-
醚、氨基及氨基酸的各种保护基及去保护方法大全
（整理有详细操作）
[
Acetate
]
[
Benzoatel
]
[
Pivaloate
]
[
Levulinate
]
[
Back to Carb.
Synthesis
]
Ac
- (acetate)
ester
Standard
Protection Procedure
To a
solution of the glycoside in dry pyridine (25 eq)
under an inert
atmosphere at room
temperature, acetic anhydride (10 eq) is added and
stirred until complete by TLC (usually
16 h).
The reaction mixture is then
poured into ice/water and extracted
three times with chloroform.
The
combined organic layers are extracted
with 3% HCl, saturated aqueous
sodium
bicarbonate, and water.
The organic
layer is then dried and
concentrated
in vacuo
.
The
resulting residue is purified by flash
chromatography
(SiO
2
) if
necessary.
Removal
The
glycoside is dissolved in methanol and a solution
of sodium methoxide
in methanol (0.1 eq
per -OAc) is added drop wise at 0°.
The solution is
warmed to
room temperature and stirred under an inert
atmosphere until
complete by TLC
(usually within a few hours).
Amberlite cationic exchange
resin is then added with vigorous
stirring until the pH of the mixture is
neutral.
The mixture is
then filtered and concentrated.
The
resulting
residue is purified by flash
chromatography (SiO
2
) if
necessary.
OR
The Glycoside is dissolved in methanol
and hydrazine hydrate (15 eq per
-OAc)
is added in two portions over 1.5 hours.
The solution is stirred at
room temperature under an inert
atmosphere until complete by TLC
(usually 6 hours).
The
solution is then neutralized with glacial acetic
acid.
The mixture is
filtered through celite and concentrated.
The
resulting residue is
purified by flash chromatography
(SiO
2
) if
necessary.
References
J. Org. Chem.,
1996
,
61
, 6442-6445.
J. Chem. Soc., Perkin Trans. 1,
1996
, 985-993.
Bz -
(benzoate) ester
Standard Protection
Procedure
To a solution of
the glycoside dissolved in dry pyridine (0.3M),
benzoyl
chloride (4 eq per -OH) is
added at room temperature under an inert
atmosphere and stirred until complete
by TLC (usually 16 h).
Methanol is
added and the solution was concentrated
in vacuo
.
The
residue was
dissolved in DCM and washed
with water, saturated copper sulfate, and
brine.
The organic layer is
dried and concentrated
in
vacuo
.
The
resulting residue is purified by flash
chromatography (SiO
2
) if
necessary.
Removal
The
glycoside is dissolved in MeOH and a solution of
NaOH (2.5 eq per -OH)
in MeOH is added
slowly.
The mixture is stirred at room
temperature
under an inert atmosphere
till complete by TLC (usually 1 h) and then
concentrated
in
vacuo
.
The residue is
dissolved in ethyl acetate and the
organic solution is washed twice with
water, dried (sodium sulfate), and
concentrated
in
vacuo
.
The resulting
residue is purified by flash
chromatography
(SiO
2
) if
necessary.
References
Tetrahedron,
1970
,
26
, 803-812.
Carb. Res.,
1993
,
244
, 237-246.
Piv
- (pivaloate) ester
Standard Procedure
The glycoside is dissolved in
pyridine:DCM 2:1 and cooled to -20°.
PivCl
(1.2 eq per -OH) is
then added drop wise under an inert atmosphere and
the result is stirred at 0° until
complete by TLC (usually 8 h).
The
mixture
is then diluted with DCM and
extracted with 5% HCl twice and once with
water.
The organic layer is
then dried (sodium sulfate) and concentrated
in vacuo
.
The
resulting residue is purified by flash
chromatography (SiO
2
)
if necessary.
Removal
The
glycoside is dissolved in MeOH, and a solution of
sodium methoxide in
methanol (10 eq per
-OH) is added drop wise at room temperature under
an
inert atmosphere and stirred until
the reaction is complete by TLC (usually
24 h).
Aqueous HCl (10%) is
added to the solution until neutral and the
resulting mixture is concentrated
in vacuo
.
The
residue is purified by
flash
chromatography (SiO
2
) if
necessary.
References
Tet. Asym.
2000
,
295-303.
J.
Am. Chem. Soc.
1990
,
112
, 3693-3695.
Lev
- (levulinate) ester
Standard Protection
Procedure
To a solution of
the glycoside in dry pyridine at room temperature
under an
inert atmosphere, levulinic
anhydride (2 eq) is added drop wise.
The
reaction was stirred
until complete by TLC (usually 24 h) and ice water
is
added.
The mixture is
extracted with chloroform and then the organic
layer is back extracted with brine,
dried (sodium sulfate), and
concentrated
in
vacuo
.
The resulting
residue is purified by flash
chromatography
(SiO
2
) if
necessary.
Removal
The
glycoside is dissolved in pyridine and hydrazine
hydrate (1M in
pyridine:acetic acid
3:2) is added at room temperature under an inert
atmosphere.
After addition
of hydrazine is sufficient to consume
starting material completely by TLC
(usually a few minutes),
pentane-2,4-dione is added with cooling
to quench the reaction.
The
mixture is diluted with chloroform and
extracted once with water and once
with
brine.
The organic layer is dried
(sodium sulfate) and concentrated
in
vacuo
.
The residue is
purified by flash chromatography
(SiO
2
) if
necessary.
References
JACS,
1975
,
97
, 1614-1615.
Tet. Lett.,
1976
,
52
, 4875-4878.
[
Benzyl
]
[
Trityl
]
[
PMP
]
[
Allyl
]
[
pMB
] [
Back to
Carb. Synthesis
]
Bn
- (benzyl)
ether
Standard
Protection Procedure
To a
solution of sodium hydride (1.3 eq per -OH) in
DMF, the glycoside
(dissolved in DMF)
is added drop wise at 0° under an inert
atmosphere.
The mixture is
stirred for 30 minutes at 0° and benzyl
bromide (1.3 eq per -OH) is added drop
wise.
*Note - a catalytic amount
of TBAI or crown ether can be added.
The reaction is stirred at room
temperature until complete by TLC
(usually 16 h) and methanol is added
slowly to quench the reaction.
The solution is then diluted with
chloroform and water, extracted 3 times
with water and once with
brine.
The organic layer is dried (sodium
sulfate) and concentrated
in
vacuo
.
The
resulting residue is purified by flash
chromatography (SiO
2
) if
necessary.
OR
To a solution
of the glycoside in DCM, benzyl
trichloroacetimidate (2 eq
per -OH) is
added drop wise (as a solution in cyclohexane -
see third
reference) with TfOH
(catalytic - >1mol%).
The result is
stirred at room
temperature under inert
atmosphere until complete by TLC (usually
overnight).
Saturated
aqueous sodium bicarbonate is added and the
mixture is diluted with DCM.
The organic layer is extracted once
with
water, once with brine, dried
(sodium sulfate), and concentrated
in
vacuo
.
The
resulting residue is purified by flash
chromatography (SiO
2
) if
necessary.
Removal
The
glycoside is dissolved in 1:1 MeOH:tBuOH and
palladium hydroxide (0.1
eq) is added
at room temperature.
A hydrogen
atmosphere is added
(balloon pressure)
and the reaction is stirred until complete by TLC
(usually 16 h).
The mixture
is then filtered and concentrated.
*Note -
catalytic glacial
acidic acid may be added if the reaction isn't
complete.
The resulting
residue is purified by flash chromatography
(SiO
2
) if
necessary.
References
J. Org. Chem.,
1979
,
44
, 3442.
J. Am. Chem. Soc.,
1971
,
93
, 1746.
Tr
-
(triphenyl methyl) or trityl ether
Standard Protection
Procedure
To a solution of
the glycoside, trityl chloride (1.1 eq for primary
over
secondary, 1.5 eq for each -OH
otherwise), and triethylamine (1.5 eq for
primary over secondary, 2 eq for each
-OH otherwise) stirring in DMF
under an
inert atmosphere at room temperature, DMAP (0.05
eq) is
added.
The reaction
is stirred until complete by TLC (usually
overnight)
and then poured into ice-
water.
The mixture is extracted with
chloroform and the organic layer is
washed with saturated aqueous
ammonium
chloride and water, dried (sodium sulfate), and
concentrated
in
vacuo
.
The
resulting residue is purified by flash
chromatography (SiO
2
) if
necessary.
Removal
The
glycoside is dissolved in ethanol and 5% palladium
on charcoal is added
under a hydrogen
atmosphere.
The reaction is stirred
until complete by
TLC (usually
overnight) and filtered.
The solution
is concentrated and the
residue is
purified by flash chromatography
(SiO
2
) if
necessary.
References
Tet. Lett.,
1979
,
2
, 95-98.
JOC,
1978
,
18
, 2877-2881.
pMB
- (
para
-methoxy benzyl)
ether
Standard
Protection Procedure
To a
solution of sodium hydride (1.3 eq per -OH) in
DMF, the glycoside
(dissolved in DMF)
is added drop wise at 0° under an inert
atmosphere.
The mixture is
stirred for 30 minutes at 0° and
para
-methoxybenzyl bromide
(1.3 eq per -OH) is added drop wise.
*Note -
a catalytic amount
of TBAI or crown ether can be added.
The reaction is
stirred at
room temperature until complete by TLC (usually 16
h) and
methanol is added slowly to
quench the reaction.
The solution is
then
diluted with chloroform and water,
extracted 3 times with water and once
with brine.
The organic
layer is dried (sodium sulfate) and concentrated
in vacuo
.
The
resulting residue is purified by flash
chromatography (SiO
2
)
if necessary.
Removal
The
glycoside is dissolved in
DCM/H
2
O 20:1 and DDQ (up to
10 eq) is added
at room temperature
under an inert atmosphere.
The
reaction is stirred
until complete by
TLC (usually 24 h, may require heat) and diluted
with
DCM.
The solution is
extracted with saturated aqueous sodium
bicarbonate, dried (sodium sulfate),
and concentrated
in vacuo
.
Product
can then be purified
by column chromatography if necessary.
The
resulting residue is
purified by flash chromatography
(SiO
2
) if
necessary.
References
JACS,
1992
,
114
, 2524-2536.
JACS,
1996
,
118
, 9265-9270.
Allyl
- (allyl)
ether
Standard
Protection Procedure
To a
solution of sodium hydride (1.3 eq per -OH) in
DMF, the glycoside
(dissolved in DMF)
is added drop wise at 0° under an inert
atmosphere.
The mixture is
stirred for 30 minutes at 0° and ally bromide
(1.3 eq per -OH) is added drop wise.
*Note - a catalytic amount of TBAI
or crown ether can be added.
The reaction is stirred at room
temperature until complete by TLC
(usually 16 h) and methanol is added
slowly to quench the reaction.
The solution is then diluted with
chloroform and water, extracted 3 times
with water and once with
brine.
The organic layer is dried (sodium
sulfate) and concentrated
in
vacuo
.
The
resulting residue is purified by flash
chromatography (SiO
2
) if
necessary.
OR
To a solution
of the glycoside in DCM, benzyl
trichloroacetimidate (2 eq
per -OH) is
added drop wise (as a solution in cyclohexane -
see third
reference) with TfOH
(catalytic - >1mol%).
The result is
stirred at room
temperature under inert
atmosphere until complete by TLC (usually
overnight).
Saturated
aqueous sodium bicarbonate is added and the
mixture is diluted with DCM.
The organic layer is extracted once
with
water, once with brine, dried
(sodium sulfate), and concentrated
in
vacuo
.
The
resulting residue is purified by flash
chromatography (SiO
2
) if
necessary.
Removal
The
glycoside is dissolved in AcOH:water 20:1 and
Palladium chloride (1.5
eq) followed by
sodium acetate (5 eq) is added.
The
mixture is stirred
under an inert
atmosphere at room temperature until complete by
TLC
(usually overnight).
Ethyl acetate is added and the mixture
is extracted 2
times with saturated
aqueous sodium bicarbonate.
The
organic layer is
then extracted once
with brine, dried (sodium sulfate), and
concentrated
in vacuo
.
The resulting residue is purified by
flash chromatography (SiO
2
)
if necessary.
References
Tet. Lett.,
1997
,
40
,
13,509-13,556.
JOC,
1973
,
18
, 3224.
J. Chem. Soc. Perkin
Trans. I,
1985
,
2247-2250.
JACS,
1991
,
113
, 2092-2112.
PMP
-
(
p-
methoxyphenyl)
ether
Standard Protection
Procedure
To a solution of
the glycoside in THF under an inert atmosphere is
added
triphenylphosphine (1.3 eq),
diethylazocarboxylate (1.3 eq), and
p
-methoxyphenol (3 eq).
The resulting solution is heated to 80°
and
stirred until complete by TLC
(usually 2 h).
The mixture is
concentrated
in vacuo
and
purified by flash chromatography
(SiO
2
).
Removal
The
glycoside is dissolved in acetonitrile:water 4:1
at room temperature
under an inert
atmosphere and CAN (5 eq) is added.
The mixture is
stirred until
complete by TLC (usually less than 1 h) and
diluted with
chloroform.
The resulting solution is washed with
water and saturated
sodium chloride
solution.
The organic layer is dried
(sodium sulfate) and
concentrated
in vacuo
.
The
residue can then be purified by flash
chromatography
(SiO
2
) if
necessary.
References
Tet. Lett.,
1988
,
29
, 1389-1390.
Heterocycles,
1990
,
31
, 1555-1563.
[
TMS
]
[
TES
]
[
TIPS
]
[
TBS
]
[
TBDPS
] [
Back to
Carb. Synthesis
]
TMS
- (trimethyl silyl)
ether
Standard
Protection Procedure
To a
solution of the glycoside and triethylamine (2 eq)
stirring in THF at 0°
under an inert
atmosphere, is added drop wise TMS-Cl (1.5 eq).
The result
was allowed to
warm to room temperature and stirred until
complete by
TLC (usually 6 h).
The solution is then concentrated
in vacuo
and the
residue taken on directly to next
step.
Removal
The glycoside is dissolved in THF (~2M)
and TBAF (1M solution in THF) is
added
drop wise at 0° under inert atmosphere.
The reaction is allowed to
warm to room temperature and stirred
until complete by TLC (usually a few
hours - if not complete in this time
more TBAF solution may be
added).
*Note - equal volumes of glacial acetic
acid (compared to TBAF
solution.) may
be added to prevent removal of acetates or other
sensitive
protecting groups.
The reaction mixture is concentrated
in vacuo
and the
residue is purified by flash
chromatography (SiO
2
) if
necessary.
References
JACS,
1972
,
94
, 2549-2550.
TES
- (triethyl silyl) ether
Standard Protection
Procedure
To a solution of
the glycoside and imidazole (2 eq) stirring in DMF
at 0°
under an inert atmosphere, is
added drop wise TES-Cl (2 eq).
The
result is
allowed to warm to room
temperature and stirred until complete by TLC
(usually overnight).
An
equal volume of ether is added and the reaction
mixture is extracted three times with
water and once with brine.
The
organic layer is dried (sodium sulfate)
and concentrated
in vacuo
.
The
product can then be
purified by flash chromatography
(SiO
2
) if
necessary.
Removal
The
glycoside is dissolved in THF (~2M) and TBAF (1M
solution in THF) was
added drop wise at
0° under an inert atmosphere.
The
result is allowed to
warm to room
temperature and stirred until complete by TLC
(usually a few
hours - if not complete
in this time more TBAF solution may be
added).
*Note - equal
volume of glacial acetic acid (compared to TBAF
solution.) may be added to prevent
removal of acetates or other sensitive
protecting groups.
The
reaction mixture is concentrated
in
vacuo
and the
residue is
purified by flash chromatography
(SiO
2
) if
necessary.
References
Helv. Chim. Acta,
1981
,
64
, 2002-2021.
TIPS
- (triisopropyl silyl) ether
Standard Protection
Procedure
To a solution of
the glycoside stirring in DMF at 0° under an inert
atmosphere, TIPS-Cl (1.3 eq) and
imidazole (1.5 eq) were added
succinctly.
The result was
allowed to warm to room temperature and
stirred until complete by TLC (usually
overnight).
The mixture is diluted
with equal volume of chloroform and
extracted three times with water and
once with brine.
The
organic layer is dried (sodium sulfate) and
concentrated
in
vacuo
.
The resulting
residue is purified by flash
chromatography
(SiO
2
) if
necessary.
Removal
The
glycoside is dissolved in THF (~2M) and TBAF (1M
solution in THF) was
added drop wise at
0° under an inert atmosphere.
The
result is allowed to
warm to room
temperature and stirred until complete by TLC
(usually a few
hours - if not complete
in this time more TBAF solution may be
added).
*Note - equal
volume of glacial acetic acid (compared to TBAF
solution.) may be added to prevent
removal of acetates or other sensitive
protecting groups.
The
reaction mixture is concentrated
in
vacuo
and the
residue is
purified by flash chromatography
(SiO
2
) if
necessary.
References
JOC,
1980
,
45
, 4797-4798.
TBS
- (
tert
-butyl dimethyl
silyl) ether
Standard Procedure
To a solution of the glycoside in DMF
at 0° under an inert atmosphere,
TBS-Cl
(1.1 eq for selective primary -OH protection, 1.3
eq otherwise) and
imidazole (1.3 to 1.5
eq) were added succinctly.
The result
was allowed to
warm to room temperature
and stirred until complete by TLC (usually
overnight).
The mixture is
diluted with equal volume of chloroform and
extracted three times with water and
once with brine.
The organic layer
is dried (sodium sulfate) and
concentrated
in vacuo
.
The resulting residue
is
purified by flash chromatography
(SiO
2
) if
necessary.
OR
To a solution of the glycoside and
distilled 2,6-lutidine (2.1 eq) in dry DCM
under an inert atmosphere at -78°, TBS-
OTf is added drop wise over 30
minutes.
The result is stirred until complete by
TLC (usually 30 minutes -
if not
complete more TBS-OTf may be added) and methanol
is added.
The
mixture is
diluted with chloroform, washed with water and
brine, dried
over magnesium sulfate and
concentrated
in vacuo
.
The resulting residue
is
purified by flash chromatography
(SiO
2
) if
necessary.
Removal
The
glycoside is dissolved in THF (~2M) and TBAF (1M
solution in THF) was
added drop wise at
0° under an inert atmosphere.
The
result is allowed to
warm to room
temperature and stirred until complete by TLC
(usually a few
hours - if not complete
in this time more TBAF solution may be
added).
*Note - equal
volume of glacial acetic acid (compared to TBAF
solution.) may be added to prevent
removal of acetates or other sensitive
protecting groups.
The
reaction mixture is concentrated
in
vacuo
and the
residue is
purified by flash chromatography
(SiO
2
) if
necessary.
References
JACS,
1997
,
119
, 449-450.
JACS,
1972
,
94
, 6190-6191.
JOC,
1987
,
52
, 622-635.
TBDPS
-
(
tert
-butyl diphenyl silyl)
ether
Standard
Procedure
The glycoside is
dissolved in DMF at room temperature under an
inert
atmosphere and treated with
imidazole (2 eq per -OH) followed by
TBDPS-Cl (1.5 eq per -OH).
The reaction mixture is stirred until
complete
by TLC (usually overnight),
diluted with ether and washed with 1M HCl
followed by brine.
The
organic layer is dried (magnesium sulfate) and
concentrated
in
vacuo
.
The resulting
residue is purified by flash
chromatography
(SiO
2
) if
necessary.
Removal
To a
solution of the glycoside in THF at room
temperature in a Nalgene
container,
commercially available 30% HF in pyridine is added
drop wise
under an inert atmosphere.
The result is stirred until complete by
TLC
(usually 16 h) and diluted with
slow addition of saturated sodium
bicarbonate.
Chloroform is
added and the mixture is extracted
successively with water, saturated
copper sulfate, and brine.
The organic
layer is then dried (sodium sulfate)
and concentrated.
The resulting
residue is purified by flash
chromatography (SiO
2
) if
necessary.
References
JACS,
1997
,
119
, 449-450.
Alcohol protection -
[
MOM
]
[
MEM
]
[
BOM
]
[
SEM
]
Diol protection -
[
Acetonide
]
[
Benzylidene
]
[
p
-Methoxybenzylidene
] [
DTBS(OR)
2
]
MOM -
(methoxy methyl) ether
Standard Protection
Procedure
To a solution of
the glycoside in DCM (approx. 0.1M) and Hunig's
base
(N,N-diisopropylethyl amine, 2.0
eq) at 0°, MOM-Cl (1.5 eq) is added under
an inert atmosphere.
The
reaction is warmed to room temperature and
stirred until complete by TLC (usually
>8 h).
Ether is added and the
mixture is washed 3 times with water
and once with brine.
The organic
layer is dried (magnesium sulfate),
filtered and concentrated
in
vacuo
.
The
resulting residue is purified by flash
chromatography (SiO
2
) if
necessary.
Removal
The
glycoside is dissolved in 1:1 THF:6N HCl and
heated to 55° with
stirring until the
reaction is complete by TLC (usually 8 h).
Saturated
sodium chloride
solution is then added and the reaction mixture is
extracted three times with ether.
The combined organic layers are dried
(sodium sulfate), filtered and
concentrated
in vacuo
.
The residue is
purified by
flash chromatography (SiO
2
)
if necessary.
References
JACS,
1977
,
99
, 1275-1276.
JOC,
1975,
40
, 2025-2029.
MEM
- (methoxy ethoxy methyl) ether
Standard Protection
Procedure
To a solution of
the glycoside and MEM-Cl (1.5 eq) in dry DCM,
diisopropylethylamine (1.5 eq) is added
and stirred at room temperature
under
an inert atmosphere until complete by TLC (usually
5 h).
The
reaction is
diluted with DCM and extracted twice with water,
once with
brine, dried (sodium
sulfate), and concentrated
in
vacuo
.
The resulting
residue is purified by flash
chromatography (SiO
2
) if
necessary.
OR
To a mixture of NaH (1.2 eq) stirring
in THF at 0°, the glycoside is added
drop wise (as solution in
THF)
.
After stirring for 30
minutes, MEM-Cl (1.5
eq) is added drop
wise and reaction is allowed to warm to room
temperature.
The mixture is
stirred until complete by TLC (usually
overnight) and diluted with DCM.
The mixture is then extracted twice
with water, once with brine, dried
(sodium sulfate), and concentrated
in
vacuo
.
The
product is purified by flash chromatography
(SiO
2
) if
necessary.
Removal
The
glycoside is dissolved in DCM and magnesium
bromide etherate
(excess) is added at
room temperature under an inert atmosphere.
The
reaction is stirred
until complete by TLC (usually >24 h), at which
time
water is added and stirred for 30
additional minutes.
Aqueous HCl (1N)
is
added drop wise until the pH is 1-2
and the solution is clear.
The
resulting
solution is extracted three
times with ethyl acetate, dried (magnesium
sulfate), and concentrated
in vacuo
.
The
resulting residue is purified by
flash
chromatography (SiO
2
) if
necessary.
References
Tet. Lett.,
1976
,
11
, 809-812.
JOC,
1994
,
59
, 2314-2323.
J. Chem. Soc. Perkin
Trans. I,
1985
,
2247-2250.
BOM
- (benzyloxy methyl)
ether
Standard
Protection Procedure
To a
solution of the glycoside in DCM (approx. 0.1M)
and Hunig's base
(N,N-diisopropylethyl
amine, 2.0 eq) at 0°, BOM-Cl (1.2 eq) is added
under
an inert atmosphere.
The reaction is warmed to room
temperature and
stirred until complete
by TLC (usually >24 h).
Ether is then
added and the
mixture is washed 3 times
with water and once with brine.
The
organic
layer is dried (magnesium
sulfate), filtered and concentrated
in
vacuo
.
The
resulting residue is purified by flash
chromatography (SiO
2
) if
necessary.
Removal
The
glycoside is dissolved in EtOAc:Hex (1:2) and
catalytic Pd(OH)
2
is
added (10mol%) under a hydrogen
atmosphere.
The reaction is stirred at
room temperature until complete by TLC
(usually a few hours).
The
mixture is then filtered and
concentrated
in vacuo
.
The residue is
purified by
flash chromatography (SiO
2
)
if necessary.
References
JACS,
1975
,
97
, 6260.
JACS,
1994
,
116
, 4674-4688.
Tetrahedron,
1987
,
43
, 4395-4406.
SEM
- (trimethylsilyl) ethoxymethyl ether
Standard
Procedure
To a solution of
the glycoside under inert atmosphere at room
temperature
in DCM or THF (~2M),
diisopropylethylamine (4 eq for each -OH) is added
followed by the addition of SEM-Cl (3
eq for each -OH).
The reaction is
stirred until complete by TLC, at which
time saturated ammonium chloride
is
added.
The mixture is extracted with
two portions of DCM and the
combined
organic layers are extracted twice with saturated
bicarbonate
and once with brine.
The solution is then dried (magnesium
sulfate),
filtered, and concentrated
in vacuo
.
The
resulting residue is purified by
flash
chromatography (SiO
2
) if
necessary.
Removal
The
glycoside is dissolved in a 0.5M solution of
sulfuric acid in 2:1
MeOH:THF at 0°
under inert atmosphere.
The reaction
is stirred until
complete by TLC
(usually <3 h) and saturated sodium bicarbonate
solution
is added slowly.
The mixture is then diluted with ethyl
acetate and
separated.
The
aqueous layer is back extracted twice with ethyl
acetate
and the combined organic layers
are extracted with saturated sodium
bicarbonate and brine.
The
organic solution is then dried (magnesium
sulfate), filtered, and concentrated
in vacuo
.
The
resulting residue is
purified by flash
chromatography (SiO
2
) if
necessary.
References
Tet. Lett,
1993
,
12
, 1991-1994
Tet. Lett,
1980
,
21
, 3343-3346
Acetonide
- (isopropylidene) ketal
Standard Protection
Procedure
To a solution of
the glycoside stirring in DMF,
p
-toluenesulfonic acid
(10mol%) and 2,2-dimethoxypropane are
added.
The result is stirred at
room temperature under inert atmosphere
until complete by TLC
(usually >6 h).
The reaction is neutralized with 5%
aqueous sodium
bicarbonate and
concentrated
in vacuo
.
The material is dissolved in ethyl
acetate, washed with water, saturated
sodium chloride, dried (sodium
sulfate), and concentrated
in vacuo
. The product is
then purified by flash
chromatography
(SiO
2
) if
necessary.
Removal
The
glycoside is dissolved in 80-90% AcOH in water and
stirred at 60-90°
until
complete by TLC (usually <3 h).
The
solution is then concentrated
in
vacuo
and purified by flash
chromatography (SiO
2
) if
necessary.
References
Chem. Pharm. Bull.,
1990
,
38
, 3366-3372.
Benzylidene
Acetal
Standard
Protection Procedure
The
glycoside is dissolved in DMF and benzyaldehyde
dimethyl acetal (5 eq)
is added.
To this solution stirring at room
temperature under an inert
atmosphere,
toluene-
p
-sulfonic acid (0.3
eq) is added.
After the reaction
is complete by TLC (usually overnight),
the mixture is neutralized with
triethylamine.
The solution
is then concentrated
in vacuo
and purified by
flash
chromatography (SiO
2
) if
necessary.
OR
The glycoside is dissolved in
acetonitrile and benzyaldehyde dimethyl
acetal (5 eq) is added.
To
this solution stirring at room temperature
under inert atmosphere,
toluene-
p
-sulfonic acid (0.3
eq) is added.
After
the
reaction is complete by TLC (usually overnight),
the mixture is diluted
with chloroform
and extracted twice with water.
The
aqueous layer is
then back extracted
with chloroform.
The combined organic
layers are
dried and concentrated
in vacuo
. The resulting
residue is purified by flash
chromatography
(SiO
2
) if
necessary.
Complete
Removal
The glycoside is
dissolved in 50-80% AcOH in water and heated to
60-70°
with stirring until
complete by TLC (usually >4 h).
The
solution is then
concentrated and
coevaporated with toluene 3 times.
The
residue is
purified by flash
chromatography (SiO
2
) if
necessary.
OR
To a solution of the glycoside in
methanol at room temperature under an
inert atmosphere,
toluene-
p
-sulfonic acid (0.3
eq) is added.
The reaction
is stirred until complete by TLC
(usually overnight) and triethylamine is
added to neutralize. The mixture is
concentrated
in vacuo
and
the residue
is purified by flash
chromatography (SiO
2
) if
necessary.
OR
To a solution of the glycoside in
methanol:
t
-butanol 1:1 at
room
temperature under a hydrogen
atmosphere, Pd(OH)
2
-C
(20mol%) is
added.
The
reaction is stirred until complete by TLC (usually
overnight, if
not complete up to one eq
of HCl may be added) and filtered washing with
methanol. The solution is concentrated
in vacuo
and the resulting
residue is
purified by flash
chromatography (SiO
2
) if
necessary.
Partial
Removal
For
primary
benzyl
and
secondary -OH
- To a solution of the glycoside in
DCM
under inert atmosphere at 0°, triethylsilane (5
eq) is
added.
Trifluoroacetic acid (5 eq) is then
added drop wise and the
reaction
mixture is allowed to warm to room temperature.
The reaction is
stirred
until complete by TLC (usually <3 h) and diluted
with DCM.
The
organic
solution is then extracted twice with saturated
aqueous sodium
bicarbonate solution,
dried (sodium sulfate), and concentrated
in
vacuo
.
The resulting residue is purified by
flash chromatography (SiO
2
)
if
necessary.
For secondary benzyl and primary -OH -
To a solution of the glycoside
dissolved in DCM under an inert
atmosphere at room temperature, 4A
molecular sieves are added and stirred
for one hour.
The mixture is then
cooled to -78° and triethylsilane (3
eq) is added followed by
PhBCl
2
(3.4
eq).
After stirring for one hour,
triethylamine and methanol are added
and the mixture is diluted with
chloroform.
The organic solution is
washed with saturated aqueous sodium
bicarbonate solution, dried (sodium
sulfate), and concentrated
in vacuo
.
The
resulting residue is purified by
flash
chromatography (SiO
2
) if
necessary.
References
J. Chem. Soc., Perkin Trans. 1,
1996
, 985-993.
JOC,
1996
,
61
, 2401-2406.
Tet. Lett.,
1995
,
36
, 669-672.
Tet. Lett.,
2000
,
41
, 5547-5551.
p-Methoxybenzylidene
Acetal
Standard
Protection Procedure
The
glycoside and anhydrous zinc chloride are
dissolved in dry pyridine and
p-
anisaldehyde (15 eq) is
added at room temperature under an inert
atmosphere.
The mixture is
stirred until complete by TLC (usually >24 h)
and then diluted with ethyl acetate,
washed twice with water, dried
(sodium
sulfate), and concentrated
in
vacuo
.
The resulting
residue is
purified by flash
chromatography (SiO
2
) if
necessary.
Removal
The
glycoside is dissolved in 50-80% AcOH in water and
heated to 60-70°
with
stirring until complete by TLC (usually >4 h).
The solution is then
concentrated and coevaporated with
toluene 3 times.
The residue is
purified by flash chromatography
(SiO
2
) if
necessary.
OR
To a solution of the glycoside in
methanol:
t
-butanol 1:1 at
room
temperature under a hydrogen
atmosphere, Pd(OH)
2
-C
(20mol%) is
added.
The
reaction is stirred until complete by TLC (usually
overnight, if
not complete up to one eq
of HCl may be added) and filtered washing with
methanol. The solution is concentrated
in vacuo
and the resulting
residue is
purified by flash
chromatography (SiO
2
) if
necessary.
OR
To a solution of the glycoside in
acetonitrile:water (9:1), cerium ammonium
nitrate (2 eq) is added at room
temperature under an inert
atmosphere.
The reaction is stirred until complete
by TLC (usually 15
minutes) and the
reaction is diluted with ethyl acetate.
The mixture is
extracted
twice with water, dried (sodium sulfate) and
concentrated
in
vacuo
.
The
resulting residue is purified by flash
chromatography (SiO
2
) if
necessary.
References
Chem. Commun.
1984
, 201-202.
JACS,
1962
,
84
, 430-440.
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