A novel selectfluor-mediated regioselective O-benzyl ether acetolysis of perbenzylated monosaccharides

Article abstract of DOI:10.1080/07328303.2015.1108423

Selectfluor, a source of the super electrophile F⁺, has replaced conventional reagents that supply F⁺ for fluorination due to its attractive physical and chemical properties. This study is the first report of using Selectfluor as a d

Full text of DOI:10.1080/07328303.2015.1108423

Journal of Carbohydrate Chemistry
ISSN: 0732-8303 (Print) 1532-2327 (Online) Journal homepage: http://www.tandfonline.com/loi/lcar20
A Novel Selectfluor-Mediated Regioselective
O-Benzyl Ether Acetolysis of Perbenzylated
Monosaccharides
Marlon S. Tambie & Nigel Kevin Jalsa
To cite this article: Marlon S. Tambie & Nigel Kevin Jalsa (2015) A Novel Selectfluor-Mediated
Regioselective O-Benzyl Ether Acetolysis of Perbenzylated Monosaccharides, Journal of
Carbohydrate Chemistry, 34:9, 545-559, DOI: 10.1080/07328303.2015.1108423
To link to this article: http://dx.doi.org/10.1080/07328303.2015.1108423
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Date: 19 February 2016, At: 07:50

Journal of Carbohydrate Chemistry, 34:545–559, 2015
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Copyright Taylor & Francis Group, LLC
ISSN: 0732-8303 print / 1532-2327 online
DOI: 10.1080/07328303.2015.1108423
A Novel Selectfluor-Mediated
Regioselective O-Benzyl Ether
Acetolysis of Perbenzylated
Monosaccharides
Marlon S. Tambie and Nigel Kevin Jalsa
Department of Chemistry, The University of the West Indies, St. Augustine, Trinidad
and Tobago
GRAPHICAL ABSTRACT
Selectfluor, a source of the super electrophile F+, has replaced conventional reagents
that supply F+ for fluorination due to its attractive physical and chemical properties.
This study is the first report of using Selectfluor as a debenzylating reagent. Selectfluor
has been found to effect regioselective O-benzyl acetolysis from the per-O-benzylated
derivatives of glucose and mannose, which are among the most commonly occurring
monosaccharides. For both derivatives, one equivalent of Selectfluor first cleaves the
primary benzyl, while a second equivalent subsequently removes the anomeric ben-
zyl. Regioselective removal at higher equivalents proved difficult, with complex mix-
tures being obtained. The reaction proceeded under mild conditions with good yields
Received August 12, 2015; accepted October 12, 2015.
Address correspondence to Nigel Kevin Jalsa, Department of Chemistry, The University
of the West Indies, St. Augustine, Trinidad and Tobago. E-mail: nigel.jalsa@sta.uwi.edu
545

M.S. Tambie and N.K. Jalsa
546
and high regioselectivity, resulting in quick access to partially benzylated monosaccha-
ride derivatives. This study provides shortened access to attractive building blocks for
oligosaccharide synthesis.
Keywords Selectfluor; Oligosaccharides; Monosaccharides; Benzyl group; Regioselec-
tive deprotection
INTRODUCTION
Synthetic carbohydrates have found widespread applications due to their im-
portance in many biological and physiological roles. Carbohydrates and their
derivatives are involved in cell recognition, signal transduction, adhesion pro-
cesses, and energy storage.[1–3] A major problem encountered in carbohydrate
synthesis is that the monosaccharide building blocks are polyhydroxylated
molecules with multiple centers of reactivity.[4–6] This increases the suscep-
tibility of competing glycosylation reactions, and it is therefore necessary to
develop protecting group strategies to synthesize particular targets.[7] Apart
from the Fischer glycosylation and installation of bulky protecting groups on
the primary position,[5–8] very few other reactions display high regioselectivity
for a particular hydroxyl group on the sugar. Synthetic routes generally require
multiple steps with judicious choice of protecting groups, featuring expensive
and time-consuming purification steps and low overall yields.[8]
Sakai and coworkers have shown that acetolysis using Ac2O containing 1%
(v/v) H2SO4 can be used to effect stepwise acetolysis of benzyl ethers from per-
O-benzylated derivatives.[9] This method, however, requires the use of H2SO4
and needs careful monitoring since product degradation can occur, resulting in
reduced yields. In another study,[10] Cao and Yamada utilized a similar method
as an easy route to obtain partially protected derivatives following stepwise de-
protection of methyl 2,3,4,6-tetra-O-benzyl-α-D-glucopyranoside. They found
that the order of debenzylation was 6-O-Bn > 3-OBn > 4-O-Bn > 2-O-Bn.
Pastore and coworkers utilized I2 and Et3SiH to effect the regioselective de-
O-benzylation of a range of carbohydrate substrates, with the least sterically
accessible benzyl group being cleaved in most cases.[11] Mechanistic investi-
gation reveals that when I2 and Et3SiH are used, anhydrous HI is generated
and functions as the promoter. Lecourt and coworkers demonstrated the use
of diisobutylaluminium hydride and triisobutylaluminium hydride as effec-
tive reagents for regioselective O-benzyl removal.[12] Various per-O-benzylated
mono- and disaccharide derivatives were examined, and their method showed
high regioselectivity toward a single benzyl group. They demonstrated the ef-
fectiveness of their method to produce novel cyclodextrin derivatives by treat-
ing per-O-benzylated α and β cyclodextrin with triisobutylaluminium hydride.
This facilitated the regioselective de-O-benzylation on the primary rim of the

Selectfluor Regioselective O-benzyl Acetolysis
547
cyclodextrin, leading to the formation of an A-D diol. Yang and coworkers uti-
lized the combination of ZnCl2 and Ac2O-HOAc and demonstrated its effec-
tiveness for regioselective removal of the primary benzyl from a variety of
substrates while the secondary benzyl groups are preserved.[13] The method
showed good orthogonality with other protecting groups and works well at
room temperature. Giordano and coworkers developed a method for the regios-
elective deprotection of benzylated derivatives using iodine and silane.[14] This
method utilized isopropyl acetate instead of the usual acetic anhydride and
acidic conditions employed under acetolytic conditions, and the preservation of
O-glycosidic bonds is a particularly attractive feature of this method.
Other methods exist that are often used in the preparation of partially ben-
zylated carbohydrate derivatives. Complexation by Lewis acids, such as TiCl4
or SnCl4, has been effectively used in the regioselective deprotection of ben-
zyl ethers.[7,15] However, this often involves the use of toxic and/or expensive
reagents. The use of boron trichloride has been reported as a novel method
for the regioselective deprotection of C-glycosides containing 1,2-cis or 1,3-cis
benzyl groups by Xiea and coworkers.[16]
A glycosyl acceptor bearing a free primary hydroxyl group can be prepared
from selective ring opening of a 4,6-O-benzylidene acetal using LiAlH4 and
[17]
AlCl3
or by initially protecting the primary position with sterically bulky
groups (e.g., silyl and trityl groups), followed by deprotection at a later stage of
the synthesis.[15–20] Catalytic transfer hydrogenation (CTH) is an effective and
mild method that can be used to prepare protected derivatives bearing a free
anomeric hydroxyl group.[21] A suitable leaving group can then be appended
for use as a glycosyl donor.
1-Chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluorob
orate) (Selectfluor)[22] is an electrophilic fluorinating reagent and has largely
replaced previously used sources of F+.[23] It is easy to handle (free-flowing
white crystals), very stable, and commercially available on a large scale.[23–25]
Fluorine substitution has been previously shown to significantly alter the
physical and chemical properties of many molecules.[24–28] Selectfluor has also
been effectively used in the preparation of glycosyl fluorides, fluorination of
aromatic compounds, fluorination of alkenes, and many oxidation reactions.[23]
However, in this study, Selectfluor was found to be an effective reagent in the
regioselective O-benzyl removal of per-O-benzylated monosaccharides. Select-
fluor was utilized at both catalytic and stoichiometric equivalents to determine
its effect on the fully benzylated derivatives of glucose, mannose, and galac-
tose. Per-O-benzylated monosaccharides are easy to prepare in good yield in a
single step from the free monosaccharide. The benzyl ether is a popular pro-
tecting group and is well known for its robustness and stability to a wide range
of conditions. Using Selectfluor, we demonstrate that the benzyl group on the
primary position was removed first followed by the anomeric benzyl group.

M.S. Tambie and N.K. Jalsa
548
Scheme 1: Reactions of Selectfluor and 1–3.
RESULTS AND DISCUSSION
The per-O-benzylated glucopyranose and mannopyranose derivatives 1 and 2
were prepared by treating the free sugar with excess NaH and BnBr in DMF in
good yields. The galactopyranoside 3 could not be obtained using this method
since the α furanoside was the major product along with an inseparable mix-
ture of the β furanoside, β pyranoside, and α pyranoside.[29,30] Derivative 3 was
prepared according to literature protocols starting from free galactose.[31,32]
Compounds 1, 2, and 3 were used as the starting material for the regiose-
lective de-O-benzylation studies with Selectfluor. Scheme 1 outlines the reac-
tions utilized to investigate the effect of Selectfluor on the per-O-benzylated
derivatives.
When 1–3 were each treated with catalytic amounts of Selectfluor, only
starting material persisted. Stoichiometric amounts were then investigated,
and when 1 equivalent of Selectfluor in Ac2O was utilized at room tempera-
ture, no significant reaction was observed (Tables 1–3). The experiment was
then repeated with gentle heating, and TLC analysis revealed the appearance
of a spot below that of the starting material. The reaction was allowed to con-
tinue; however, product formation was very slow even with prolonged reac-
tion times. Optimization studies were then carried out as shown in Tables 1
Table 1: Optimization of reaction between 1 equivalent of Selectfluor and 1
Starting material Eq. Selectfluor Temperature/oC
Time
Product (yield%)
1
1
1
1
1
1
1
1
1
1
1
1
RT
30
Overnight
Overnight
6 h
No reaction
4 (< 5)
4 (58)
60
60
Reflux
Reflux
Overnight
2 h
4 (67)
4 (65)
4 (52)
Overnight

Selectfluor Regioselective O-benzyl Acetolysis
549
through 3 to vary the temperature and time in order to maximize product
formation.
When 1 or 2 was used as the starting material, the major product of
the reaction was its monoacetylated derivative 4 or 5, respectively. The ben-
zyl group at C-6 was the first to be acetolyzed due to its greater steric ac-
cessibility. The reaction was heated at 60◦C, and after 6 h, considerable re-
action progress was observed. The derivatives 4 and 5 were obtained in a
yield of 58% and 55%, respectively, and unreacted starting material was recov-
ered. The reaction was repeated at 60◦C overnight and improved yields were
obtained.
The reaction was then repeated under reflux and conversion was rapid;
after 2 h, most of the starting material was consumed and products 6 and 7
were obtained in a yield of 65% and 61%, respectively. The yields of 4 and 5
were lower when the reaction was performed under extensive reflux as prod-
uct degradation occurred. A complex mixture of partially benzylated deriva-
tives was detected after column chromatography, as elucidated by 1H and
13C NMR.
When the reaction was carried out with galactoside 3 using the con-
ditions optimized for 1 and 2, poor regioselectivity was observed and the
monoacetylated derivative was obtained only in minor yield. This proved dif-
ficult to purify since the desired product eluted with other partially benzy-
lated derivatives, possibly bearing a single acetate group at a nonprimary
position.
Table 2: Optimization of reaction between 1 equivalent of Selectfluor and 2
Starting material Eq. Selectfluor Temperature/oC
Time
Product (yield%)
2
2
2
2
2
2
1
1
1
1
1
1
RT
30
Overnight
Overnight
6 h
No reaction
5 (< 5)
5 (55)
60
60
Reflux
Reflux
Overnight
2 h
5 (63)
5 (61)
5 (51)
Overnight
Table 3: Optimization of reaction between 1 equivalent of Selectfluor and 3
Starting material Eq. Selectfluor Temperature/oC
Time
Yield%
3
3
3
3
3
3
1
1
1
1
1
1
RT
30
Overnight
Overnight
6 h
No reaction
< 5
60
Complex mixture
60
Reflux
Reflux
Overnight Complex mixture
2 h
Complex mixture
Overnight Complex mixture

M.S. Tambie and N.K. Jalsa
550
Tables 4 through 6 detail the reaction conditions and the results of the ex-
periments with 2 equivalents of Selectfluor when 1, 2, and 3 were used as the
substrates. The anomeric benzyl was the second benzyl to be cleaved, resulting
in the 1,6-di-O-acetates 6 and 7 as the major product (60% and 59% yields, re-
spectively). As previously reported with 3, poor regioselectivity was observed
and attempts at further benzyl group acetolysis using higher equivalents of
Selectfluor proved difficult, since there was a loss of regioselectivity and com-
plex mixtures were obtained. Despite the unsuccessful attempts with 3, many
literature protocols exist for the regioselective acetolysis of highly benzylated
galacto-derivatives.[11–16] We postulate that the lone pair of electrons on the
carbonyl oxygen of acetic anhydride attacks the F+, facilitating the activation
of the carbonyl centre. This is typical of known acetolysis pathways and the
oxygen of the substrate is then able to attack the activated nucleophilic center,
effecting benzyl group acetolysis.[9,10,13,14]
Deacetylation of the Product
Partially benzylated derivatives are useful synthetic intermediates.
Scheme 3shows that 4 and 6 could be readily converted to 8 and 9 in a yield
of 97% and 82%, respectively, as useful glycosyl acceptor and donor for the
synthesis of oligosaccharides Scheme 2.
Table 4: Optimization of reaction between 2 equivalents of Selectfluor and 1
Starting material Eq. Selectfluor Temperature/oC
Time
Product (yield%)
1
1
1
1
1
1
2
2
2
2
2
2
RT
30
Overnight
Overnight
6 h
No reaction
6 (< 5)
6 (50)
60
60
Reflux
Reflux
Overnight
2 h
6 (54)
6 (60)
6 (44)
Overnight
Table 5: Optimization of reaction between 2 equivalents of Selectfluor and 2
Starting material Eq. Selectfluor Temperature/oC
Time
Product (yield%)
2
2
2
2
2
2
2
2
2
2
2
2
RT
30
Overnight
Overnight
6 h
No reaction
7 (< 5)
7 (54)
60
60
Reflux
Reflux
Overnight
2 h
7 (60)
7 (59)
7 (40)
Overnight

Selectfluor Regioselective O-benzyl Acetolysis
551
Table 6: Optimization of reaction between 2 equivalents of Selectfluor and 3
Starting material Eq. Selectfluor Temperature/oC
Time
Yield%
3
3
3
3
3
3
2
2
2
2
2
2
RT
30
Overnight
Overnight
6 h
No reaction
< 5
60
Complex mixture
60
Reflux
Reflux
Overnight Complex mixture
2 h
Complex mixture
Overnight Complex mixture
Scheme 2: Deacetylation reactions of 4 and 6.
CONCLUSION
Selectfluor-mediated benzyl group acetolysis was proved to be a mild and
easy method to obtain partially benyzlated and partially acetylated glucose
and mannose derivatives. These are useful intermediates and can be used for
oligosaccharide synthesis. The primary benzyl ether was the first to be ace-
tolyzed followed by the benzyl ether linkage at the anomeric position. This
method has limitations at higher equivalents of Selectfluor, as under these con-
ditions the reactions were complex and could not afford regioselective benzyl
ether acetolysis.
EXPERIMENTAL
General Methods
All chemicals used were reagent grade and used as purchased unless oth-
erwise stated. DMF was dried over calcium hydride for 24 h, distilled under re-
˚
duced pressure in an inert atmosphere of nitrogen, and stored over 4 A molec-
ular sieves under argon. TLC was performed using precoated silica gel 60 F254
plates with compounds visualized using acidic ammonium molybdate solution

M.S. Tambie and N.K. Jalsa
552
1
[ammonium molybdate (VI) tetrahydrate (25 g) in 1 M H2SO4 (500 mL)]. H,
13C, COSY, and HSQC NMR experiments were recorded on a Bruker 600, 400,
or 300 NMR spectrometer in the deuterated solvents stated. Chemical shifts
are stated in ppm. Multiplicities are stated as s (singlet), bs (broad singlet),
ps (pseudo singlet), d (doublet), apptd (apparent doublet), t (triplet), apptt (ap-
parent triplet), q (quartet), dd (doublet of doublets), ddd (doublet of doublet
of doublets), ABq (AB quartet), or m (multiplet). High-resolution mass spec-
tral (HRMS) analyses were obtained using a Bruker Daltonics micrOToF-Q in-
strument in the electron spray ionization mode. Column chromatography was
˚
performed using high-purity-grade silica gel, 70–250 mesh/60 A.
Benzyl 2,3,4,6-tetra-O-benzyl-β-D-glucopyranoside (1)
D-Glucose (5 g, 27.8 mmol) was suspended in 100 mL anhydrous DMF
in a 250 mL round-bottom flask. The reaction vessel was flushed with argon
and cooled in an ice bath to 5◦C. NaH (60% dispersion in mineral oil; 6.6 g,
166.5 mmol) was then added over a period of 10 min. This was allowed to
stir for 60 min followed by the addition of BnBr (19.8 mL, 166.5 mmol) over
a 30-min period and stirring continued for 24 h. Methanol (20 mL) was then
added to the reaction and the DMF removed under high vacuum. The crude
residue was dissolved in CH2Cl2 (100 mL), transferred to a separatory funnel,
and washed with H2O (3 × 150 mL). The organic layer was dried over an-
hydrous sodium sulphate and filtered. The filtrate was concentrated in vacuo
and the crude residue subjected to purification by column chromatography us-
ing petroleum ether/ethyl acetate (gradient elution) to afford 1 (14.18 g, 81%);
1
Rf (Pet. Ether: EtOAc; 4:1) = 0.44; H NMR (600 MHz, CDCl3): δ: 3.47 (1H,
ddd, J4,5 = 9.4 Hz, J5,6a = 5.5, J5,6b = 4.2 Hz, H-5), 3.53 (1H, t, J1,2 = 7.8 Hz,
J2,3 = 7.8 Hz, H-2), 3.64 (2H, m, H-3, H-4), 3.71 (1H, dd, J5,6b = 4.8 Hz, J6a,6b
=
10.8, H-6b), 3.76 (1H, dd, J5,6a = 2.0 Hz, J6a,6b = 10.8, H-6a), 4.52 (1H, d, J1,2
= 7.8 Hz, H-1), 4.54, 4.72 (2H, ABq, J = 10.9 Hz, PhCH2O-), 4.57, 4.63 (2H,
ABq, J = 12.2 Hz, PhCH2O-), 4.67, 4.98 (2H, ABq, J = 11.9 Hz, PhCH2O-),
4.78, 4.92 (2H, ABq, J = 10.9 Hz, PhCH2O-), 4.82, 4.96 (2H, ABq, J = 10.8 Hz,
PhCH2O-), 7.16–7.39 (25H, m, Ar-H); 13C NMR (100 MHz, CDCl3): δ: 69.0 (1C,
C-6), 71.2 (1C, PhCH2O), 73.5 (1C, PhCH2O), 74.91 (1C, PhCH2O), 74.94 (1C,
PhCH2O), 75.0 (1C, C-5), 75.7 (1C, PhCH2O), 77.9 (1C, C-4), 82.3 (1C, C-2),
84.8 (1C, C-3), 102.6 (1C, JC1-H1 = 160.0 Hz, C-1), 127.6–128.4 (25C, Ar-C),
137.5 (1C, Ar-quat), 138.1 (1C, Ar-quat), 138.2 (1C, Ar-quat), 138.4 (1C, Ar-
quat), 138.6 (1C, Ar-quat). HRMS calculated for C41H42O6Na: 653.2879; found:
653.2874 (M + Na)+.
Benzyl 2,3,4,6-tetra-O-benzyl-β-D-mannopyranoside (2)
D-Mannose (5 g, 27.8 mmol) was suspended in 100 mL anhydrous DMF
in a 250 mL round-bottom flask. The reaction vessel was flushed with argon

Selectfluor Regioselective O-benzyl Acetolysis
553
and cooled in an ice bath to 5◦C. NaH (60% dispersion in mineral oil; 6.6 g,
166.5 mmol) was then added over a period of 10 min. This was allowed to
stir for 60 min followed by the addition of BnBr (19.8 mL, 166.5 mmol) over
a 30-min period and stirring continued for 24 h. Methanol (20 mL) was then
added to the reaction and the DMF removed under high vacuum. The crude
residue was dissolved in CH2Cl2 (100 mL), transferred to a separatory funnel,
and washed with H2O (3 × 150 mL). The organic layer was dried over anhy-
drous sodium sulphate and filtered. The filtrate was concentrated in vacuo
and the crude residue subjected to purification by column chromatography
using petroleum ether/ethyl acetate (gradient elution) to afford 2 (13.65 g,
1
78%); Rf (EtOAc : Pet. Ether; 2:3) = 0.57; H NMR (600 MHz, CDCl3): δ: 3.45
(1H, ddd, J4,5 = 9.5 Hz, J5,6a = 2.0, J5,6b = 6.0 Hz, H-5), 3.49 (1H, dd, J2,3
=
5.6 Hz, J3,4 = 9.5 Hz, H-3), 3.78 (1H, dd, J5,6b = 6.0 Hz, J6a,6b = 10.8, H-6b),
3.83 (1H, dd, J5,6a = 2.0 Hz, J6a,6b = 10.8, H-6a), 3.90 (1H, t, J3,4 = 9.5 Hz,
J4,5 = 9.5 Hz, H-4), 3.92 (1H, dd, J1,2 = 3.7 Hz, J2,3 = 5.6 Hz, H-2), 4.43, 4.50
(2H, ABq, J = 11.8 Hz, PhCH2O-), 4.44 (1H, s, H-1), 4.54, 4.90 (2H, ABq, J =
10.8 Hz, PhCH2O-), 4.59, 5.00 (2H, ABq, J = 12.0 Hz, PhCH2O-), 4.60, 4.65
(2H, ABq, J = 12.1 Hz, PhCH2O-), 4.89, 5.01 (2H, ABq, J = 12.3 Hz, PhCH2O-
), 7.18–7.46 (25H, m, Ar-H); 13C NMR (150 MHz, CDCl3): δ: 69.8 (1C, C-6), 71.0
(1C, PhCH2O), 71.6 (1C, PhCH2O), 73.6 (1C, PhCH2O), 73.9 (1C, PhCH2O),
74.0 (1C, C-4), 75.0 (1C, C-2), 75.2 (1C, PhCH2O), 76.1 (1C, C-5), 82.5 (1C, C-3),
100.4 (1C, JC1-H1 = 152.4 Hz, C-1), 127.6–128.5 (25C, Ar-C), 137.6 (1C, Ar-
quat), 138.3 (1C, Ar-quat), 138.5 (1C, Ar-quat), 138.6 (1C, Ar-quat), 138.9 (1C,
Ar-quat). HRMS calculated for C41H42O6Na: 653.2879; found: 653.2874 (M +
Na)+.
Benzyl 2,3,4,6-tetra-O-benzyl-β-D-galactopyranoside (3)
Benzyl-β-D-galactopyranoside, 11. (2 g, 7.40 mmol) was suspended in
10 mL anhydrous DMF in a 100 mL round-bottom flask. The reaction vessel
was flushed with argon and cooled in an ice bath to 5◦C. NaH (60% disper-
sion in mineral oil; 1.5 g, 37.0 mmol) was then added over a period of 10 min.
This was allowed to stir for 60 min followed by the addition of BnBr (4.4 mL,
37.0 mmol) over a 30-min period and stirring continued for 24 h. Methanol
(20 mL) was then added to the reaction and the DMF removed under high vac-
uum. The crude residue was dissolved in CH2Cl2 (100 mL), transferred to a
separatory funnel, and washed with H2O (3 × 150 mL). The organic layer was
dried over anhydrous sodium sulphate and filtered. The filtrate was concen-
trated in vacuo and the crude residue subjected to purification by column chro-
matography using petroleum ether/ethyl acetate (gradient elution) to afford 3
1
(3.9 g, 84%); Rf (Pet. Ether: EtOAc; 4:1) = 0.42; H NMR (600 MHz, CDCl3):
δ: 3.51 (1H, dd, J2,3 = 9.8, J3,4 = 3.0 Hz, H-3), 3.53 (1H, m, H-5), 3.60 (1H, m,
H-6a), 3.63 (1H, dd, J5,6b = 6.5 Hz, J6,6b = 9.7, H-6b), 3.90 (2H, m, H-2, H-4),
4.42, 4.46 (2H, ABq, J = 11.8 Hz, PhCH2O-), 4.47 (1H, d, J1,2 = 7.7 Hz, H-1),

M.S. Tambie and N.K. Jalsa
554
4.60, 4.96 (2H, ABq, J = 12.3 Hz, PhCH2O-), 4.63, 4.94 (2H, ABq, J = 11.7 Hz,
PhCH2O-), 4.69, 4.47 (2H, ABq, J = 11.8 Hz, PhCH2O-), 4.77, 4.92 (2H, ABq,
J = 10.8Hz, PhCH2O-), 7.23–7.36 (25H, m, Ar-H); 13C NMR (75 MHz, CDCl3):
δ: 69.0 (1C, C-6), 71.0 (1C, PhCH2O), 73.2 (1C, PhCH2O), 73.6 (2C, C-5,
PhCH2O), 73.7 (1C, C-4), 74.6 (1C, PhCH2O), 75.4 (1C, PhCH2O), 79.7 (1C,
C-2), 82.4 (1C, C-3), 103.0 (1C, JC1-H1 = 158.5 Hz, C-1), 127.6–128.5 (25C, Ar-
C), 137.8 (1C, Ar-quat), 138.1 (1C, Ar-quat), 138.6 (1C, Ar-quat), 138.7 (1C, Ar-
quat), 138.8 (1C, Ar-quat). HRMS calculated for C41H42O6Na: 653.2879; found:
653.2874 (M + Na)+.
Benzyl 6-O-acetyl-2,3,4-tri-O-benzyl-β-D-glucopyranoside (4)
Benzyl 2,3,4,6-tetra-O-benzyl-β-D-glucopyranoside (2 g, 3.2 mmol) was dis-
solved in 15 mL Ac2O in a 100 mL round-bottom flask. Selectfluor (1.12 g,
3.2 mmol) was added and the reaction heated under reflux for 2 h. The Ac2O
was removed under high vacuum and the crude residue dissolved in CH2Cl2
(25 mL), transferred to a separatory funnel, and washed with H2O (3 ×
150 mL). The organic layer was dried over anhydrous sodium sulphate and fil-
tered. The filtrate was concentrated in vacuo and the crude residue subjected
to purification by column chromatography using petroleum ether/ethyl acetate
(gradient elution) to afford 4 (1.2 g, 65%); Rf (Pet. Ether : EtOAc; 8:2) = 0.38;
1H NMR (600 MHz, CDCl3): δ: 2.05 (3H, s, CH3CO-), 3.50 (1H, m, J4,5 = 9.3 Hz,
J5,6a = 2.1, J5,6b = 4.9 Hz, H-5), 3.52 (1H, dd, J1,2 = 7.8 Hz, J2,3 = 9.3 Hz, H-2),
3.56 (1H, t, J2,3 = 9.3 Hz, J3,4 = 9.3 Hz, H-4), 3.67 (1H, t, J3,4 = 9.3 Hz, J4,5
=
9.3 Hz, H-3), 4.25 (1H, dd, J5,6b = 4.9 Hz, J6a,6b = 11.9, H-6b), 4.37 (1H, dd, J5,6a
= 2.1 Hz, J6a,6b = 11.9, H-6a), 4.51 (1H, d, J1,2 = 7.8 Hz, H-1), 4.57, 4.86 (2H,
ABq, J = 10.9 Hz, PhCH2O-), 4.66, 4.93 (2H, ABq, J = 11.9 Hz, PhCH2O-),
4.73, 4.95 (2H, ABq, J = 10.9 Hz, PhCH2O-), 4.79, 4.96 (2H, ABq, J = 10.9 Hz,
PhCH2O-), 7.26–7.37 (20H, m, Ar-H); 13C NMR (100 MHz, CDCl3): δ: 20.9 (1C,
CH3CO-), 63.1 (1C, C-6), 71.2 (1C, PhCH2O), 72.8 (1C, C-5), 74.9 (1C, PhCH2O),
75.0 (1C, PhCH2O), 75.7 (1C, PhCH2O), 77.3 (1C, C-4), 82.2 (1C, C-2), 84.7 (1C,
C-3), 102.4 (1C, JC1-H1 = 158.5 Hz, C-1), 127.9–128.5 (20C, Ar-C), 137.1 (1C,
Ar-quat), 137.7 (1C, Ar-quat), 138.2 (1C, Ar-quat), 138.4 (1C, Ar-quat), 170.8
(1C, CH3CO-). HRMS calculated for C36H38O7Na: 605.2512; found: 605.2467
(M + Na)+.
Benzyl 6-O-acetyl-2,3,4-tri-O-benzyl-β-D-mannopyranoside (5)
Benzyl 2,3,4,6-tetra-O-benzyl-β-D-mannoopyranoside (2 g, 3.2 mmol) was
dissolved in 15 mL Ac2O in a 100 mL round-bottom flask. Selectfluor (1.12 g,
3.2 mmol) was added and the reaction heated under reflux for 2 h. The Ac2O
was removed under high vacuum and the crude residue dissolved in CH2Cl2
(25 mL), transferred to a separatory funnel, and washed with H2O (3 ×
150 mL). The organic layer was dried over anhydrous sodium sulphate and fil-
tered. The filtrate was concentrated in vacuo and the crude residue subjected

Selectfluor Regioselective O-benzyl Acetolysis
555
to purification by column chromatography using petroleum ether/ethyl acetate
(gradient elution) to afford 5 (1.1 g, 61%); Rf (Pet. Ether : EtOAc; 8:2) = 0.36; 1H
NMR (400 MHz, CDCl3): δ: 2.03 (3H, s, CH3CO-), 3.44 (1H, ddd, J4,5 = 9.4 Hz,
J5,6a = 5.7, J5,6b = 2.0 Hz, H-5), 3.47 (1H, dd, J2,3 = 3.0, J3,4 = 9.3 Hz, H-3), 3.92
(2H, m, H-2, H-4), 4.41 (2H, m, H-1, H-6b), 4.40, 4.48 (2H, ABq, J = 11.8 Hz,
PhCH2O-), 4.43 (1H, dd, J5,6a = 5.7 Hz, J6,6b = 11.8, H-6a), 4.57, 4.96 (2H, ABq,
J = 12.0 Hz, PhCH2O-), 4.59, 4.94 (2H, ABq, J = 10.9 Hz, PhCH2O-), 4.87,
5.00 (2H, ABq, J = 12.5 Hz, PhCH2O-), 7.22–7.33 (20H, m, Ar-H); 13C NMR
(100 MHz, CDCl3): δ: 20.9 (1C, CH3CO-), 63.7 (1C, C-6), 70.8 (1C, PhCH2O),
71.3 (1C, PhCH2O), 73.6 (1C, C-5), 73.7 (1C, C-2), 73.8 (1C, PhCH2O), 74.5
(1C, C-4), 75.1 (1C, PhCH2O), 82.3 (1C, C-3), 100.1 (1C, JC1-H1 = 153.9 Hz,
C-1), 127.4–128.4 (20C, Ar-C), 137.2 (1C, Ar-quat), 138.0 (1C, Ar-quat), 138.1
(1C, Ar-quat), 138.6 (1C, Ar-quat), 170.8 (1C, CH3CO-). HRMS calculated for
C36H38O7Na: 605.2512; found: 605.2523 (M + Na)+.
Acetyl 6-O-acetyl-2,3,4-tri-O-benzyl-α-D-glucopyranoside (6)
Benzyl 2,3,4,6-tetra-O-benzyl-β-D-glucopyranoside (2 g, 3.2 mmol) was dis-
solved in 15 mL Ac2O in a 100 mL round-bottom flask. Selectfluor (2.25 g,
6.3 mmol) was added and the reaction heated under reflux for 2 h. The Ac2O
was removed under high vacuum and the crude residue dissolved in CH2Cl2
(25 mL), transferred to a separatory funnel, and washed with H2O (3 ×
150 mL). The organic layer was dried over anhydrous sodium sulphate and fil-
tered. The filtrate was concentrated in vacuo and the crude residue subjected
to purification by column chromatography using petroleum ether/ethyl acetate
(gradient elution) to afford 6 (1.02 g, 60%); Rf (EtOAc : Pet. Ether; 3:2) = 0.57;
1H NMR (600 MHz, CDCl3): δ: 2.02 (3H, s, CH3CO-), 2.15 (3H, s, CH3CO-), 3.57
(1H, dd, J3,4 = 9.3 Hz, J4,5 = 10.2 Hz, H-4), 3.67 (1H, dd, J1,2 = 3.6 Hz, J2,3
= 9.3 Hz, H-2), 3.94 (1H, ddd, J4,5 = 10.2 Hz, J5,6a = 2.3, J5,6b = 4.0 Hz, H-5),
3.98 (1H, t, J2,3 = 9.3 Hz, J3,4 = 9.3 Hz, H-3), 4.24 (1H, dd, J5,6a = 2.3 Hz, J6a,6b
= 12.2, H-6a), 4.28 (1H, dd, J5,6b = 4.0 Hz, J6a,6b = 12.2, H-6b), 4.57, 4.89 (2H,
ABq, J = 10.7 Hz, PhCH2O-), 4.64, 4.71 (2H, ABq, J = 10.5 Hz, PhCH2O-),
4.83, 4.99 (2H, ABq, J = 10.8 Hz, PhCH2O-), 6.32 (1H, d, J1,2 = 3.6 Hz, H-1),
7.26–7.35 (15H, m, Ar-H); 13C NMR (150 MHz, CDCl3): δ: 20.9 (1C, CH3CO-
), 21.2 (1C, CH3CO-), 62.7 (1C, C-6), 71.2 (1C, C-5), 73.3 (1C, PhCH2O), 75.4
(1C, PhCH2O), 75.8 (1C, PhCH2O), 76.6 (1C, C-4), 78.9 (1C, C-2), 81.7 (1C,
C-3), 89.7 (1C, JC1-H1 = 173.6 Hz, C-1), 127.9–128.6 (15C, Ar-C), 138.5 (1C, Ar-
quat), 137.7 (1C, Ar-quat), 137.5 (1C, Ar-quat), 169.4 (1C, CH3CO-), 170.7 (1C,
CH3CO-). HRMS calculated for C31H34O8Na: 557.2151; found: 557.2092 (M +
Na)+.
Acetyl 6-O-acetyl-2,3,4-tri-O-benzyl-α-D-mannopyranoside (7)
Benzyl 2,3,4,6-tetra-O-benzyl-β-D-mannopyranoside (2 g, 3.2 mmol) was
dissolved in 15 mL Ac2O in a 100 mL round-bottom flask. Selectfluor (2.25 g,

M.S. Tambie and N.K. Jalsa
556
6.3 mmol) was added and the reaction heated under reflux for 2 h. The Ac2O
was removed under high vacuum and the crude residue dissolved in CH2Cl2
(25 mL), transferred to a separatory funnel, and washed with H2O (3 ×
150 mL). The organic layer was dried over anhydrous sodium sulphate and fil-
tered. The filtrate was concentrated in vacuo and the crude residue subjected
to purification by column chromatography using petroleum ether/ethyl acetate
(gradient elution) to afford 7 (1.00 g, 59%); Rf (EtOAc : Pet. Ether; 3:2) = 0.57;
1H NMR (600 MHz, CDCl3): δ: 1.98 (3H, s, CH3CO-), 2.00 (3H, s, CH3CO-), 3.75
(1H, m, H-2), 3.88 (1H, m, H-3, H-5), 4.00 (1H, t, J3,4 = 9.6 Hz, J4,5 = 9.6 Hz,
H-4), 4.30 (1H, dd, J5,6b = 4.5 Hz, J6a,6b = 12.0, H-6b), 4.33 (1H, dd, J5,6
=
2.3 Hz, J6a,6b = 12.0, H-6a), 4.57 (2H, appts, PhCH2O-), 4.60, 4.94 (2H, ABq, J
= 10.8 Hz, PhCH2O-), 4.70, 4.74 (2H, ABq, J = 12.3 Hz, PhCH2O-), 6.20 (1H,
d, J1,2 = 2.0 Hz, H-1), 7.12–7.39 (15H, m, Ar-H); 13C NMR (100 MHz, CDCl3):
δ: 20.8 (1C, CH3CO-), 20.9 (1C, CH3CO-), 63.1 (1C, C-6), 71.9 (1C, PhCH2O),
72.3 (2C, C-5, PhCH2O), 73.1 (1C, C-2), 73.7 (1C, C-4), 75.2 (1C, PhCH2O), 79.0
(1C, C-3), 91.5 (1C, JC1-H1 = 175.1 Hz, C-1), 127.7–128.4 (15C, Ar-C), 137.7 (1C,
Ar-quat), 137.9 (2C, Ar-quat), 168.7 (1C, CH3CO-), 170.7 (1C, CH3CO-). HRMS
calculated for C31H34O8Na: 557.2151; found: 557.2156 (M + Na)+.
Benzyl 2,3,4-tri-O-benzyl-β-D-glucopyranoside (8)
Benzyl 6-O-acetyl-2,3,4-tri-O-benzyl-β-D-glucopyranoside, 4 (1 g, 11.4
mmol) was dissolved in 10 mL of an 8:2 mixture of MeOH:CH2Cl2. To this,
NaOMe (0.1 g, 2.0 mmol) was added and the reaction monitored via TLC un-
til complete consumption of the starting material was observed. The reaction
mixture was neutralized to pH 7 using Amberlyst H+ exchange resin and fil-
tered, and the solvent was removed in vacuo. The crude residue was subjected
to purification by column chromatography using petroleum ether/ethyl acetate
(gradient elution) to afford 8 (0.90 g, 97%); Rf (EtOAc : Pet. Ether; 2 : 3) =
1
0.39; H NMR (400 MHz, CDCl3): δ: 1.81 (1H, bs, OH-6), 3.36 (1H, ddd, J4,5
= 8.4 Hz, J5,6a = 4.4, J5,6b = 2.7 Hz, H-5), 3.49 (1H, t, J1,2 = 8.4 Hz, J2,3
= 8.4 Hz, H-2), 3.57 (1H, t, J3,4 = 8.4 Hz, J4,5 = 8.4 Hz, H-4), 3.66 (1H, dd,
J2,3 = 8.4 Hz, J3,4 = 8.4 Hz, H-3), 3.71 (1H, dd, J5,6a = 4.4 Hz, J6,6b = 12.0,
H-6a), 3.87 (1H, dd, J5,6b = 2.7 Hz, J6,6b = 12.0, H-6b), 4.57 (1H, d, J1,2
=
8.4 Hz, H-1), 4.64, 4.86 (2H, ABq, J = 10.9 Hz, PhCH2O-), 4.69, 4.92 (2H, ABq,
J = 11.9 Hz, PhCH2O-), 4.73, 4.95 (2H, ABq, J = 10.9 Hz, PhCH2O-), 4.81,
4.94 (2H, ABq, J = 10.9 Hz, PhCH2O-), 7.23, 7.38 (20H, m, Ar-H); 13C NMR
(100 MHz, CDCl3): δ: 62.0 (1C, C-6), 71.6 (1C, PhCH2O), 74.9 (2C, PhCH2O),
75.0 (1C, C-5), 75.7 (1C, PhCH2O), 77.5 (1C, C-4), 82.3 (1C, C-2), 84.5 (1C,
C-3), 102.8 (1C, JC1-H1 = 162.0 Hz, C-1), 127.6–128.4 (20C, Ar-C), 137.2 (1C,
Ar-quat), 137.9 (1C, Ar-quat), 138.2 (1C, Ar-quat), 138.4 (1C, Ar-quat). HRMS
calculated for C34H36O6Na: 563.2410; found: 563.2427 (M + Na)+.

Selectfluor Regioselective O-benzyl Acetolysis
557
6-O-acetyl-2,3,4,-tri-O-benzyl-α,β-D-glucopyranose (9)
Acetyl 2,3,4,-tri-O-benzyl-6-O-acetyl-α-D-glucopyranoside (2 g, 3.7 mmol)
was dissolved in THF (25 mL) in a 100 mL round-bottom flask. To this was
added AcOH (0.3 mL, 5.2 mmol) and ethylenediamine (0.3 mL, 4.5 mmol). This
was allowed to stir for 24 h and then the THF was removed under reduced
pressure. The crude residue was dissolved in CH2Cl2 (25 mL), transferred to a
separatory funnel, and washed with 2M HCl (100 mL) and saturated sodium
bicarbonate (100 mL), followed by H2O (3 × 150 mL). The organic layer was
dried over anhydrous sodium sulphate and filtered. The filtrate was concen-
trated in vacuo and the crude residue subjected to purification by column chro-
matography using petroleum ether/ethyl acetate (gradient elution) to afford 9
(1.51 g, 82%) (α:β, 2:1); Rf (EtOAc : Pet. Ether; 3:2) = 0.45; 1H NMR (600 MHz,
CDCl3): δ: 1.95 (6H, m, (α + β) CH3CO-), 3.42 (1H, dd, J1,2 = 7.9 Hz, J2,3
=
8.9 Hz, H-2β), 3.48 (2H, m, H-5β, OH-1α), 3.51 (2H, m, H-4α, H-4β), 3.54 (1H,
dd, J1,2 = 3.5 Hz, J2,3 = 9.2 Hz, H-2α), 3.65 (1H, t, J2,3 = 8.9 Hz, J3,4 = 8.9 Hz,
H-3β), 4.06 (1H, t, J2,3 = 9.2 Hz, J3,4 = 9.4 Hz, H-3α), 4.08 (1H, ddd, J4,5
10.2 Hz, J5,6a = 2.2, J5,6b = 4.2 Hz, H-5α), 4.16 (1H, dd, J5,6b = 4.7 Hz, J6a,6b
=
=
11.9 Hz, H-6b-β), 4.23 (1H, dd, J5,6b = 4.2 Hz, J6a,6b = 12.0 Hz, H-6b-α), 4.29
(1H, dd, J5,6a = 2.2 Hz, J6a,6b = 12.0 Hz, H-6a-α), 4.34 (1H, dd, J5,6a = 2.0 Hz,
J6a,6b = 11.9 Hz, H-6a-β), 4.56, 4.85 (2H, ABq, J = 10.8 Hz, PhCH2O-β), 4.58,
4.87 (2H, ABq, J = 11.0 Hz, PhCH2O-α), 4.64 (1H, d, J1,2 = 7.9 Hz, H-1β),
4.66, 4.70 (2H, ABq, J = 12.0 Hz, PhCH2O-α), 4.74, 4.97 (2H, ABq, J = 11.1 Hz,
PhCH2O-β), 4.80, 4.94 (2H, ABq, J = 10.9 Hz, PhCH2O-β), 4.83, 4.98 (2H, ABq,
J = 10.9 Hz, PhCH2O-α), 5.17 (1H, d, J1,2 = 3.5 Hz, H-1α), 127.5–128.3 (30H,
m, (α + β) Ar-H); 13C NMR (100 MHz, CDCl3): δ: 20.7 (2C, (α + β) CH3CO-),
63.0 (2C, C-6α, C-6β), 68.4 (1C, C-5α), 72.6 (1C, C-5β), 72.8 (1C, PhCH2O-α),
74.5 (2C, PhCH2O-β), 74.8 (1C, PhCH2O-α), 75.5 (2C, (α + β) PhCH2O-), 77.0
(2C, C-4α, C-4β), 79.8 (1C, C-2α), 81.4 (1C, C-3α), 82.8 (1C, C-2β), 84.3 (1C,
C-3β), 90.7 (1C, JC1-H1 = 169.0 Hz, C-1α), 97.2 (1C, JC1-H1 = 163.0 Hz, C-1β),
127.5–128.3 (30C, (α + β) Ar-C), 137.4–138.3 (6C, (α + β) Ar-quat), 170.8 (2C,
(α + β) CH3CO-). HRMS calculated for C29H32O7Na: 515.2046; found: 515.2007
(M + Na)+.
ACKNOWLEDGMENTS
The authors are grateful to Dr. Nadia Singh and Mr. Keegan Dial for the pro-
vision of NMR spectroscopy data and Mr. Franklyn Julien for the provision of
high-resolution mass spectroscopy data.
FUNDING
Many thanks to the University of the West Indies, St. Augustine Campus,
Trinidad and Tobago, for their financial support.

M.S. Tambie and N.K. Jalsa
558
REFERENCES
1. Soliman, S.E.; Kova´cˇ, P. Stereoselective syntheses of the conjugation-ready, down-
stream disaccharide and phosphorylated upstream, branched trisaccharide fragments
of the O-PS of Vibrio cholerae O139. J Org Chem. 2015, 80, 4851–4860.
2. Kratz, E.M.; Kałuz˙a, A.; Zimmer, M.; Ferens-Sieczkowska, M. The analysis of sia-
lylation, N-glycan branching, and expression of O-glycans in seminal plasma of infertile
men. Dis Markers. 2015, 2015, 941871–941878.
3. Handerson, T.; Pawelek, J.M. β 1,6-Branched oligosaccharides and coarse vesicles:
a common, pervasive phenotype in melanoma and other human cancers. Cancer. Res.
2003, 63, 5363–5369.
4. Boons, G.-J. Protecting groups. In Organic Synthesis with Carbohydrates.
Sheffield Academic Press: Massachusetts, 2000; pp. 26–53.
5. Lindhorst, T.K. Protecting groups for carbohydrates. In Essentials of Carbohydrate
Chemistry and Biochemistry. Wiley-VCH: Weinheim, Germany, 2007; pp. 53–55.
6. Osborn, H.M. Best Synthetic Methods. Academic Press: New York, 2003.
7. Wuts, P.G.M.; Greene, T.W. Protection for the hydroxyl group, including 1, 2 and 1,
3 diols. In Green’s Protective Groups in Organic Synthesis, 4th ed. Wiley-Interscience:
New Jersey, 2007; pp. 24–221.
8. Kova´cˇ, P. Proven Synthetic Methods, Vol. 1. CRC Press: Boca Raton, FL, 2012.
9. Sakai, J.-I.; Takeda, T.; Ogihara, Y. Selective acetolysis of benzyl ethers of methyl
D-glucopyranosides. Carbohydr. Res. 1981, 95, 125–131.
10. Cao, Y.; Yamada, H. Corrected order in the simultaneous debenzylation-acetolysis
of methyl 2,3,4,6-tetra-O-benzyl-α-D-glucopyranoside. Carbohydr. Res. 2006, 341,
909–911.
11. Pastore, A.; Valerio, S.; Adinolfi, M.; Iadonisi, A. An easy and versatile approach
for the regioselective de-O-benzylation of protected sugars based on the I2 / Et3SiH
combined system. Chem. Eur. J. 2011, 17, 5881–5889.
12. Lecourt, T.; Herault, A.; Pearce, A.J.; Sollogoub, M.; Sinay, P. Triisobutylalu-
minium and diisobutylaluminium hydride as molecular scalpels: the regioselective
stripping of perbenzylated sugars and cyclodextrins. Chem. Eur. J. 2004, 10, 2960–2971.
13. Yang, G.; Ding, X.; Kong, F. Selective 6-O-debenzylationof mono-and disaccharide
derivatives using ZnC12-Ac2O-HOAc. Tetrahedron Lett. 1997, 38, 6725–6728.
14. Giordano, M.; Iadonisi, A.; Pastore, A. Regioselective acetolysis of highly O-
benzylated carbohydrates promoted by iodine or an iodine / silane combined reagent:
use of isopropenyl acetate as an alternative to acetic anhydride. Eur. J. Org. Chem.
2013, 3137–3147.
15. Hori, H.; Nishida, Y.; Ohrui, H.; Meguro, H. Regioselective de-O-benzylation with
Lewis acids. J. Org. Chem. 1989, 54, 1346–1353.
16. Xiea, J.; Me´nanda, M.; Vale´rya, J.-M. Regioselective debenzylation of C-glycosyl
compounds by boron trichloride. Carbohydr. Res. 2005, 340, 481–487.
17. Lipta´k, A.; Joda´l, I.; Na´na´si, P. Stereoselective ring-cleavage of 3-O-benzyl- and
2,3-di-O-benzyl-4,6-O-benzylidenehexopyranoside derivatives with the LiAlH4 / AlCl3,
reagent. Carbohydr. Res. 1975, 44, 1–11.
18. Ogilvie, K.K.; Hakimelahi, G.H. A general method for selective silylation of pri-
mary hydroxyl groups in carbohydrates and related compounds. Carbohydr. Res. 1983,
115, 234–239.

Selectfluor Regioselective O-benzyl Acetolysis
559
19. Lewisa, A.; Stefanutia, I.; Swaina, S.A.; Smith, S.A.; Taylor, R.J.K. Carbohydrate-
based routes to salicylate natural products: formal total synthesis of (+)-apicularen A
from D-glucal. Tetrahedron. Lett. 2001, 42, 5549–5552.
20. Chaudhary, S.K.; Hernandez, O. A simplified procedure for the preparation of
triphenylmethylethers. Tetrahedron. Lett. 1979, 20, 95–98.
21. Jalsa, N.K. Regioselective removal of the anomeric O-benzyl from differentially
protected carbohydrates. Tetrahedron. Lett. 2011, 52, 6587–6590.
22. Banks, R.E. Fluorinated diazabicycloalkane derivatives. US Patent 5,086,178,
1992.
23. Nyffeler, P.T.; Duro´n, S.G.; Burkart, M.D.; Vincent, S.P.; Wong, C.H. Selectfluor:
mechanistic insight and applications. Angew. Chem. Int. Ed. 2004, 44, 192–212.
24. Banks, R.E. SelectfluorTM reagent F-TEDA-BF4 in action: tamed fluorine at your
service. J. Flourine Chem. 1998, 87, 1–17.
25. Hart, J.J.; Syvret, R.G. Industrial scale production of SelectfluorTM fluorination
agent: from initial concept to full scale commercial production in a 5 year period. J.
Flourine Chem. 1999, 100, 157–161.
26. Banks, R.E.; Mohialdin-Khaffaf, S.N.; Lal, G.S.; Sharif, I.; Syvret, R.G. 1-Alkyl-4-
fluoro-1,4-diazoniabicyclo[2.2.2]octane salts: a novel family of electrophilic fluorinating
agents. J. Chem. Soc. Chem. Commun. 1992, 8, 595–596.
27. Shimizu, M.; Hiyama, T. Modern synthetic methods for fluorine-substituted target
molecules. Angew. Chem. Int. Ed. 2004, 44, 214–231.
28. Singh, R.P.; Shreeve, J.M. Recent highlights in electrophilic fluorination with
1
chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate). Acc.
Chem. Res. 2004, 37, 31–44.
29. Decoster, E.; Lacombe, J.M.; Strebler, J.L.; Ferrari, B.; Pavia, A.A. Une Autre Ap-
proche A La Synthese De Derives Benzyles Des Monosaccharides Reducteurs. Etude
Des Equilibres Pyrannose- Furannose Par R.M.N. Du Carbone-13. J. Carbohydr. Chem.
1983, 2, 329–341.
30. Beier, R.C.; Mundy, B.P.; Strobel, G.A. Assignment of anomeric configuration and
identification of carbohydrate residues by 13C NMR. 1. Galacto- and glucopyranosides
and furanosides. Can. J. Chem. 1980, 58, 2800–2804.
31. Lehtila¨a, R.L.; Lehtila¨a, J.O.; Roslunda, M.U.; Leinoa, R. Selectively protected
galactose derivatives for the synthesis of branched oligosaccharides. Tetrahedron 2004,
60, 3653–3661.
32. Roslund, M.U.; Aitio, O.; Wa¨rna˚, J.; Maaheimo, H.; Murzin, D.Y.; Leino, R., Acyl
group migration and cleavage in selectively protected-D-galactopyranosides as studied
by NMR spectroscopy and kinetic calculations. J. Am. Chem. Soc. 2008, 130, 8769–8772.