Minakawa, N.; Matsuda, A. J. Org.
Chem. 1997, 62, 1368.
Pradaux, F.; Bouzbouz, S.; Reymond, S.; Capdevielle, P.;
Cossy, J. J. Org. Chem. 2008, 73, 1864. (c) Smith, A. B. III;
Razler, T. M.; Meis, R. M.; Pettit, G. R. J. Org. Chem. 2008,
73, 1201.
(13) Pilli, R. A.; Victor, M. M. Tetrahedron Lett. 1998, 39, 4421.
(14) Trauner, D.; Schwarz, J. B.; Danishefsky, S. J. Angew.
Chem. Int. Ed. 1999, 38, 3542.
(15) Chandrasekhar, S.; Mohanty, P. K.; Takhi, M. J. Org. Chem.
1997, 62, 2628.
(21) Menche, D.; Arikan, F.; Perlova, O.; Horstmann, N.;
Ahlbrecht, W.; Wenzel, S. C.; Jansen, R.; Irschik, H.;
Müller, R. J. Am. Chem. Soc. 2008, 129, 14234.
(22) Baker, R.; Castro, J. L. J. Chem. Soc., Perkin Trans. 1 1990,
47.
(16) Koeller, S.; Lellouche, J.-P. Tetrahedron Lett. 1999, 40,
7043.
(23) Gogoi, P.; Sarmah, G. K.; Konwar, D. J. Org. Chem. 2004,
69, 5153.
(17) Hwu, J. R.; Jain, M. L.; Tsai, F.-Y.; Tsay, S.-C.; Balakumar,
A.; Hakimelahi, G. H. J. Org. Chem. 2000, 65, 5077.
(18) Chen, M.-Y.; Lu, K.-C.; Lee, A. S.-Y.; Lin, C.-C.
Tetrahedron Lett. 2002, 43, 2777.
(24) Yasuda, M.; Onishi, Y.; Ueba, M.; Miyai, T.; Baba, A.
J. Org. Chem. 2001, 66, 7741.
(25) White, J. D.; Carter, J. P.; Kezar, H. S. III J. Org. Chem.
1982, 47, 929.
(19) Tandon, N.; Begley, T. P. Synth. Commun. 1997, 27, 2953.
(20) For recent examples, see: (a) Clark, J. S.; Baxter, C. A.;
Dossetter, A. G.; Poigny, S.; Castro, J. L.; Whittingham, W.
G. J. Org. Chem. 2008, 73, 1040. (b) Ferrie, L.; Boulard, L.;
(26) Menche, D.; Hassfeld, J.; Li, J.; Rudolph, S. J. Am. Chem.
Soc. 2007, 129, 6100.
(27) Arikan, F.; Li, J.; Menche, D. Org. Lett. 2008, 10, 3521.
Synthesis 2009, No. 11, 1904–1908 © Thieme Stuttgart · New York