ortho-Methylphenylthioglycosides as glycosyl building blocks for preactivation-based oligosaccharide synthesis

Carbohydrate Research 384 (2014) 1–8

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Carbohydrate Research journal homepage: www.elsevier.com/locate/carres

ortho-Methylphenylthioglycosides as glycosyl building blocks for preactivation-based oligosaccharide synthesis Peng Peng, De-Cai Xiong, Xin-Shan Ye ⇑ State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, Xue Yuan Rd No. 38, Beijing 100191, China

a r t i c l e

i n f o

Article history: Received 29 October 2013 Received in revised form 13 November 2013 Accepted 14 November 2013 Available online 22 November 2013 Keywords: o-Methylphenylthioglycoside Preactivation Oligosaccharide Aglycon transfer Glycosylation

a b s t r a c t Thioglycosides are widely used in orthogonal glycosylation, armed-disarmed chemoselective glycosylation, and preactivation-based glycosylation. Nevertheless, aglycon transfer occasionally occurred in the glycosylation process of thioglycosides. This problem was also encountered in preactivation-based reactions, which limited the applications of preactivation-based glycosylation to some extent. To tackle this problem, sterically hindered aglycon ortho-methylphenylthioglycosides were introduced as glycosyl building blocks. These thioglycosides prevented the aglycon transfer and enhanced the efficiency of glycosyl coupling reactions, especially in the reactions of disarmed donors with armed acceptors. Moreover, these thioglycosides were employed in preactivation-based one-pot oligosaccharide assembly. Ó 2013 Elsevier Ltd. All rights reserved.

1. Introduction Oligosaccharides and glycoconjugates have attracted much attention due to their important roles in biological processes.1–3 However, understanding functions of carbohydrates is hampered by the lack of general methods for the preparation of this class of compounds. In the past decades, many advances on oligosaccharide synthesis have been achieved, including solid-phase strategy,4 solution-phase protocol,5–7 and chemo-enzymatic method.8–10 Among these strategies, thioglycosides have been frequently used, since they are convenient to prepare and stable in many functional group transformations and glycosylations. On the other hand, because the sulfur atom in thioglycosides is able to react selectively with thiophilic promoters, they are also effective glycosyl donors. In one word, thioglycosides can serve as both donors and acceptors in glycosylations.11 However, when thioglycosides are used as glycosyl acceptors, the electrophilic intermediates resulted from the activation of donors, could be also attacked by the sulfur atom of acceptors. This phenomenon is known as the aglycon transfer. In the previous studies, it was reported that sometimes the aglycon transfer could be problematic when thioglycosides were used as blocks.12–25 The aglycon transfer could affect both armed and disarmed thioglycosides and destroy glycosylation products.24 Therefore, it may seriously reduce the efficiency of glycosidic bond formation in a number of glycosylation strategies.

⇑ Corresponding author. Tel.: +86 10 82805736; fax: +86 10 82802724. E-mail address: [email protected] (X.-S. Ye). 0008-6215/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.carres.2013.11.009

Recently, in our group, the aglycon transfer was also encountered in the preactivation-based one-pot glycosylation protocol.26 For example, as shown in Scheme 1, when the disarmed donor 1 was completely activated, which was followed by the coupling with the armed acceptor 2, the coupled product disaccharide 3 was obtained in only 45% yield along with the recovery of donor 1 (15%). It was found that after the addition of acceptor 2, donor 1 which had been completely consumed regenerated. This phenomenon happened especially in the glycosylations of armed acceptors with disarmed donors. This regenerated donor 1 not only reduced the coupling efficiency but also influenced the subsequent glycosylation in one-pot strategy. The unfavorable regeneration of donors is caused by the aglycon transfer of thioglycosides. In this article, we intended to explore a new approach to overcome this problem in the preactivation-based glycosylations. 2. Results and discussion Many endeavors have been made to solve the aglycon transfer problem. Boons and co-workers18 changed the protective groups of building blocks. This conversion could address the problem of aglycon transfer, but it needed extensive protective group manipulations. Yu et al.17 observed that the higher reaction temperature benefitted the aglycon transfer in some cases. Du and co-workers25 found that the aglycon transfer problem could be avoided by using an inverse procedure (acceptors were added prior to donors). But the inverse procedure was not suitable to the preactivation protocol. Gildersleeve et al.24,27–29 installed sterically hindered

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P. Peng et al. / Carbohydrate Research 384 (2014) 1–8

OH BzO BzO

OBz O STol

BzO

BzO

O

BnO BnO

BnO 2

Ph2SO/Tf2O

STol

BzO

OBz O BzO BnO BnO

1 CH3

Tol =

O O BnO 3 45%

+

1

STol 15%

Scheme 1. Aglycon transfer occurred in preactivation-based glycosylations.

aglycon (2,6-dimethylphenylthioglycosides) to surmount aglycon transfer process, for the steric hindrance of the leaving group in acceptors could prevent the reaction with the intermediates produced from donors. We supposed this approach would be useful in the preactivation protocol. However, it was reported that the activation of 2,6-dimethylphenylthioglycoside donors needed higher temperature (15 °C).24 At this temperature, the active intermediates derived from donors could be unstable in the preactivation glycosylation process.30 To make sure the glycosyl donors can be activated at low temperature, we choose o-methylphenylthioglycosides as donors.31 This type of thioglycoside donors are less sterically hindered, we want to investigate whether these thioglycosides can be used to prevent the aglycon transfer in glycosylation reactions. We anticipated this leaving group would meet our requirements. Firstly, we chose the glycosylation of o-methylphenyl (oTol) thioglycoside donor 4 and acceptor 5 as the model reaction. After screening the reaction conditions, we found that it was not until at 20 °C that the disarmed donor 4 was activated completely. Luckily, at this temperature the activated intermediate of benzoylated donor 4 could survive.30 In order to make the activated intermediate stable, the reaction system was cooled down back to 72 °C. Nearly one equivalent of armed acceptor 5 was then added to the reaction mixture, affording the desired disaccharide 6 in 72% yield with no donor 4 isolated (Scheme 2). Since the aglycon transfer could affect armed thioglycosides as well as disarmed thioglycosides,24 it was believed that thioglycoside acceptors would be the major factor in aglycon transfer. Thus, various o-methylphenylthioglycosides were prepared as glycosyl acceptors, and glycosylations were checked in pre-activation protocol. Next, an acceptor with a secondary hydroxyl group exposed was tested toward glycosylation. In our experiments, using preactivation protocol, when the disarmed benzoylated p-methylphenylthioglycoside donor 1 was reacted with the corresponding armed thioglycoside acceptor 7 bearing a free hydroxyl group at the C-4 position, no desired disaccharide product was formed. Therefore, o-methylphenylthioglycoside 9 having the very similar structure to compound 7 was used to react with donor 4. As our anticipation, this reaction was carried out smoothly, providing the disaccharide 10 in 68% isolated yield. In this reaction, there

was some amount of unreacted acceptor 9 recovered. When 1.5 equiv of donor was used, the acceptor was consumed completely, affording compound 10 in 80% isolated yield (Scheme 3). Consequently, a series of acceptors were investigated under preactivation-based conditions (Table 1). The acceptor 11 with a C-3 hydroxyl group exposed was also glycosylated well with donor 4 to obtain disaccharide 12 in 93% yield (Table 1, entry 2). The disarmed benzoyl-protected acceptor 13 also coupled smoothly with 4 to produce disaccharide 14 in 92% isolated yield (Table 1, entry 3), whereas the analogue of 13 with ethylthio-substitute instead of o-methylphenylthio-substitute did not react with the benzoylated thioglycoside donor.32 The glucosamine diol 15, underwent the regioselective glycosylation with donor 4 to give the 1-4 linked disaccharide 16 in 75% yield, this regioselectivity is well-known in carbohydrate chemistry (Table 1, entry 4). The thiogalactoside acceptor 17 with a secondary hydroxyl group exposed was reacted with donor 4 to provide disaccharide 18 in 73% yield (Table 1, entry 5). The galactosamine donor 24 also coupled with acceptor 13, affording disaccharide 25 in 75% yield (Table 1, entry 9). When acceptor 19 was used, the coupling product 20 was isolated in 60% yield (Table 1, entry 6). It was found that acceptor 19 could not undergo the reaction with the activated intermediate derived from donor 4 until 40 °C and the coupling reaction was slow. The glycosylation could also be influenced by the nucleophilicity of acceptor. The acetylated acceptor 22 which was considered to possess low nucleophilicity was examined. It was found that acceptor 22 did not react with the activated intermediate until 20 °C, and the disaccharide product was isolated in only 27% yield (Table 1, entry 8). Similarly, another acceptor 21 with low nucleophilicity did not couple with the activated donor at all, regardless of the promoters (Ph2SO/Tf2O or p-TolSCl/AgOTf) used, getting the recovery of acceptor 21 (Table 1, entry 7). Although it was reported that aglycon transfer could also occur in the disarmed thioglycoside cases,24 we did not observe this phenomenon in these reactions. Why did some disarmed acceptors not react well with disarmed donors in some cases? Our results indicated that the inefficient glycosylation might be not affected by aglycon transfer, but could be probably attributed to the low nucleophilicity of hydroxyl in acceptors toward the unreactive intermediates derived from donors. It was noted that in all the reactions mentioned

OH BnO BnO

OBz O

BzO BzO

BzO

SoTol

4 o

Tol =

CH3

a

BzO

O o

BnO 5

S Tol

BzO

OBz O BzO BnO BnO

O O BnO

SoTol

6 72%

Scheme 2. Reagents and conditions: (a) Ph2SO, Tf2O, 4 Å molecular sieves, 72 °C to 20 °C, then cooled to 72 °C.

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OBn BzO

HO BnO

OBz O

BzO

BzO

STol

Ph2SO,Tf2O

O BnO 7

DCM, 4Å MS

STol

BzO

OBz O

BzO

BzO

1

BzO BzO

HO BnO

OBz O BzO

SoTol

Ph2SO,Tf2O DCM, 4Å MS

4

o

Tol =

Tol =

O BnO

O BnO

STol

8 0%

OBn O BnO 9

OBn

SoTol BzO

OBz O

BzO

BzO

OBn O BnO

10 68%a (80%b)

O BnO

SoTol

CH3

CH3 Scheme 3. Conditions: (a) donor/acceptor = 1.1:1; (b) donor/acceptor = 1.5:1.

above, the regenerated donor and its anomerized product were not isolated. That means the aglycon transfer phenomenon was avoided in the preactivation-based glycosylation process. To investigate the scope of o-methylphenylthioglycosides in glycosylations, the o-methylphenylthioglycoside donors with higher reactivity were prepared. As expected, both the armed donor 26 and the moderate donor 28 were activated quickly at 72 °C, and the coupled products were obtained in good yields (Table 1, entries 10 and 11). It is noteworthy that the coupling of 26 and 21 yielded the exclusive a-linked product 27 due to the anomeric effect. These reactions needed to be quenched at 72 °C. Otherwise, the formed disaccharide products would be decomposed by the unfavorable Sthiophenyl sulfonium by-product33 from Ph2SO, whereas this problem did not occur in the examples of disarmed donors mentioned above. The reason might be that S-thiophenyl sulfonium also decomposed when the preactivation temperature was raised. The next issue was to determine if o-methylphenylthioglycosides could be applied to preactivation-based iterative one-pot oligosaccharide synthesis. Indeed, they worked well. As exemplified in Scheme 4, glycosyl donor 4 coupled with acceptor 13 very smoothly when promoted by Ph2SO/Tf2O. After the glycosyl coupling reaction was completed, the newly formed disaccharide without isolation was activated again by the same promoter system, which was followed by the addition of acceptor 30, providing the final trisaccharide 31 in 76% isolated yield with good stereoselectivity. 3. Conclusions In summary, a series of sterically hindered o-methylphenylthioglycosides working as building blocks for oligosaccharide synthesis were designed and synthesized for preactivation-based glycosylation protocol. These thioglycosides were able to efficiently prevent the aglycon transfer, thus enhancing the efficiency of glycosyl coupling reactions. These thioglycosides overcome some limitations of the conventional thioglycosides currently used in the preactivation protocol and can be employed in iterative one-pot oligosaccharide assembly. 4. Experimental 4.1. General All chemicals were purchased as reagent grade and used without further purification, unless otherwise noted. Dichloromethane

(CH2Cl2) was distilled over calcium hydride (CaH2). All reactions were performed in flame-dried modified Schlenk (Kjeldahl shape) flasks fitted with a glass stopper or rubber septa under a positive pressure of argon or nitrogen. Analytical TLC was performed on silica gel 60-F254 precoated on aluminum plates (E. Merck), with detection by UV (254 nm) and/or by staining with acidic ceric ammonium molybdate. Solvents were evaporated under reduced pressure and below 35 °C (bath). Organic solutions of crude products were dried over anhydrous Na2SO4. Column chromatography was performed employing silica gel (200–300 mesh). 1H NMR spectra were recorded on Advance DRX Bruker-400 spectrometers at 25 °C. Chemical shifts (in ppm) were referenced to tetramethylsilane (d = 0 ppm) in deuterated chloroform. 13C NMR spectra were obtained by using the same NMR spectrometers and were calibrated with CDCl3 (d = 77.00 ppm). High-resolution mass spectra were recorded on a Bruker APEX IV. Optical rotations were measured with an AA-10R automatic polarimeter. 4.2. General procedure for preactivation-based glycosylation Method A: A solution of donor (50 lmol, 1.5 equiv), Ph2SO (55 lmol, 1.6 equiv), and activated 4 Å powdered molecular sieves in dichloromethane (2 mL) was stirred at room temperature under an argon atmosphere for 30 min. Then the mixture was cooled to 72 °C and Tf2O (55 lmol, 1.6 equiv) was added. The temperature was raised to 20 °C slowly. The reaction mixture was stirred at this temperature for 5 min and then cooled back to 72 °C. Subsequently, acceptor (33 lmol, 1.0 equiv) was added. The reaction was further stirred for 15 min and warmed gradually to room temperature. The reaction was quenched by triethylamine (0.2 mL) and the precipitated was filtered off through a pad of Celite. The filtrate was concentrated and the residue was purified by column chromatography on silica gel. Method B: A solution of donor (34 lmol, 1.2 equiv), Ph2SO (38 lmol, 1.3 equiv) and activated 4 Å powdered molecular sieves in dichloromethane (2 mL) was stirred at room temperature under an argon atmosphere for 30 min. The mixture was cooled to 72 °C and Tf2O (38 lmol, 1.3 equiv) was added. After the TLC detection indicated that donor was completely consumed, acceptor (29 lmol, 1.0 equiv) was added. The reaction was further stirred for 30 min and quenched by triethylamine (0.2 mL). The precipitated was filtered off through a pad of Celite. The filtrate was concentrated and the residue was purified by column chromatography on silica gel.

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P. Peng et al. / Carbohydrate Research 384 (2014) 1–8

Table 1 Glycosylations with o-methylphenylthioglycosides (o-Tol) as building blocks Entry

a b

Donor

Acceptor

Product

Yield (%)

1

80a

2

93a

3

92a

4

75a

5

73a

6

60a

7

0

8

27a

9

75a

10

85b

11

77b

Donor/acceptor = 1.5:1. Donor/acceptor = 1.2:1 and quenched at 72 °C.

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OH

OH BzO BzO BzO

OBz O

BzO

BzO 4 (1.5 eq)

Ph2SO (1.6 eq)

Tf2O (1.6 eq)

BzO BzO

O

O

BzO BzO SoTol OMe BzO Ph2SO (1.1 eq) 30 (1.1 eq) BzO 13 (1.0 eq) Tf2O (1.1 eq)

SoTol -72oC -20oC -72oC

rt

-72oC

OBz O BzO BzO BzO

O O

BzO BzO BzO 31 76 %

O O BzO

OMe

Scheme 4. Pre-activation based one-pot assembly of trisaccharide 31 using o-methylphenylthioglycosides as building blocks.

4.2.1. p-Tolyl 6-O-(2,3,4,6-tetra-O-benzoyl-b-D-galactopyrano syl)-2,3,4-tri-O-benzyl-1-thio-b-D-glucopyranoside (3) Compound 3 (13.0 mg, 45% yield as a semisolid) was prepared according to the general procedure (Method B) from donor 1 (20.0 mg, 28 lmol) and acceptor 2 (14.3 mg, 25 lmol), and was purified by column chromatography (toluene/acetonitrile = 30:1). 1 ½a25 D +30.3° (c 1.19 in CHCl3); H NMR (400 MHz, CDCl3): d 8.10 (d, 2H, J = 8.4 Hz), 8.03 (d, 2H, J = 8.4 Hz), 7.84 (d, 2H, J = 8.4 Hz), 7.84 (d, 2H, J = 8.4 Hz), 7.22–7.62 (m, 31H), 7.15 (d, 2H, J = 8.0 Hz), 7.10–7.12 (m, 2H), 5.95 (d, 1H, J = 3.2 Hz, H-40 ), 5.85 (dd, 1H, J = 8.0, 10.4 Hz, H-20 ), 5.55 (dd, 1H, J = 3.6, 10.4 Hz, H-30 ), 4.94 (d, 1H, J = 8.0 Hz), 4.85 (d, 1H, J = 10.0 Hz, PhCH2), 4.82 (d, 1H, J = 10.0 Hz, PhCH2), 4.73 (d, 1H, J = 11.2 Hz, PhCH2), 4.64–4.69 (m, 2H, H-6a, PhCH2), 4.60 (1H, J = 10.8 Hz, PhCH2), 4.55 (d, 1H, J = 9.6 Hz, H-1), 4.45 (d, 1H, J = 10.8 Hz, PhCH2), 4.42 (dd, 1H, J = 6.8, 11.2 Hz, H-6b), 4.19–4.22 (m, 2H, H-5, H-6a0 ), 3.90 (dd, 1H, J = 4.4, 11.2 Hz, H-6b0 ), 3.59 (t, 1H, J = 8.8 Hz, H-3), 3.42– 3.48 (m, 2H, H-4, H-5), 3.37 (t, 1H, J = 9.6 Hz, H-2), 2.26 (s, 3H, Me). 13C NMR (100 MHz, CDCl3): d 165.98, 165.57, 165.53, 165.11, 138.33, 138.72, 137.93, 137.81, 133.51, 133.22, 133.07, 132.71, 130.02, 129.87, 129.81, 129.77, 129.57, 129.45, 129.29, 129.09, 128.80, 128.62, 128.45, 128.39, 128.37, 128.31, 128.26, 128.19, 127.80, 127.69, 127.63, 101.25, 87.57, 86.56, 78.98, 77.41, 75.62, 75.31, 74.87, 71.82, 71.29, 69.75, 68.15, 67.85, 61.92, 21.03. Calcd for C68H62NaO14S [M+Na]+ 1157.3753. Found: 1157.3741.

4.2.3. o-Tolyl 4-O-(2,3,4,6-tetra-O-benzoyl-b-D-galactopyran osyl)-2,3,6-tri-O-benzyl-1-thio-b-D-glucopyranoside (10) Compound 10 (33.0 mg, 80% yield as a semisolid) was prepared according to the general procedure (Method A) from donor 4 (38.0 mg, 54 lmol) and acceptor 9 (20.0 mg, 36 lmol), and was purified by column chromatography (toluene/acetonitrile = 30:1). 1 ½a25 D 4.5° (c 2.65 in CHCl3); H NMR (400 MHz, CDCl3): d 8.02 (dd, 2H, J = 1.6, 8.8 Hz), 7.92 (dd, 2H, J = 1.2, 8.4 Hz), 7.87 (dd, 2H, J = 1.2, 8.4 Hz) 7.76 (dd, 2H, J = 1.2, 8.4 Hz), 7.19–7.56 (m, 35 H), 7.11–7.14 (m, 1H), 5.88 (d, 1H, J = 2.8 Hz, H-40 ), 5.73 (dd, 1H, J = 8.0, 10.4 Hz, H-20 ), 5.43 (dd, 1H, J = 3.6, 10.6 Hz, H-30 ), 5.25 (d, 1H, J = 10.8 Hz, PhCH2), 4.99 (d, 1H, J = 8.0 Hz, H-10 ), 4.87 (d, 1H, J = 10.8 Hz, PhCH2), 4.85 (d, 1H, J = 10.4 Hz, PhCH2), 4.79 (d, 1H, J = 10.4 Hz, PhCH2), 4.71 (d, 1H, J = 12.0 Hz, PhCH2), 4.57 (d, 1H, J = 10.0 Hz, H-1), 4.39–4.41 (m, 2H, H-6a0 , PhCH2), 4.14–4.24 (m, 2H, H-6b0 , H-4), 4.00 (t, 1H, J = 6.8 Hz, H-50 ), 3.67–3.71 (m, 2H, H3, H-6a), 3.51–3.60 (m, 2H, H-6b, H-2), 3.25–3.28 (dd, 1H, J = 2.0, 10.0 Hz, H-5), 2.41 (s, 3H, Me). 13C NMR (100 MHz, CDCl3): d 165.79, 165.44, 165.38, 164.89, 139.18, 138.91, 138.03, 137.99, 133.68, 133.39, 133.19, 131.75, 130.07, 129.78, 129.69, 129.62, 129.46, 129.00, 128.75, 128.59, 128.52, 128.47, 128.42, 128.24, 128.20, 128.15, 128.07, 128.00, 127.69, 127.33, 127.28, 126.49, 100.40, 87.72, 84.56, 80.60, 78.39, 76.43, 75.63, 75.39, 73.52, 71.78, 71.08, 70.30, 67.84, 61.37, 20.91. HRMS (ESI) Calcd for C68H66NO14S [M+NH4]+ 1152.4199. Found: 1152.4181. Calcd for C68H62NaO14S [M+Na]+ 1157.3753. Found: 1157.3761.

4.2.2. o-Tolyl 6-O-(2,3,4,6-tetra-O-benzoyl-b-D-galactopyrano syl)-2,3,4-tri-O-benzyl-1-thio-b-D-glucopyranoside (6) Compound 6 (21.0 mg, 72% yield as a semisolid) was prepared according to the general procedure (Method A) from donor 4 (20.0 mg, 28 lmol) and acceptor 5 (14.3 mg, 25 lmol), and was purified by column chromatography (toluene/acetonitrile = 30:1). 1 ½a25 D +37.7° (c 1.06 in CHCl3); H NMR (400 MHz, CDCl3): d 8.09 (d, 2H, J = 7.6 Hz), 8.03 (d, 2H, J = 7.6 Hz), 7.78–7.83 (m, 4H), 7.66 (d, 1H, J = 7.6 Hz), 7.61 (t, 1H, J = 7.2 Hz), 7.55 (t, 1H, J = 7.2 Hz), 7.40–7.49 (m, 6H), 7.12–7.37 (m, 29H), 5.95 (d, 1H, J = 2.8 Hz, H40 ), 5.81 (dd, 1H, J = 8.0, 10.4 Hz, H-20 ), 5.50 (dd, 1H, J = 3.2, 10.4 Hz, H-30 ), 4.89 (d, 1H, J = 10.8 Hz, PhCH2), 4.86 (d, 1H, J = 8.4 Hz, H-10 ), 4.85 (d, 1H, J = 10.8 Hz, PhCH2), 4.75 (d, 1H, J = 10.8 Hz, PhCH2), 4.73 (d, 1H, J = 10.4 Hz, PhCH2), 4.62–4.67 (m, 3H, H-1, H-6a0 , PhCH2), 4.47 (d, 1H, J = 10.8 Hz, PhCH2), 4.39 (dd, 1H, J = 6.8, 11.6 Hz, H-6b0 ), 4.14–4.17 (m, 2H, H-50 , H-6a), 3.88 (dd, 1H, J = 4.8, 11.2 Hz, H-6b), 3.61 (t, 1H, J = 8.4 Hz), 3.42–3.51 (m, 3H), 2.43 (s, 3H, Me). 13C NMR (100 MHz, CDCl3): d 165.92, 165.53, 165.47, 165.07, 139.14, 138.28, 137.88, 137.71, 133.47, 133.32, 133.19, 133.01, 131.86, 130.23, 129.97, 129.75, 129.71, 129.61, 129.38, 129.23, 129.01, 128.73, 128.56, 128.41, 128.37, 128.33, 128.25, 128.21, 128.13, 127.80, 127.71, 127.60, 126.88, 101.07, 87.24, 86.54, 80.90, 79.04, 77.37, 75.58, 75.47, 74.86, 71.71, 71.21, 69.68, 68.07, 67.80, 61.93, 20.96. HRMS (ESI) Calcd for C68H66NO14S [M+NH4]+ 1152.4199. Found: 1152.4188.

4.2.4. o-Tolyl 3-O-(2,3,4,6-tetra-O-benzoyl-b-D-galactopyrano syl)-2-O-benzyl-4,6-O-benzylidene-1-thio-b-D-glucopyranoside (12) Compound 12 (31.2 mg, 93% yield as a semisolid) was prepared according to the general procedure (Method A) from donor 4 (34.0 mg, 48 lmol) and acceptor 11 (15.0 mg, 32 lmol), and was purified by column chromatography (petroleum ether/ethyl acetate = 3:1). ½a25 +33.7° (c 2.85 in CHCl3); 1H NMR (400 MHz, D CDCl3): d 8.05 (d, 2H, J = 7.2 Hz), 7.95 (d, 2H, J = 7.2 Hz), 7.73– 7.80 (m, 3H), 7.50–7.60 (m, 5H), 7.37–7.47 (m, 9H), 7.10–7.30 (m, 19H), 5.93 (d, 1H, J = 3.2 Hz, H-40 ), 5.88 (dd, 1H, J = 8.4, 10.4 Hz, H-20 ), 5.61 (s, 1H, PhCH), 5.54 (dd, 1H, J = 3.6, 10.4 Hz, H30 ), 5.25 (d, 1H, J = 8.0 Hz, H-10 ), 4.77 (d, 1H, J = 10.4 Hz, PhCH2), 4.72 (d, 1H, J = 11.2 Hz, PhCH2), 4.69 (d, 1H, J = 10.0 Hz, H-10 ), 4.48 (dd, 1H, J = 6.4, 11.2 Hz, H-6a0 ), 4.31–4.39 (m, 2H, H-6b0 , H6a), 4.17 (t, 1H, J =8.8 Hz, H-3), 4.03 (t, 1H, J = 6.8 Hz, H-50 ), 3.84 (t, 1H, J = 9.6 Hz, H-4), 3.79 (t, 1H, J = 10.4 Hz, H-6b), 3.62 (dd, 1H, J = 8.4, 9.6 Hz, H-2), 3.40–3.46 (dt, 1H, J = 4.8, 9.6 Hz, H-5). 2.32 (s, 3H, Me). 13C NMR (100 MHz, CDCl3): d 165.77, 165.57, 165.46, 165.32, 139.38, 137.78, 137.12, 133.46, 133.19, 133.10, 131.80, 130.28, 129.94, 129.79, 129.72, 129.65, 129.34, 129.12, 129.06, 128.72, 128.58, 128.39, 128.27, 128.22, 128.19, 127.65, 127.56, 126.59, 126.00, 124.77, 101.30, 100.72, 88.36, 81.95, 80.65, 79.16, 75.65, 71.98, 71.07, 70.34, 70.18, 68.64, 67.95, 61.41, 20.84. HRMS (ESI) Calcd for C61H58NO14S1 [M+NH4]+

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1060.3573. Found: 1060.3541. Calcd for C61H54NaO14S1 [M+K]+ 1081.2860. Found: 1081.2822. 4.2.5. o-Tolyl 6-O-(2,3,4,6-tetra-O-benzoyl-b-D-galactopyrano syl)-2,3,4-tri-O-benzoyl-1-thio-b-D-glucopyranoside (14) Compound 14 (36.0 mg, 92% yield as foams) was prepared according to the general procedure (Method A) from donor 4 (35.2 mg, 50 lmol) and acceptor 13 (20.0 mg, 33 lmol), and was purified by column chromatography (petroleum ether/ethyl ace1 tate = 3:1). ½a25 H NMR (400 MHz, D + 58.3° (c 1.72 in CHCl3); CDCl3): d 8.03–8.07 (m, 4H), 7.75–7.93 (m, 10H), 7.17–7.61 (m, 28H), 5.96 (d, 1H, J = 2.8 Hz, H-40 ), 5.76–5.82 (m, 2H, H-20 , H-3), 5.51 (dd, 1H, J = 3.2, 10.4 Hz, H-30 ), 5.44 (t, 1H, J = 9.6 Hz, H-2), 5.33 (t, 1H, J = 9.6 Hz, H-4), 4.95 (d, 1H, J = 8.0 Hz, H-10 ), 4.94 (d, 1H, J = 10.0 Hz, H-1), 4.57 (dd, 1H, J = 6.4, 11.2 Hz, H-6a0 ), 4.38 (dd, 1H, J = 6.4, 11.6 Hz, H-6b0 ), 4.22 (t, 1H, J = 6.8 Hz, H-50 ), 3.99– 4.06 (m, 3H, H-5, H-6a, H-6b), 2.25 (s, 3H, Me). 13C NMR (100 MHz, CDCl3): d 165.94, 165.65, 165.53, 165.50, 165.29, 164.97, 140.20, 133.52, 133.48, 133.30, 133.22, 133.16, 133.10, 133.02, 131.86, 130.36, 129.99, 129.78, 129.68, 129.37, 129.32, 129.14, 129.04, 128.77, 128.59, 128.52, 128.47, 128.40, 128.34, 128.29, 128.25, 128.23, 126.97, 101.25, 86.38, 78.64, 74.08, 71.75, 71.42, 70.60, 69.61, 69.36, 68.13, 68.10, 61.95, 20.93. HRMS (ESI) Calcd for C68H60NO17S [M+NH4]+: 1194.3577. Found: 1194.3541. Calcd for C68H56NaO17S [M+Na]+: 1199.3130. Found: 1199.3101. 4.2.6. o-Tolyl 4-O-(2,3,4,6-tetra-O-benzoyl-b-D-galactopyrano syl)-2-N-phthalimido-6-O-benzyl-2-deoxy-1-thio-b-D-glucop yranoside (16) Compound 16 (33.0 mg, 75% yield as a semisolid) was prepared according to the general procedure (Method A) from donor 4 (41.8 mg, 60 lmol) and acceptor 15 (20.0 mg, 40 lmol), and was purified by column chromatography (petroleum ether/ethyl ace1 tate = 1.5:1). ½a25 D + 85.2° (c 1.55 in CHCl3); H NMR (400 MHz, CDCl3): d 7.96–8.05 (m, 6H), 7.89–7.91 (m, 1H), 7.70–7.82 (m, 5H), 7.16–7.63 (m, 40H), 7.06–7.10 (m, 2H), 6.96–7.00 (m, 1H), 5.94 (d, 1H, J = 3.2 Hz, H-40 ), 5.83 (dd, 1H, J = 8.0, 10.4 Hz, H-20 ), 5.56 (dd. 1H, J = 3.6, 10.4 Hz, H-30 ), 5.52 (d, 1H, J = 10.8 Hz, H-1), 4.92 (d, 1H, J = 8.0 Hz, H-10 ), 4.59–4.69 (m, 2H, H-3, H-6a0 ), 4.37– 4.43 (m, 2H, H-2, –OH), 4.31–4.35 (m, 2H, H-50 , H-6b0 ), 4.22 (d, 1H, J = 12.0 Hz, PhCH2), 4.14 (d, 1H, 12.4 Hz, PhCH2), 3,86 (t, 1H, J = 9.6 Hz, H-4), 3.62–3.65 (m, 1H, H-5), 3.44–3.51 (m, 2H, H-6a, H-6b), 2.19 (s, 3H, Me). 13C NMR (100 MHz, CDCl3): d 168.12, 167.42, 166.13, 165.40, 165.34, 164.95, 140.06, 138.25, 134.01, 133.72, 133.57, 133.35, 133.25, 133.01, 132.02, 131.85, 131.70, 130.11, 129.98, 129.87, 129.84, 129.74, 129.00, 128.92, 128.67, 128.55, 128.46, 128.32, 128.30, 127.87, 127.58, 127.44, 126.51, 123.60, 123.20, 101.96, 83.83, 82.43, 77.83, 73.02, 72.34, 71.40, 70.85, 69.53, 68.18, 68.02, 62.57, 55.26, 20.82. HRMS (ESI) Calcd for C62H57N2O15S [M+NH4]+: 1101.3488. Found: 1101.3474. 4.2.7. o-Tolyl 3-O-(2,3,4,6-tetra-O-benzoyl-b-D-galactopyran osyl)-2,4,6-tri-O-benzyl-1-thio-b-D-galactopyranoside (18) Compound 18 (15.2 mg, 73% yield as a semisolid) was prepared according to the general procedure (Method A) from donor 4 (20.0 mg, 28 lmol) and acceptor 17 (10.0 mg, 18 lmol), and was purified by column chromatography (petroleum ether/ethyl acetate = 4:1). ½a25 +38.2° (c 1.52 in CHCl3); 1H NMR (400 MHz, D CDCl3): d 8.03 (d, 2H, J = 8.4 Hz), 7.98 (d, 2H, J = 8.4 Hz), 7.84 (d, 2H, J = 8.4 Hz), 7.76 (d, 2H, J = 8.4 Hz), 7.07–7.58 (m, 33 H), 6.95– 6.97 (m, 1H), 6.00 (m, 2H, H-20 , H-40 ), 5.63 (dd, 1H, J = 3.6, 10.8 Hz, H-30 ), 5.32 (d, 1H, J = 7.6 Hz, H-10 ), 5.22 (d, 1H, J = 11.2 Hz, PhCH2), 4.73 (d, 1H, J = 11.2 Hz, PhCH2), 4.69 (dd, 1H, J = 6.8, 11.2 Hz), 4.61 (d, 1H, J = 10.4 Hz), 4.53 (d, 1H, J = 9.6 Hz, H-1), 4.39–4.47 (m, 4H), 4.27 (t, 1H, J = 6.4 Hz), 4.10 (d, 1H, J = 2.8 Hz, H-4), 3.97 (dd, 1H, J = 2.8, 9.2 Hz, H-3), 3.86 (t, 1H,

J = 9.2 Hz, H-2), 3.61–3.64 (m, 1H), 3.49–3.55 (m, 2H), 2.28 (s, 3H, Me). 13C NMR (100 MHz, CDCl3): d 165.89, 165.53, 165.44, 165.24, 138.79, 138.33, 138.09, 137.90, 134.23, 133.59, 133.35, 133.30, 133.19, 131.04, 129.90, 129.85, 129.71, 129.63, 129.27, 129.00, 128.96, 128.64, 128.51, 128.38, 128.31, 128.26, 128.23, 127.73, 127.66, 127.63, 127.60, 127.58, 127.46, 127.34, 126.80, 126.49, 101.81, 87.74, 82.59, 77.63, 77.55, 76.42, 75.18, 74.85, 73.42, 71.52, 71.47, 70.23, 69.30, 68.26, 61.96, 20.75. HRMS (ESI) Calcd for C68H62NaO14S [M+Na]+: 1157.3717. Found: 1157.3753. Calcd for C68H66NO14S [M+NH4]+: 1152.4228. Found: 1152.4198. 4.2.8. o-Tolyl 2-O-(2,3,4,6-tetra-O-benzoyl-b-D-galactopyran osyl)-3-O-benzoyl-4,6-O-benzylidene-1-thio-b-D-galactopy ranoside (20) Compound 20 (28.0 mg, 60% yield as a semisolid) was prepared according to the general procedure (Method A) from donor 4 (44.0 mg, 63 lmol) and acceptor 19 (20.0 mg, 42 lmol), and was purified by column chromatography (petroleum ether/ethyl ace1 tate = 1.5:1). ½a25 D +60.2° (c 2.33 in CHCl3); H NMR (400 MHz, CDCl3): d 8.06 (d, 2H, J = 1.2, 8.0 Hz), 7.77–8.02 (m, 4H), 7.89 (d, 1H, J = 7.2 Hz), 7.35–7.70 (m, 21H), 7.15–7.23 (m, 6H), 7.07–7.09 (m, 1H), 5.93 (d, 1H, J = 3.2 Hz, H-40 ), 5.76 (dd, 1H, J = 8.0, 10.4 Hz, H-20 ), 5.47 (s, 1H, PhCH), 5.35 (dd, 1H, J= 3.2, 10.4 Hz, H-30 ), 5.17 (d, 1H, J = 8.0 Hz, H-10 ), 5.13 (dd, 1H, J = 3.6, 9.6 Hz, H-3), 4.78 (d, 1H, J = 9.6 Hz, H-1), 4.64 (t, 1H, J = 9.6 Hz, H-2), 4.49 (d, 1H, J = 3.2 Hz, H-4), 4.38–4.43 (m, 2H, H-6a0 , H-6a), 4.28 (dd, 1H, J = 8.0, 11.2 Hz, H-6b0 ), 4.20 (t, 1H, J = 6.8 Hz, H-50 ), 3.99 (dd, 1H, J = 1.2, 10.4 Hz, H-6b), 3.56 (s, 1H, H-5), 2.52 (s, 3H, Me). 13C NMR (100 MHz, CDCl3): d 165.99, 165.50, 165.47, 165.35, 165.13, 139.19, 137.67, 133.71, 133.60, 133.48, 133.18, 132.92, 131.89, 130.25, 129.95, 129.76, 129.67, 129.48, 129.38, 129.27, 129.09, 128.97, 128.95, 128.71, 128.67, 128.56, 128.44, 128.19, 128.16, 128.12, 127.04, 126.47, 126.32, 100.92, 100.69, 85.83, 76.79, 73.71, 71.85, 70.94, 70.83, 69.99, 69.53, 69.10, 67.63, 61.20, 21.01. HRMS (ESI) Calcd for C61H56NO15S [M+NH4]+: 1074.3366. Found: 1074.3365. 4.2.9. o-Tolyl 3-O-(2,3,4,6-tetra-O-benzoyl-b-D-galactopyran osyl)-2,4,6-tri-O-acetyl-1-thio-b-D-galactopyranoside (23) Compound 23 (13.0 mg, 27% yield as a semisolid) was prepared according to the general procedure (Method A) from donor 4 (51.0 mg, 63 lmol) and acceptor 22 (20.0 mg, 48 lmol), and was purified by column chromatography (petroleum ether/ethyl acetate = 1:1). ½a25 +63.9° (c 1.66 in CHCl3); 1H NMR (400 MHz, D CDCl3): d 8.12 (d, 2H, J = 7.6 Hz), 8.02 (d, 2H, J = 7.6 Hz), 7.92 (d, 2H, J = 7.6 Hz), 7.76 (d, 2H, J = 7.6 Hz), 7.63 (t, 1H, J = 7.6 Hz), 7.49–7.56 (m, 5H), 7.36–7.44 (m, 5H), 7.00–7.23 (m, 5H), 5.94 (d, 1H, J = 3.2 Hz, H-40 ), 5.70 (dd, 1H, J = 8.0, 10.8 Hz, H-20 ), 5.63 (d, 1H, J = 3.2 Hz, H-4), 5.57 (dd, 1H, J = 3.2, 10.4 Hz, H-30 ), 5.27 (t, 1H, J = 9.6 Hz, H-2), 4.94 (d, 1H, J = 7.6 Hz, H-10 ), 4.70 (dd, 1H, J = 6.4, 11.2 Hz, H-6a0 ), 4.51 (d, 1H, J = 10.0 Hz, H-1), 4.37 (dd, 1H, J = 6.4, 10.8 Hz, H-6b0 ), 4.29 (t, 1H, J = 6.4 Hz, H-50 ), 4.06–4.14 (m, 2H, H-6a, H-6b), 3.91 (dd, 1H, J = 3.6, 9.6 Hz, H-3), 3.76 (t, 1H, J = 6.8 Hz, H-5), 2.32 (s, 3H, Me), 2.23 (s, 3H, OAc), 2.03 (s, 3H, OAc), 1.59 (s, 3H, OAc). 13C NMR (100 MHz, CDCl3): d 170.39, 169.88, 168.79, 165.98, 165.58, 165.44, 164.74, 139.66, 133.62, 133.30, 133.23, 132.10, 130.22, 130.12, 129.76, 129.44, 129.36, 129.03, 128.65, 128.50, 128.32, 128.29, 127.86, 126.47, 101.62, 87.16, 78.39, 75.14, 71.39, 71.29, 69.87, 69.36, 68.83, 67.73, 62.68, 61.75, 20.78, 20.68, 20.18. HRMS (ESI) Calcd for C53H54NO17S [M + NH4]+: 1008.3112. Found: 1008.3099. 4.2.10. o-Tolyl 6-O-(2-N-(2,2,2-trichloroethoxylcarbonylamino)3,4,6-tri-O-acetyl-2-deoxy-b-D-galactopyranosyl)-2,3,4-tri-Obenzoyl-1-thio-b-D-glucopyranoside (25) Compound 25 (20.0 mg, 75% yield as a semisolid) was prepared according to the general procedure (Method A) from donor 24

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(20.0 mg, 34 lmol) and acceptor 13 (15.0 mg, 25 lmol), and was purified by column chromatography (petroleum ether/ethyl ace1 tate = 2:1). ½a25 D 9.0° (c 3.11 in CHCl3); H NMR (400 MHz, CDCl3): d 7.96 (d, 2H, J = 7.6 Hz), 7.89 (d, 2H, J = 7.6 Hz), 7.78 (d, 2H, J = 7.6 Hz), 7.64 (d, 1H, J = 7.2 Hz), 7.52 (t, 2H, J = 7.2 Hz), 7.35–7.43 (m, 5H), 7.24–7.27 (m, 10H), 5.88 (t, 1H, J = 9.6 Hz, H-3), 5.43–5.52 (m, 2H, H-2, H-4), 5.35 (d, 1H, J = 2.8 Hz, H-40 ), 5.12 (d, 1H. J = 10.0 Hz, H-1), 4.91 (d, 1H, J = 10.4 Hz, H-30 ), 4.69–4.75 (m, 3H), 4.47 (d, 1H, J = 8.4 Hz, H-10 ), 4.11 (d, 2H, J = 6.4 Hz), 3.88–4.04 (m, 3H), 3.76–3.82 (m, 2H), 2.36 (s, 3H), 2.14 (s, 3H), 2.04 (s, 3H), 2.00 (s, 3H). 13C NMR (100 MHz, CDCl3): d 170.35, 170.20, 170.18, 165.69, 165.49, 164.96, 154.39, 140.95, 133.71, 133.34, 133.24, 131.58, 130.84, 129.83, 129.81, 129.68, 129.04, 128.74, 128.68, 128.50, 128.43, 128.38, 128.26, 127.06, 101.68, 95.68, 86.49, 78.83, 74.48, 74.01, 70.67, 70.63, 70.35, 69.04, 67.79, 66.43, 61.35, 52.41, 21.05, 20.64, 20.57. HRMS (ESI) Calcd for C49Cl3H49NO17S [M+H]+: 1060.1781. Found: 1060.1761. HRMS (ESI) Calcd for C49Cl3H52N2O17S [M+NH4]+: 1077.2047. Found: 1077.2025. 4.2.11. o-Tolyl 3-O-(2,3,4,6-tetra-O-benzyl-a-D-galactopyran osyl)-2,4,6-tri-O-benzoyl-1-thio-b-D-galactopyranoside (27) Compound 27 (27.0 mg, 85% yield as a semisolid) was prepared according to the general procedure (Method B) from donor 26 (20.0 mg, 31 lmol) and acceptor 21 (16.7 mg, 28 lmol), and was purified by column chromatography (petroleum ether/ethyl acetate = 5:1). ½a25 +43.6° (c 1.10 in CHCl3); 1H NMR (400 MHz, D CDCl3): d 8.02–8.05 (m, 6H), 7.38–7.62 (m, 9H), 7.10–7.30 (m, 27H), 6.95 (t, 1H, J = 6.8 Hz), 5.90 (d, 1H, J = 2.8 Hz, H-4), 5.76 (t, 1H, J = 10.0 Hz, H-2), 5.23 (d, 1H, J = 3.2 Hz, H-10 ), 4.78 (d, 1H, J = 10.0 Hz, H-1), 4.70 (d, 1H, J = 11.6 Hz, PhCH2), 4.39–4.49 (m, 6H), 4.19–4.30 (m, 4H), 3.98 (t, 1H, J = 6.4 Hz, H-5), 3.83–3.89 (m, 2H, H-20 , H-50 ), 3.47 (dd, 1H, J = 2.8, 10.4 Hz, H-30 ), 3.33 (dd, 1H, J = 6.8, 9.6 Hz, H-6a0 ), 3.22 (d, 1H, J = 1.6 Hz, H-40 ), 3.17 (dd, 1H, J = 5.6, 9.6 Hz, H-6b0 ), 2.26 (s, 3H, Me). 13C NMR (100 MHz, CDCl3): d 166.05, 165.89, 164.83, 140.30, 138.79, 138.49, 138.34, 133.28, 133.18, 132.98, 132.68, 130.22, 130.18, 129.82, 129.67, 129.57, 129.19, 128.46, 128.41, 128.40, 128.30, 128.15, 128.11, 128.08, 127.96, 127.63, 127.55, 127.45, 127.29, 127.20, 127.04, 126.47, 94.33, 87.06, 78.76, 75.46, 75.23, 74.96, 74.43, 74.05, 73.26, 73.22, 72.34, 70.10, 69.30, 66.52, 63.15, 20.93. HRMS (ESI) Calcd for C68H68NO13S [M+NH4]+: 1138.4006. Found: 1138.4442. Calcd for C68H64O13SK [M+K]+: 1159.3694. Found: 1159.3652. 4.2.12. o-Tolyl 6-O-(2,3-di-O-benzoyl-4,6-O-benzylidene-b-Dgalactopyranosyl)-2,3,4-tri-O-benzoyl-1-thio-b-Dglucopyranoside (29) Compound 29 (24.0 mg, 77% yield as a semisolid) was prepared according to the general procedure (Method B) from donor 28 (20.0 mg, 34 lmol) and acceptor 13 (16.0 mg, 29 lmol), and was purified by column chromatography (petroleum ether/ethyl acetate = 2:1). ½a25 +40.0° (c 1.00 in CHCl3); 1H NMR (400 MHz, D CDCl3): d 7.99 (d, 2H, J = 7.6 Hz), 7.92 (d, 2H, J = 7.2 Hz), 7.86 (d, 4H, J = 7.6 Hz), 7.75 (d, 2H, J = 7.2 Hz), 7.09- 7.50 (m, 29H), 5.85 (dd, 1H, J = 8.4, 10.4 Hz, H-20 ), 5.78 (t, 1H, J = 9.6 Hz, H-3), 5.51 (s, 1H, PhCH), 5.44 (t, 1H, J = 9.6 Hz, H-2), 5.36 (t, 1H, J = 9.6 Hz, H4), 5.28 (dd, 1H, J = 3.6, 10.4 Hz, H-30 ), 4.90 (d, 1H, J = 8.0 Hz, H10 ), 4.89 (d, 1H, J = 10.0 Hz, H-1), 4.57 (d, 1H, J = 3.2 Hz, H-40 ), 4.27 (d, 1H, J = 12.4 Hz, H-6a0 ), 3.96–4.08 (m, 4H, H-6b0 , H-5, H6a, H-6b), 3.60 (s, 1H, H-50 ), 2.20 (s, 3H, Me). 13C NMR (100 MHz, CDCl3): d 166.17, 165.64, 165.42, 165.29, 165.01, 139.87, 137.45, 133.44, 133.31, 133.22, 133.11, 132.91, 132.13, 130.19, 129.95, 129.81, 129.73, 129.69, 129.64, 129.20, 129.17, 128.85, 128.72, 128.38, 128.32, 128.20, 128.07, 127.06, 126.20, 101.00, 100.74, 86.66, 78.56, 74.18, 73.50, 72.94, 70.63, 69.43, 68.97, 68.83, 67.73, 66.57, 20.87. HRMS (ESI) Calcd for C61H56NO15S [M+NH4]+: 1074.3365. Found: 1074.3377.

7

4.2.13. Methyl 6-O-(6-O-(2,3,4,6-tetra-O-benzoyl-b-Dgalactopyranosyl)-2,3,4-tri-O-benzoyl-b-D-glucopyranosyl)2,3,4-tri-O-benzoyl-a-D-glucopyranoside (31) Compound 31 was synthesized by a preactivation-based iterative one-pot procedure. After the donor 4 (26.4 mg, 38 lmol), Ph2SO (8.5 mg, 42 lmol) and activated 4 Å powdered molecular sieves were stirred at room temperature in dichloromethane (2 mL) for 30 min under an argon atmosphere, the solution was cooled to 72 °C and Tf2O (7.0 lL, 42 lmol) was added. The temperature was raised to 20 °C slowly. Stirring at this temperature for 5 min, the reaction mixture was cooled back to 72 °C and building block 13 (15.0 mg, 25 lmol) was added. The reaction was warmed to room temperature and further stirred for 15 min before cooling back to 72 °C. Subsequently, Ph2SO (5.1 mg, 25 lmol) and Tf2O (4.1 lL, 25 lmol) was added to the mixture. After the mixture was stirred vigorously for 10 min, the acceptor 30 (13.9 mg, 30 lmol) was added. The reaction was warmed gradually to room temperature and quenched by triethylamine (0.2 mL). The precipitated was filtered off through a pad of Celite. The filtrate was concentrated and the residue was purified by column chromatography on silica gel (petroleum ether/ethyl acetate = 1:1), affording compound 31 as semisolid (29.0 mg, 76% yield). ½a25 D +40.7° (c 2.95 in CHCl3); 1H NMR (400 MHz, CDCl3): d 8.08 (d, 2H, J = 8.4 Hz), 8.01–8.03 (m, 4H), 7.92–7.96 (m, 6H), 7.84 (d, 2H, J = 8.4 Hz), 7.74–7.81 (m, 6H), 7.21–7.62 (m, 33H), 6.09 (t, 1H, J = 9.6 Hz, H3), 6.00 (d, 1H, J = 3.2 Hz, H-400 ), 5.86 (dd, 1H, J = 3.6, 10.4 Hz, H300 ), 5.77 (dd, 1H, J = 8.0, 9.6 Hz, H-20 ), 5.74 (t, 1H, J = 9.6 Hz, H30 ), 5.47 (t, 1H, J = 10.0 Hz, H-4), 5.33 (dd, 1H, J = 7.6, 9.6 Hz, H200 ), 5.21 (t, 1H, J = 9.6 Hz, H-40 ), 5.16 (dd, 1H, J = 3.6, 10.4 Hz, H2), 5.10 (d, 1H, J = 8.0 Hz, H-10 ) 5.08 (d, 1H, J = 3.6 Hz, H-1), 4.69 (d, 1H, J = 8.0 Hz, H-100 ), 4.57 (dd, 1H, J = 9.2, 13.6 Hz, H-6a00 ), 4.32–4.37 (m, 2H, H-500 , H-6b00 ), 4.00–4.06 (m, 3H, H-5, H-6a, H6a0 ), 3.89–3.95 (m, 2H, H-50 , H-6b0 ), 3.56 (dd, 1H, J = 6.4, 11.6 Hz, H-6b), 3.12 (s, 3H, OMe). 13C NMR (100 MHz, CDCl3): d 165.94, 165.74, 165.70, 165.65, 165.57, 165.51, 165.41, 165.38, 165.31, 164.96, 133.49, 133.44, 133.37, 133.27, 133.24, 133.20, 133.13, 133.05, 132.96, 130.01, 129.95, 129.88, 129.80, 129.69, 129.66, 129.51, 129.44, 129.32, 129.15, 129.01, 128.93, 128.87, 128.72, 128.59, 128.49, 128.45, 128.40, 128.35, 128.23, 128.19, 101.49, 101.06, 96.64, 74.80, 72.73, 72.10, 71.87, 71.45(2), 70.27(2), 70.08, 69.54, 68.69, 68.48, 68.47, 67.82, 62.08, 55.15. HRMS (ESI) Calcd for C89H78NO26 [M+NH4]+: 1576.4818. Found: 1576.4807. Acknowledgments This work was financially supported by the Grants (2012AA021504, 2012ZX09502001-001, 2012CB822100) from the Ministry of Science and Technology of China, the National Natural Science Foundation of China (Grant No. 21232002), and Beijing Higher Education Young Elite Teacher Project. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.carres.2013.11.009. References 1. 2. 3. 4. 5. 6.

Varki, A. Glycobiology 1993, 3, 97. Ohtsubo, K.; Marth, J. D. Cell 2006, 126, 855. Pratt, M. R.; Bertozzi, C. R. Chem. Soc. Rev. 2005, 34, 58. Seeberger, P. H. Chem. Soc. Rev. 2008, 37, 19. Zhu, X.; Schmidt, R. R. Angew. Chem., Int. Ed. 2009, 48, 1900. Zhang, Z.; Ollmann, I. R.; Ye, X.-S.; Wischnat, R.; Baasov, T.; Wong, C.-H. J. Am. Chem. Soc. 1999, 121, 734. 7. Wang, Y.; Ye, X.-S.; Zhang, L.-H. Org. Biomol. Chem. 2007, 5, 2189. 8. Fang, J.; Li, J.; Chen, X.; Zhang, Y.; Wang, J.; Guo, Z.; Zhang, W.; Yu, L.; Brew, K.; Wang, P. G. J. Am. Chem. Soc. 1998, 120, 6635.

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