Introducing Oxo-Phenylacetyl (OPAc) as a Protecting Group for Carbohydrates

Article abstract of DOI:10.1021/acs.joc.9b00126

A series of oxo-phenylacetyl (OPAc)-protected saccharides, with divergent base sensitivity profiles against benzoyl (Bz) and acetyl (Ac) were synthesized, and KHSO₅/AcCl in methanol was identified as an easy, mild, selective, and efficient deprotecting reagent for their removal in the perspective of carbohydrate synthesis. Timely monitoring of AcCl reagent was supportive in both sequential and simultaneous deprotecting of OPAc, Bz, and Ac. The salient feature of our method is the orthogonal stability against different groups, its ease to generate different valuable acceptors using designed monosaccharides, and use of OPAc as a glycosyl donar.

Full text of DOI:10.1021/acs.joc.9b00126

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Article
Introducing Oxo-Phenylacetyl (OPAc) as
a Protecting Group for Carbohydrates.
Atul Kumar, Veeranjaneyulu Gannedi, Suhail A. Rather, Ram A. Vishwakarma, and Qazi Naveed Ahmed
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.9b00126 • Publication Date (Web): 19 Mar 2019
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Introducing Oxo-Phenylacetyl (OPAc) as a Protecting Group
for Carbohydrates.
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Atul Kumar,† Veeranjaneyulu Gannedi,†,‡,║ Suhail A. Rather, Ram A. Vishwakarma
,‡,║
†,‡
†,
and Qazi Naveed Ahmed †,‡*
†
Medicinal Chemistry Division, Indian Institute of Integrative Medicine (IIIM), Jammu,
India.
‡
Academy of Scientific and Innovative Research (AcSIR-IIIM), Jammu-180001, India.
║
Both authors contributed equally
Supporting Information Placeholder
Protection
PhCOCO2H/PhCOCOCl/
OOPAc
PhCOCHO
AcPOO
O
O
O
OOPAc
O
OH
7
7
O
KHSO5/AcCl
O
OMe
29 examples
Yields up to 93%
in MeOH
7
7
Deprotection
O
ABSTRACT: A series of oxo-phenylacetyl (OPAc) protected saccharides, with divergent base
sensitivity profiles against benzoyl (Bz) and acetyl (Ac), were synthesized and KHSO /AcCl in
5
methanol was identified as an easy, mild, selective and efficient deprotecting reagent for their removal
in the perspective of carbohydrate synthesis. Timely monitoring of AcCl reagent was supportive in
both sequential as well as simultaneous deprotecting of OPAc, Bz and Ac. The salient feature of our
method is the orthogonal stability against different groups, its ease to generate different valuable
acceptors using designed monosaccharides and use of OPAc as a glycosyl donar.
INTRODUCTION
Oligosaccharides, which are essential to all cellular organisms, play vital roles in cell
1
recognition, signalling, and are involved in a broad range of biological processes. They are
more complex than any other biological polymers, and are frequently present as
2
heterogeneous mixtures in nature. The chemical synthesis of carbohydrates represents a
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powerful tool to provide homogeneous glycans. In carbohydrate synthesis, the major concern
is the orthogonal protection of hydroxyl groups that can be unmasked independently.4
Classical protecting groups include benzyl ethers (Bn), which are normally cleaved through
hydrogenolysis or by means of metal reduction, and acetate (Ac), benzoate (Bz) or pivaloate
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esters, which are removed using base promoted hydrolysis. The protecting group approaches
in oligosaccharide synthesis generally rely on benzyl ethers (Bn) as the dominant protecting
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groups for hydroxyl functionalities. However, the reaction conditions required for Bn
removal are not compatible with the double bonds present in the lipid moiety of various
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glycolipids (Figure 1). Previously, these issues were addressed through the use of benzoyl
8
esters, PMB ethers, and napthyl ethers. Despite being successful to some extent, these groups
faced challenges in context to the saponification of the fatty acid esters during base mediated
Bz/Ac removal, the low stability of PMB ethers under the mild acidic conditions commonly
used for glycosylations, use of multiple reagent system for the removal of napthyl group and
their low efficiency in the orthogonal protecting group manipulation during multistep transfo-
O

3
HN
17

4
14
O
OH

3

1
Gangliosides

3
6

4

2
6
O
OH
P
O
O
O
O O
O
7
7
7
7
GPI anchors
PEtN
Man GlcAInositol Neu5Ac GalA Glu Gal
Figure 1: Representative structures of glycolipids.
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rmations at the late stage of any given oligosaccharide synthesis. In contrast, standardized
mild, slightly labile, single-step, base-mediated deprotection procedure is widely desirable in
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glycolipids (containing unsaturation) synthesis that surmounts the limitations of earlier
procedures. To address this practical issue with esters, we envisage the possibility of design-
Scheme 1: Summary of this work
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Our design:
Bz
O

O
base (B)
O
O
O
OH
+
B
more electrophilic
O
O O 
base (B)
CO

Free saccharide
O
OPAc
Due to enhanced electrophilic charater
of CO group in oxoesters, deprotection
strategy could be tested under milder
conditions in comparison to Bz
Thereby, deprotection strategy in our
group (OPAc) can be fine tuned
seletively under milder conditions
keeping Bz intact
This work:
a) Oxo-Phenylacetyl as novel protecting group
Protection
PhCOCO H 2, DIC, DMAP
2
O
O
O
OH
PhCOCOCl 3
Bz
or
O
PhCOCHO 4, CuBr, pyridine
O
KHSO in dry
MeOH (65 C)
5
o
OOPAc
or AcCl in dry MeOH (rt)
Deprotection
b) Deprotection strategy with in the ester group
AcPOO
HO
HO
O
AcCl in dry MeOH (rt)
O
AcCl in dry MeOH (rt)
OAc
O
OAc
OH
BzO
BzO
BzO
HO
Sequential deprotection strategy with in the group (esters)
AcCl in dry
MeOH, (rt)
HO
AcCl in dry MeOH (rt)
O
OH
Simultaneous deprotection of all ester groups
c) Application towards acceptor synthesis
OH
OOPAc
O
O
2, DIC, DMAP
HO
AcPOO
HO
HO
BzO
BzO
Acceptor
OMe
OMe
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ing oxo-phenylacetyl (OPAc) as a new protecting group for carbohydrates (Scheme 1). The
main inspiration behind this work is the enhanced electrophilic character of OPAc in
1
0
comparison to simple Bz. This type of protecting groups besides being the surrogate of
benzoate, and acetate can overcome the limitations to some extent. In this communication, we
synthesized different OPAc protected saccharides using phenylglyoxalic acid 2, 2-oxo-2-
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phenylacetyl chloride 3 or phenylglyoxal 4 as coupling reagent and also found that KHSO in
5
methanol was recognized as an efficient, mild deprotecting reagent for their selective
deprotection. AcCl in dry methanol was also effective in the removal of OPAc group.
However, timely monitoring of AcCl reagent was helpful in establishing both sequential as
well as simultaneous deprotecting of OPAc, Bz and Ac. This method further proved valuable
in the synthesis of different acceptors using designed monosaccharides.
RESULTS AND DISCUSSION
Our investigation began with the coupling between Methyl-2,3,4-tri-O-benzyl-α-D-
glucopyranoside 1a and phenylglyoxalic acid 2 using conventional DIC and DMAP coupling
1
1
procedure in DCM (entry 1, Table 1). Herein, we isolated desired product 5a in 91% yield,
when 1 mmol of 1a was treated with 1.2 mmol of 2, 1.2 mmol of DIC and 1.2 mmol of
DMAP in 3 mL of DCM at rt for 3 h. Further, reaction was performed with 2-oxo-2-phenyl-
acetyl chloride 3 (1.2 mmol) as coupling partner to 1a (1 mmol) in pyridine:DCM (1:1) at rt
1
2
for 8 h as per literature proceure that led to the synthesis of 5a in 93% yields (entry 2). In
order to have diversity in coupling partners, we also performed reaction of 1a (1 mmol) with
phenylglyoxal 4 (1.2 mmol) as per Ning Jiao’ procedure and successfully isolated 5a in good
1
3
yields (entry 3). Next, we performed different sets of experiments to remove the OPAc
groups under milder conditions (entries 4-9). Luckily, in one of our previous works, we
observed that α-oxoesters are unstable in oxone environment and undergoes CO-CO cleavage
to simple ester and respective alcohol.14 Based on this finding, we performed different
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o
experiments with varied concentrations of KHSO at 65 C (entries 4-7) and found that 5
5
o
mmol of oxone gave the best results in dry methanol at 65 C (entry 7). In addition, we also
tried to optimize the deprotection of OPAc group in compound 5a using acetylchloride
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(
AcCl) in dry methanol (entries 8-9). Interestingly, we found that 0.7 mmol of AcCl in 3 mL
of dry methanol at rt completely deprotected the OPAc with in 30 min (entry 9).
Table 1. Optimization of the reaction
Protection
/3/4, reagent, additive
2
AcPOO
HO
BnO
BnO
solvent
O
BnO
BnO
O
reagent
solvent
Deprotection
BnO
BnO
OMe
OMe
5a
1
a
For protection:
entry 2/3/4 (mmol)
o
yields (%)g
reagent
mmol)
DIC (1.2) DMAP(1.2)
additive (mmol)
solvent
DCM
temp ( C) time (h)
(
1a
2b
3c
2 (1.2)
3 (1.2)
4 (1.2)
rt
rt
65
3
8
8
91
93
61
-
-
-
pyridine/DCM(1:1)
toluene
CuBr (0.1), pyridine
(1.2)
For deprotection:
5a (1.0) KHSO
4
5
5
5
(1.0)
(2.0)
(4.0)
(5.0)
-
-
-
-
-
-
dry MeOH
dry MeOH
dry MeOH
dry MeOH
dry MeOH
dry MeOH
65
65
65
65
rt
8
8
8
8
0.5
0.5
13
27
67
92
89
96
5
5a (1.0) KHSO
5a (1.0) KHSO
5a (1.0) KHSO
6
7d
8
5
5a (1.0)
AcCl (0.5 )
9e
5a (1.0)
AcCl (0.7 )
rt
a
For protection: Phenylglyoxalic acid 2 (1.2 mmol), DIC (1.2 mmol) and DMAP (1.2 mmol) in 3 mL of DCM at rt for 3 h,
-Oxo-2-phenylacetyl chloride 3 (1.2 mmol), in 3 mL of pyridine:DCM (1:1) at rt for 8 h, Phenylglyoxal 4 (1.2 mmol),
CuBr (1.2 mmol) and pyridine (1.2 mmol) in 3 mL of toluene at 65 C for 8 h, For deprotection: 5a (1.0 mmol), KHSO
5.0 mmol in 3mL of dry MeOH at 65 C for 8 h, 5a (1.0 mmol), AcCl (0.7 mmol), in 3 mL of dry MeOH at rt for 30 min,
b
c
2
o
d
5
o
e
(
g
Isolated yields.
Following these optimized conditions for OPAc protections, a series of protected saccharides
a-5ac were synthesised (Table 2). In one set of experiments, different mono- OPAc
5
protected saccharides were synthesised (5a-5r). As depicted in Table 2, we isolated different
mono oxo-phenylacetyl protected products at different hydroxyl position in good yields. It
was observed that despite change in nature of hydroxyl group (C1, C2, C3, C4 or C6),
protecting groups (Bn, Me, TIPS, Bz, Ac, benzylidene, TBDMS, All, PMB, acetal, NAP,
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Lev, Piv etc.), and sugar/pseudosugar (mono, di/tri-saccharide), the yields of desired products
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were appreciable. Another set of experiments were performed to generate different di OPAc
Table 2. Scope of the reaction
OH n1
OOPAc
reagent
n1 n1= 1 to 4
n2= 4 to 1
0
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PO
PO
n2
n2
5
AcPOO
OTIPS
O
O
O
TIPSO
AcPOO
(5d, 90%)
Ph
Ph
O
O
O
O
BnO
BnO
O
AcPOO
BnO
AcPOO
BnO
BzO OMe
OMe
BnO
OMe
OMe
(
5c, 89%)
(5a, 91%)
(
5b, 87%)
OBn
OTIPS
OTBDPS
O
OMe
O
O
O
O
BnO
BnO
AcPOO
AcPOO
AcO
AcPOO
BzO
PMBO
BnO
5e, 85%)
OOPAc
SPh
PMBO
BzO
BzO
OAllyl
OMe
OMe
(
(
Ph
5f, 87%)
(5h, 81%)
(
5g, 83%)
Ph
O
AcPOO
BnO
OOPAc
O
O
BnO
BnO
BnO
O
O
AcPOO
BnO
BnO
O
O
NHCOCCl3
5i, 85%)
O
(
OMe
ONAP
AcPOO
(5k, 83%)
(5l, 88%)
OMe
BzO
(5j, 79%)
O
OOPAc
BnO
O
O
O
BnO
O
BnO
AcPOO
O
BnO
PMBO
OBn
OBn
O
O
BnO
O
OMe
(5p, 84%)
AcPOO
AcPOO
(
5o, 87%)
(5m, 92%)
O
O
OOPAc
OOPAc
O
O
AcPOO
AcPOO
BnO
(
5n, 91%)
LevO
OOPAc
OOPAc
O
Ph
O
O
BnO
PivO
BnO
O
OMe
BnO
OMe
5t, 88%)
BnO
BnO
(5s, 83%)
(
O
O
BnO
BnO
BnO
Ph
O
O
O
BzO
BnO
BnO
BnO
O
O
AcPOO
O
BnO
BnO
BnO
O
AcPOO
AcPOO
O
AcPOO OMe
(5u, 86%)
ONAP
BzO
OMe
(
5q, 81%)
ONAP
(
5v, 82%)
(
5r, 78%)
BnO
OOPAc
OBn
OBn
OOPAc
OBz
OOPAc
BnO
AcPOO
AcPOO
BzO
O
O
AcPOO
AcPOO
AcPOO
AcPOO
AcPOO
OBn
O
(
5w, 79%)
BzO
OMe
(
5y, 79%)
AcPOO
OAllyl
(5x, 84%)
(
5z, 75%)
OOPAc
O
OOPAc
O
OOPAc
O
AcPOO
AcPOO
AcPOO
AcPOO
AcPOO
AcPOO
SPh
SPhMe
AcPOO
AcPOO
5ab, 73%)
NHCOCCl3
OMe
(5ac, 71%)
(
5aa, 72%)
(
Reaction condition: (a) For mono protection; 2 (1.2 mmol), DIC (1.2 mmol) and DMAP (1.2 mmol) in 3 mL of DCM at
rt for 3 h, (b) For di protection; 2 (2.4 mmol), DIC (2.4 mmol) and DMAP (2.4 mmol) in 5 mL of DCM at rt for 6 h, (c)
For tri protection; 2 (3.6 mmol), DIC (3.6 mmol) and DMAP (3.6 mmol), in 8 mL of DCM at rt for 12 h, (d) For tetra
protection; 2 (4.8 mmol), DIC (4.8 mmol) and DMAP (4.8 mmol), in 10 mL of DCM:DMF (1:1) at rt for 36 h.
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protected saccharides (5s-5w). Yields were generally good for all di protected substrates as
well. After having established the mono- and di- protected substrate scope, a small library of
different tri- and tetra- OPAc protected saccharides were also generated (5x-5ac). In these
cases as well, yields were good for all the reactions conducted.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
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3
4
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4
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4
4
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5
5
5
5
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0
Next, we performed different sets of experiments to deprotect all the OPAc protected
substrates as per the optimized conditions (Table 3). Primarily, oxone based deprotection
strategy was selected for further investigations against all the series of saccharides
synthesized in Table 2 (5a-5ac). In all the reactions, we isolated the corresponding hydroxyl
products in good yields. In oxone environment, we found that most of the common protecting
groups such as Bn, Bz, Ac, Me, TIPS, TBDMS, All, NAP, Lev, Piv etc. (6a-6ac) were stable.
However acetal, ketal and PMB based protections were sensitive to oxone (6c, 6d, 6f, 6i, 6j,
6
m, 6n, 6p, 6r, & 6u). This unstable nature of substrates containing benzylidene (5c, 5d, 5i,
5j, 5r, & 5u) could be useful in the construction of branched oligosaccharides through
selective ring opening, then glycosylation followed by OPAc deprotection and again
glycosylation. In a similar way, different reactions were carried out under AcCl environment
in dry MeOH as per the optimized conditions (6a-6ac) and in all cases we isolated slightly
better yields of the corresponding hydroxyl products. As expected, the acetals and ketals were
also found to be unstable and generated products with additional free hydroxyl groups (6c,
6
d, 6i, 6j, 6m, 6n, 6r & 6u). However, PMB group was found orthogonally stable under
AcCl environment (6f* and 6p*). The paramount feature of both the deprotection conditions
was the ease of deprotection of OPAc in presence of allyl group under milder conditions (6h
&
6z).
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1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
Table 3. Compatibility of OPAc removal with common protecting groups in all substrates
using oxone, AcCl in dry MeOH
OH n1
OOPAc
n1
reagent
n1= 1 to 4
n2= 4 to 1
PO
PO
n2
n2
6
5
HO
OTIPS
O
OH
HO
OBn
O
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
O
O
HO
BnO
BnO
HO
BnO
O
TIPSO
HO
HO
BnO
HO
BnO
BnO
BnO
OMe
OMe
OMe
BzO
BnO
OH
a
b
OMe
(6d, 85%, 92%)
a
b
(6b,
a
85%,
b
89%)
a
b
(
6a, 84%, 90%)
a
b
(6e, 86%, 93%)
(
6c, 83%, 91%)
OTIPS
O
OTIPS
O
OTBDPS
OMe
O
HO
O
HO
HO
O
SPh
HO
HO
HO
AcO
HO
BzO
O
PMBO
PMBO
NHCOCCl3
PMBO
PMBO
BzO
BzO
OMe
OMe
OMe
87%)
OAllyl
a
b
(
6i, 81%, 83%)
a
b
(6g,
a
83%,
b
(
6f, 82%),
(6f* 88%)
a
b
(
6h, 82%, 86%)
OH
OH
O
OH
OHOH
O
BnO
BnO
HO
HO
BnO
HO
O
HO
O
O
BnO
BnO
BnO
HO
HO
ONAP
HO
OH
HO
OH
OMe
a
b
a
b
BzO
(6n, 91%, 93%)
OMe
(6l, 88%, 91%)
a
b
a
b
(6m, 89%, 90%)
(
6j, 84%, 86%)
a
b
(6k, 86%, 89%)
OH
O
OH
O
BnO
BnO
BnO
HO
HO
BnO
BnO
O
BnO
BnO OH
BnO OH
O
O
HO
BnO
OBn
OBn PMBO
BnO
OBn
OBn
O
BnO
BnO
BnO
BnO
HO
BnO
O
OMe
BnO
a
b
BnO
(6o, 86%, 89%)
a
b
(
6p, 83%,)
(6p*, 87%)
BnO
O
O
ONAP
BnO
a
b
.
.(6q, 81%, 84%)
BnO
ONAP
a
b
(
6r, 79%, 81%)
OH
O
OH
O
HO
HO
BnO OH
OH
O
BnO
OBn
OBn
HO
HO
O
HO
LevO
HO
BnO
HO
HO
a
b
HO
OMe
(6w, 83%, 85%)
PivO
BnO
a
b
BzO
(6v, 86%, 89%)
OMe
OMe
OMe
a
b
a
b
a
b
(
6s, 76%, 83%)
(6t, 87%, 88%)
(6x, 78%, 79%)
OBz
O
OH
HO
HO
O
HO
HO
HO
HO
HO
HO
HO
O
O
HO
SPh
SPhMe
HO
HO
OBn
O
NHCOCCl3
HO
BzO
HO
OMe
HO
a
b
a
b
(
6aa, 76%, 79%)
a
b
(6ac, 79%, 83%)
a
b
HO
(6ab, 77%, 81%)
(6y, 77%, 81%)
OAllyl
a
b
(
6z, 74%, 76%)
Reaction condition: For deprotection of each OPAc group, we employed either a5.0 mmol of KHSO
in 5 mL of dry
5
MeOH at 65 C or b0.7 mmol of AcCl in 5 mL of dry MeOH at rt (for details, see SI). 6f* and 6p* represents the
o
deprotected compound in the presence of AcCl in MeOH condition.
Furthermore, the judicious monitoring of AcCl reagent against substrate 7 was beneficial in
establishing sequential as well as simultaneous deprotecting OPAc, Bz and Ac (Scheme 2a).
Compound 7 when monitored under the AcCl in dry MeOH environment for 30 min at rt
selectively released OPAc (compound 8). However, the continue stirring of 8 with AcCl
reagent for 3 h removed Ac (compound 9). Finally, compound 9 when stirred for 12 h
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released Bz as well. The substrate 7, when stirred continuously with the same reagent for 12 h
removed all ester protections in one pot. It might be ambiguous that the sequential
deprotection (OPAc, Ac, Bz) resulted whether from the properties of each protecting groups,
or from the intrinsic reactivity derived from the structural factor of the employed sugar. In
Scheme 2. a) Sequential and simultaneous deprotection. b) Validation of the concept for
selective OPAc deprotection
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
OTIPS
O
(
a)
OTIPS
O
OTIPS
O
AcCl (0.7 mmol)
HO
HO
AcPOO
HO
AcO
AcCl (0.7 mmol)
dry MeOH, 6 h, (rt)
AcO
dry MeOH, 30 min, (rt)
BzO
BzO
BzO
OMe
OMe
OMe
9, 85%
7
8
, 82%
Sequential deprotection
AcCl (0.7 mmol) dry
MeOH, 12 h, (rt)
OTIPS
AcCl (2.5 mmol) dry
MeOH, 12 h, (rt)
O
HO
HO
Simultaneous deprotection
HO
(b)
OMe
OAc
6f, 87%
OAc
O
AcCl (0.7 mmol)
dry MeOH, 30 min, (rt)
AcO
AcPOO
O
AcO
HO
BzO
OMe
BzO
OMe
10
11, 84%
this contest, we performed a control experiment using the compound 10 where in we
exchanged the positions of OPAc and Ac. It is quite evident that despite change in positions,
OPAc was successfully removed (Scheme 2b). These experiments clearly highlight the
advantage of using OPAc as a labile group within ester protecting groups, which could be
useful for the synthesis of different oligosaccharides.
With the detailed deprotection profile revealed, we sought to examine the compatibility of
OPAc with other commonly used acid labile protecting groups, SEt, Bn, and allyl groups
(Scheme 3). Orthogonality between PMB, TIPS and OPAc was established using
differentially protected glucoside 5f, where in regiospecific removal of all the three groups
was readily achieved. In this case, we also presented the selective removal of TIPS in
presence of PMB in 2N HCl system. Furthermore, the selective cleavage of NAP in 5l was
also achieved by stirring with DDQ in DCM:MeOH. In addition, glucosides 15, 17 and 5t
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1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
were prepared and their orthogonality between OPAc against SEt, All and OBn were
demonstrated. These observations reveal the nature of our group that are orthogonal to
classical acid labile and other commonly used protecting groups, and set the stage for
exploring them in the synthesis of complex glycolipids possessing unsaturation.
Scheme 3. Orthogonal stability against different groups
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
OTIPS
O
OH
OTIPS
O
O
a
AcPOO
PMBO
PMBO
b
AcPOO
PMBO
PMBO
AcPOO
HO
HO
OMe
OMe
OMe
13, 82%
1
2, 93%
5f
OOPAc
O
OOPAc
O
BnO
BnO
BnO
BnO
14, 84%
BnO
c
BnO
5l
ONAP
OH
OOPAc
O
OOPAc
O
d
AcPOO
AcPOO
SEt
AcPOO
AcPOO
PhthN
PhthN
OH
1
5
16, 79%
OOPAc
O
BnO
OOPAc
O
BnO
e
BnO
BnO
BnO
BnO
OH
OAll
18, 76%
17
OOPAc
OOPAc
O
O
f
AcPOO
AcPOO
BnO
HO
BnO
HO
OMe
OMe
5t
19, 72%
Reaction condition: a) TFA (1.0 mmol), DCM, rt. 30 min; b) 2N HCl, MeOH, rt. 15 h; c) DDQ (3 mmol), DCM, rt. 8 h; d)
NBS (2.5 equiv), Acetone:H
DCM/H O; f) BCl
2
3 3 2 2
O (9:1), rt, 1 h; e) 1) Rh(PPh ) Cl, DIPEA, EtOH: toluene: H O (7:3:1). 2) HgO/HgCl ,
o
2
3
(5 equiv), 2 h, -78 C.
The potential of the OPAc protection was next evaluated for the generation of different
valuable acceptors under modified conditions (Scheme 4a, 20a-20d). We were fortunate to
observe that in different reactions of tri-OH free designer saccharides with 2.4 mmol of
phenylglyoxalic acid, DIC (2.4 mmol), and DMAP (2.4 mmol), a complete regioselective
OPAc protection was observed based on the expected reactivity order of different hydroxyl
15
groups. The reason behind the better selectivity of OPAc protection in comparison to Bz is
assumed to be its better reactivity/steric hindrance with neighbouring OPAc group in
comparison to normal acids under DIC and DMAP conditions. In order to compare, the better
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regioselective OPAc protections of the above selected sugars in comparison to Bz, we
conducted the same experiment in case of the benzoylation with substrate 21 (Scheme 4b),
wherein we isolated mixture of three different products (21a: 21b: 6v).
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Scheme 4. a) Acceptor Synthesis b) Regioselectivity comparision between OPAc and Bz
protections.
HO
OP1 2 (2.4 mmol), DIC (2.4 mmol)
OP1
OP2
HO
DMAP (2.4 mmol)
a)
3
AcPOO
OP2
2
20
OOPAc
O
OBz
HO
OOPAc
O
AcPOO
HO
O
HO
HO
AcPOO
OBn
O
AcPOO
BzO
SPh
AcPOO
AcPOO
BzO
OMe
AcPOO
NHCOCCl3
OAll
(
20b, 73%)
(
20a, 76%)
(
20c, 71%)
( 69%)
20d,
b)
OBz
OBz
OBz
OH
Bz-Cl (2.2 equiv)
pyridine
O
O
O
O
HO
BzO
BzO
HO
HO
HO
HO
HO
BzO
BzO
BzO
BzO
OMe
OMe
OMe
21b, 32%
OMe
6v, 9%
21
21a, 56%
Finally, to check the compatibility of our group towards normal glycosylation conditions and
the application of OPAc as a glycosylation donor, we performed two different sets of
experiments (Scheme 5). On one hand, a reaction was conducted between 20a and TCA
1
6
based donor 22 by using different activators (Scheme 5a) where in we isolated the expected
Scheme 5. Glycosylation: a) OPAc protected glycosyl acceptor b) OPAc as glycosyl donor
a)
OOPAc
O
OAc
HO
AcPOO
20a BzO
OOPAc
O
OAc
O
AcO
AcO
O
O
NH
CCl3
AcO
AcO
OMe
activator, DCM
AcPOO
AcO
BzO
O
OMe
AcO
23
2
2
activator = TMSOTf (73%)/ BF ·OEt
3
2
(47%)/ TfOH (65%)
b)
TMSOTf (0.5 equiv)
propargyl alcohol
OBn
TMSOTf (0.5 equiv)
EtOH (1.2 equiv)
DCM, rt, 4 h
OBn
O
OBn
O
O
(1.2 equiv)
BnO
BnO
BnO
BnO
BnO
BnO
DCM, rt, 4 h
OOPAc
BnO
OEt
O
BnO
BnO
24, 78%
5e
25, 81%
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1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
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4
4
4
4
4
4
4
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5
5
5
5
5
5
5
5
5
6
product 23 in all experiments in good yields. However, the best yield was observed with
TMSOTf (Scheme 5a). On the other hand, two different reactions were conducted with
designed donor 5e with EtOH/propargyl alcohol as per conditions mentioned below (Scheme
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
5
b). In both the cases, we successfully isolate the desired products in good yields.
After evaluating its glycosylation potential, we aimed to test the stability of OPAc against the
post introduction of Ac, Bz, benzylidene, Bn, & PMB groups. In this context, saccharide 26
was taken as model substrate to launch benzylidene 5u, Bz 27, and Ac 28. In all these
reactions, we were gratified to isolate the products in appreciable yields. Being sensitive to
strong basic environment, we strategically introduced Bn and PMB on saccharide 29 in
moderate yields using TCA donors of Bn and PMB (scheme 6).
Scheme 6. Post Protection of other groups in presence of OPAc.
Ph
AcPOO
AcPOO
O
O
O
OMe
5u, 87%
a
OBz
OH
O
OAc
O
O
BzO
AcPOO
AcPOO
b
HO
AcPOO
AcPOO
c
AcO
AcPOO
AcPOO
OMe
OMe
OMe
26
27, 83%
28, 79%
OOPAc
O
OOPAc
O
OOPAc
O
d
e
PMBO
BnO
HO
BnO
BnO
BnO
BnO
BnO
BnO
OMe
OMe
30, 77%
OMe
5a, 72%
29
Reaction condition: a) PhCH(OMe)
2
(1.1 mmol), CSA (0.2 mmol), ACN. b) Bz-Cl (2.2 mmol), DMAP (0.5 mmol),
o
o
Pyridine, rt. c) Ac O, pyridine (6:4), rt. d) Bn-TCA (1.2 mmol),, DCM, rt. 0 C. e) PMB-TCA (1.2 mmol), DCM, rt. 0 C
2
After establishing the flexible nature of OPAc, we tested our hypothesis on model system 31
containing two unsaturated (oleic acid) lipid esters (Scheme 7). In this case, we isolated 69%
of expected product using optimized procedure with oxone in MeOH-DCM (1:1) as
deprotecting reagent.
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Scheme 7. Deprotection of OPAc group in model substrate containing unsaturated lipid.
OH
OOPAc
HO
O
O
AcPOO
O
KHSO (10.0 mmol),
O
7
5
O
7
7
O
dry MeOH-DCM (1:1), 10 h,
7
7
OMe
O
o
O
OMe
6
5 C
7
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
O
7
7
O
31
32, 69%
CONCLUSION
In conclusion, we presented OPAc as a better, orthogonally convenient protecting group that
is effective surrogate of benzoate (Bz) and acetate (Ac) and other esters. We envision that our
protecting group can readily find broad applications in complex carbohydrate assemblies of
glycolipids containing unsaturation. In addition, we also demonstrated the application of our
protection strategy in the synthesis of different valuable acceptors under modified conditions,
successfully used it as a donor and also tested our hypothesis on model substrate containing
unsaturated dilipid 31. Further, application towards the synthesis of GPI and others is in
progress.
EXPERIMENTAL SECTION
A. General Information.
Solvents were purified according to standard procedures, and reagents used were of highest
purity available. All reactions were performed in flame-dried glass apparatus under
argon/nitrogen atmosphere unless mentioned otherwise. Anhydrous solvents like CH Cl ,
2
2
CH OH, CH CN, DMF, pyridine, and Et N were freshly dried using standard methods. NMR
3
3
3
1
13
1
1
1
13
measurements ( H, C, 2D H- H-COSY and H- C HMBC, HMQC, and NOESY) were
recorded on a 400 and 500 MHz spectrometer fitted with pulse-field gradient probe, and
trimethylsilane (TMS) or residual resonance of deuterated solvent were used as internal
1
3
1
reference. C NMR spectra were broadband H decoupled or inverse HMQC experiments.
Chemical shifts are expressed in ppm and coupling constants J in Hz. High-resolution mass
spectral data were obtained from Q-ToF Mass Spectrometer coupled LC system. The
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1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
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3
3
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4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
ο
following conditions were used: capillary voltage 3500 V, capillary temperature 350 C,
auxiliary gas flow rate 7.0 L/min, spray voltage 4.5 kV, mass range 100-1000 amu
(maximum resolution 30000). Optical rotations were measured on a digital polarimeter.
Analytical TLC was performed on 60 F254 plates, and compounds visualized by methanol-
sulphuric acid/ceric-sulfate developing reagent. Silica column chromatography was carried
out with silica gel 60 (60-120 mesh) or flash silica gel (230-400 mesh). Analytical and semi-
preparative HPLC purification were carried out on reversed-phase (C18, 250 X 10 mm, L
i.d.) column connected to an binary pump and monitored using an photodiode array detector.
B. General Procedure for protection:
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
For each hydroxyl present 1.2 mmol DMAP, DIC and Phenylglyoxalic acid is necessary. DIC
(
151.4 mg, 1.2 mmol) was added to the stirred solution of alcohol (1.0, mmol),
phenylglyoxalic acid (180.1 mg, 1.2 mmol) and DMAP (146.6 mg, 1.2 mmol) in anhydrous
DCM (3.0 mL) under nitrogen atmosphere, and then stirred for 3.0 h at rt. After completion
of the reaction, confirmed by thin layer chromatography, the solvent was removed under
reduced pressure. The reaction mass was dissolved in EtOAc and washed with 3% aqueous
HCl (20 mL), followed by washed with saturated NaHCO sloution. The organic layer was
3
collected and dried over Na SO , and concentrated in vacuum. The products (5a-5ac, 7, 10,
2
4
1
2-19, 20a-20d, 23, 26-30, 31) were purified by column chromatography on silica gel using
Hexanes/EtOAc = 9:1 to 8:2 as eluent.
Procedure for Bz protected 16a, 16b and 6v.
To a solution of Methyl-2-benzoyl-α-D-glucopyranoside (1.0 equiv) in DMF 10.0 mL
methanol at room temperature was added Bz-Cl (2.2 equiv) in pyridine at room temperature
for 6-10 h. After 10 h, the starting materials were consumed and we got a mixture of three
products. The mixture of two regioisomers (16a and 16b) was separated through HPLC and
the HPLC chromatogram of the two regioisomers shown in SI.
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C. General Procedure for deprotection:
Deprotection by using KHSO5:
For each deprotection 5.0 mmol of KHSO is necessary. To a solution of OPAc protected
5
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saccharide (1.0 mmol) in anhydrous 5.0 mL methanol at room temperature was added
KHSO (0.761 mg, 5.0 mmol) and the solution refluxed for 6-10 h, then cooled to rt. The
5
mixture was filtered and washed with ethyl acetate. The filtrate was concentrated to dryness,
suspended in 30 mL of water and extracted with ethyl acetate (2 × 15 mL). After which the
organic layer was dried over Na SO , and concentrated in vaccum. The products (6a-6ac, 8,
2
4
1
1) were purified by column chromatography on silica gel using for mono deprotection
Hexanes:EtOAc = 9:1, for di Hexanes:EtOAc = 7:3, for tri Chloroform:MeOH = 9.5:0.5 and
for tetra Chloroform:MeOH = 8:2 as eluent.
Deprotection by using AcCl:
For each deprotection 0.7 mmol of AcCl is necessary. To a solution of OPAc protected
saccharide (1.0 mmol) in anhydrous 5.0 mL methanol at room temperature was added AcCl
(49.9 µL, 0.7 mmol), after stirring for 0.5-1.0 h, then the reaction mass was quenched with
triethyl amine, concentrated to dryness. The crude material was suspended in 20 mL of water
and extracted with ethyl acetate (2 × 20mL). After which the organic layer was dried over
Na SO , and concentrated in vacuum. The products (6a-6ac) were purified by column
2
4
chromatography on silica gel using for mono deprotection Hexanes:EtOAc = 9:1, for di
Hexanes:EtOAc = 7:3, for tri Chloroform:MeOH = 9.5:0.5 and for tetra Chloroform:MeOH =
8
:2 as eluent.
D. Procedure for some starting material synthesis.
. (±)-3,4,5,6-tetra-O-benzyl-myo-inositol ( Starting material of 5w)
1
Starting compound was synthesized from literature protocol.28 To a solution of (±)-1,2-
cyclohexylidene myo-inositol (10.0 g, 38.44 mmol) in anhydrous DMF (100 mL) stirring
o
under Nitrogen at 0 C was slowly added sodium hydride (60% dispersion in mineral oil, 7.38
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g, 307.54 mmol). After stirring for 30 min, benzyl bromide (21.91mL, 184.56 mmol) was
added dropwise. The reaction was stirred overnight at room temperature, then quenched with
ice, diluted with EtOAc, and poured into water. The aqueous layer was extracted 2x with
EtOAc, after which the combined organic layer was washed with brine, dried over Na SO ,
0
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2
4
+
and concentrated in vaccum. (HRMS (ESI-TOF) m/z: [M + H] calculated for C H O
6
4
0
45
6
21.3216, found: 621.3221. ) The residue was dissolved in CH Cl /MeOH (2:1, 200 mL),
2 2
added acetyl chloride (2.0 mL) dropwise. After 3 h, the reaction was quenched with
triethylamine and concentrated in vacuum. The crude material was purified by silica gel
column chromatography to give ±3,4,5,6-tetra-O-benzyl-myo-inositol(18.69 g, 90 %) as a
white solid. R 0.18 (Hexanes/EtOAc = 7:3).
f
1
H NMR (400 MHz, CDCl ) δ 7.37 – 7.26 (m, 20H), 4.93 (dd, J = 13.3, 11.0 Hz, 3H), 4.84
3
(
dd, J = 10.8, 3.9 Hz, 2H), 4.73 (dd, J = 12.3, 6.4 Hz, 3H), 4.20 (t, J = 2.7 Hz, 1H), 3.97 (t, J
= 9.5 Hz, 1H), 3.84 (t, J = 9.5 Hz, 1H), 3.47 (td, J = 9.5, 3.9 Hz, 3H), 2.54 – 2.34 (m, 2H).
. 3,4,5,6-tetra-O-benzyl-1-O-(4-methoxybenzyl)-myo-inositol ( Starting material of 5p)
2
2
8
Starting compound was synthesized from literature protocol. A mixture of 3,4,5,6-tetra-O-
benzyl-myo-inositol (2.00 g, 3.70 mmol) and dibutyltin oxide (0.925 g, 3.70 mmol) in
anhydrous Methanol (60 mL) was refluxed for 4 h, until solution becomes clear. After
concentration in vacuum, the residue was dissolved in anhydrous Toluene/DMF (1:1, 40 mL)
and freshly activated 4 Å molecular sieves were added. And cooled to 0 ºC, after which
Tetrabutyl ammonium bromide (2.37 g, 7.41 mmol) and p-methoxybenzyl chloride (0.60 mL,
4
.4 mmol) were added to the solution. After stirring overnight under an Nitrogen atmosphere
o
at 80 C, reaction mixture filtered through Celite and washed with EtOAc. The organic layer
was washed with water, dried over Na SO4, and concentrated in vacuum. This after silica gel
2
column chromatography gave compound (2.2 g, 90 %) as a white solid. R 0.55
f
(Hexanes/EtOAc = 7:3).
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1
H NMR (400 MHz, CDCl ) δ 7.46 – 7.31 (m, 22H), 6.93 (d, J = 8.6 Hz, 2H), 4.95 (dd, J =
3
1
6.8, 6.5 Hz, 3H), 4.91 – 4.83 (m, 3H), 4.71 (dd, J = 23.2, 11.8 Hz, 2H), 4.59 (d, J = 11.4 Hz,
1H), 4.51 (d, J = 11.4 Hz, 1H), 4.21 (t, J = 9.5 Hz, 1H), 4.11 (dd, J = 17.2, 7.7 Hz, 2H), 3.86
s, 3H), 3.48 – 3.36 (m, 2H), 3.23 (dd, J = 9.9, 2.1 Hz, 1H).
. Napthyl-3,4,6-tri-O-Benzyl-α-D-mannopyranoside( Starting material of 5l).
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
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0
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9
0
(
3
7
b
Starting compound was synthesized from literature protocol. The trichloroacetimidate donor
2.0 g, 3.16 mmol) and the acceptor (500 mg, 3.16 mmol) were first dried through co-
evaporation with anhydrous toluene, further dried for 2 h under high vacuum and then
dissolved in anhydrous CH Cl (40 mL) and freshly activated 1 g of 4Å molecular sieves
(
2
2
were added. The suspension was then stirred under Nitrogen at room temparature for 30 min.
o
The reaction mixture was cooled at -20 C and treated with TMSOTf solution (40 μL, 0.179
mmol) and then warm to room temperature. After stirring for 3 h, the reaction was
neutralized with trimethylamine followed by filtration through Celite to remove molecular
sieves, concentration in vacuum, the crude material was further used for next step.
To a solution of crude material from the above step in 50 mL of (1:1) mixture of
DCM/MeOH, added catalytic amount of NaOMe (100 mg). The mixture was stirred at room
+
temperature for 3 h. It was neutralized to pH 6-7 using Amberlyst H resin. The solution was
filtered and concentrated which after silica gel column chromatography gave compound as a
colourless syrup (1.68 g, 90%).R 0.40 (Hexanes/EtOAc = 7:3).
f
1
H NMR (400 MHz, CDCl ) δ 7.82 (dd, J = 8.9, 4.4 Hz, 3H), 7.75 (s, 1H), 7.50 – 7.44 (m,
3
2
H), 7.43 (d, J = 8.4 Hz, 1H), 7.40 – 7.26 (m, 13H), 7.21 – 7.10 (m, 2H), 5.04 (d, J = 1.1 Hz,
H), 4.85 (dd, J = 17.3, 11.4 Hz, 2H), 4.71 – 4.64 (m, 4H), 4.54 (dd, J = 17.5, 11.5 Hz, 2H),
1
4.09 (d, J = 1.6 Hz, 1H), 3.96 (dd, J = 9.1, 3.2 Hz, 1H), 3.89 (d, J = 5.8 Hz, 2H), 3.75 (dt, J =
1.4, 10.5 Hz, 2H).
2
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. Napthyl -(3,4,6-tri-O-benzyl-α-D-mannopyranosyl)(1→2)-3,4,6-tri-O-benzyl-α-D
mannopyranoside ( Starting material of 5q) .
Starting compound was synthesized from literature protocol.7b The trichloroacetimidate
donor(1.29 g, 2.03mmol) and the acceptor (1.0 g, 1.69 mmol) were first dried through co-
evaporation with anhydrous toluene, further dried for 2 h under high vacuum and then
0
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9
0
dissolved in anhydrous CH Cl (30 mL) and freshly activated 1 g of 4Å molecular sieves
2
2
were added. The suspension was then stirred under Nitrogen at room temparature for 30 min.
o
The reaction mixture was cooled at -20 C and treated with TMSOTf solution (20 μL, 0.089
mmol) and then warm to room temperature. After stirring for 3 h, the reaction was
neutralized with trimethylamine followed by filtration through Celite to remove molecular
sieves, concentration in vacuum, the crude material was further used for next step.
To a solution of crude material from the above step in 30 mL of (1:1) mixture of
DCM/MeOH, added catalytic amount of NaOMe (100 mg). The mixture was stirred at room
+
temperature for 3 h. It was neutralized to pH 6-7 using Amberlyst H resin. The solution was
filtered and concentrated which after silica gel column chromatography gave compound as a
colourless syrup (1.52 g, 88 %).R 0.40 (Hexanes/EtOAc = 7:3).
f
1
H NMR (400 MHz, CDCl ) δ 7.87 – 7.81 (m, 3H), 7.77 (s, 1H), 7.52 – 7.43 (m, 5H), 7.41 –
3
7
.36 (m, 4H), 7.36 – 7.20 (m, 24H), 5.61 (s, 1H), 5.19 (d, J = 1.2 Hz, 1H), 5.01 (d, J = 1.6
Hz, 1H), 4.87 (dd, J = 18.3, 11.3 Hz, 2H), 4.71 (m, J = 19.9, 14.9, 11.5 Hz, 4H), 4.61 (d, J =
9.9 Hz, 2H), 4.56 (t, J = 5.3 Hz, 3H), 4.50 (d, J = 12.0 Hz, 1H), 4.22 (t, J = 9.6 Hz, 1H), 4.18
–
3
4.05 (m, 2H), 4.03 – 3.95 (m, 2H), 3.89 (m, J = 8.2, 3.5, 1.6 Hz, 3H), 3.85 – 3.75 (m, 4H),
.75 – 3.68 (m, 1H).
5. Napthyl-(3-O-benzyl-4,6-O-benzylidene-α-D-mannopyranosyl)(1→2)-( 3,4,6-tri-O-
benzyl-α-D-mannopyranosyl) )(1→2)-3,4,6-tri-O-benzyl-α-D-mannopyranoside(
Starting material of 5r).
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Starting compound was synthesized from literature protocol. A solution of donor 6 (173
mg, 0.293 mmol), acceptor (300 mg, 0.293 mmol) BSP (88 mg, 0.421 mmol), TTBP (130.9
mg, 0.527 mmol) and freshly activated 4 Å molecular sieves (500 mg) in 10 mL CH Cl was
2
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o
stirred at room temperature for 30 min, and cooled to -78 C, which was followed by addition
of Tf O (59.3 µL, 0.0.358 mmol) in CH Cl . The reaction mixture was stirred for further 2 h.
2
2
2
o
at -78 C, and allowed to reach room temperature. The reaction mixture was diluted with
dichloromethane (10 mL) and molecular sieves were filtered off and washed with saturated
NaHCO . The organic layer was separated and dried and concentrated. The crude residue was
3
dissolved in 10 mL of (1:1) mixture of DCM/MeOH, added catalytic amount of NaOMe (20
mg). The mixture was stirred at room temperature for 3 h. It was neutralized to pH 6-7 using
+
Amberlyst H resin. The solution was filtered and concentrated which after silica gel column
chromatography gave compound as a colourless syrup (0.319 g, 80 %).R 0.35
f
(Hexanes/EtOAc = 7:3).
1
H NMR (400 MHz, CDCl ) δ 7.85 – 7.75 (m, 3H), 7.69 (s, 1H), 7.50 – 7.44 (m, 4H), 7.40 –
3
7
7
.05 (m, 40H), 5.51 (s, 1H), 5.07 – 4.98 (m, 2H), 4.86 (d, J = 10.7 Hz, 1H), 4.80 – 4.65 (m,
H), 4.62 – 4.43 (m, 6H), 4.36 – 4.22 (m, 4H), 4.13 (m, J = 24.6, 14.6, 7.1 Hz, 3H), 3.96 (t, J
=
5.5 Hz, 2H), 3.91 – 3.65 (m, 8H), 3.48 (dd, J = 10.6, 4.6 Hz, 1H), 3.33 (d, J = 3.9 Hz, 2H),
2
.99 (dd, J = 14.4, 9.7 Hz, 1H).
E. Characterization data for Protected compounds
5a.Methyl-6-O-oxobenzoyl-2,3,4-tri-O-benzyl-α-D-glucopyranoside.
17
Starting material was synthesized from literature . Isolated as a syrup (117 mg, 91% yield);
1
H NMR (400 MHz, CDCl ) δ 8.03 – 7.94 (m, 2H), 7.64 (t, J = 7.4 Hz, 1H), 7.45 (t, J = 7.8
3
Hz, 2H), 7.37 – 7.27 (m, 14H), 5.00 (d, J = 10.9 Hz, 1H), 4.91 (d, J = 11.0 Hz, 1H), 4.85 –
4
3
.77 (m, 2H), 4.68 – 4.58 (m, 4H), 4.47 (dd, J = 11.7, 5.1 Hz, 1H), 4.03 (t, J = 9.2 Hz, 1H),
1
3
.93 (ddd, J = 10.0, 5.0, 2.0 Hz, 1H), 3.54 – 3.48 (m, 2H), 3.37 (s, 3H). C NMR {1H} (101
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MHz, CDCl ) δ 185.9, 163.6, 138.6, 138.1, 137.9, 134.9, 132.4, 130.1, 128.9, 128.5, 128.4,
3
1
28.1, 128.0, 128.0, 127.9, 127.7, 98.2 (C1), 81.8, 79.9, 77.6, 75.8, 75.2, 73.4, 68.6, 64.4,
55.4.; HRMS (ESI-TOF) m/z: [M + NH ]+ Calcd for C H NO 614.2748 found 614.2742.
4
36 40
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b.Methyl-4-oxobenzoyl-6-O-(triisopropylsilyl)-2,3,-di-O-benzyl-α-D-glucopyranoside.
1
8
Starting material was synthesized from literature . Isolated as a syrup (109 mg, 87% yield);
1
H NMR (400 MHz, CDCl ) δ 7.92 (dd, J = 8.3, 1.2 Hz, 2H), 7.59 (dd, J = 10.6, 4.3 Hz, 1H),
3
7
.39 – 7.26 (m, 12H), 5.27 (t, J = 9.7 Hz, 1H), 4.97 (d, J = 11.2 Hz, 1H), 4.80 (d, J = 12.0 Hz,
H), 4.75 – 4.63 (m, 3H), 4.08 (t, J = 9.5 Hz, 1H), 3.92 – 3.78 (m, 3H), 3.65 (dd, J = 9.6, 3.6
1
1
3
Hz, 1H), 3.42 (s, 3H), 1.06 (d, J = 4.0 Hz, 21H). C NMR {1H} (101 MHz, CDCl ) δ 186.0,
3
162.8, 138.3, 137.9, 134.9, 132.2, 130.0, 128.9, 128.5, 128.4, 128.1, 128.0, 127.6, 127.5, 97.8
(
C1), 80.0, 78.9, 75.3, 73.5, 71.9, 70.4, 62.6, 55.1, 17.9, 17.9, 12.0; HRMS (ESI-TOF) m/z:
M + H]+ Calcd for C H O Si 663.3348 found 663.3354.
[
3
8
51
8
5c. Methyl-3-O-oxobenzoyl-2-benzoyl-4,6-O-benzylidene-α-D-glucopyranoside.
19
Starting material was synthesized from literature . Isolated as a syrup (119 mg, 89% yield);
1
H NMR (400 MHz, CDCl ) δ 8.10 (dd, J = 8.3, 1.2 Hz, 2H), 7.80 (dd, J = 8.3, 1.2 Hz, 2H),
3
7
.65 – 7.58 (m, 1H), 7.51 (m, J = 15.4, 10.7, 5.6 Hz, 5H), 7.44 – 7.37 (m, 3H), 7.09 (t, J = 7.9
Hz, 2H), 6.10 (t, J = 9.9 Hz, 1H), 5.59 (s, 1H), 5.24 (d, J = 3.7 Hz, 1H), 5.16 (dd, J = 10.0,
3
2
.7 Hz, 1H), 4.39 (dd, J = 10.3, 4.9 Hz, 1H), 4.09 (td, J = 9.9, 4.8 Hz, 1H), 3.86 (td, J = 10.0,
1
3
.7 Hz, 2H), 3.45 (s, 3H). C NMR {1H} (126 MHz, CDCl ) δ 186.2, 165.8, 163.6, 136.8,
3
134.8, 133.7, 132.0, 130.1, 129.9, 129.3, 128.9, 128.7, 128.6, 128.4, 126.3, 101.9, 97.7 (C1),
7
5
8.9, 72.20, 70.7, 68.9, 62.5, 55.7; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C H NaO
29 26 9
41.1469 found 541.1453.
5
d. Methyl-2-O-oxobenzoyl-3-O-(triisopropylsilyl)-4,6-O-benzylidene-α-D-
glucopyranoside.
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Starting material was synthesized from literature . Isolated as a syrup(117 mg, 90%
1
yield); H NMR (400 MHz, CDCl ) δ 8.11 – 8.02 (m, 2H), 7.73 – 7.63 (m, 1H), 7.53 (t, J =
3
7.8 Hz, 2H), 7.50 – 7.46 (m, 2H), 7.38 – 7.35 (m, 3H), 5.53 (s, 1H), 5.23 (d, J = 3.8 Hz, 1H,
H1), 4.97 – 4.91 (m, 1H), 4.44 (t, J = 9.1 Hz, 1H), 4.32 (dd, J = 10.1, 4.7 Hz, 1H), 3.91 (td, J
1
1
1
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1
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2
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7
8
9
0
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5
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7
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9
0
=
9.9, 4.7 Hz, 1H), 3.80 (dd, J = 12.5, 8.0 Hz, 1H), 3.58 (t, J = 9.3 Hz, 1H), 3.49 (s, 3H), 0.90
1
3
(
d, J = 6.1 Hz, 21H). C NMR {1H} (101 MHz, CDCl ) δ 185.4, 163.2, 137.1, 134.9, 132.7,
3
1
1
5
30.1, 129.2, 128.8, 128.1, 126.3, 102.3, 97.3 (C1), 82.3, 69.7, 68.9, 62.3, 55.5, 18.1, 18.0,
2.5; HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C H O Si 571.2722 found 571.2744.
3
1
43
8
e.Oxobenzoyl-2, 3,4,6-tetra-O-benzyl-D-glucopyranoside.
2
1
Starting material was synthesized from literature . Isolated as a syrup (106 mg, 85% yield);
1
H NMR (400 MHz, CDCl ) δ 7.95 (dd, J = 15.3, 7.3 Hz, 3H), 7.58 (t, J = 7.4 Hz, 1H), 7.53
3
(
t, J = 7.5 Hz, 1H), 7.38 (t, J = 7.8 Hz, 1H), 7.34 – 7.19 (m, 28H), 7.14 – 7.09 (m, 1H), 7.05
(dd, J = 6.8, 2.6 Hz, 2H), 6.64 (d, J = 3.3 Hz, 1H), 5.81 (d, J = 7.9 Hz, 1H), 4.86 (dd, J =
1
1.0, 4.7 Hz, 2H), 4.74 (dtd, J = 14.2, 11.0, 6.1 Hz, 6H), 4.60 – 4.40 (m, 5H), 3.94 – 3.79 (m,
1
3
2
H), 3.80 – 3.58 (m, 8H). C NMR {1H} (101 MHz, CDCl ) δ 186.0, 185.2, 162.6, 162.1,
3
1
38.5, 138.3, 138.0, 137.8, 137.7, 137.4, 135.1, 134.9, 132.3, 132.2, 130.2, 130.2, 129.0,
28.9, 128.6, 128.4, 128.4, 128.4, 128.3, 128.1, 128.1, 128.0, 127.9, 127.9, 127.8, 127.8,
27.8, 127.7, 127.7, 95.7, 92.5, 84.6, 81.5, 80.6, 79.1, 77.2, 76.2, 75.8, 75.7, 75.2, 75.1, 73.8,
1
1
7
3.6, 73.6, 73.6, 68.3, 68.0;HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C H O 673.2796
42 41
8
found 673.2811.
5
f. Methyl-4-O-oxobenzoyl-2,3-di-O-(4-methoxybenzyl)-6-O-(triisopropylsillyl)- α- D-
glucopyranoside.
18
Starting material was synthesized from literature . Isolated as a syrup (106 mg, 87% yield);
1
H NMR (400 MHz, CDCl ) δ 7.97 (dd, J = 8.4, 1.2 Hz, 2H), 7.67 – 7.59 (m, 1H), 7.45 –
3
7
.36 (m, 2H), 7.34 – 7.29 (m, 2H), 7.26 – 7.22 (m, 2H), 6.95 – 6.85 (m, 2H), 6.85 – 6.76 (m,
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H), 5.25 (t, J = 9.7 Hz, 1H), 4.88 (d, J = 10.7 Hz, 1H), 4.77 (d, J = 11.7 Hz, 1H), 4.64 (dd, J
=
17.4, 7.8 Hz, 3H), 4.07 (t, J = 9.5 Hz, 1H), 3.92 – 3.79 (m, 6H), 3.77 (s, 3H), 3.63 (dd, J =
1
3
9.6, 3.6 Hz, 1H), 3.42 (s, 3H), 1.12 – 1.02 (m, 21H). C NMR {1H} (101 MHz, CDCl ) δ
3
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
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7
8
9
0
1
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6
7
8
9
0
1
2
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6
7
8
9
0
1
1
85.9, 162.7, 159.5, 159.2, 134.9, 132.3, 130.6, 130.1, 130.1, 129.8, 129.4, 128.9, 113.9,
13.8, 97.9 (C1), 79.6, 78.6, 75.1, 73.1, 72.0, 70.4, 62.7, 55.3, 55.2, 55.1, 18.0, 17.9, 12.0;
HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C H O Si723.3559 found 723.3547.
40 55 10
5
g.Methyl-4-O-oxobenzoyl-2-O-benzoyl-3-O-acetyl-6-O-(tert-butyldiphenylsilyl)-α-D-
glucopyranoside.
2
2
Starting material was synthesized from literature . Isolated as a syrup (102mg, 83% yield);
1
H NMR (400 MHz, CDCl ) δ 8.05 (d, J = 7.3 Hz, 2H), 7.90 (d, J = 7.3 Hz, 2H), 7.75 – 7.70
3
(
m, 4H), 7.62 (dt, J = 20.8, 7.5 Hz, 2H), 7.48 – 7.37 (m, 10H), 5.87 (t, J = 9.8 Hz, 1H), 5.60
t, J = 9.8 Hz, 1H), 5.18 (d, J = 3.6 Hz, 1H, H1), 5.13 (dd, J = 10.1, 3.6 Hz, 1H), 4.04 (ddd, J
(
= 10.1, 3.7, 2.1 Hz, 1H), 3.89 (qd, J = 11.7, 3.0 Hz, 2H), 3.37 (s, 3H), 2.03 (s, 3H), 1.10 (s,
13
9
1
7
H). C NMR {1H} (101 MHz, CDCl ) δ 185.4, 170.0, 165.8, 162.6, 135.8, 135.7, 135.0,
3
33.5, 133.3, 133.0, 132.2, 130.0, 129.9, 129.8, 129.2, 129.0, 128.6, 127.8, 127.7, 96.8 (C1),
2.2, 70.1, 70.1, 69.6, 62.3, 55.3, 26.8, 20.7, 19.3; HRMS (ESI-TOF) m/z: [M + H]+ Calcd
for C H O Si 711.2620 found 711.2627.
4
0
43 10
5
h. Methyl (allyl-4-O-oxobenzoyl-2,3-di-O-benzyl-α-D-glucopyranosyluronate).
2
3
1
Starting material was synthesized from literature . Isolated as a syrup (99 mg, 81% yield); H
NMR (400 MHz, CDCl ) δ 8.09 – 7.97 (m, 4H), 7.81 – 7.67 (m, 2H), 7.65 – 7.52 (m, 3H),
3
7
.44 (dt, J = 17.2, 7.7 Hz, 4H), 7.19 (t, J = 7.9 Hz, 2H), 6.19 (t, J = 9.9 Hz, 1H), 5.92 – 5.76
(m, 2H), 5.49 (d, J = 3.6 Hz, 1H, H1), 5.37 – 5.31 (m, 2H), 5.20 (dd, J = 10.4, 1.2 Hz, 1H),
4.69 (d, J = 10.2 Hz, 1H), 4.32 (dd, J = 13.1, 5.1 Hz, 1H), 4.13 (dd, J = 13.0, 6.2 Hz, 1H),
13
3
1
.89 (s, 3H). C NMR {1H} (126 MHz, CDCl ) δ 185.2, 168.0, 165.7, 165.2, 162.7, 135.0,
3
33.6, 133.5, 132.7, 131.8, 130.0, 129.8, 129.0, 128.8, 128.6, 128.5, 118.6, 95.4 (C1), 71.4,
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0.7, 69.5, 69.5, 68.0, 53.2; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C H NaO
9
3
2
32
83.1939 found 583.1937.
i.Phenyl-3-O-oxobenzoyl-4,6-O-benzylidene-2-N-(trichloroacetyl)-amino-2-deoxy-1-
5
1
1
1
1
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8
9
0
deoxy-1-thio-α-D-glucopyranoside.
2
4
Starting material was synthesized from literature . Isolated as a syrup (108 mg, 85% yield);
1
H NMR (400 MHz, CDCl ) δ 7.85 (d, J = 7.3 Hz, 2H), 7.56 (t, J = 7.5 Hz, 1H), 7.51 – 7.46
3
(m, 3H), 7.35 (ddd, J = 10.2, 7.1, 5.0 Hz, 6H), 7.26 – 7.22 (m, 2H), 7.16 (d, J = 8.7 Hz, 1H),
5.92 (t, J = 9.8 Hz, 1H), 5.53 (s, 1H), 5.18 (d, J = 10.3 Hz, 1H, H1), 4.35 (dd, J = 10.5, 4.8
Hz, 1H), 4.02 (dd, J = 19.0, 10.1 Hz, 1H), 3.79 (td, J = 9.8, 6.4 Hz, 2H), 3.69 (dd, J = 9.6, 4.7
1
3
Hz, 1H). C NMR {1H} (101 MHz, CDCl ) δ 185.6, 164.0, 162.0, 136.6, 135.1, 133.4,
3
1
7
6
5
31.9, 131.4, 130.0, 129.4, 129.2, 128.9, 128.8, 128.4, 126.2, 101.7 (C1), 86.7, 78.5, 73.2,
0.8, 68.4, 55.2; HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C H Cl NO S 636.0412 found
2
9
25
3
7
36.0397.
j. Methyl-3-O-oxobenzoyl-2-O-benzoyl-4,6-O- benzylidene-α-D-galactopyranoside.
2
5
Starting material was synthesized from literature . Isolated as a syrup (106 mg, 79% yield);
1
H NMR (400 MHz, CDCl ) δ 8.09 (dd, J = 12.4, 5.0 Hz, 3H), 7.84 (ddd, J = 8.4, 3.8, 1.2 Hz,
3
3
H), 7.61 (t, J = 7.4 Hz, 2H), 7.55 (ddd, J = 9.4, 7.3, 2.7 Hz, 4H), 7.50 – 7.44 (m, 5H), 7.42 –
7.35 (m, 5H), 7.14 (t, J = 7.9 Hz, 1H), 7.01 (t, J = 7.9 Hz, 2H), 5.94 (dd, J = 10.7, 3.5 Hz,
H), 5.87 (dd, J = 10.7, 3.6 Hz, 1H), 5.70 – 5.62 (m, 2H), 5.58 (d, J = 5.6 Hz, 1H), 5.33 (d, J
3.5 Hz, 1H), 5.27 (t, J = 4.0 Hz, 1H), 4.78 (d, J = 3.6 Hz, 1H), 4.70 (d, J = 3.4 Hz, 1H),
.38 (ddd, J = 12.5, 6.5, 1.4 Hz, 2H), 4.22 – 4.10 (m, 2H), 3.92 (s, 1H), 3.53 (s, 2H), 3.47 (s,
1
=
4
3
1
1
1
3
H). C NMR {1H} (101 MHz, CDCl ) δ 186.0, 185.8, 165.9, 165.7, 163.9, 163.5, 137.6,
3
37.4, 134.9, 133.5, 133.4, 132.1, 132.1, 130.0, 129.9, 129.9, 129.5, 129.5, 129.2, 129.0,
28.7, 128.7, 128.6, 128.6, 128.3, 128.2, 126.4, 126.1, 101.2, 100.8, 97.9 (C1), 97.8 (C1),
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4.1, 73.8, 70.8, 69.7, 69.3, 69.2, 69.1, 68.8, 62.3, 62.1, 55.8, 55.8; HRMS (ESI-TOF) m/z:
[M + NH ]+ Calcd for C H NO 536.1915 found 536.1911.
4 29 30 9
5k.Methyl-6-O-oxobenzoyl-2,3,4-tri-O-benzyl-α-D-mannopyranoside.
0
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26
Starting material was synthesized from literature . Isolated as a syrup (107 mg, 83% yield);
1
H NMR (400 MHz, CDCl ) δ 8.04 (dd, J = 8.4, 1.2 Hz, 2H), 7.64 – 7.57 (m, 1H), 7.45 (dd, J
3
=
10.7, 4.8 Hz, 2H), 7.39 – 7.28 (m, 15H), 4.99 (d, J = 11.0 Hz, 1H), 4.78 – 4.69 (m, 4H),
4
3
1
.65 (d, J = 11.2 Hz, 3H), 4.58 (dd, J = 11.6, 5.5 Hz, 1H), 4.01 – 3.88 (m, 3H), 3.82 (s, 1H),
1
3
.30 (s, 3H). C NMR {1H} (126 MHz, CDCl ) δ 186.2, 163.8, 138.3, 138.2, 138.1, 134.9,
3
32.4, 130.2, 128.9, 128.5, 128.5, 128.4, 128.1, 127.9, 127.8, 127.7, 127.7, 99.1, 80.2, 75.3,
74.6, 74.4, 72.8, 72.1, 69.8, 65.0, 55.0; HRMS (ESI-TOF) m/z: [M + NH ]+ Calcd for
4
C H NO 614.2748 found 614.2752.
3
6
40
8
5
l. Napthy-2-O-oxobenzoyl-3,4,6-O-tri-O-benzyl -α-D-mannopyranoside.
7
b
Starting material was synthesized from literature . Isolated as a syrup (112 mg, 88% yield);
1
H NMR (400 MHz, CDCl ) δ 8.03 (d, J = 7.8 Hz, 2H), 7.87 (t, J = 6.9 Hz, 3H), 7.81 (s, 1H),
3
7
6
.58 (t, J = 7.4 Hz, 1H), 7.51 (dd, J = 12.6, 7.5 Hz, 3H), 7.42 (d, J = 6.1 Hz, 2H), 7.35 (d, J =
.5 Hz, 3H), 7.30 (q, J = 7.9 Hz, 10H), 7.18 (d, J = 3.0 Hz, 2H), 5.80 (s, 1H), 5.16 (s, 1H,
H1), 4.97 – 4.83 (m, 3H), 4.77 – 4.61 (m, 3H), 4.51 (dd, J = 14.6, 11.5 Hz, 2H), 4.21 (dd, J =
1
3
9
.3, 2.8 Hz, 1H), 3.99 (d, J = 7.0 Hz, 1H), 3.83 (t, J = 9.6 Hz, 1H), 3.79 – 3.67 (m, 2H). C
NMR {1H} (101 MHz, CDCl ) δ 186.3, 163.7, 138.2, 138.1, 137.7, 134.9, 134.1, 133.3,
3
133.2, 132.4, 130.3, 128.8, 128.5, 128.5, 128.4, 128.4, 128.4, 128.1, 128.0, 127.9, 127.8,
1
27.8, 127.7, 127.6, 127.4, 126.3, 126.2, 126.1, 96.6 (C1), 78.6, 75.4, 74.4, 73.5, 72.7, 72.0,
0.8, 69.7, 68.9; HRMS (ESI-TOF) m/z: [M + NH ]+ Calcd for C H NO 740.3218 found
7
4
46 46
8
740.3238.
5
m. 1,2:5,6di-O-isopropylidene-3-O-oxobenzoyl-α-D-glucofuranoside.
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Starting material was commercially available. Isolated as a syrup (138 mg, 92% yield); H
NMR (400 MHz, CDCl ) δ 8.10 – 7.97 (m, 2H), 7.67 (t, J = 7.5 Hz, 1H), 7.50 (t, J = 7.8 Hz,
3
2H), 5.93 (d, J = 3.7 Hz, 1H), 5.65 (d, J = 3.0 Hz, 1H, H1), 4.64 (d, J = 3.7 Hz, 1H), 4.27 (dd,
J = 8.6, 3.0 Hz, 1H), 4.17 (ddd, J = 8.5, 5.8, 4.6 Hz, 1H), 4.09 (dd, J = 8.7, 6.0 Hz, 1H), 4.01
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
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5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
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4
5
6
7
8
9
0
1
2
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4
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6
7
8
9
0
1
2
3
4
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6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
3
(
dd, J = 8.8, 4.5 Hz, 1H), 1.54 (s, 3H), 1.46 (s, 3H), 1.33 (s, 6H). C NMR {1H} (101 MHz,
CDCl ) δ 185.6, 162.5, 135.2, 132.3, 130.1, 128.9, 112.5, 109.6, 105.4, 83.3, 80.2, 77.3, 72.3,
3
6
7.6, 26.9, 26.7, 26.2, 25.2; HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C H O 393.1544
20 25 8
found 393.1547.
5
n. 1,2:4,6 di-O-isopropylidene-3-oxobenzoyl- α-D-galactopyranoside.
1
Starting material was commercially available. Isolated as a syrup (137 mg, 91% yield); H
NMR (400 MHz, CDCl ) δ 8.10 – 8.01 (m, 2H), 7.65 (dd, J = 10.6, 4.3 Hz, 1H), 7.50 (t, J =
3
7
.8 Hz, 2H), 5.58 (d, J = 5.0 Hz, 1H, H1), 4.65 (dd, J = 7.8, 2.5 Hz, 1H), 4.58 – 4.53 (m, 2H),
4.36 (dd, J = 5.0, 2.5 Hz, 1H), 4.29 (dd, J = 7.9, 1.9 Hz, 1H), 4.25 – 4.20 (m, 1H), 1.49 (d, J
13
=
7.2 Hz, 6H), 1.35 (d, J = 4.6 Hz, 6H). C NMR {1H} (101 MHz, CDCl ) δ 186.4, 163.9,
3
1
2
5
34.9, 132.4, 130.3, 128.9, 109.9, 108.9, 96.3, 70.8, 70.7, 70.4, 65.8, 64.8, 26.0, 26.0, 24.9,
4.5; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C H NaO 415.1363 found 415.1355.
20 24
8
o. Methyl-3-O-oxobenzoyl-2,4,6-tri-O-benzyl-α-D-glucopyranoside.
2
7
Starting material was synthesized from literature . Isolated as a syrup (112 mg, 87% yield);
1
H NMR (400 MHz, CDCl ) δ 7.97 (dd, J = 8.3, 1.1 Hz, 2H), 7.61 (t, J = 7.5 Hz, 1H), 7.40 –
3
7.32 (m, 6H), 7.32 – 7.23 (m, 9H), 7.15 (dd, J = 7.0, 2.5 Hz, 2H), 5.15 (dt, J = 11.0, 3.7 Hz,
2
2
H), 4.80 (dd, J = 18.5, 8.6 Hz, 3H), 4.66 (d, J = 12.1 Hz, 1H), 4.55 (dd, J = 11.5, 3.5 Hz,
1
3
H), 4.17 – 4.09 (m, 1H), 3.87 – 3.70 (m, 4H), 3.45 (s, 3H). C NMR {1H} (101 MHz,
CDCl ) δ 185.9, 163.4, 138.2, 138.0, 137.9, 134.9, 132.4, 130.0, 128.9, 128.8, 128.4, 128.4,
3
1
28.4, 127.9, 127.8, 127.8, 127.6, 127.6, 125.8, 96.8 (C1), 79.5, 78.0, 75.4, 75.3, 75.1, 73.6,
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0.5, 68.4, 55.3. HRMS (ESI-TOF) m/z: [M + NH ]+ Calcd for C H NO 614.2748 found
4
36 40
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14.2751.
5p. 2-O-oxobenzoyl-3,4,5,6-tetra-O-benzyl-1-O-(4-methoxybenzyl)-myo-inositol.
0
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28
Starting material was synthesized from literature . Isolated as a syrup (101 mg, 84% yield);
1
H NMR (400 MHz, CDCl ) δ 7.95 (dd, J = 8.3, 1.1 Hz, 2H), 7.56 (t, J = 7.5 Hz, 1H), 7.44
3
(d, J = 6.4 Hz, 2H), 7.39 – 7.15 (m, 22H), 6.83 (d, J = 8.7 Hz, 2H), 5.94 (t, J = 9.9 Hz, 1H),
4
.89 (ddd, J = 26.8, 18.3, 10.7 Hz, 5H), 4.75 (d, J = 10.8 Hz, 1H), 4.64 (q, J = 11.8 Hz, 2H),
.53 (d, J = 11.5 Hz, 1H), 4.45 (d, J = 11.5 Hz, 1H), 4.22 (t, J = 9.5 Hz, 1H), 4.07 (t, J = 2.1
4
Hz, 1H), 3.81 (s, 3H), 3.60 (t, J = 9.4 Hz, 1H), 3.45 – 3.37 (m, 2H). 13C NMR {1H} (101
MHz, CDCl ) δ 186.7, 163.2, 159.3, 138.7, 138.2, 134.7, 132.4, 130.2, 129.7, 129.1, 128.8,
3
1
8
28.4, 128.3, 128.3, 128.2, 128.0, 127.9, 127.7, 127.7, 127.6, 127.5, 127.5, 113.9, 81.5, 80.9,
0.7, 77.8, 75.9, 75.6, 75.3, 74.2, 73.4, 72.9, 71.9, 55.3; HRMS (ESI-TOF) m/z: [M + Na]+
Calcd for C H NaO 815.3191 found 815.3197.
50
48
9
5
q.Napthyl-(2-O-oxobenzoyl-3,4,6-tri-O-benzyl-α-D-mannopyranosyl)(1→2)-3,4,6-tri-O-
benzyl-α-D-mannopyranoside.
7
b
Starting material was synthesized from literature . Isolated as a syrup (93 mg, 81% yield);
1
H NMR (400 MHz, CDCl ) δ 8.06 – 7.98 (m, 2H), 7.83 (dd, J = 10.8, 7.4 Hz, 3H), 7.71 (s,
3
1
H), 7.58 (t, J = 7.4 Hz, 1H), 7.50 (dd, J = 7.1, 2.3 Hz, 2H), 7.43 – 7.17 (m, 30H), 7.14 (dd, J
6.5, 3.0 Hz, 2H), 5.85 (dd, J = 2.7, 1.9 Hz, 1H), 5.17 (d, J = 1.1 Hz, 1H, H1), 5.04 (d, J =
1.4 Hz, 1H, H1), 4.92 (d, J = 10.8 Hz, 1H), 4.85 – 4.78 (m, 3H), 4.73 (dd, J = 19.3, 7.3 Hz,
H), 4.62 (t, J = 12.3 Hz, 2H), 4.55 (dd, J = 11.2, 3.4 Hz, 2H), 4.44 (t, J = 11.8 Hz, 2H), 4.27
d, J = 12.1 Hz, 1H), 4.07 (ddd, J = 11.7, 9.3, 3.0 Hz, 3H), 3.98 – 3.82 (m, 4H), 3.74 (dd, J =
=
3
(
1
3
19.4, 9.8 Hz, 2H), 3.55 (dd, J = 10.9, 4.8 Hz, 1H), 3.38 (dd, J = 10.7, 1.4 Hz, 1H). C NMR
{
1H} (101 MHz, CDCl ) δ 186.4, 163.5, 138.6, 138.5, 138.3, 138.2, 138.2, 137.7, 134.7,
3
1
34.7, 133.2, 133.1, 132.4, 130.3, 128.7, 128.6, 128.4, 128.4, 128.4, 128.3, 128.2, 128.1,
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28.0, 127.9, 127.8, 127.8, 127.7, 127.6, 127.5, 127.5, 127.4, 126.9, 126.2, 126.0, 125.9, 99.1
I
(C1), 97.9 (C1 ), 79.7, 78.4, 75.6, 75.2, 74.8, 74.3, 73.4, 73.3, 72.7, 72.2, 72.1, 70.7, 69.3,
69.2, 68.8; HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C H O 1155.4889 found
7
3
71 13
1
1
1
1
1
1
1
1
1
1
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5
6
0
1
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0
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0
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9
0
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9
0
1
155.4903.
r.Napthyl-(2-O-oxobenzoyl-3-O-benzyl-4,6-O-benzylidene-α-D-
5
mannopyranosyl)(1→2)-(3,4,6-tri-O-benzyl-α-D-mannopyranosyl))(1→2)-3,4,6-tri-O-
benzyl-α-D-mannopyranoside.
2
9
1
Starting material was synthesized from literature . Isolated as a syrup (86 mg, 78% yield); H
NMR (400 MHz, CDCl ) δ 8.08 – 8.02 (m, 2H), 7.84 – 7.77 (m, 3H), 7.68 (s, 1H), 7.51 –
3
7.45 (m, 3H), 7.45 – 7.31 (m, 16H), 7.31 – 7.16 (m, 25H), 7.07 (dd, J = 7.6, 3.6 Hz, 2H), 5.68
(d, J = 3.2 Hz, 1H), 5.50 (s, 1H), 5.16 (d, J = 3.6 Hz, 1H, H1), 5.12 (d, J = 0.8 Hz, 1H, H1).,
4
.91 (d, J = 10.4 Hz, 1H), 4.85 – 4.52 (m, 10H), 4.52 – 4.41 (m, 3H), 4.26 (m, 4H), 4.17 –
4.00 (m, 3H), 3.97 – 3.78 (m, 6H), 3.66 (m, 3H), 3.45 (dd, J = 10.0, 4.0 Hz, 2H), 3.34 (d, J =
13
8
1
1
1
1
7
.8 Hz, 1H), 3.26 (s, 1H). C NMR {1H} (101 MHz, CDCl ) δ 186.5, 163.5, 138.9, 138.4,
3
38.4, 138.3, 138.2, 138.1, 137.9, 137.5, 134.9, 134.5, 133.2, 133.0, 132.6, 130.3, 128.9,
28.8, 128.70, 128.6, 128.4, 128.3, 128.3, 128.2, 128.1, 128.1, 128.1, 128.0, 127.9, 127.9,
27.8, 127.8, 127.7, 127.7, 127.6, 127.6, 127.5, 127.4, 127.4, 126.8, 126.8, 126.2, 126.1,
26.1, 126.0, 125.9, 101.5 (C1), 100.8 (C1), 98.6 (C1), 96.5, 80.2, 78.4, 77.2, 75.6, 75.3,
4.9, 74.3, 73.7, 73.2, 73.0, 72.9, 72.7, 72.3, 71.9, 71.6, 71.3, 69.8, 69.2, 69.1, 68.3, 66.9;
HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C H O 1495.6200 found 1495.6192.
9
3
91 18
5
s.Methyl-4,6-di-O-oxobenzoyl-3-O-levulinyl-2-O-pivaloyl-α-D-glucopyranoside.
3
5
Starting material was synthesized from literature . Isolated as a syrup (150 mg, 83%
1
yield); H NMR (400 MHz, CDCl ) δ 8.05 – 7.98 (m, 2H), 7.99 – 7.92 (m, 2H), 7.64 (t, J =
3
7
.4 Hz, 2H), 7.50 (t, J = 7.7 Hz, 4H), 5.71 (t, J = 9.8 Hz, 1H), 5.30 (t, J = 9.8 Hz, 1H), 5.00
(d, J = 3.6 Hz, 1H, H1), 4.82 (dd, J = 10.2, 3.7 Hz, 1H), 4.58 (qd, J = 12.2, 3.7 Hz, 2H), 4.24
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(
ddd, J = 10.2, 4.6, 2.7 Hz, 1H), 3.37 (s, 3H), 2.74 – 2.61 (m, 2H), 2.52 (dd, J = 9.9, 4.0 Hz,
1
3
2
H), 2.07 (s, 3H), 1.17 (s, 9H). C NMR {1H} (101 MHz, CDCl ) δ 205.7, 185.5, 184.8,
3
177.7, 171.4, 163.3, 162.4, 135.2, 135.1, 132.3, 132.1, 130.1, 130.0, 129.0, 128.9, 96.8 (C1),
0.8, 70.4, 69.5, 66.7, 63.2, 55.9, 38.8, 37.7, 29.6, 27.9, 26.8. HRMS (ESI-TOF) m/z: [M +
H]+ Calcd for C H O 641.2234 found 641.2241.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
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9
0
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0
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0
7
3
3
37 13
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t.Methyl-4,6-di-O-oxobenzoyl-2,3-di-O-benzyl-α-D-glucopyranoside.
3
0
Starting material was synthesized from literature . Isolated as a syrup (150 mg, 88% yield);
1
H NMR (400 MHz, CDCl ) δ 8.02 (dd, J = 8.3, 1.1 Hz, 2H), 7.93 (dd, J = 8.3, 1.1 Hz, 2H),
3
7
.66 – 7.57 (m, 2H), 7.47 (t, J = 7.8 Hz, 2H), 7.37 – 7.23 (m, 11H), 5.32 – 5.22 (m, 1H), 4.96
(d, J = 11.2 Hz, 1H), 4.80 (d, J = 12.1 Hz, 1H), 4.73 – 4.57 (m, 4H), 4.49 (dd, J = 12.1, 2.6
13
Hz, 1H), 4.20 – 4.07 (m, 2H), 3.66 (dd, J = 9.6, 3.5 Hz, 1H), 3.40 (s, 3H). C NMR {1H}
(101 MHz, CDCl ) δ 185.7, 185.5, 163.4, 162.7, 138.1, 137.7, 135.1, 134.9, 132.4, 132.1,
3
130.2, 130.1, 128.9, 128.9, 128.6, 128.5, 128.4, 128.2, 127.6, 127.5, 98.2 (C1), 79.6, 78.4,
7
6
5
5.4, 73.6, 71.9, 67.0, 63.7, 55.6; HRMS (ESI-TOF) m/z: [M + NH ]+ Calcd for C H NO
4 37 38 10
56.2490 found 656.2482.
u. Methyl-2,3-di-O-oxobenzoyl-4,6-O-benzylidene-α-D-glucopyranoside.
3
0
Starting material was synthesized from literature . Isolated as a syrup (167 mg, 86%
1
yield); H NMR (400 MHz, CDCl ) δ 8.07 – 7.94 (m, 2H), 7.89 – 7.81 (m, 2H), 7.65 (t, J =
3
7
.4 Hz, 1H), 7.57 – 7.48 (m, 5H), 7.41 (dd, J = 6.5, 3.6 Hz, 3H), 7.19 (t, J = 7.9 Hz, 2H), 6.00
(t, J = 9.9 Hz, 1H), 5.56 (s, 1H), 5.31 (dd, J = 9.9, 3.7 Hz, 1H), 5.22 (d, J = 3.7 Hz, 1H, H1),
4
3
.38 (dd, J = 10.4, 4.9 Hz, 1H), 4.08 (td, J = 9.9, 4.9 Hz, 1H), 3.83 (td, J = 10.0, 4.7 Hz, 2H),
1
3
.52 (s, 3H). C NMR {1H} (101 MHz, CDCl ) δ 186.0, 185.4, 163.2, 163.0, 136.7, 135.2,
3
134.9, 132.0, 130.1, 130.0, 129.4, 129.1, 128.8, 128.4, 126.3, 102.1, 97.3(C1), 79.2, 72.4,
7
0.4, 68.8, 62.5, 55.8; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C H NaO 569.1418
30 26 10
found 569.1413.
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v. Methyl-3,4-di-O-oxobenzoyl-2,6-di-O-benzoyl-α-D-glucopyranoside.
3
1
Starting material was synthesized from literature . Isolated as a syrup (136 mg, 82%
1
yield); H NMR (400 MHz, CDCl ) δ 8.14 – 8.10 (m, 4H), 8.05 – 8.02 (m, 2H), 7.76 (dd, J =
3
1
1
1
1
1
1
1
1
1
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0
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0
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2
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0
8
7
3
1
1
1
.3, 1.2 Hz, 2H), 7.66 – 7.61 (m, 2H), 7.57 (dd, J = 7.8, 1.6 Hz, 1H), 7.52 – 7.45 (m, 7H),
.10 (dd, J = 8.2, 7.6 Hz, 2H), 6.21 – 6.13 (m, 1H), 5.72 (t, J = 9.9 Hz, 1H), 5.25 (dq, J = 7.3,
.6 Hz, 2H), 4.72 (dd, J = 12.5, 2.3 Hz, 1H), 4.54 (dd, J = 12.5, 4.2 Hz, 1H), 4.39 (ddd, J =
1
3
0.2, 4.0, 2.3 Hz, 1H), 3.47 (s, 3H). C NMR{1H} (101 MHz, CDCl ) δ 185.4, 184.9, 166.0,
3
65.4, 163.2, 162.1, 135.2, 134.9, 133.8, 133.3, 131.9, 131.8, 130.2, 130.1, 129.8, 129.8,
29.6, 129.1, 128.7, 128.7, 128.6, 128.5, 96.9 (C1), 71.8, 71.3, 69.5, 67.3, 62.0, 55.8; HRMS
(ESI-TOF) m/z: [M + H]+ Calcd for C H O 667.1810 found 667.1804.
3
7
31 12
5
w.1,2-Di-O-oxobenzoyl-3,4,5,6-tetra-O-benzyl-myo-inositol.
1
Isolated as a syrup (96 mg, 79% yield); H NMR (400 MHz, CDCl ) δ 8.01 (dd, J = 7.1, 5.4
3
Hz, 4H), 7.69 – 7.57 (m, 2H), 7.50 – 7.41 (m, 4H), 7.37 – 7.25 (m, 19H), 6.24 (s, 1H), 5.32
(dd, J = 10.4, 2.8 Hz, 1H), 4.90 (t, J = 10.4 Hz, 4H), 4.77 (m, 4H), 4.07 (t, J = 9.8 Hz, 1H),
1
3
3
{
1
1
.92 (t, J = 9.6 Hz, 1H), 3.84 (dd, J = 9.7, 2.8 Hz, 1H), 3.67 (t, J = 9.6 Hz, 1H). C NMR
1H} (101 MHz, CDCl ) δ 185.8, 185.1, 163.5, 163.0, 138.4, 138.2, 137.8, 137.2, 135.2,
3
35.0, 132.2, 132.1, 130.2, 130.2, 129.1, 128.9, 128.6, 128.5, 128.4, 128.3, 128.1, 128.0,
28.0, 127.9, 127.8, 127.8, 82.7, 81.1, 78.9, 78.1, 76.2, 76.2, 75.9, 73.2, 73.1, 69.7; HRMS
(ESI-TOF) m/z: [M + Na]+Calcd for C H NaO 827.2827 found 827.2825.
50 44 10
5x.Methyl-3,4,6-tri-O-oxobenzoyl-2-O-benzoyl-α-D-glucopyranoside.
19
Starting material was synthesized from literature . Isolated as a syrup (196 mg 84%
1
yield); H NMR (400 MHz, CDCl ) δ 8.14 – 8.10 (m, 2H), 8.07 – 8.00 (m, 4H), 7.73 (dd, J =
3
8.3, 1.1 Hz, 2H), 7.67 – 7.60 (m, 3H), 7.49 (dt, J = 16.3, 7.8 Hz, 7H), 7.08 (t, J = 7.9 Hz, 2H),
6
1
.15 (t, J = 9.8 Hz, 1H), 5.56 (t, J = 9.8 Hz, 1H), 5.26 (d, J = 3.6 Hz, 1H, H1), 5.20 (dd, J =
0.2, 3.6 Hz, 1H), 4.66 (qd, J = 12.2, 3.8 Hz, 2H), 4.38 (ddd, J = 10.4, 4.8, 3.2 Hz, 1H), 3.45
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