Total synthesis of sulfated glycosphingolipid SM1a, a kind of human epithelial carcinoma antigen

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DOI: 10.1002/ejoc.201403296

Total Synthesis of Sulfated Glycosphingolipid SM1a, a Kind of Human

Epithelial Carcinoma Antigen

Pengtao Zhang,^[a][‡]Kun Wang,^[a][‡]Jun Zhang,^[a]Chunxia Li,*^[a]and Huashi Guan^[a]

Keywords: Total synthesis / Glycosylation / Carbohydrates / Oligosaccharides / Glycolipids / Gangliosides

A highly efficient and practical total synthesis of the sulfated

block was formed from a new galactose acceptor 7 contain-

ganglioside SM1a, a kind of human epithelial carcinoma an- ing a potential sulfated site, GalNHTroc donor 6, and galact-

tigen identified in mammalian kidney, has been ac-

complished for the first time. The characteristic sequence of

ose donor 4. The cyclic glucosyl ceramide was glycosylated

with trisaccharide trichloroacetimidate 2 to give the pro-

tected ganglioside backbone in good yield. Selective sulf-

onation at the 3-OH of the Gal residue followed by global

deprotection gave the target molecule SM1a.

SM1a, β-

D-Galp-(1Ǟ3)-β-

D-NHAcGalp-(1Ǟ4)-β-D-(3-O-sulf-

ate)-Galp-(1Ǟ4)-β-

D-Glcp-ceramide was assembled by

a

[3+2] convergent approach. A key trisaccharide building

that their accumulation is related to different carci-

nomas.^[4–7]However, to date, their structure–activity rela-

Introduction

Gangliosides, sialic acid-containing glycosphingolipids, tionships have not been investigated using structurally

have been of great interest for more than 20 years in the homogeneous gangliosides.

search for target molecules relevant to tumor growth and

Ganglioside-series sulfatide SM1a (Figure 1) was isolated

metastasis, and also as potential targets for immunotherapy. from the rat kidney and African green monkey kidney cell

They are expressed on the cell surface, so they are accessible lines (Verots S3).^[2,3]SM1a was postulated to be a precursor

for antibodies or other ganglioside-binding molecules that of the disulfated glycolipid SB1a,^[3]which has been shown

may induce cell death, inhibit cell growth, and/or inhibit to behave as a tumor-associated antigen.^[6]Modern carbo-

tumor metastasis.^[1]Meanwhile, a variety of sulfated gangli- hydrate microarray technology found that SM1a may be a

osides have been isolated from mammalian kidney cell lines tumor-associated carbohydrate antigen since it can be rec-

and characterized;^[2,3]the sugar chains of these gangliosides ognized by the monoclonal antibody AE₃, which is the

are modified with sulfate residues instead of with sialic acid. most specific antibody for the detection of human epithelial

The attraction of ganglioside-series sulfated glycolipids is carcinoma antigens.^[8]In order to better understand the

Figure 1. The structure of SM1a.

biological functions of SM1a, a sufficient quantity of struc-

[a] Shandong Provincial Key Laboratory of Glycoscience and

turally homogeneous ganglioside is needed.

Glycoengineering, and Key Laboratory of Marine Drugs of

SM1a is the sulfoglycolipid analog of sialoglycolipid

GM1. Although the synthesis of gangliosides GM1, GQ1b,

GD1a, and their derivatives has previously been ac-

complished by several laboratories,^[9–15]the synthesis of a

ganglioside bearing a sulfate instead of a sialic acid has

never been reported. In this paper, we report the first total

synthesis of SM1a.

Ministry of Education, School of Medicine and Pharmacy,

Ocean University of China,

5 Yushan Road, Qingdao 266003, Shandong Province, P. R.

China

E-mail: lchunxia@ouc.edu.cn

http://web1.ouc.edu.cn/mp/4a/d0/c3932a19152/page.psp

[‡] These authors contributed equally to this work.

Supporting information for this article is available on the

WWW under http://dx.doi.org/10.1002/ejoc.201403296.

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amount of iodine, and p-toluenesulfonic acid (pTsOH) gave

3,4-O-isopropylidene derivative 11.^[18]Compound 11 was

converted into 12 by benzylation. Hydrolysis of the iso-

propylidene group in 12 gave compound 13. Then a tert-

butyldimethylsilyl (TBDMS) group was selectively intro-

duced at the C-3 position, taking advantage of the reactivity

difference between the 4-OH and the 3-OH groups of 13.

The TBDMS group was stable under both basic and acidic

conditions, and furthermore, it could be selectively and ef-

fectively removed before sulfonation.

Results and Discussion

The retrosynthetic analysis of the target compound

SM1a is shown in Scheme 1. The target molecule was dis-

connected into trisaccharide donor 2 and glucosyl-ceramide

(GlcCer) acceptor 3 at the β-(1–4) linkage between galact-

ose (Gal) and glucose (Glc). A cyclic glucosyl ceramide

(GlcCer) acceptor was developed by Kiso’s group as a ver-

satile building block, and the use of such a molecule could

avoid any loss of the valuable oligosaccharide unit in a cou-

pling reaction with the lipophilic, self-aggregating, bulky,

and unreactive ceramide moiety.^[16]It was shown that the

cyclic GlcCer acceptor could react with a variety of oligo-

saccharide donors.^[10,15]Thus, a [3+2] convergent approach

to the target molecule was devised. Trisaccharide 2 could

be assembled from monosaccharide building blocks 4, 6,

and 7. GlcCer unit 3 could be installed by coupling glucosyl

donor 8 with ceramide acceptor 9 through an intramolec-

ular glycosylation.

According to the above-mentioned strategy, key disac-

charide 5 was prepared by the reaction of a newly designed

galactosyl acceptor 7 and a galactosaminyl donor 6 having

a participating 2,2,2-trichloroethoxycarbonyl (Troc) pro-

tecting group at the C-2 amine to control the β anomeric

selectivity, as shown in Scheme 1.

Scheme 2. Synthesis of acceptor 7. Reagents and conditions:

a) I₂/pTsOH, acetone, 40 °C, 70%; b) BnBr, NaH, DMF,

0 °CǞroom temp.; c) AcOH/H₂O (9:1), 80 °C, 87% over two

steps; d) TBDMSCl, imidazole, CH₂Cl₂, 0 °CǞroom temp., 96%;

MP = p-methoxyphenyl.

p-Methoxyphenyl alcohol 7 was obtained from p-meth-

oxyphenyl-β-d-galactopyranoside (10) by a four-step route

Next, we designed thioglycosides 14 and 18 as candidates

(Scheme 2). Treatment of 10^[17]with acetone, a catalytic for the N-Troc-GalN donor (i.e., 6), which would be cou-

Scheme 1. Retrosynthetic analysis of the target compound 1; P = protecting group, LG = leaving group.

2

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Total Synthesis of Sulfated Glycosphingolipid SM1a

pled with acceptor 7 to give disaccharide unit 5. It is known trifluoromethanesulfonic acid (TfOH) in CH₂Cl₂at –45 °C,

that a Troc group can ensure β-selective glycosylation as disaccharide 19 was formed in 75% yield. Disaccharide 19

well as increase the reactivity of a glycosyl donor compared could be converted into 5 through a 3-O to 2-N migration

with an N-phthaloyl group.^[19]Other advantages include the of the acetyl group upon deprotection of the C-2 amine

high efficiency of the installation, and the possibility for group.^[15]However, this reaction did not proceed smoothly

chemoselective deprotection of the Troc group.

under one-pot conditions by treatment with zinc AcOH/

The synthesis of 18 starting from known 1-thio-β-d-ga- DMF (1:9) at 60 °C. Only a moderate yield (40%) of 5 was

lactopyranoside 14 is shown in Scheme 3. Thiogalactoside obtained, and side-products were generated when the reac-

14^[12]was deacetylated under Zemplen conditions, and this tion time was extended. Therefore, we completed this mi-

was followed by selective acetylation of 6-OH with catalytic gration in two steps. Removal of the Troc group with zinc

sulfuric acid in ethyl acetate^[20]to give 16. Next, 4-OH was in acetic acid / 1,2-dichloroethane (1:1) gave 20 in 80%

selectively acetylated through orthoacetate formation and yield. Then, under acidic conditions of AcOH/DMF (1:9),

regioselective hydrolysis to give galactosaminyl precursor the migration of the acetyl group at the C-3 position was

17, which has previously been used as a galactosaminyl ac- implemented successfully to give disaccharide 5. Although

ceptor in the one-pot synthesis of fucosyl GM1.^[12]We 5 was obtained in a yield of 72% over two steps, this route

shortened the synthetic route and increased the yield of 17 could not be used for large-scale synthesis as a result of

from 28 to 70%. The new galactosaminyl thioglycoside the difficulties in determining the reaction endpoint, and in

donor (i.e., 18) was obtained by further protection of the separating the product from by-products.

remaining C-3 hydroxy group with a Troc group in a yield

of 89%.

Next, we selected another donor 18 bearing a Troc group

at C-3 to couple with compound 7. Using NIS/TfOH in

CH₂Cl₂at –20 °C, disaccharide 21 was formed in 70%

yield. As expected, the resulting disasaccharide (i.e., 21)

could be efficiently converted into disaccharide acceptor 5

through removal of the Troc groups by treatment with pre-

activated zinc/AcOH, followed by selective acetylation of

the C-2 amine group of the GalN residue in 99% yield

(Scheme 4). Compared to the first method, this strategy was

a much more efficient way to reveal the free OH group of

C-3 for the next glycosylation.

To assemble the trisaccharide sequence Gal-GalNAc-Gal

(2), four galactosyl donors were evaluated to couple with

acceptor 5, and the results are summarized in Table 1. In

entry 1, the glycosylation of thioglycoside 22^[21]with 5 was

carried out in the presence of NIS/TfOH in CH₂Cl₂. How-

ever, the reaction did not work well, and hardly any of the

desired coupling product (i.e., 26) was formed. Table 1, en-

Scheme 3. Synthesis of donor 18. Reagents and conditions:

a) CH₃OH/CH₃ONa, pH 8–9, 0 °C, 99%; b) H₂SO₄, EtOAc, 45 °C;

c) (EtO)₃CCH₃, pTsOH, MeCN, then AcOH/H₂O (9:1), room

temp., 70% over three steps; d) TrocCl, Py, 89%.

Two different strategies were explored to access disaccha- tries 2 and 3 showed that trichloroacetimidate donor 23^[22]

ride acceptor 5 (Scheme 4). Firstly, thiogalactoside 14 was could give trisaccharide 26 in moderate yield. For these two

chosen to couple with 7. Using N-iodosuccinimide (NIS)/ reactions, we found that part of the major product decom-

Scheme 4. Synthesis of disaccharide unit 5. Reagents and conditions: a) NIS/TfOH, molecular sieves (4 Å), CH₂Cl₂, –45 °C, 75%; b) Zn,

ClCH₂CH₂Cl/AcOH (1:1), 50 °C, 80%; c) DMF/AcOH (9:1), 60 °C, 90%; d) NIS/TfOH, molecular sieves (4 Å), CH₂Cl₂, –20 °C, 70%;

e) i) Zn, ClCH₂CH₂Cl/AcOH (1:1), 50 °C; ii) Ac₂O, CH₂Cl₂, 0 °CǞroom temp., 99% over two steps.

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posed into disaccharide acceptor 5 again during the purifi- the major product was a mixture of imidate (26Ј) and

cation,anditwasdifficulttoobtainthepureproduct.Liaofound 26 because of a competitive reaction of N-acetylgalactos-

that imidate formation could be the predominant reaction amine.

under glycosylation conditions when N-acetylglucosamine

Two thioglycoside donors 24^[21]and 25^[24]bearing a 4,6-

derivatives were used as glycosyl acceptors.^[23]We suspected benzylidene group were evaluated as shown in Table 1, en-

Table 1. Glycosylation of 5 with different galactosyl donors.

Entry^[a]

Donor

Promoter (equiv.)

Solvent

Time [h]

Yield [%]

[b]

1

2

3

4

5

22

23

24

25

NIS (2.5) / TfOH (0.2)

TMSOTf (0.2)

NIS (2.0) / TfOH (0.1)

NIS (2.5) / TfOH (0.1)

CH₂Cl₂

CH₂Cl₂/CH₃CN

CH₂Cl₂

48

1.5

2

1.5

1

–

40^[c]

44^[c]

49

Ͼ63^[d]

[a] All reactions were carried out with 2.0 equiv. of donor except for entry 4 (1.5 equiv. of donor 24 was used for entry 4), indicated

promoters, solvents, and molecular sieves (4 Å) at 0 °C. [b] None of the desired product was obtained after 48 h. [c] Yield of the mixture

of 26 and a by-product, which were inseparable. [d] Hard to separate, crude compound was used for the next reaction, 63% over two

steps.

Scheme 5. Synthesis of trisaccharide donor 2Ј. Reagents and conditons: a) NIS, TfOH, molecular sieves (4 Å), CH₂Cl₂, 0 °C; b) Pd/C,

H₂, methanol/THF (1:2), 63% over two steps; c) Py, Ac₂O, 95%; d) i) CAN [Cerium(IV) ammonium nitrate], CH₃CN/H₂O (5:1), ii) DBU

(1,8-diazabicyclo[5.4.0]undec-7-ene), CCl₃CN, CH₂Cl₂, 0 °C, 74% over two steps.

4

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Total Synthesis of Sulfated Glycosphingolipid SM1a

tries 4 and 5. These two donors were more reactive than a trichloroacetimidate group gave compound 2Ј as the tri-

peracetate donor 22.^[21]Donor 25 performed much better, saccharide donor (i.e., 2) in a satisfactory yield, ready for

and gave Ͼ63% yield, though it was difficult to obtain pure the final glycosylation.

glycosylation product. This result suggested that glycosyl-

Kiso et al. reported the useful convergent synthesis of a

ation with the C-3 OH of acceptor 5 was favored by the series of gangliosides using a cyclic glucosyl ceramide

presence of a bulky group rather than an electron-with- (GlcCer) acceptor as a versatile building block.^{[10,15,16,25]}

drawing group at the C-4 position of the donor. So com- This approach based on use of a GlcCer building block is

pound 25 was selected as the donor (i.e., 4) for the construc- useful in that it avoids loss of the valuable oligosaccharide

tion of trisaccharide 2.

unit in a coupling reaction with the lipophilic, self-aggregat-

Thioglycoside donor 25 coupled with acceptor 5 to give ing, bulky, and unreactive ceramide moiety. In this study,

trisaccharide 28, which was then converted into imidate do- we attempted to use cyclic GlcCer acceptor 3 from the per-

nor 2Ј in three steps (Scheme 5). Replacement of the benzyl spective of overall efficiency. Previous research has shown

groups with acetyl groups, removal of the p-methoxyphenyl that the presence of an electron-donating group for protec-

group, and conversion of the resulting hydroxy group into tion of the C-3 hydroxy group, even if it is bulky, could

Scheme 6. Synthesis of glucose moiety 8. Reactions and conditions: a) NaH, PMBCl, TBAI (tetrabutylammonium iodide), DMF,

0 °CǞroom temp.; b) HCl (1 m), CH₂Cl₂, 85% over two steps; c) Et₃N, CH₂Cl₂; d) DBU, CNCCl₃, CH₂Cl₂, 0 °C, 80% over two steps;

e) TolSH, BF₃·Et₂O, molecular sieves (4 Å), CH₂Cl₂, 0 °C, 60%; f) AcOH/H₂O (4:1), 80 °C, 95%.

Scheme 7. Synthesis of GlcCer acceptor 3. Reagents and conditions: a) C₂₃H₄₇COOH, EDC, HOBt (hydroxybenzotriazole), DIPEA

(diisopropylethylamine), THF, 71%; b) TBDMSCl, Et₃N, DMAP, CHCl₃, 0 °CǞ40 °C, 80%; c) succinic anhydride, DMAP, Py,

0 °CǞ40 °C, 88%; d) EDC, DMAP, CH₃CN/CH₂Cl₂(1:2), 0 °CǞroom temp., 68%; e) TBAF, AcOH, THF, 82%; f) DMTST, molecular

sieves (4 Å), CH₂Cl₂, 0 °C, 60%.

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increase the reactivity of 4-OH of the acceptor during the 2,3-diols could be differentiated by using a strategy based

glycosylation.^[15,16]Thus, a p-methoxybenzyl (PMB) group on 4,6-O-benzylidene-protected 1,2-d-glucopyranosyl or-

was introduced to protect the C-3 OH of acceptor 3.

thoesters.^[26]According to this strategy, the PMB group was

In the design of the glucose moiety (Scheme 6), a benzoyl installed directly at the C-3 position of known 1,2-d-gluco-

group was introduced at the C-2 hydroxy group to impart pyranosyl orthoester 31^[26]to give 32. Hydrolysis of the or-

β selectivity during the intramolecular glycosylation, and thoester of 32 followed by 1,2-acyl migration gave 34, which

the C-3 hydroxy group was protected with an electron-do- was converted into thioglycoside 36 via trichloroacetimidate

nating p-methoxybenzyl (PMB) group to increase the reac- 35. Removal of the benzylidene acetal from 36 gave the de-

tivity. Differentiation between the C-2 and C-3 hydroxy sired glucose derivative (i.e., 8).

groups of d-glucopyranosides is a big challenge because

Cyclic GlcCer acceptor 3 was synthesized as the coupling

they are both secondary equatorial alcohols. Li reported partner for the trisaccharide 2Ј. This synthesis began with

that the C-2 and C-3 hydroxy groups of glucopyranoside the tethering of Glc donor 8 and ceramide derivative 9 with

Scheme 8. Final glycosylation, sulfonation and deprotection. Reagents and conditions: a) TMSOTf, CHCl₃, AW300 molecular sieves,

0 °C, 70%; b) TBAF, AcOH, THF, 0 °CǞroom temp., 80%; c) SO₃·Py, DMF, 90 °C, 76%; d) i) TFA (trifluoroacetic acid), CH₂Cl₂, 0 °C;

ii) CH₃OH, CH₃ONa, pH 10, 79% over two steps.

6

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Total Synthesis of Sulfated Glycosphingolipid SM1a

was carried out on silica gel GF254 with detection by UV absorp-

tion (254 nm), or by spraying with a solution of vanillin (25 g/L)

in sulfuric acid (10% in ethanol) followed by charring at ca. 150 °C.

Column chromatography was conducted by elution of a column of

a succinyl bridge (Scheme 7). Ceramide derivative 9 was

synthesized from Sphingosine 37.^[27]n-Tetracosanoic acid

was coupled with sphingosine 37 to give ceramide 38, which

was regioselectively protected at the primary hydroxy group

with a tert-butyldimethylsilyl (TBDMS) group to give 39.

Then, 39 was treated with succinic anhydride in the pres-

ence of catalytic 4-(dimethylamino)pyridine (DMAP) to

give 9. The succinoylated Cer derivative (i.e., 9) and the 4,6-

diol thioglucoside (i.e., 8) could thus be condensed with the

1

silica gel (200–300 mesh). H and ¹³C NMR spectra were recorded

with a JEOL JNM-ECP-600 (600/150 MHz) or an Agilent DD2–

500 (500/125 MHz) instrument. Chemical shifts are reported on the

δ scale. CHCl₃(δ = 7.26 ppm) or tetramethylsilane (δ = 0.00 ppm)

was used as an internal reference. COSY and HMQC experiments

were routinely used to definitively assign the signals of ¹H and ¹³C

aid of a carbodiimide coupling reagent [EDC; 1-ethyl-3-(3- NMR spectra.

dimethylaminopropyl)carbodiimide] and a catalytic amount

p-Methoxyphenyl

3,4-O-Isopropylidene-β-D-galactopyranoside

(11):^[18]A catalytic amount of I₂(2 mg) and pTsOH (2 mg) were

added to a solution of 10 (350 mg, 1.23 mmol) in dry acetone

(20 mL). The mixture was stirred at 40 °C for 2 h, then TLC (petro-

leum ether/EtOAc, 1:1) showed that the reaction was complete. The

reaction was quenched by the addition of saturated Na₂S₂O₃until

the mixture became colorless. Et₃N (1.0 mL) was added, and then

the mixture was evaporated to dryness. The residue was diluted

with water (50 mL), and the mixture was extracted with CH₂Cl₂

(3ϫ 50 mL). The combined organic extracts were dried with

Na₂SO₄, and concentrated. The residue was purified by silica gel

column chromatography (petroleum ether/EtOAc, 1:2) to give 11

of DMAP to give tethered compound 40. The hydroxy

group at the C-1 position of the Cer moiety was deprotected

by exposure to TBAF (tetrabutylammonium fluoride).

Then, intramolecular coupling of 41 promoted by DMTST

[dimethyl(methylthio)sulfonium tetrafluoroborate] success-

fully produced cyclic GlcCer acceptor 3 in very high yield

without affecting the C-4,5 olefin moiety.

Cyclic GlcCer acceptor 3 and trisaccharide donor 2Ј were

allowed to react in the presence of TMSOTf (0.1 equiv.) in

CHCl₃at 0 °C, and the desired compound (i.e., 42) was

obtained in 70% yield (Scheme 8). Selective removal of the

TBDMS group of 42 was carried out in the presence of

TBAF/AcOH in THF at room temperature, and we found

that an acetyl migration between the C-2 and C-3 hydroxy

groups took place without the addition of AcOH. After a

facile work-up, and purification by silica gel column

chromatography, the resulting compound (i.e., 43) was sulf-

onated using sulfur-trioxide–pyridine complex to give the

desired sulfated ganglioside. Selective removal of the PMB

group of compound 44 (TFA, 0 °C), followed by deacetyl-

ation by the Zemplen method gave the target compound 1,

SM1a, in good yield.

1

(250 mg, 70%) as a white powder. H NMR (600 MHz, CDCl₃): δ

= 6.99–6.96 (m, 2 H, Ar-H), 6.84–6.81 (m, 2 H, Ar-H), 4.71 (d, J

= 8.3 Hz, 1 H, 1-H), 4.21 (dd, J = 5.5, 2.1 Hz, 1 H, 4-H), 4.18 (d,

J = 5.6 Hz, 1 H), 4.00 (dd, J = 11.3, 2.9 Hz, 1 H), 3.97–3.94 (m, 1

H), 3.86 (dd, J = 9.2, 3.4 Hz, 1 H), 3.83–3.80 (m, 1 H), 3.77 (s, 3

H, -OCH₃), 2.6 (d, J = 2.5 Hz, 1 H, -OH), 2.13 (dd, J = 9.4, 3.2 Hz,

1 H, -OH), 1.56 (s, 3 H, -CH₃), 1.37 (s, 3 H, -CH₃) ppm. MS (ESI):

calcd. for C₁₆H₂₂O₇Na [M + Na]⁺349.1; found 349.3.

p-Methoxyphenyl 2,6-Di-O-benzyl-1-O-β-D-galactopyranoside (13):

Compound 11 (245 mg, 0.75 mmol) was dissolved in dry DMF

(7 mL), and the solution was cooled in an ice bath. NaH (102 mg,

2.55 mmol) was added over 0.5 h. BnBr (0.3 mL, 2.55 mmol) was

added, and the reaction mixture was stirred under argon for 5 h.

The solvent was evaporated, the residue was diluted with ethyl acet-

ate, and this mixture was washed with water, and with a saturated

aqueous NaCl solution. The organic phase was dried with Na₂SO₄,

and the solvent was evaporated.

Conclusions

The residue was dissolved in AcOH (90% aq.; 20 mL). The solution

was stirred at 80 °C for 2 h. TLC (petroleum ether/EtOAc, 1:1)

showed that the reaction was complete, and then the solution was

concentrated. The residue was purified by column chromatography

on silica gel (petroleum ether/EtOAc, 2:1) to give compound 13

(303 mg, 87% over two steps) as a white powder. ¹H NMR

(600 MHz, CDCl₃): δ = 7.41–7.27 (m, 10 H, Ar-H), 7.07–7.03 (m,

2 H, Ar-H), 6.83–6.79 (m, 2 H, Ar-H), 5.07 (d, J = 11.4 Hz, 1 H,

PhCH₂-1), 4.86 (d, J = 7.7 Hz, 1 H, 1-H), 4.78 (d, J = 11.4 Hz, 1

We have achieved a highly efficient and practical synthe-

sis of the complex sulfated ganglioside SM1a by a conver-

gent synthetic route. This convergent approach using a tri-

saccharide building block with a potential sulfation posi-

tion and a cyclic glucosyl ceramide (GlcCer) acceptor gave

access to homogeneous SM1a in sufficient quantity for bio-

logical studies. Furthermore, the approach described above

can guide the chemical synthesis of other unnatural gangli-

oside derivatives, such as a series of differently sulfated gan- H, PhCH₂-2), 4.58 (s, 2 H, PhCH₂), 4.05 (t, J = 2.9 Hz, 1 H, 4-H),

3.83 (dd, J = 10.2, 5.2 Hz, 1 H, 6a-H), 3.80–3.75 (m, 5 H, 6b-H,

ArOCH₃, 2-H), 3.72 (t, J = 5.5 Hz, 1 H, 5-H), 3.69–3.65 (m, 1 H,

3-H), 2.64 (d, J = 3.0 Hz, 1 H, OH), 2.54 (d, J = 4.3 Hz, 1 H, OH)

ppm. MS (ESI): calcd. for C₂₇H₃₀O₇Na [M + Na]⁺489.2; found

489.1.

gliosides, which we aim to prepare. This feature makes it

possible to rapidly prepare a library of structurally related

compounds for structure–activity relationship research.

p-Methoxyphenyl 2,6-Di-O-benzyl-3-O-tert-butyldimethysilyl-β-D-

galactopyranoside (7): Compound 13 (100 mg, 0.214 mmol) was

dissolved in CH₂Cl₂(0.6 mL). Imidazole (58 mg, 0.857 mmol) and

TBDMSCl (96 mg, 0.642 mmol) were added at 0 °C. The reaction

mixture was stirred at room temperature for 2 h. TLC (petroleum

ether/EtOAc, 5:1) showed that the reaction was complete, and then

CH₃OH (1 mL) was added. The mixture was diluted with CH₂Cl₂,

Experimental Section

General Methods: All chemicals were reagent grade, and were ob-

tained from commercial sources. Dichloromethane was freshly dis-

tilled using standard procedures. Molecular sieves were flame dried

under high vacuum before use. Thin-layer chromatography (TLC)

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P. Zhang, K. Wang, J. Zhang, C. Li, H. Guan

FULL PAPER

and washed with water, and with a saturated aqueous NaCl solu-

tion. The organic phase was dried with Na₂SO₄, and the solvent

was evaporated. The residue was purified by chromatography (pe-

troleum ether/EtOAc, 8:1) to give compound 7 (120 mg, 96%) as a

the residue was purified by silica gel chromatography (petroleum

ether/EtOAc, 4:1) to give compound 18 (483 mg, 89%) as a white

1

solid. H NMR (500 MHz, CDCl₃): δ = 7.44 (d, J = 8.1 Hz, 2 H,

Ar-H), 7.13 (d, J = 7.9 Hz, 2 H, Ar-H), 5.53 (d, J = 2.8 Hz, 1 H,

colorless oil. ¹H NMR (600 MHz, CDCl₃): δ = 7.36–6.76 (m, 14 4-H), 5.32 (d, J = 9.7 Hz, 1 H, NH), 5.22 (d, J = 7.3 Hz, 1 H, 1-

H, Ar-H), 5.03 (d, J = 10.8 Hz, 1 H, PhCH₂), 4.84 (d, J = 7.5 Hz, H), 5.11 (d, J = 10.0 Hz, 1 H, 3-H), 4.80 (d, J = 11.8 Hz, 1 H,

1 H, 1-H), 4.72 (d, J = 10.8 Hz, 1 H, PhCH₂), 4.60 (d, J = 11.8 Hz, CH₂CCl₃), 4.78–4.68 (m, 2 H, CH₂CCl₃), 4.66 (d, J = 11.8 Hz, 1

1 H, PhCH₂), 4.57 (d, J = 11.8 Hz, 1 H, PhCH₂), 3.85 (dd, J =

H, CH₂CCl₃), 4.19 (dd, J = 11.3, 6.9 Hz, 1 H, 6a-H), 4.14 (dd, J

10.2, 5.3 Hz, 1 H, 6a-H), 3.83 (d, J = 2.7 Hz, 1 H, 4-H), 3.80 (dd, = 11.3, 6.3 Hz, 1 H, 6b-H), 3.96 (t, J = 6.4 Hz, 1 H, 5-H), 3.73–

J = 10.1, 6.7 Hz, 1 H, 6b-H), 3.76 (s, 3 H, OCH₃), 3.75–3.71 (m, 2 3.63 (m, 1 H, 2-H), 2.35 (s, 3 H, ArCH₃), 2.11, 2.05 (s, 6 H, 2

H, 3-H, 2-H), 3.74 (dd, J = 5.3, 6.6 Hz, 1 H, 5-H), 0.92 (s, 9 H, CH₃CO) ppm. ¹³C NMR (125 MHz, CDCl₃): δ = 170.57, 170.23,

tBu), 0.10 (s, 3 H, SiCH₃), 0.08 (s, 3 H, SiCH₃) ppm. ¹³C NMR 153.74, 153.15, 138.91, 133.64, 129.90, 127.94, 110.13, 94.04, 85.94,

(125 MHz, CDCl₃): δ = 155.31, 151.65, 138.51, 138.30, 128.50,

128.36, 128.19, 127.85, 127.79, 127.67, 118.60, 114.58, 103.03,

79.45, 75.36, 74.51, 73.87, 73.70, 69.85, 69.54, 55.75, 25.93, 18.15,

–4.33, –4.70 ppm. HRMS (ESI): calcd. for C₃₃H₄₄O₇Na [M +

Na]⁺603.2749; found 603.2759.

77.21, 74.95, 74.54, 74.35, 66.52, 61.75, 51.45, 21.33, 20.86,

20.73 ppm. HRMS (ESI): calcd. for C₂₃H₂₅O₁₀NSCl₆Na [M +

Na]⁺741.9199; found 741.9203.

p-Methoxyphenyl (2-Acetamido-4,6-di-O-acetyl-2-deoxy-β-D-galac-

topyranosyl)-(1Ǟ4)-2,6-di-O-benzyl-3-O-tert-butyldimethysilyl-β-D-

galactopyranoside (5)

p-Methylphenyl

4,6-Di-O-acetyl-2-deoxy-2-(2Ј,2Ј,2Ј-trichloroeth-

-galactopyranoside (17): Compound

oxycarbonylamino)-1-thio-β-

D

Method A: A suspension of compound 7 (198 mg, 0.34 mmol),

compound 14 (300 mg, 0.51 mmol), and molecular sieves (4 Å;

400 mg) in CH₂Cl₂(25.0 mL) was stirred for 1 h, and then cooled

to –45 °C. N-Iodosuccinimide (NIS; 230 mg, 0.68 mmol) and tri-

fluoromethanesulfonic acid (TfOH; 6 μL, 0.06 mmol) were added,

and the mixture was stirred for a further 0.5 h. TLC (petroleum

ether/EtOAc, 2:1) showed that the reaction was complete. Et₃N was

added to quench the reaction. The mixture was filtered through

Celite. The combined filtrate was washed sequentially with satu-

rated Na₂S₂O₃solution (2ϫ 30 mL), and brine (2ϫ 30 mL), dried

with Na₂SO₄, and concentrated. The residue was purified by col-

umn chromatography on silica gel (petroleum ether/EtOAc, 5:1) to

give 19 (264 mg, 75%). ¹H NMR (600 MHz, CDCl₃): δ = 7.40–

7.27 (m, 10 H, Ar-H), 6.98 (d, J = 8.9 Hz, 2 H, Ar-H), 6.78–6.74

(m, 2 H, Ar-H), 5.81 (d, J = 6.8 Hz, 1 H, NH), 5.36 (d, J = 2.4 Hz,

1 H, 4Ј-H), 5.09 (d, J = 11.6 Hz, 1 H, PhCH₂), 5.04 (d, J = 10.7 Hz,

1 H, CH₂CCl₃), 5.02–4.97 (m, 2 H, 3Ј-H, 1Ј-H), 4.83 (d, J = 7.2 Hz,

1 H, 1-H), 4.73 (d, J = 10.9 Hz, 1 H, CH₂CCl₃), 4.59 (d, J =

11.8 Hz, 1 H, PhCH₂), 4.54 (d, J = 11.8 Hz, 1 H, PhCH₂), 4.48 (d,

J = 12.3 Hz, 1 H, PhCH₂), 4.16 (dd, J = 11.1, 7.5 Hz, 1 H, 6aЈ-H),

4.12–4.08 (m, 1 H, 2Ј-H), 4.06 (dd, J = 11.1, 6.0 Hz, 1 H, 6bЈ-H),

4.00 (d, J = 2.1 Hz, 1 H, 4-H), 3.84 (t, J = 6.8 Hz, 1 H, 5Ј-H),

3.81–3.76 (m, 3 H, 2-H, 3-H, 5-H), 3.75 (s, 3 H, ArOCH₃), 3.74–

3.69 (m, 2 H, 6-H), 2.18, 2.00, 1.26 (3 s, 9 H, 3 CH₃CO), 0.97 (s,

9 H, tBu), 0.13, 0.12 (s, 6 H, 2 SiCH₃) ppm. ¹³C NMR (150 MHz,

CDCl₃): δ = 170.47, 155.37, 151.48, 138.30, 129.92, 128.65, 128.59,

128.57, 128.39, 127.84, 127.77, 127.68, 118.61, 114.57, 103.30,

101.89, 95.82, 79.56, 75.80, 75.35, 74.59, 73.80, 73.51, 72.12, 71.33,

71.32, 70.67, 69.36, 66.80, 61.24, 55.74, 53.14, 27.04, 26.30,

20.78, 18.45, –4.20, –4.45 ppm. HRMS (ESI): calcd. for

C₄₈H₆₂O₁₆NCl₃SiNa [M + Na]⁺1064.2796; found 1064.2815.

14^[12](1.30 g, 2.2 mmol) was dissolved in dry MeOH (50 mL), and

a solution of NaOMe (0.5 m in MeOH) was added at 0 °C to obtain

a basic pH (8–9, pH paper). The mixture was stirred for 30 min,

then it was neutralized with ion-exchange resin (H⁺). The resin was

removed by filtration, and the solvent was concentrated to give 15

(1.02 g, 99%) as a white solid.

Compound 15 (850 mg, 1.8 mmol) was dissolved in EtOAc

(50 mL), and a catalytic amount of concentrated H₂SO₄(96% aq.)

was added at room temperature. The reaction mixture was stirred

at 45 °C for 18 h. TLC (CH₂Cl₂/CH₃OH, 9:1) showed that the acet-

ylation was complete, and the mixture was neutralized with satu-

rated NaHCO₃solution (20 mL). The organic layer was separated,

and the aqueous layer was washed with EtOAc (2ϫ 20 mL). The

combined organic layers were dried with NaSO₄, filtered, and then

concentrated to dryness.

The crude product (16 and by-products) was then dissolved in dry

MeCN (20 mL). Triethyl orthoacetate (1.6 mL, 11 mmol) and

pTsOH (20 mg, 0.11 mmol) were added at room temperature, and

the mixture was stirred for 1.5 h. Et₃N was added to quench the

reaction, and the mixture was concentrated. The residue was puri-

fied by chromatography (petroleum ether/EtOAc, 1:2.5) to give the

orthoacetate intermediate product.

The intermediate product was dissolved in AcOH (90% aq.;

20 mL), and the solution was stirred at room temperature for 1 h.

TLC (petroleum ether/EtOAc, 1:1) showed that the reaction was

complete. The reaction mixture was concentrated, and the residue

was coevaporated once with toluene (5 mL). The residue was puri-

fied by column chromatography on silica gel (petroleum ether/

EtOAc, 1:1) to give compound 17 (703 mg, 70% over three steps)

1

as a white powder. H NMR (600 MHz, CDCl₃): δ = 7.43 (d, J =

Zinc powder (2.0 g) was added to a solution of 19 (1.0 g,

0.97 mmol) in AcOH (10 mL) and 1,2-dichloroethane (10 mL). The

mixture was stirred for 4 h at 50 °C. TLC (petroleum ether/EtOAc,

1:1) showed that the reaction was complete. The reaction mixture

was filtered through Celite, and the removed zinc powder was

washed with EtOAc. The solution was concentrated and diluted

with EtOAc. The organic layer was washed sequentially with satu-

rated aqueous NaHCO₃(2ϫ 30 mL), and brine (2ϫ 30 mL), dried

with Na₂SO₄, and concentrated. The residue was purified by col-

umn chromatography on silica gel (petroleum ether/EtOAc, 3:2) to

give 20 (667 mg, 80%).

8.0 Hz, 2 H, Ar-H), 7.11 (d, J = 8.0 Hz, 2 H, Ar-H), 5.33 (d, J =

3.1 Hz, 1 H, 4-H), 5.22 (d, J = 7.2 Hz, 1 H, NH), 4.80–4.73 (m, 3

H, 1-H, CH₂CCl₃), 4.16 (d, J = 6.44 Hz, 2 H, 6-H), 4.04 (m, 1 H,

3-H), 3.86 (t, J = 6.4 Hz, 1 H, 5-H), 3.62–3.59 (m, 1 H, 2-H), 2.84

(d, J = 4.5 Hz, 1 H, 3-OH), 2.34 (s, 3 H, ArCH₃), 2.13, 2.06 (s, 6

H, 2 CH₃CO) ppm. MS (ESI): calcd. for C₂₀H₂₄O₈NSCl₃Na [M +

Na]⁺557.0; found 557.2.

p-Methylphenyl 4,6-Di-O-acetyl-3-O-(2Ј,2Ј,2Ј-trichloroethoxycarb-

onyl)-2-(2Ј,2Ј,2Ј-trichloroethoxycarbonylamino)-2-deoxy-thio-β-D-

galactopyranoside (18): Compound 17 (410 mg, 0.75 mmol) was

dissolved in pyridine (5 mL), and trichloroethoxycarbonyl chloride

(124 μL, 0.90 mmol) was added. The reaction mixture was stirred

for 2 h at room temperature. The mixture was concentrated, and

The product was dissolved in DMF (9.0 mL) and AcOH (1.0 mL).

The mixture was stirred for 24 h at 60 °C. Then the solution was

8

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Job/Unit: O43296

/KAP1

Date: 08-12-14 13:20:56

Pages: 15

Total Synthesis of Sulfated Glycosphingolipid SM1a

concentrated, and the residue was purified by column chromatog-

troleum ether/EtOAc, 1:1) to give 5 (740 mg, 99% over two steps)

raphy on silica gel (petroleum ether/EtOAc, 1:1) to give 5 (600 mg,

as a white solid. This compound gave data consistent with that of

90%) as a white foam. ¹H NMR (600 MHz, CDCl₃): δ = 7.36–7.27 the compound prepared by Method A.

(m, 10 H, Ar-H), 7.01–6.97 (m, 2 H, Ar-H), 6.79–6.75 (m, 2 H, Ar-

p-Methoxyphenyl (4,6-O-Benzylidene-2,3-di-O-benzoyl-β-

pyranosyl)-(1Ǟ3)-(4,6-di-O-acetyl-2-acetamido-2-deoxy-β-

lactopyranosyl)-(1Ǟ4)-2,6-di-O-benzyl-3-O-tert-butyldimethysilyl-

β- -galactopyranoside (27): A suspension of 5 (624 mg, 0.73 mmol),

D

-galacto-

H), 5.88 (s, 1 H, NH), 5.32 (d, J = 3.1 Hz, 1 H, 4Ј-H), 5.17 (d, J

= 10.7 Hz, 1 H, PhCH₂), 4.87 (d, J = 7.6 Hz, 1 H, 1-H), 4.72 (d, J

= 8.6 Hz, 1 H, 1Ј-H), 4.64 (d, J = 10.8 Hz, 1 H, PhCH₂), 4.59 (d,

J = 11.8 Hz, 1 H, PhCH₂), 4.54 (d, J = 11.7 Hz, 1 H, PhCH₂), 4.18

(dd, J = 11.2, 6.9 Hz, 1 H, 6aЈ-H), 4.05 (dd, J = 11.2, 6.3 Hz, 1 H,

6bЈ-H), 4.00–3.96 (m, 1 H, 2Ј-H), 3.92 (d, J = 2.9 Hz, 1 H, 4-H),

3.86 (dd, J = 9.4, 2.9 Hz, 1 H, 5-H), 3.81 (dd, J = 9.0, 4.1 Hz, 1

H, 6a-H), 3.78–3.71 (m, 7 H, 6b-H, 2-H, 5Ј-H, 3-H, ArOCH₃), 3.68

(d, J = 9.9 Hz, 1 H, 3Ј-H), 2.17, 2.12, 2.01 (3 s, 9 H, 3 COCH₃),

0.94 (s, 9 H, tBu), 0.16, 0.11 (2 s, 6 H, 2 SiCH₃) ppm. ¹³C NMR

(150 MHz, CDCl₃): δ = 173.98, 170.59, 170.45, 155.45, 151.20,

138.22, 137.87, 128.53, 128.52, 128.45, 128.43, 127.96, 127.94,

127.93, 127.91, 127.81, 127.71, 127.69, 118.50, 114.58, 103.17,

102.19, 79.89, 78.23, 75.71, 75.34, 74.25, 73.74, 73.59, 71.52, 69.47,

61.83, 56.06, 55.68, 26.18, 26.16, 23.32, 18.56, 18.55, –4.04,

–4.59 ppm. MS (ESI): calcd. for C₄₅H₆₁O₁₄NSiNa [M + Na]⁺890.4;

found 890.5.

D

-ga

D

24^[21](640 mg, 1.1 mmol), and molecular sieves (4 Å; 400 mg) in

CH₂Cl₂(30.0 mL) was stirred for 1 h, and then cooled to 0 °C. N-

Iodosuccinimide (NIS; 412 mg, 1.83 mmol) and trifluoromethane-

sulfonic acid (TfOH; 7 μL, 0.07 mmol) were added, and the mixture

was stirred for a further 1.5 h. TLC (petroleum ether/EtOAc, 1:1)

showed that the reaction was complete. Et₃N was added to quench

the reaction. The mixture was filtered through Celite. The com-

bined filtrate was washed sequentially with saturated Na₂S₂O₃(2ϫ

30 mL), and brine (2ϫ 30 mL), dried with Na₂SO₄, and concen-

trated. The residue was purified by column chromatography on sil-

ica gel (petroleum ether/EtOAc, 3:1) to give 27 (460 mg, 49%) as a

1

white powder. H NMR (600 MHz, CDCl₃): δ = 8.02–7.26 (m, 25

H, Ar-H), 6.99–6.96 (m, 2 H, Ar-H), 6.76–6.74 (m, 2 H, Ar-H),

5.79 (dd, J = 10.5, 7.8 Hz, 1 H, 2ЈЈ-H), 5.55 (d, J = 5.7 Hz, 1 H,

NH), 5.49 (d, J = 7.8 Hz, 1 H, 1Ј-H), 5.49 (s, 1 H, PhCH), 5.44 (d,

J = 3.6 Hz, 1 H, 4Ј-H), 5.29 (dd, J = 10.5, 3.5 Hz, 1 H, 3ЈЈ-H), 4.99

(dd, J = 10.7, 4.0 Hz, 1 H, 3Ј-H), 4.93 (d, J = 10.7 Hz, 1 H,

PhCH₂), 4.84 (d, J = 7.8 Hz, 1 H, 1ЈЈ-H), 4.79 (d, J = 7.6 Hz, 1 H,

1-H), 4.59–4.53 (m, 3 H, PhCH₂), 4.51 (d, J = 3.8 Hz, 1 H, 4ЈЈ-H),

4.39 (d, J = 12.2, 1.3 Hz, 1 H, 6aЈЈ-H), 4.28 (dd, J = 11.9, 3.8 Hz,

1 H, 6aЈ-H), 4.12 (d, J = 2.7 Hz, 1 H, 4-H), 4.01 (d, J = 12.2,

1.5 Hz, 1 H, 6bЈЈ-H), 3.93 (dd, J = 11.8, 8.0 Hz, 1 H, 6bЈ-H), 3.79

(dd, J = 8.4, 3.4 Hz, 1 H, 5Ј-H), 3.75 (s, 3 H, OCH₃), 3.74–3.64

(m, 4 H, 3-H, 6a-H, 6b-H, 5-H), 3.61 (d, J = 0.7 Hz, 1 H, 5ЈЈ-H),

3.59 (dd, J = 9.5, 7.7 Hz, 1 H, 2ЈЈ-H), 3.19–3.14 (m, 1 H, 2ЈЈ-H),

2.11, 2.00, 1.98 (s, 9 H, 3 CH₃CO), 0.88 (s, 9 H, tBu), 0.03, 0.01 (s,

6 H, 2 SiCH₃) ppm. ¹³C NMR (125 MHz, CDCl₃): δ = 170.81,

170.49, 170.34, 166.12, 164.81, 155.11, 151.50, 138.31, 138.16,

137.86, 133.30, 133.24, 129.99, 129.89, 129.81, 129.74, 129.55,

129.20, 129.10, 128.86, 128.53, 128.44, 128.35, 128.33, 128.26,

128.19, 128.03, 127.89, 127.61, 126.92, 126.39, 118.19, 114.39,

103.01, 101.74, 101.55, 100.81, 97.60, 79.72, 75.23, 75.12, 74.20,

73.68, 73.31, 72.62, 72.42, 71.46, 69.97, 69.34, 69.14, 68.49, 68.43,

66.28, 63.61, 55.85, 55.59, 29.69, 26.08, 22.91, 20.91, 20.80, 18.35,

–4.52, –4.95 ppm. HRMS (ESI): calcd. for C₇₂H₈₃O₂₁NSiNa [M +

Na]⁺1348.5119; found 1348.5159.

Method B: A suspension of compound 18 (3.3 g, 4.58 mmol), 7

(2.3 g, 3.96 mmol), and molecular sieves (4 Å; 500 mg) in CH₂Cl₂

(100 mL) was stirred for 1 h, and then cooled to –20 °C. N-Iodos-

uccinimide (NIS; 1.54 g, 6.87 mmol) and trifluoromethanesulfonic

acid (TfOH; 69 μL, 0.77 mmol) were added, and the mixture was

stirred for a further 0.5 h. TLC (petroleum ether/EtOAc, 2:1)

showed that the reaction was complete. Et₃N was added to quench

the reaction. The mixture was filtered through Celite. The com-

bined filtrate was washed sequentially with saturated Na₂S₂O₃solu-

tion (2ϫ 50 mL), and brine (2ϫ 50 mL), dried with Na₂SO₄, and

concentrated. The residue was purified by column chromatography

on silica gel (petroleum ether/EtOAc, 5:1) to give 21 (3.26 g, 70%)

1

as a white solid. H NMR (500 MHz, CDCl₃): δ = 7.38–6.75 (m,

14 H, Ar-H), 5.74 (d, J = 6.0 Hz, 1 H, NH), 5.51 (d, J = 2.7 Hz,

1 H, 4Ј-H), 5.16–5.00 (m, 3 H, 1Ј-H, 3Ј-H, PhCH₂), 4.91 (d, J =

11.7 Hz, 1 H, CH₂CCl₃), 4.83 (d, J = 7.0 Hz, 1 H, 1-H), 4.78 (d, J

= 11.8 Hz, 1 H, CH₂CCl₃), 4.75–4.68 (m, 2 H, CH₂CCl₃, PhCH₂),

4.67–4.61 (m, 1 H, CH₂CCl₃), 4.59 (d, J = 11.8 Hz, 1 H, PhCH₂),

4.55 (d, J = 11.8 Hz, 1 H, PhCH₂), 4.18 (dd, J = 11.2, 7.2 Hz, 1

H, 6aЈ-H), 4.07 (dd, J = 11.2, 6.2 Hz, 1 H, 6bЈ-H), 4.04–3.97 (m,

1 H, 2ЈЈ-H), 3.86 (t, J = 6.8 Hz, 1 H, 5Ј-H), 3.83–3.77 (m, 3 H, 2-

H, 3-H, 5-H), 3.77–3.70 (m, 5 H, ArOCH₃, 6-H), 2.18, 2.02 (s, 6

H, 2 COCH₃), 0.95 (s, 9 H, tBu), 0.12, 0.11 (s, 6 H, 2 SiCH₃) ppm.

¹³C NMR (125 MHz, CDCl₃): δ = 170.46, 155.33, 151.44, 138.24,

128.57, 128.38, 127.86, 127.75, 118.51, 114.55, 103.26, 94.16,

77.22, 75.35, 73.80, 71.03, 68.70, 66.19, 61.27, 55.72, 53.24,

26.28, 20.80, 18.47, –4.21, –4.52 ppm. HRMS (ESI): calcd. for

C₄₉H₆₁O₁₇NCl₆SiNa [M + Na]⁺1196.1732; found 1196.1760.

p-Methoxyphenyl (4,6-O-Benzylidene-2,3-di-O-acetyl-β-

pyranosyl)-(1Ǟ3)-(4,6-di-O-acetyl-2-acetamido-2-deoxy-β-

lactopyranosyl)-(1Ǟ4)-2,6-di-O-benzyl-3-O-tert-butyldimethysilyl-

β- -galactopyranoside (28): A suspension of 5 (170 mg, 0.19 mmol),

D

-galacto-

D

-ga-

D

25^[24](179 mg, 0.39 mmol), and molecular sieves (4 Å; 400 mg) in

CH₂Cl₂(10.0 mL) was stirred for 1 h, and then cooled to 0 °C. N-

Iodosuccinimide (NIS; 112 mg, 0.47 mmol) and trifluoromethane-

sulfonic acid (TfOH, 4 μL, 0.04 mmol) were added, and the mixture

was stirred for a further 0.5 h. TLC (petroleum ether/EtOAc, 3:4)

showed that the reaction was complete. Et₃N was added to quench

the reaction. The mixture was filtered through Celite. The filtrate

was washed sequentially with saturated Na₂S₂O₃solution (2ϫ

20 mL), and brine (2ϫ 20 mL), dried with Na₂SO₄, and concen-

trated. The residue was purified by column chromatography on sil-

ica gel (petroleum ether/EtOAc, 5:3) to give 28 (232 mg, crude

product). Since it was difficult to separate, only a limited amount

Zinc powder (2.0 g) was added to a solution of 21 (1.0 g,

0.84 mmol) in AcOH (10 mL) and 1,2-dichloroethane (10 mL). The

mixture was stirred for 4 h at 50 °C. TLC (petroleum ether/EtOAc,

1:1) showed that the reaction was complete. The reaction mixture

was filtered through Celite, and the filter residue was washed with

EtOAc. The filtrate was concentrated, and EtOAc was added. The

organic phase was washed sequentially with saturated aqueous

NaHCO₃solution (2ϫ 30 mL), and brine (2ϫ 30 mL), dried with

Na₂SO₄, and concentrated.

1

The residue was dissolved in CH₂Cl₂(10.0 mL), and Ac₂O (84 μL,

0.89 mmol) was added at 0 °C. The mixture was stirred for 2 h at

room temperature. Then the solution was concentrated, and the

residue was purified by column chromatography on silica gel (pe-

of pure 28 was obtained. H NMR (500 MHz, CDCl₃): δ = 7.52–

7.26 (m, 15 H, Ar-H), 7.05–7.01 (m, 2 H, Ar-H), 6.78–6.74 (m, 2

H, Ar-H), 5.88 (d, J = 6.7 Hz, 1 H, NH), 5.46 (d, J = 7.9 Hz, 1 H,

1Ј-H), 5.45 (s, 1 H, PhCH), 5.39 (dd, J = 9.8, 3.5 Hz, 1 H, 4Ј-H),

Eur. J. Org. Chem. 0000, 0–0

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Date: 08-12-14 13:20:56

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P. Zhang, K. Wang, J. Zhang, C. Li, H. Guan

5.29 (dd, J = 10.3, 7.8 Hz, 1 H, 2ЈЈ-H), 5.03 (d, J = 10.6 Hz, 1 H, acetyl-3-O-tert-butyldimethysilyl-β- -galactopyranosyl Trichloro-

FULL PAPER

D

PhCH₂), 4.92–4.85 (m, 2 H, 3ЈЈ-H, 3ЈЈ-H), 4.85 (d, J = 7.1 Hz, 1

H, 1-H), 4.68 (d, J = 10.7 Hz, 1 H, PhCH₂), 4.62 (d, J = 7.9 Hz, 1

acetimidate (2Ј): Compound 30 (100 mg, 91 μmol) was dissolved

in a mixture of MeCN and H₂O (5:1; 6.0 mL), and diammonium

H, 1ЈЈ-H), 4.59–4.54 (m, 2 H, PhCH₂), 4.35–4.28 (m, 2 H, 4ЈЈ-H, cerium(IV) nitrate (CAN; 280 mg, 510 μmol) was added. The mix-

6aЈ-H), 4.23 (dd, J = 11.6, 4.2 Hz, 1 H, 6aЈЈ-H), 4.13 (d, J = 2.2 Hz, ture was stirred for 2 h at room temperature, and the reaction was

1 H, 4-H), 3.99–3.88 (m, 2 H, 3-H, 5ЈЈ-H), 3.79 (dd, J = 7.5, 4.6 Hz,

monitored by TLC (petroleum ether/EtOAc, 1:2). The reaction

1 H, 6bЈ-H), 3.76 (s, 3 H, OCH₃), 3.75–3.64 (m, 5 H, 2-H, 5-H, 6a- mixture was extracted with CHCl₃, and the organic layer was

H, 6b-H, 6bЈЈ-H), 3.51–3.44 (m, 1 H, 5Ј-H), 3.33 (dt, J = 10.4, washed with NaHCO₃(satd.; 2 ϫ 20 mL) and NaCl (satd.; 2ϫ

7.9 Hz, 2Ј-H), 2.10, 2.07, 2.05, 2.01, 2.00 (s, 15 H, 5 CH₃CO), 0.91 20 mL), dried with Na₂SO₄, and concentrated. The residue was

(s, 9 H, tBu), 0.07 (s, 6 H, 2 SiCH₃) ppm. ¹³C NMR (125 MHz, purified by column chromatography on silica gel (petroleum ether/

CDCl₃): δ = 170.69, 170.63, 170.46, 170.11, 169.16, 155.16, 151.49, EtOAc, 1:1) to give the intermediate product (81 mg) as a white

138.29, 138.21, 137.70, 129.01, 128.33, 128.22, 128.11, 128.01, solid.

128.01, 127.87, 127.59, 126.49, 126.35, 118.21, 118.13, 114.43,

The intermediate product was dissolved in CH₂Cl₂(5.0 mL), and

103.06, 101.01, 100.59, 98.15, 98.09, 79.73, 75.23, 74.51, 74.17,

trichloroacetonitrile (85 μL, 820 μmol) and DBU (12 μL, 82 μmol)

73.66, 73.14, 72.01, 71.37, 69.95, 68.85, 68.77, 68.54, 66.27, 55.60,

were added. The mixture was stirred for 2 h at 0 °C, and the reac-

55.55, 31.91, 29.68, 29.34, 26.10, 23.92, 22.67, 20.92, 20.88, 20.86,

tion was monitored by TLC (petroleum ether/EtOAc, 1:2). The re-

20.76, 18.37, 14.10, –4.47, –4.89 ppm. HRMS (ESI): calcd. for

action mixture was concentrated, and the residue was purified by

C₆₂H₇₉O₂₁NSiNa [M + Na]⁺1224.4806; found 1224.4834.

column chromatography on silica gel (petroleum ether/EtOAc,

1:1.5) to give 2Ј (75 mg, 73 % over two steps) as a white solid.

HRMS (ESI): calcd. for C₄₄H₆₅O₂₄N₂Cl₃SiNa [M + Na]⁺

1161.2654; found 1161.2676. Since glycosyl trichloroacetimidates

are not stable, this compound was used for further reaction without

detailed characterization.

p-Methoxyphenyl (2,3,4,6-Tetra-O-acetyl-β-

(1Ǟ3)-(4,6-di-O-acetyl-2-acetamido-2-deoxy-β-

(1Ǟ4)-2,6-Di-O-acetyl-3-O-tert-butyldimethysilyl-β-

D

-galactopyranosyl)-

-galactopyr-

D

anoside (30): Pd/C (10%, 84 mg) was added to a solution of crude

compound 28 (232 mg) in methanol (5.0 mL) and THF (10.0 mL).

The mixture was stirred at room temperature under a hydrogen

atmosphere (balloon) for 24 h. The mixture was filtered through

Celite, and the filtrate was concentrated in vacuo. The residue was

purified by column chromatography on silica gel (CH₂Cl₂/MeOH,

15:1) to give 29 (125 mg, 63% over two steps) as a white solid.

HRMS (ESI): calcd. for C₄₁H₆₃O₂₁NSiNa [M + Na]⁺956.3554;

found 956.3573.

Benzoyl 3-O-(p-Methoxybenzyl)-4,6-O-benzylidene-α-D-glucopyr-

anoside (33): Compound 31^[26](386 mg, 1.0 mmol) was dissolved in

DMF (5 mL), and the solution was cooled to 0 °C. NaH (60% in

oil; 60 mg, 1.5 mmol) was added. The solution was warmed to

room temperature, and stirred for 30 min. Then the solution was

cooled to 0 °C. TBAI (37 mg, 0.1 mmol) was added, and then

PMBCl (203 μL, 1.5 mmol) was added dropwise. The solution was

warmed to room temperature gradually, and stirred for 30 min at

room temperature. CH₃OH (1.5 mmol) was added, and the reaction

mixture was stirred for 30 min. The solution was diluted with

CH₂Cl₂(50 mL). Subsequently, HCl (1 m aqueous; 30 mL) was

added. The reaction mixture was stirred until TLC (petroleum

ether/EtOAc, 4:1) indicated that the 1,2-orthoesters had been com-

pletely hydrolyzed. The organic phase was washed with saturated

aqueous NaHCO₃solution and brine, dried with Na₂SO₄, and con-

centrated. The residue was purified by column chromatography on

silica gel (petroleum ether/EtOAc, 3:1) to give 33 (418 mg, 85%

over two steps). ¹H NMR (500 MHz, CDCl₃): δ = 8.06–6.88 (m,

14 H, Ar-H), 6.48 (d, J = 3.8 Hz, 1 H, 1-H), 5.63 (s, 1 H, Ph-CH),

5.01 (d, J = 11.0 Hz, 1 H, Ph-CH₂), 4.74 (d, J = 11.0 Hz, 1 H, Ph-

CH₂), 4.32 (dd, J = 4.9, 10.5 Hz, 1 H, 4-H), 4.01–4.05 (m, 2 H, 3-

H, 6a-H), 3.96 (dd, J = 3.8, 9.3 Hz, 1 H, 2-H), 3.80 (s, 3 H,

-OCH₃), 3.72–3.79 (m, 2 H, 5-H, 6b-H) ppm. ¹³C NMR (125 MHz,

CDCl₃): δ = 165.05, 159.61, 137.19, 133.78, 130.24, 130.06, 130.04,

130.02, 129.41, 129.17, 128.67, 128.43, 128.41, 126.06, 114.06,

101.42, 92.30, 81.86, 78.00, 74.76, 71.23, 68.85, 65.42, 55.38 ppm.

HRMS (ESI): calcd. for C₂₈H₂₈O₈Na [M + Na]⁺515.1683; found

515.1676.

Compound 29 (357 mg, 382 μmol) was dissolved in pyridine

(5.0 mL), and acetic anhydride (200 μL, 1.97 mmol) was added.

The mixture was stirred for 16 h at room temperature, and the reac-

tion was monitored by TLC (petroleum ether/EtOAc, 2:1). The re-

action mixture was coevaporated with toluene, and then CH₂Cl₂

was added to the residue. The organic layer was washed with HCl

(10% aq.; 20 mL), NaHCO₃(satd.; 2ϫ 20 mL), and NaCl (satd.;

2ϫ 20 mL), dried with Na₂SO₄, and concentrated. The residue was

purified by column chromatography on silica gel (petroleum ether/

EtOAc, 1:1) to give 30 (400 mg, 95%) as a white solid. ¹H NMR

(600 MHz, CDCl₃): δ = 6.92 (dd, J = 9.0, 1.9 Hz, 2 H, Ar-H), 6.81–

6.77 (m, 2 H, Ar-H), 5.99 (s, 1 H, NH), 5.39–5.36 (m, 1 H, 2-H),

5.36 (d, J = 8.3 Hz, 1 H, 1Ј-H), 5.34 (d, J = 3.6 Hz, 1 H, 4Ј-H),

5.33 (d, J = 3.5 Hz, 1 H, 4ЈЈ-H), 5.09 (dd, J = 10.1, 7.9 Hz, 1 H,

2ЈЈ-H), 4.96 (dd, J = 10.9, 3.6 Hz, 1 H, 3Ј-H), 4.92 (dd, J = 10.5,

3.5 Hz, 1 H, 3ЈЈ-H), 4.73 (d, J = 7.8 Hz, 1 H, 1-H), 4.59 (d, J =

7.9 Hz, 1 H, 1ЈЈ-H), 4.31 (dd, J = 11.9, 4.4 Hz, 1 H, 6aЈ-H), 4.27–

4.22 (m, 1 H, 6bЈ-H), 4.16 (dd, J = 11.7, 4.5 Hz, 1 H, 6a-H), 4.12–

4.06 (m, 2 H, 6ЈЈ-H), 3.94 (dd, J = 11.5, 7.6 Hz, 1 H, 6b-H), 3.84

(t, J = 6.7 Hz, 1 H, 5ЈЈ-H), 3.81–3.74 (m, 7 H, 5Ј-H, 5-H, 4-H, 3-

H, ArOCH₃), 3.23 (m, 1 H, 2Ј-H), 2.13, 2.11, 2.10, 2.06, 2.06, 2.04,

2.04, 2.02, 1.95 (s, 27 H, 9 CH₃CO), 0.90 (s, 9 H, tBu), 0.11 (s, 3 H,

SiCH₃), 0.08 (s, 3 H, SiCH₃) ppm. ¹³C NMR (150 MHz, CDCl₃): δ

= 171.61, 170.82, 170.60, 170.52, 170.28, 170.23, 169.68, 155.65,

151.50, 118.64, 114.54, 101.09 (C-1, C-1ЈЈ), 98.03 (C-1Ј), 74.08,

74.06, 73.77, 72.57, 72.43, 71.57, 71.42, 70.96, 70.65, 69.24, 69.01,

67.00, 63.66, 63.04, 61.12, 55.76, 25.97, 23.83, 21.28, 20.98, 20.94,

20.90, 20.88, 20.81, 20.69, 18.35, –4.61, –4.65 ppm. HRMS (ESI):

calcd. for C₄₉H₇₁O₂₅NSiNa [M + Na]⁺1124.3977; found

1124.3993.

4,6-O-Benzylidene-2-O-benzoyl-3-O-(p-methoxybenzyl)-1-thio-β-D-

glucopyranosyl Trichloroacetimidate (35): Compound 33 (900 mg,

1.99 mmol) was dissolved in CH₂Cl₂(20.0 mL). Et₃N (5.0 mL) was

added, and the mixture was stirred for 12 h. After this time, 33 had

been converted into 34. The reaction mixture was concentrated to

dryness.

The crude product was dissolved in CH₂Cl₂(20.0 mL), and

trichloroacetonitrile (997 μL, 9.95 mmol) and DBU (151 μL,

1.0 mmol) were added. The mixture was stirred for 2 h at 0 °C, and

the reaction was monitored by TLC (petroleum ether/EtOAc,

2.5:1). The reaction mixture was concentrated, and the residue was

(2,3,4,6-Tetra-O-acetyl-β-

acetyl-2-acetamido-2-deoxy-β-

D

-galactopyranosyl)-(1Ǟ3)-(4,6-di-O-

-galactopyranosyl)-(1Ǟ4)-2,6-di-O-

D

10

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Pages: 15

Total Synthesis of Sulfated Glycosphingolipid SM1a

purified by column chromatography on silica gel (petroleum ether/

EtOAc, 6:1) to give 35 (1.014 g, 80% over two steps). Since glycosyl

trichloroacetimidates are not stable, this compound was used for

further reaction without characterization.

2 H, NHCOCH₂), 2.28–2.23 (m, 2 H, CH₂-6^cer), 2.08 (dd, J = 14.1,

7.1 Hz, 2 H, NHCOCH₂CH₂), 1.70–1.58 (m, 4 H, 2 CH₂), 1.27 (br.

s, 58 H, 29 CH₂), 0.90 (t, J = 6.8 Hz, 6 H, 2 CH₃) ppm. ¹³C NMR

(125 MHz, CDCl₃): δ = 174.16, 134.52, 128.86, 74.88, 62.67, 54.56,

36.98, 33.81, 32.44, 32.08, 29.86, 29.83, 29.82, 29.80, 29.78, 29.76,

29.67, 29.60, 29.52, 29.44, 29.38, 29.26, 29.23, 25.92, 24.88, 22.85,

14.29 ppm. HRMS (ESI): calcd. for C₄₂H₈₃NO₃Na [M + Na]⁺

672.6277; found 672.6265.

p-Methylphenyl 4,6-O-Benzylidene-2-O-benzoyl-3-O-(p-meth-

oxybenzyl)-1-thio-β-D-glucopyranoside (36): A suspension of com-

pound 35 (1420 mg, 2.23 mmol), TolSH (277 mg, 2.23 mmol), and

molecular sieves (4 Å; 300 mg) in CH₂Cl₂(20.0 mL) was stirred for

0.5 h, and then it was cooled to 0 °C. BF₃·Et₂O (19 μL, 35 μmol)

was added, the mixture was stirred for a further 1 h. TLC (petro-

leum ether/EtOAc, 2:3) showed that the reaction was complete.

Et₃N was added to quench the reaction. The mixture was filtered

through Celite. The filtrate was washed with saturated NaHCO₃

(2S,3R,4E)-1-O-tert-Butyldimethylsilyl-2-tetracosanamido-4-octa-

dec-ene-1,3-diol (39): Triethylamine (128 μL, 921 μmol), TBDMSCl

(51 mg, 338 μmol), and DMAP (112.5 mg, 921 μmol) were added

to a solution of 38 (200 mg, 307 μmol) in CHCl₃(5 mL) at 0 °C.

The mixture was stirred for 6 h at 40 °C. TLC (Et₂O/hexane, 1:1)

(2ϫ 20 mL), and brine (2ϫ 20 mL), dried with Na₂SO₄, and con- showed that the reaction was complete. The reaction mixture was

centrated. The residue was purified by column chromatography on

concentrated, and the residue was purified by column chromatog-

silica gel (petroleum ether/EtOAc, 6:1) to give 36 (801 mg, 60%) as

raphy on silica gel (Et₂O/hexane, 1:3) to give 39 (188 mg, 80%) as

a white powder. ¹H NMR (600 MHz, CDCl₃): δ = 8.02–6.55 (m, a white solid. ¹H NMR (500 MHz, CDCl₃): δ = 6.20 (d, J = 7.7 Hz,

14 H, Ar-H), 5.60 (s, 1 H, PhCH), 5.22 (dd, J = 10.0, 8.7 Hz, 1 H, 1 H, NH), 5.82–5.70 (m, 1 H, 5-H), 5.50 (dd, J = 15.4, 5.7 Hz, 1

2-H), 4.76 (d, J = 10.0 Hz, 1 H, 1-H), 4.72 (d, J = 11.6 Hz, 1 H, H, 4-H), 4.16 (br. s, 1 H, 3-H), 3.98–3.89 (m, 2 H, 1a-H, 2-H), 3.74

PhCH₂), 4.58 (d, J = 11.7 Hz, 1 H, PhCH₂), 4.41 (dd, J = 10.6,

(dd, J = 9.9, 2.4 Hz, 1 H, 1b-H), 3.62 (d, J = 8.8 Hz, 1 H, -OH),

5.0 Hz, 1 H, 4-H), 3.87–3.81 (m, 2 H, 6-H), 3.78 (t, J = 9.3 Hz, 1 2.21 (t, J = 7.6 Hz, 2 H, NHCOCH₂), 2.05 (dd, J = 14.2, 7.1 Hz,

H, 3-H), 3.68 (s, 3 H, PhOCH₃), 3.54 (td, J = 9.9, 5.0 Hz, 1 H, 5-

2 H, CH₂-6^cer), 1.69–1.56 (m, 2 H, NHCOCH₂CH₂), 1.44–1.09 (m,

62 H, 31 CH₂), 0.97–0.81 (m, 15 H, 5 CH₃), 0.06, 0.06 (s, 6 H, 2

H), 2.32 (s, 3 H, PhCH₃) ppm. ¹³C NMR (150 MHz, CDCl₃): δ =

164.94, 159.05, 138.51, 137.18, 133.64, 133.13, 129.90, 129.84, SiCH₃) ppm. ¹³C NMR (125 MHz, CDCl₃): δ = 173.31, 133.26,

129.76, 129.63, 129.02, 128.32, 128.27, 128.14, 125.99, 113.51, 129.30, 74.76, 63.61, 53.35, 37.05, 32.46, 32.08, 29.86, 29.83, 29.82,

101.23, 87.16, 81.43, 78.75, 73.83, 72.00, 70.58, 68.60, 55.08, 29.80, 29.68, 29.65, 29.55, 29.52, 29.45, 29.38, 29.37, 25.97,

21.15 ppm. HRMS: calcd. for C₃₅H₃₄NO₇SNa [M + Na]⁺

621.1917; found 621.1917.

25.94, 22.85, 18.23, 14.29, –5.48 ppm. HRMS (ESI): calcd. for

C₄₈H₉₇NO₃SiNa [M + Na]⁺786.712; found 786.7130.

p-Methylphenyl 2-O-Benzoyl-3-O-(p-methoxybenzyl)-1-thio-β-

D

-

(2S,3R,4E)-1-O-tert-Butyldimethylsilyl-3-O-succinoyl-2-tetracosan-

glucopyranoside (8): Compound 36 (210 mg, 0.35 mmol) was added amido-4-octadecene-1,3-diol (9): Succinic anhydride (120 mg,

to a mixture of AcOH and H₂O (4:1; 15 mL). The resulting solu- 1.2 mmol) and DMAP (5 mg, 41 μmol) were added to a solution

tion was stirred at 80 °C for 3 h. TLC (petroleum ether/CH₂Cl₂, of 39 (200 mg, 261 μmol) in pyridine (7.5 mL) at 0 °C. The mixture

1:2) showed that the reaction was complete, and the solution was

concentrated coevaporated once with toluene (5 mL). The residue

was purified by column chromatography on silica gel (petroleum

was stirred for 23 h at 40 °C. TLC (petroleum ether/EtOAc, 1:2)

showed that the reaction was complete. The reaction mixture was

coevaporated with toluene. The residue was dissolved in CHCl₃,

ether/EtOAc, 1:1) to give 8 (173 mg, 95%) as a white solid. ¹H and the solution was washed with H₂O, dried with Na₂SO₄, and

NMR (500 MHz, CDCl₃): δ = 8.08–6.74 (m, 13 H, Ar-H), 5.20 (t,

concentrated. The residue was purified by column chromatography

J = 9.5 Hz, 1 H, 2-H), 4.77 (d, J = 10.0 Hz, 1 H, 1-H), 4.65 (d, J on silica gel (Et₂O/hexane, 1:2) to give 9 (200 mg, 88%) as a white

= 11.2 Hz, 1 H,PhCH₂), 4.50 (d, J = 11.2 Hz, 1 H, PhCH₂), 3.92 solid. ¹H NMR (500 MHz, CDCl₃): δ = 5.80–5.69 (m, 2 H, NH,

(d, J = 11.0 Hz, 1 H, 6a-H), 3.79 (d, J = 11.2 Hz, 1 H, 6b-H), 3.73 5-H), 5.42 (dd, J = 15.3, 7.5 Hz, 1 H, 4-H), 5.34 (t, J = 7.0 Hz, 1

(s, 3 H, PhOCH₃), 3.70–3.63 (m, 2 H, 3-H, 4-H), 3.45 (s, 1 H, 5-

H, 3-H), 4.23 (td, J = 9.7, 3.9 Hz, 1 H, 2-H), 3.71 (dd, J = 10.3,

3.2 Hz, 1 H, 1a-H), 3.58 (dd, J = 10.3, 4.4 Hz, 1 H, 1b-H), 2.71–

H), 2.32 (s, 3 H, PhCH₃) ppm. ¹³C NMR (125 MHz, CDCl₃): δ =

165.32, 159.48, 138.49, 133.46, 133.24, 130.00, 129.90, 129.86, 2.55 (m, 4 H, OCOCH₂CH₂OCO), 2.17 (m, 2 H, NHCOCH₂), 2.00

129.84, 128.77, 128.62, 114.02, 86.75, 83.58, 79.53, 74.54, 72.53, (m, 2 H, CH₂-6^cer), 1.57 (m, 2 H, NHCOCH₂CH₂), 1.44–1.09 (m,

70.42, 62.72, 55.29, 21.27 ppm. HRMS: calcd. for C₂₈H₃₀O₇SNa

[M + Na]⁺533.1604; found 533.1604.

62 H, 31 CH₂), 0.93–0.82 (m, 15 H, 5 CH₃), 0.04, 0.04 (s, 6 H, 2

SiCH₃) ppm. ¹³C NMR (125 MHz, CDCl₃): δ = 176.75, 173.13,

171.05, 137.04, 124.70, 74.20, 61.64, 52.01, 37.07, 32.50, 32.08,

29.87, 29.81, 29.69, 29.67, 29.58, 29.52, 29.43, 29.41, 29.14, 29.02,

25.97, 25.91, 22.85, 18.34, 14.29, –5.41, –5.49 ppm. HRMS (ESI):

calcd. for C₅₂H₁₀₁NO₆SiNa [M + Na]⁺886.730; found 886.7290.

(2S,3R,4E)-2-Tetracosanamido-4-ene-1,3-diol (38): DIPEA (327 μL,

1.87 mmol) was added dropwise to a stirred mixture of 37^[27]

(487 mg, 1.63 mmol), carnaubic acid (777 mg, 2.10 mmol), HOBt

(220 mg, 1.63 mmol), and EDC (311 mg, 1.63 mmol) in anhydrous

THF (15 mL) under nitrogen. The reaction mixture was stirred for

about 5 h. TLC (CH₂Cl₂/CH₃OH, 20:1) showed that the reaction

was complete. The reaction mixture was evaporated, and the resi-

p-Methylphenyl 6-O-{[(2S,3R,4E)-1-O-tert-Butyldimethylsilyl-2-tet-

racosanamido-octadecene-4-yloxy]carbonylpropanoyl}-2-O-benzoyl-

3-O-(p-methoxybenzyl)-1-thio-β-D-glucopyranoside (40): Compound

due was dissolved in CHCl₃(50 mL). The organic phase was 8 (41 mg, 80 μmol) and compound 9 (70 mg, 80 μmol) were dis-

washed successively with water (20 mL) and brine (20 mL), then it

was dried with Na₂SO₄, and concentrated. The residue was purified

by silica gel column chromatography (CH₂Cl₂/CH₃OH, 30:1) to

give 38 (762 mg, 71 %) as a white solid. ¹H NMR (500 MHz,

CDCl₃): δ = 6.32 (d, J = 7.5 Hz, 1 H, NH), 5.85–5.76 (m, 1 H, 5-

solved in CH₂Cl₂(2 mL) and CH₃CN (1 mL), and the solution was

cooled to 0 °C. DMAP (3.0 mg, 18 μmol) and EDC·HCl (18.0 mg,

94 mmol) were added. The mixture was stirred for 5 h at room tem-

perature. TLC (toluene/EtOAc 2:1) showed that the reaction was

complete. The reaction mixture was diluted with CHCl₃(50 mL),

H), 5.55 (dd, J = 15.5, 6.4 Hz, 1 H, 4-H), 4.37–4.32 (m, 1 H, 3-H), and the solution was washed with H₂O (20 mL) and brine (20 mL),

3.99 (dd, J = 11.3, 3.7 Hz, 1 H, 1a-H), 3.93 (dd, J = 7.3, 3.6 Hz, 1 dried (Na₂SO₄), and concentrated. The residue was purified by col-

H, 1b-H), 3.73 (dd, J = 11.3, 3.2 Hz, 1 H, 2-H), 2.37 (t, J = 7.5 Hz, umn chromatography on silica gel (toluene/EtOAc, 4:1) to give 40

Eur. J. Org. Chem. 0000, 0–0

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P. Zhang, K. Wang, J. Zhang, C. Li, H. Guan

FULL PAPER

(75 mg, 68%). H NMR (500 MHz, CDCl₃): δ = 8.04–6.64 (m, 13 H, 4^cer-H), 5.18 (t, J = 7.4 Hz, 1 H, 2-H), 4.71 (d, J = 11.3 Hz, 1

H, Ar-H), 5.75 (m, 2 H, NH, 5^cer-H), 5.47–5.35 (m, 2 H, 4^cer-H, H, PhCH₂), 4.56 (d, J = 11.5 Hz, 1 H, PhCH₂), 4.55 (d, J = 7.0 Hz,

3^cer-H), 5.17 (t, J = 9.5 Hz, 1 H, 2-H), 4.71 (d, J = 10.0 Hz, 1 H, 1 H, 1-H), 4.43 (dd, J = 11.7, 8.2 Hz, 1 H, 6a-H), 4.26 (m, 2 H,

1-H), 4.68–4.61 (m, 2 H, PhCH₂), 4.45 (dd, J = 12.0, 3.8 Hz, 1 H, 6b-H, 2^cer-H), 3.89 (dd, J = 9.7, 3.5 Hz, 1 H, 1a^cer-H), 3.75 (s, 3 H,

6a-H), 4.39 (d, J = 11.9 Hz, 1 H, 6b-H), 4.24 (m, 1 H, 2^cer-H), 4.01 ArOCH₃), 3.68–3.60 (m, 4 H, 3-H, 4-H, 5-H, 1b^cer-H), 2.79–2.51

(s, 1 H, OH), 3.77–3.62 (m, 6 H, 4-H, 3-H, PhOCH₃, 1a^cer-H), 3.58 (m, 4 H, OCOCH₂CH₂OCO), 2.47 (d, J = 2.8 Hz, 1 H, OH), 2.03

(dd, J = 10.3, 4.6 Hz, 1 H, 1b^cer-H), 3.53 (d, J = 9.6 Hz, 1 H, 5- (t, J = 7.7 Hz, 2 H, NHCOCH₂), 1.95 (dq, J = 14.5, 7.3 Hz, 2 H,

1

H), 2.65 (m, 4 H, OCOCH₂CH₂OCO), 2.31 (s, 3 H, PhCH₃), 2.15

(t, J = 7.4 Hz, 2 H, NHCOCH₂), 2.01 (dd, J = 14.0, 6.8 Hz, 2 H,

6^cer-H), 1.49 (d, J = 3.6 Hz, 2 H, NHCOCH₂CH₂), 1.36–1.17 (m,

62 H, 31 CH₂), 0.88 (t, J = 6.9 Hz, 6 H, 2 CH₃) ppm. ¹³C NMR

CH₂-6^cer), 1.59 (m, 2 H, NHCOCH₂CH₂), 1.44–1.10 (m, 62 H, 31 (125 MHz, CDCl₃): δ = 172.85, 172.02, 170.75, 165.31, 159.61,

CH₂), 0.94–0.79 (m, 15 H, 5 CH₃), 0.06, 0.06 (s, 6 H, 2 SiCH₃) 138.45, 133.57, 130.01, 129.81, 129.74, 128.70, 124.97, 114.14,

ppm. ¹³C NMR (125 MHz, CDCl₃): δ = 173.22, 172.71, 170.85, 100.12, 82.17, 74.07, 73.88, 73.52, 73.07, 71.03, 66.83, 64.26, 55.34,

165.23, 159.25, 138.27, 136.82, 133.34, 133.27, 130.18, 130.04, 50.15, 48.83, 36.87, 32.43, 32.08, 29.90, 29.86, 29.83, 29.81, 29.79,

129.99, 129.83, 129.64, 129.03, 128.50, 124.50, 113.76, 86.89, 83.02,

77.98, 74.56, 74.17, 72.17, 69.80, 63.31, 61.89, 55.22, 51.93, 37.10,

32.54, 32.07, 29.86, 29.80, 29.71, 29.67, 29.63, 29.58, 29.51, 29.45,

29.40, 29.18, 25.97, 22.84, 21.28, 18.33, 14.28, –5.35, –5.47 ppm.

HRMS (ESI): calcd. for C₈₀H₁₂₉NO₁₂SSiNa [M + Na]⁺1378.8887;

found 1378.8897.

29.72, 29.65, 29.56, 29.52, 29.51, 29.46, 29.40, 29.05, 25.72, 22.84,

14.27 ppm. HRMS (ESI): calcd. for C₆₇H₁₀₇NO₁₂Na [M + Na]⁺

1140.7692; found 1264.8032.

(2,3,4,6-Tetra-O-acetyl-β-

acetyl-2-acetamido-2-deoxy-β-

acetyl-3-O-tert-butyldimethysilyl-β-

D

-galactopyranosyl)-(1Ǟ3)-(4,6-di-O-

-galactopyranosyl)-(1Ǟ4)-(2,6-di-O-

-galactopyranoside)-(1Ǟ4)-2-

-glucopyranosyl-(1Ǟ1)-

D

p-Methylphenyl 6-O-{[(2S,3R,4E)-2-Tetracosanamido-octadecene-4- O-benzo-yl-3-O-(p-methoxybenzyl)-β-

D

yloxy]carbonylpropanoyl}-2-O-benzoyl-3-O-(p-methoxybenzyl)-1-

thio-β- -glucopyranoside (41): AcOH (500 μL) and TBAF (1.0 m

solution in THF; 500 μL, 500 μmol) were added to a solution of

40 (140 mg, 0.103 mmol) in THF (1.5 mL) at 0 °C. The mixture

(2S,3R,4E)-2-tetracosanamido-octadecene-4,6-succinate (42): A sus-

pension of compound 2Ј (60 mg, 52 μmol), compound 3 (28 mg,

25 μmol), and molecular sieves (AW-300; 80 mg) in CHCl₃(3.0 mL)

was stirred for 0.5 h, and then cooled to 0 °C. TMSOTf (2 μL,

D

was stirred for 3 h at room temperature. TLC (EtOAc/toluene, 1:1) 11 μmol) was added, and the mixture was stirred for a further 1 h.

showed that the reaction was complete. The reaction mixture was

diluted with CHCl₃(30 mL), and the solution was washed with

saturated aqueous NaHCO₃(10 mL) and brine (10 mL), dried with

Na₂SO₄, and concentrated. The residue was purified by column

chromatography on silica gel (EtOAc/toluene, 1:2) to give 41

TLC (petroleum ether/EtOAc, 1:2) showed that the reaction was

complete. Et₃N was added to quench the reaction. The mixture

was filtered through Celite. The filtrate was washed with saturated

NaHCO₃solution (2ϫ 20 mL), and brine (2ϫ 20 mL), dried with

Na₂SO₄, and concentrated. The residue was purified by column

chromatography on silica gel (petroleum ether/EtOAc, 1:1.2) to

1

(105 mg, 82%) as a white solid. H NMR (500 MHz, CDCl₃): δ =

8.05–6.65 (m, 13 H, Ar-H), 6.03 (d, J = 8.9 Hz, 1 H, NH), 5.80– give 42 (36 mg, 70 %) as a white solid. ¹H NMR (500 MHz,

5.73 (m, 1 H, 5^cer-H), 5.46–5.34 (m, 2 H, 4^cer-H, 3^cer-H), 5.19–5.14 CDCl₃): δ = 7.97–6.75 (m, 9 H, ArH), 5.82–5.76 (m, 1 H, 5^cer-H),

(m, 1 H, 2-H), 4.72 (d, J = 10.0 Hz, 1 H, 1-H), 4.66–4.58 (m, 2 H, 5.63 (d, J = 6.98 Hz, 1 H, NHCOCH₃), 5.60 (d, J = 9.68 Hz, 1 H,

PhCH₂), 4.55 (dd, J = 12.0, 3.9 Hz, 1 H, 6a-H), 4.32 (dd, J = 12.0, NHCO), 5.38–5.30 (m, 2 H, 4ЈЈ-H, 4ЈЈЈ-H), 5.30–5.23 (dd, 2 H, 1ЈЈ-

2.0 Hz, 1 H, 6b-H), 4.18–4.13 (m, 1 H, 2^cer-H), 3.70 (s, 3 H, Ar-

OCH₃), 3.69–3.64 (m, 3 H, 4-H, 3-H, 5-H), 3.61 (dd, J = 11.7, 10.4, 7.9 Hz, 1 H, 2ЈЈЈ-H), 4.91 (dd, J = 10.4, 3.5 Hz, 1 H, 3ЈЈЈ-H),

3.4 Hz, 1 H, 1a^cer-H), 3.57–3.51 (m, 1 H, 1b^cer-H), 2.75–2.63 (m, 4

4.80–4.74 (m, 2 H, PhCH₂, 3ЈЈ-H), 4.71 (d, J = 11.2 Hz, 1 H,

H, 3^cer-H), 5.23–5.13 (m, 3 H, 2-H, 2Ј-H, 4^cer-H), 5.07 (dd, J =

H, OCOCH₂CH₂OCO), 2.32 (s, 3 H, ArCH₃), 2.19–2.15 (m, 2 H, PhCH₂), 4.66 (d, J = 8.0 Hz, 1 H, 1-H), 4.59–4.55 (m, 2 H, 1Ј-H,

NHCOCH₂), 2.06–1.97 (m, 2 H, 6^cer-H), 1.62–1.56 (m, 2 H, 1ЈЈЈ-H), 4.30 (m, 3 H, 6aЈЈ-H, 6a-H, 2^cer-H), 4.21–4.14 (m, 2 H, 6b-

NHCOCH₂CH₂), 1.41–1.17 (m, 62 H, 31 CH₂), 0.88 (t, J = 7.0 Hz, H, 4Ј-H), 4.10–4.07 (m, 2 H, 6ЈЈЈ-H), 3.97–3.68 (m, 13 H, 6bЈЈ-H,

6 H, 2 CH₃) ppm. ¹³C NMR (125 MHz, CDCl₃): δ = 173.82, 1^cer-H, 3-H, 4-H, 5-H, 5Ј-H, 5ЈЈЈ-H, 6aЈ-H, 6bЈ-H, ArOCH₃), 3.66

172.95, 171.65, 165.27, 159.42, 138.38, 137.53, 133.41, 133.38, (t, J = 5.7 Hz, 1 H, 5ЈЈ-H), 3.48 (d, J = 6.5 Hz, 1 H, 3Ј-H), 3.34–

130.00, 129.92, 129.68, 128.94, 128.57, 124.59, 113.89, 86.91, 83.32,

77.80, 74.74, 74.73, 72.26, 69.65, 63.43, 61.90, 55.26, 53.05, 36.90,

32.44, 32.08, 29.88, 29.85, 29.82, 29.81, 29.79, 29.72, 29.65, 29.59,

29.51, 29.48, 29.42, 29.30, 29.07, 25.85, 22.84, 21.29, 14.27 ppm.

3.27 (m, 1 H, 2ЈЈ-H), 2.78–2.47 (m, 4 H, OCCH₂CH₂CO), 2.15–

2.10 (m, 11 H, NHCOCH₂, 3 COCH₃), 2.07–2.02 (m, 7 H, 6a^cer

-

H, 2 COCH₃), 1.99, 1.98 (s, 6 H, 2 COCH₃), 1.97–1.93 (m, 4 H,

6b^cer-H, COCH₃), 1.91 (s, 3 H, COCH₃), 1.45 (br. s, 2 H,

HRMS (ESI): calcd. for C₇₄H₁₁₅NO₁₂SNa [M + Na]⁺1264.8036; NHCOCH₂CH₂), 1.35–1.17 (m, 62 H, 31 CH₂), 0.90 (s, 9 H, tBu),

found 1264.8032.

0.88 (t, J = 6.9 Hz, 6 H, 2 CH₃), 0.12, 0.08 (s, 6 H, 2 SiCH₃) ppm.

¹³C NMR (125 MHz, CDCl₃): δ = 172.78, 172.71, 171.44, 171.42,

171.25, 170.56, 170.49, 170.44, 170.18, 169.73, 169.38, 165.54,

165.30, 159.19, 139.10, 133.63, 130.57, 129.80, 129.59, 128.91,

128.65, 125.17, 113.92, 101.93, 101.04, 99.25, 98.37, 80.90, 78.79,

74.63, 74.06, 73.87, 73.80, 73.46, 73.08, 72.90, 72.69, 72.58, 72.39,

72.18, 71.62, 71.40, 71.01, 70.76, 69.05, 66.99, 63.78, 63.31, 63.11,

62.97, 61.15, 55.26, 50.08, 36.90, 32.44, 32.07, 29.85, 29.80, 29.72,

29.66, 29.55, 29.50, 29.45, 29.05, 26.65, 26.25, 26.06, 26.00, 25.75,

25.66, 23.77, 22.83, 21.41 20.98, 20.90, 20.86, 20.82, 20.75, 20.69,

18.30, 14.26, –4.48, –4.67 ppm. HRMS (ESI): calcd. for

C₁₀₉H₁₇₀O₃₅N₂SiNa [M + Na]⁺2118.1216; found 2118.1246.

2-O-Benzoyl-3-O-(p-methoxybenzyl)-β-D-glucopyranosyl-(1Ǟ1)-

(2S,3R,4E)-2-tetracosanamido-octadecene-4,6-succinate (3): Molec-

ular sieves (4 Å; 85 mg) were added to a solution of 41 (100 mg,

80.4 μmol) in CH₂Cl₂(2.0 mL). The suspension was stirred for 1 h

at room temperature. DMTST (63 mg, 241 μmol) was added at

0 °C, and the mixture was stirred for a further 2 h at 0 °C. TLC

(toluene/EtOAc, 1:1) showed that the reaction was complete. The

reaction mixture was filtered through Celite, and the filter residue

was washed with CHCl₃. The filtrate was washed with saturated

aqueous NaHCO₃and H₂O, dried with Na₂SO₄, and concentrated.

The residue was purified by column chromatography on silica gel

(EtOAc/toluene, 1:2.5) to give 3 (54 mg, 60 %). ¹H NMR (2,3,4,6-Tetra-O-acetyl-β-

(500 MHz, CDCl₃): δ = 8.03–6.78 (m, 9 H, Ar-H), 5.82–5.76 (m, 1 acetyl-2-acetamido-2-deoxy-β-

H, 5^cer-H), 5.71 (d, J = 9.6 Hz, 1 H, NH), 5.31–5.23 (m, 2 H, 3^cer

acetyl-β- -galactopyranoside)-(1Ǟ4)-2-O-benzoyl-3-O-(p-methoxy-

D

-galactopyranosyl)-(1Ǟ3)-(4,6-di-O-

-galactopyranosyl)-(1Ǟ4)-(2,6-di-O-

D

-

D

12

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/KAP1

Date: 08-12-14 13:20:56

Pages: 15

Total Synthesis of Sulfated Glycosphingolipid SM1a

benzyl)-β-

D

-glucopyranosyl-(1Ǟ1)-(2S,3R,4E)-2-tetracosanamido- (CHCl₃/MeOH/H₂O, 5:4:0.5), then column chromatography

octadecene-4,6-succinate (43): AcOH (450 μL) and TBAF (1.0 m

solution in THF; 450 μL, 450 μmol) were added to a solution of

(CH₃OH) on Sephadex LH-20 (2 g) to give 1 (7 mg, 79%). ¹H

NMR (600 MHz, CD₃OD/CDCl₃, 1:1): δ = 5.69 (m, 1 H, 5^cer-H),

42 (26 mg, 12.4 μmol) in THF (1.5 mL) at 0 °C. The mixture was 5.45 (dd, J = 15.3, 7.7 Hz, 1 H, 4^cer-H), 4.68 (s, 1 H, 1ЈЈЈ-H), 4.44

stirred for 3 h at room temperature. TLC (CH₂Cl₂/CH₃OH, 20:1)

showed that the reaction was complete. The reaction mixture was

diluted with CHCl₃(30 mL), and the solution was washed with

saturated aqueous NaHCO₃(10 mL) and brine (10 mL), dried with

Na₂SO₄, and concentrated. The residue was purified by column

chromatography on silica gel (CH₂Cl₂/CH₃OH, 30:1) to give 43

(d, J = 7.3 Hz, 1 H, 1Ј-H), 4.36 (d, J = 7.1 Hz, 1 H), 4.32–4.28 (m,

2 H, 3Ј-H, 1ЈЈ-H), 4.22–4.16 (m, 2 H, 2Ј-H, 1^cer-H), 4.11–4.04 (m,

2 H, 3^cer-H, 4ЈЈЈ-H), 3.99 (s, 1 H, 2^cer-H), 3.39 (m, 1 H, 2ЈЈ-H), 2.18

(t, J = 7.6 Hz, 2 H, NHCOCH₂), 2.06 (s, 3 H, COCH₃), 2.02 (dt,

J = 15.2, 7.8 Hz, 2 H, 6^cer-H), 1.61 (m, 2 H, NHCOCH₂CH₂),

1.49–1.15 (m, 64 H, 32 CH₂), 0.89 (t, J = 6.8 Hz, 6 H, 2 CH₃) ppm.

¹³C NMR (150 MHz, CD₃OD/CDCl₃, 1:1): δ = 174.65, 168.12,

1

(20 mg, 80%) as a white solid. H NMR (500 MHz, CDCl₃): δ =

7.96–6.74 (m, 9 H, ArH), 5.94 (d, J = 6.4 Hz, 1 H, NHCOCH₃), 134.07, 129.61, 105.25, 103.48, 103.10, 102.97, 79.58, 75.25, 75.11,

5.79 (m, 1 H, 5^cer-H), 5.63 (d, J = 9.8 Hz, 1 H, NHCO), 5.54 (d, J 74.97, 74.77, 74.55, 74.10, 73.41, 73.10, 71.70, 71.13, 69.49, 68.85,

= 8.0 Hz, 1 H, 1ЈЈ-H), 5.41 (d, J = 3.0 Hz, 1 H, 4ЈЈ-H), 5.34 (d, J

68.60, 68.08, 65.54, 61.26, 60.24, 59.85, 53.23, 36.23, 32.23, 31.79,

= 3.2 Hz, 1 H, 4ЈЈЈ-H), 5.29–5.12 (m, 4 H, 4^cer-H, 3^cer-H, 2ЈЈЈ-H, 31.76, 31.24, 30.88, 30.39, 29.58, 29.53, 29.46, 29.43, 29.37, 29.24,

2-H), 4.96 (dd, J = 10.4, 3.4 Hz, 1 H, 3ЈЈЈ-H), 4.90 (dd, J = 9.9, 29.21, 29.18, 29.14, 25.89, 25.04, 22.48, 22.46, 13.50, 13.49 ppm.

8.3 Hz, 1 H, 2Ј-H), 4.79–4.69 (m, 3 H, PhCH₂, 1Ј-H), 4.59–4.57 HRMS (ESI): calcd. for C₆₈H₁₂₅O₂₆N₂S [M – H]^–1417.8236; found

(m, 2 H, 1-H, 1ЈЈЈ-H), 4.38–4.24 (m, 4 H, 6a-H, 6aЈ-H, 2^cer-H, 3ЈЈ- 1417.8199.

H), 4.20 (dd, J = 11.5, 6.6 Hz, 1 H, 6b-H), 4.17–4.09 (m, 2 H, 6ЈЈЈ-

Supporting Information (see footnote on the first page of this arti-

H), 4.08 (br. s, 1 H, 4Ј-H), 4.07–4.00 (m, 3 H, 6bЈ-H, 6aЈЈ-H, 4-H),

cle): ¹H and ¹³C NMR spectra for key intermediates and final prod-

3.97–3.76 (m, 6 H, 6bЈЈ-H, 3-H, 5ЈЈЈ-H, 5ЈЈ-H, 5-H, 1a^cer-H), 3.73

ucts.

(s, 3 H, ArOCH₃), 3.66 (t, J = 5.8 Hz, 1 H, 5Ј-H), 3.61 (d, J =

9.2 Hz, 1 H, 3Ј-H), 3.49–3.45 (m, 1 H, 1b^cer-H), 3.33–3.25 (m, 1 H,

2ЈЈ-H), 2.77–2.49 (m, 4 H, OCCH₂CH₂CO), 2.15, 2.13, 2.11, 2.06,

Acknowledgments

2.05, 2.05, 2.04 (s, 21 H, 7 COCH₃), 1.98–1.93 (m, 7 H, 6^cer-H,

COCH₃, NHCOCH₂), 1.91 (s, 3 H, COCH₃), 1.49–1.15 (m, 64 H,

32 CH₂), 0.88 (t, J = 6.8 Hz, 6 H, 2 CH₃) ppm. ¹³C NMR

(125 MHz, CDCl₃): δ = 173.05, 172.69, 171.44, 171.09, 170.67,

170.57, 170.48, 170.46, 170.30, 170.13, 170.02, 169.50, 165.27,

159.14, 138.86, 133.63, 130.55, 129.79, 129.50, 128.94, 128.65,

128.62, 125.17, 113.77, 101.30, 99.97, 99.49, 99.18, 81.10, 78.75,

75.49, 75.30, 74.18, 73.43, 73.36, 73.11, 73.06, 73.03, 72.89, 72.54,

71.79, 71.65, 71.15, 71.05, 70.75, 69.53, 67.97, 66.90, 63.46, 62.45,

61.04, 55.83, 55.25, 50.03, 36.80, 32.44, 32.07, 29.86, 29.85, 29.82,

29.80, 29.72, 29.65, 29.55, 29.51, 29.50, 29.45, 29.43, 29.04, 26.65,

25.75, 25.66, 23.69, 22.83, 21.17, 20.97, 20.88, 20.86, 20.83, 20.79,

2 0 . 7 7 , 2 0 . 6 5 , 1 4 . 2 6 p p m . H R M S ( E S I ) : c a l c d . f o r

This work was supported by the NSFC-Shandong Joint Fund for

Marine Science Research Centers (grant number U1406402) and

the Special Fund for Marine Scientific Research in the Public Inter-

est (grant number 201005024).

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C

₁₀₃H₁₅₆O₃₅N₂Na [M + Na]⁺2004.0381; found 2004.0383.

β- -Galactopyranosyl-(1Ǟ3)-2-acetamido-2-deoxy-β- -galactopyr-

anosyl-(1Ǟ4)-(3-O-sulfonate-β- -galactopyranoside)-(1Ǟ4)-β-D-

D

glucopyranosyl-(1Ǟ1)-(2S,3R,4E)-2-tetracosanamido-octadecene-

4,6-succinate (1): SO₃·Py (20 mg, 125 μmol) was added to a solu-

tion of 43 (20 mg, 10.1 μmol) in DMF (1.5 mL). The mixture was

stirred for 36 h at 90 °C. TLC (CHCl₃/MeOH, 10:1) showed that

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and the residue was diluted with CHCl₃(30 mL). The solution was

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P. Zhang, K. Wang, J. Zhang, C. Li, H. Guan

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Received: October 3, 2014

Published Online: ᭿

14

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Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O43296

/KAP1

Date: 08-12-14 13:20:56

Pages: 15

Total Synthesis of Sulfated Glycosphingolipid SM1a

Gangliosides

P. Zhang, K. Wang, J. Zhang, C. Li,*

H. Guan .......................................... 1–15

Total Synthesis of Sulfated Glycosphingoli-

pid SM1a, a Kind of Human Epithelial

Carcinoma Antigen

Keywords: Total synthesis / Glycosylation /

Carbohydrates / Oligosaccharides / Gly-

colipids / Gangliosides

An endogenous sulfoglycolipid from mam-

malian kidney, SM1a, has been synthe-

sized. A [3+2] convergent approach to the

target molecule was used. Coupling of the

trisaccharide containing a potential sulf-

ation site with a cyclic glucosyl ceramide

(GlcCer) unit gave the backbone structure

of SM1a, which was converted into gang-

lioside SM1a after selective sulfonation and

global deprotection.

Eur. J. Org. Chem. 0000, 0–0

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15

Article Doi

Total synthesis of sulfated glycosphingolipid SM1a, a kind of human epithelial carcinoma antigen

DOI: 10.1002/ejoc.201403296

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Article abstract of DOI:10.1002/ejoc.201403296

Full text of DOI:10.1002/ejoc.201403296

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