Study of glycosylation with N-trichloroacetyl-D-glucosamine derivatives in the syntheses of the spacer-armed pentasaccharides sialyl lacto-N-neotetraose and sialyl lacto-N-tetraose, their fragments, and analogues

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Carbohydrate Research 336 (2001) 13–46

Study of glycosylation with

N-trichloroacetyl-

D-glucosamine derivatives in the

syntheses of the spacer-armed pentasaccharides sialyl

lacto-N-neotetraose and sialyl lacto-N-tetraose, their

fragments, and analogues

Andrei A. Sherman,^aOlga N. Yudina,^aYury V. Mironov,^bElena V. Sukhova,^a

Alexander S. Shashkov,^aVladimir M. Menshov,^aNikolay E. Nifantiev^a,*

^aN.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky prospect 47,

B-334 Moscow 119991, Russia

^bHigher Chemical College, Russian Academy of Sciences, Miusskaya square 9, Moscow, Russia

Received 10 May 2001; accepted 19 July 2001

Abstract

The syntheses of 2-aminoethyl glycosides of the pentasaccharides Neu5Ac-a(23)-Gal-b(14)-GlcNAc-b(13)-

Gal-b(14)-Glc and Neu5Ac-a(23)-Gal-b(13)-GlcNAc-b(13)-Gal-b(14)-Glc, their asialo di-, tri-, and

tetrasaccharide fragments, and analogues included a systematic study of glycosylation with variously protected

mono- and disaccharide donors derived from N-trichloroacetyl-D-glucosamine of galactose, lactose, and lactosamine

glycosyl acceptors bearing benzoyl protection around the OH group to be glycosylated. Despite the low reactivity of

these acceptors, stereospeciﬁcity and good to excellent yields were obtained with NIS–TfOH-activated thioglycoside

donors of such type, or with AgOTf-activated glycosyl bromides, while other promotors, as well as a trichloroacetim-

idate donor, were less effective, and a b-acetate donor was inactive. In NIS–TfOH-promoted glycosylation with the

thioglycosides, the use of TfOH in catalytic amount led to rapid formation of the corresponding oxazoline, but the

quantity of TfOH necessary for further efﬁcient coupling with an acceptor depended on the reactivity of the donor,

varying from 0.07 equiv for a 3,6-di-O-benzylated monosaccharide derivative to 2.1 equiv for a peracetylated

disaccharide one. In the glycosylation products, the N-trichloroacetyl group was easily converted into N-acetyl by

Keywords: Thioglycosides; 2-Deoxy-2-trichloroacetamido-D-glucose; Sialyl-oligosaccharides

1. Introduction

tions directed towards determining the struc-

tural requirements necessary for speciﬁc

recognition by these proteins, deﬁning the

binding mode, and understanding the biologi-

cal functions of the corresponding natural gly-

coconjugates.¹In this paper we describe the

syntheses of the pentasaccharides sialyl-N-

acetyllactosaminyl-lactose 8, sialyl-iso-N-

Synthetic oligosaccharides and neoglyco-

conjugates thereof are indispensable tools for

the research into carbohydrate lectin interac-

* Corresponding author. Fax: +7-095-1358784.

E-mail address: nen@ioc.ac.ru (N.E. Nifantiev).

PII: S0008-6215(01)00213-0

14

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

Successful preparation of the group of

oligosaccharides 1–10 required an efﬁcient

method for the stereoselective construction of

the b-glycosaminyl linkage. Among the nu-

merous procedures reported, the phthalimido

method^21,22is still the most widely used. How-

ever, rather harsh conditions of dephthaloyla-

tion have led to the development of other

glucosamine derivatives with novel participat-

ing groups. Examples of new methods de-

scribed recently include donors with such

moieties as tetrachlorophthaloyl,^23,24sulfon-

amido,^25,26trichloroethoxycarbonyl,²⁷N,N-

dithiasuccinylimido,^28,29dimethylmaleoyl,^11,30

and N-acetylacetamido.³¹

acetyllactosaminyl-lactose 9, and their asialo

tetra- (5, 6, respectively), tri- (2), and disac-

charide (1) fragments (Fig. 1). For further

comparison, tetrasaccharides bis-(N-acetylglu-

cosaminyl)-lactose

4

and N-acetyllacto-

saminyl-N-acetyllactosamine 7 which are ana-

logues of compounds 2 and 5, respectively,

were also synthesized. All the target com-

pounds were obtained as the spacer-armed

b-2-aminoethyl glycosides for further prepara-

tion of neoglycoconjugates, but oligosaccha-

rides 3 and 10 were prepared as allyl

glycosides as well. The group of oligosaccha-

rides 1–10 was synthesized in order to study

the carbohydrate speciﬁcity of galectins^2–5and

a new colon tumor-associated antigen called

Tk.⁶

Recently, Jacquinet and his coworkers³²

suggested the use of 2-deoxy-2-trichloroac-

etamido derivatives of glucose and galactose

which were then successfully applied for the

syntheses of oligosaccharide fragments of

hyaluronic acid,^33,34chondroitin sulfate,^35–37

and dermatan sulfate.³⁸Compatibility with

such delicate structures, high glycosylation

yields, and complete stereoselectivity reported,

encouraged us to investigate this new promis-

ing type of glucosamine glycosyl donor in the

preparation of oligosaccharides 1–10. In the

present work, an attempt was made to per-

form a systematic study of variously protected

mono- and disaccharide glycosyl donors 11–

14, 18, 19, 23, 24, 30, 36 with the 2-deoxy-2-

trichloroacetamido moiety. Selectively sub-

stituted derivatives of galactose (45), lactose

(41, 43, 50), and lactosamine (55) with benzoyl

protections around the glycosylation position

were employed as glycosyl acceptors.

The syntheses of the glycosyl ceramides of

lacto-N-neotetraose,⁷sialyl-lacto-N-neotetra-

ose,⁸and sialyl-lacto-N-tetraose^9,10have been

described earlier. Also, the syntheses have

been reported of lacto-N-neotetraose,¹¹its

methyl,^12,132-trimethylsilylethyl,¹⁴and benzyl

glycosides,^15,16lacto-N-tetraose,^11,17and its p-

nitrophenyl glycoside.¹⁸Reducing N-acetyllac-

tosamine b(13%) dimer¹⁹and GlcNAc-b(1

3)-Gal disaccharide¹²have already been pre-

pared, as well as methyl glycoside analogues

of tetrasaccharide 4²⁰and trisaccharide 2.¹³

In the present work, oligosaccharides 1 and

4 were synthesized through a scheme^39,40

which involved their preparation as the corre-

sponding allyl glycosides 59 and 61 followed

by conversion into 2-azidoethyl glycosides 60,

62, and deprotection. Other spacer-armed

oligosaccharides 2, 5–9 were obtained by the

shorter route, based on the glycosylation of

the acceptors with the 2-azidoethyl function

already present.

2. Results and discussion

In order to study the various types of N-

Fig. 1. (a) Inner salt. (b) Potassium salt.

trichloroacetyl- -glucosaminyl donors, we se-

D

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

15

Scheme 1. Reagents and conditions: (i) MeONa, MeOH; (ii) PhCH(OMe)₂, 9CSA, DMF, 70 °C; (iii) NaH (3 equiv), BnBr (1.1

equiv), DMF, −15 °C; (iv) Me₃N·BH₃(4 equiv), AlCl₃(6 equiv), H₂O (2 equiv), THF, rt; (v) Ac₂O, Py; (vi) NIS, TfOH (0.1

,

equiv), CH₂Cl₂, MS-4 A, −30 °C.

isolated by crystallization, in 91% yield. In

this reaction, the excess of NaH was used for

protection of the base-liable N-trichloroacetyl

group by metallation.⁴⁴The dianion formed

upon treatment of 15 with excess of NaH was

regioselectively O-alkylated with benzyl bro-

mide and then protonated with acetic acid to

give 16 in high yield. The origin of the regiose-

lective O-alkylation of O,N-bis-anion may be

attributed to the preferential and faster reac-

tion of the hard electrophile benzyl bromide

with the hard nucleophile alcoholate anion,

rather than with the much softer nucleophile

trichloroacetamide anion. Therefore, conduct-

ing the reaction at a low temperature and

using only small excess of benzyl bromide was

essential for avoiding undesired overalkylation

into O,N-bis-benzylated derivative. Similar

conditions have recently been recommended³⁸

for the benzylation of p-methoxyphenyl 4,6-

O-benzylidene-2-deoxy-2-trichloroacetamido-

lected the monosaccharide derivatives thiogly-

cosides 11 and 18, bromide 12, b-acetate 13,

imidate 14, oxazoline 19 (Scheme 1), and their

disaccharide analogues 23, 24, 30, and 36.

Donors 11,³³13,³²and 14³²were synthesized

as described, while the known oxazoline 19³²

was prepared by treatment of thioglycoside 11

with NIS in the presence of a catalytic amount

(0.1 equiv) of TfOH at −30 °C as described

for its galacto analogue.³⁶Glycosyl bromide

12³²was obtained in 95% yield by treatment

of the acetate 13 with HBr–AcOH.⁴¹It is

worth noting that the instability of 12 in

aqueous acidic media required the workup to

be performed as fast as possible, and therefore

lower yields with the need of chromatographic

puriﬁcation were obtained in gram scale reac-

tions. The pure compound 12 was stable and

could be stored at −20 °C for at least 1 year.

In order to prepare the 3,6-di-O-benzylated

thioglycoside 18, triacetate 11 was subjected to

catalytic deacetylation with MeONa followed

by treatment with PhCH(OMe)₂and CSA to

give the highly crystalline benzylidene acetal

15 in 94% yield.

For the benzylation of 15 into 16, various

conditions were tested. Alkylation of 15, with

BnBr promoted by BaO and Ba(OH)₂in

DMF,⁴²gave the crystalline 16 in ca. 50%

yield, and the major byproduct was N,O-bis-

benzylated derivative, while the minor ones

were originated from the loss of the N-

trichloroacetyl group. The use of BnBr, KI,

and Ag₂O in DMF⁴³diminished N,O-bis-ben-

zylation, but gave irreproducible yields of 16

(from 20 to 70%) and recovered the starting

compound, 15.

b-D

-glucopyranoside.

Reductive benzylidene acetal ring opening

in 16 was performed with Me₃N·BH₃and

AlCl₃in THF in the presence of water.⁴⁴In

complete agreement with our previous re-

port,⁴⁴virtually no reaction took place in the

absence of water, indicating that the protic

acid formed from AlCl₃and water is a much

more powerful reagent rather than the equiva-

lent Lewis acid. Acetylation of the crude 4-

OH derivative 17 afforded 18, isolated by

crystallization, in 83% overall yield. Location

of the benzyloxy group at C-6 and not at C-4

in 18 was conﬁrmed by the downﬁeld shift of

C-6 (69.6 ppm) and upﬁeld shift of C-4 (71.4

ppm), while the value l_H-45.19 ppm indicated

that position 4 was acetylated. The isomeric

4-O-benzyl derivative was not detected in the

reaction mixture.

Treatment of 15 with NaH (3 equiv) and

BnBr (1.1 equiv) in DMF at −20 °C gave 16,

16

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

,

Scheme 2. Reagents and conditions: (i) TMSOTf, CH₂Cl₂; (ii) AgOTf, 2,4,6-collidine, MS-4 A, CH₂Cl₂; (iii) 90% aq CF₃CO₂H,

CH₂Cl₂; (iv) Ac₂O, Py.

B B

C C

value 8 Hz of both J

and J

showed b

The key step in the preparation of N-

trichloroacetyl-iso-lactosaminyl donor 23 was

3-O-b-galactosylation of 4,6-O-benzylidenated

thioglycoside 15 (Scheme 2). Recently, glyco-

sylation with methyl glucuronyl trichloroace-

timidates of phenyl 2-deoxy-4,6-O-isopropyl-

1, 2

conﬁguration of both galactose residues in

compound 25, while (16) linkage was de-

duced from the downﬁeld shift of C-6^A69.4

ppm.

For the preparation of N-trichloroacetyl-

lactosaminyl donor 30, 4-O-b-galactosylation

of thioglycoside acceptor 17 was studied

(Scheme 3). The use of temporary 3-O-acetyl

protected galactosyl bromide 29 as a donor

was suggested by a possibility to utilize the

resulting disaccharide derivative in the synthe-

sis of longer oligosaccharide chains containing

repeated lactosamine units. Galactosyl bro-

mide 29 was obtained from the known diol

26⁴⁵through the reaction sequence involving

preparation of 4-O-benzoate 27 via the or-

thoester procedure (99%), 3-O-acetylation fol-

lowed by acetolysis (28, 97%), and ﬁnally

bromination (29, 96%).

idene-1-thio-2-trichloroacetamido-b- -gluco-

D

and galactopyranoside have been studied³⁵

and reported to yield efﬁciently the disaccha-

ride GlcA–GlcN products; however when the

acceptor with galacto conﬁguration was used,

the main product was glucuronic acid thiogly-

coside originated from the aglycon transfer.

TMSOTf promoted glycosylation of 15 (1.6

equiv) with acetylated galactosyl trichloroace-

timidate 21 afforded disaccharide 23 and agly-

con transfer product 22 in 70 and 30% yields

based on the imidate 21, respectively. On the

contrary, in glycosylation of 15 with acetobro-

mogalactose 20 (1.5 equiv) promoted by

AgOTf, thiogalactoside 22 formation was not

detected, and disaccharide 23 was obtained in

Stoichiometric condensation of bromide 29

and thioglycoside acceptor 17 promoted by

AgOTf in CH₂Cl₂(−250 °C) gave the gly-

cosylation product, lactosamine 30, and the

aglycon transfer product, thiogalactoside 31,

60% yield. The b-galactose linkage in 23 was

B B

1, 2

conﬁrmed by the value of J

7.5 Hz (super-

script capital letter denotes the monosaccha-

ride residue starting from the reducing end of

an oligosaccharide as shown in Scheme 2).

Despite the use of 2,4,6-trimethylpyridine, a

branched trisaccharide 25 was also isolated in

11% yield, apparently because of partial cleav-

age of the benzylidene acetal, followed by

primary hydroxy group glycosylation.^†The

in 45 and 40% yields, respectively. The value

B B

of J

8 Hz conﬁrmed the b-Gal linkage,

1, 2

while the preservation of 1-thioethyl moiety in

30 was evident from the characteristic upﬁeld

chemical shift of C-1^A(82.5 ppm). A plethora

of byproducts originating from the aglycon

transfer was obtained, but among them only

trisaccharide 37 (3.2% yield) could be isolated

and characterized. Such acceptor self-conden-

sation has already been observed during gly-

cosylations of thioglycosides in which aglycon

^†The alternative mechanism was proposed by a referee: the

trisaccharide 25 may be formed by glycosylation of com-

pound 23 on O-6, with subsequent cleavage of the benzyli-

dene acetal.

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

17

transfer took place.⁴⁶Neither lowering the

temperature to −40 °C nor changing the sol-

vent to toluene improved the yield of lac-

tosamine 30 and suppressed an aglycon

transfer byprocess.

For the preparation of hexabenzoate 41,

allyl b-lactoside⁵⁰was subjected to dibutyltin-

mediated

3^B-O-(p-methoxy)-benzylation^9,50

into 38. Total benzoylation of the crude 38

followed by removal of the p-methoxybenzyl

group with triﬂuoroacetic acid⁵¹gave 41 (26%

overall yield for three steps) in which the

presence of free OH group at C-3^Bwas evi-

The preparation of the alternative N-

trichloroacetyl-lactosamine thioglycoside 36

was started from the known 2-azido derivative

32⁴⁷which, in turn, is available from

D

-lactal

dent from H NMR spectrum (Table 2, l_H^B_-3

1

by azidonitration methodology. Treatment of

3.98 ppm).

48

the a-bromide 32 with Hg(OAc)₂afforded

The above mentioned 3^B-O-(p-methoxy)-

benzylation of allyl b-lactoside afforded a

dark-brown reaction mixture, from which wa-

ter-soluble 38 was isolated sufﬁciently pure by

simple partitioning between water and

CH₂Cl₂.⁵²The dark-colored organic phase

contained, in turn, an inseparable mixture of

bis-alkylated derivatives 39 and 40. Treatment

of this crude mixture, as described above for

38, afforded readily separable 2^A,3^B- and

3^B,6^B-diols 42 and 43 each in 5% overall yield.

In compound 42, unsubstitution of the 2^Aand

3^Bpositions was deduced from the upﬁeld

shifts of H-2^A(3.70 ppm) and H-3^B(3.91

ppm), while in 43 the values of l^B_H-3(3.92

ppm), l^B_H-6a(2.88 ppm), l_H^B_-6b(2.53 ppm) indi-

cated the 3^B,6^B-diol structure.

the b-acetate 33 nearly quantitatively. Hydro-

genation of 33 could be best performed over

Pd–C in THF in the presence of TsOH to give

amine 34, which was immediately N-

trichloroacetylated into 35 (76% overall). In

contrast, hydrogenation of 33 both in acetic

acid and in methanol, both with and without

1 equiv of dilute aq HCl was accompanied by

partial loss⁴⁹or ON migration of acetyl

groups. The use of Pt–C as a catalyst gave

very similar results as compared to Pd–C in

terms of the reaction rate, the yield of 34, and

the formation of byproducts. Finally, the

ethylthio function was introduced into 35 by

treatment with EtSH and BF₃·Et₂O to give 36,

isolated by crystallization, in 80% yield.

Preparation of glycosyl acceptors derived

from galactose (45), lactose (41, 43, 50), and

lactosamine (55) was the next synthetic stage.

Tri-O-benzoyl galactoside 45 was obtained

from the known diol 44⁵⁰via the orthoester

procedure (Scheme 4).

Conversion of allyl lactoside 41 into 2-azi-

doethyl glycoside 50 was performed following

the reaction sequence described previously^39,40

which involved acetylation of 41 (Ac₂O–Py,

46), ozonolysis followed by reduction with

NaBH₄into alcohol 47, its mesylation (MsCl–

Scheme 3. Reagents and conditions: (i) PhC(OEt)₃, 9CSA, C₆H₆, then aq AcOH; (ii) Ac₂O, Py; (iii) AcOH, Ac₂O, H₂SO₄; (iv)

HBr, AcOH, CH₂Cl₂; (v) AgOTf, CH₂Cl₂, −25 °C; (vi) Hg(OAc)₂, AcOH; (vii) H₂, Pd–C, TsOH, THF; (viii) Cl₃CC(O)Cl, Et₃N;

(ix) EtSH, BF₃·Et₂O, CH₂Cl₂.

18

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

Scheme 4. Reagents and conditions: (i) Bu₂SnO, MeOH, reﬂux, then p-methoxybenzyl chloride, Bu₄NBr, C₆H₆, 50 °C; (ii) BzCl,

Py, CH₂Cl₂; (iii) 90% aq TFA, CH₂Cl₂; (iv) PhC(OEt)₃, TsOH, 40 °C, then aq AcOH.

trisaccharide 56 took place upon treatment of

41 with b-acetate 13 and TMSOTf in

CH₂Cl₂,⁵³whereas with BF₃·Et₂O only

anomerization of the donor into a-acetate was

observed. Glycosyl b-acetates have been stud-

ied and summarized as glycosyl donors of

medium reactivity,⁵⁴which is likely to be in-

sufﬁcient in the case of the low-reactive accep-

tor 41.

Et₃N–CH₂Cl₂, 48, 75% overall), treatment

with sodium azide and 18-crown-6 in DMF

(49, 72%), and ﬁnally 3^B-O-deacetylation

(50, 86%) with AcCl–MeOH.

Condensation of glycosyl bromide 12 with

41, promoted by AgOTf in CH₂Cl₂, afforded

trisaccharide 56 in 88% yield (Scheme 6),

whereas only 25% yield of 56 was obtained in

glycosylation of 41 with imidate 14 and TM-

,

SOTf and MS-4 A in the same solvent (exper-

In order to obtain lactosaminide acceptor

55, the known allyl glucosaminide diol 51⁴²

was 6-O-benzoylated (52) and then glycosy-

lated with selectively protected galactosyl bro-

mide 29 (Scheme 5). This coupling, promoted

by AgOTf, gave disaccharide allyl glycoside 53

in 90% yield. Further transformation of 53

into 2-azidoethyl lactosaminide acceptor 55

was performed in the same manner as de-

scribed above for the transformation of allyl

lactoside 41 into 50.

imental details are not presented). The latter

Glycosylations of the acceptors 41, 43, 45,

50, 55 with mono- and disaccharide donors

11–14, 18, 19 and 23, 24, 30, 36 was studied

next (Table 1). The results obtained indicate,

that bromide- and thioglycoside-type donors

gave higher yields, while trichloroacetimidate

14 was less effective. No formation of the

Scheme 5. Reagents and conditions: (i) BzCl, Et₃N, CH₂Cl₂;

(ii) AgOTf, MS-4 A, CH₂Cl₂; (iii) O₃, 2:1 MeOH–CH₂Cl₂,

then NaBH₄; (iv) MsCl, Et₃N, CH₂Cl₂; (v) NaN₃, 18-crown-6,

DMF, rt; (vi) AcCl, MeOH.

,

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

19

Table 1

Glycosylation of acceptors 41, 43, 45, 50, 55 with donors 11–14, 18, 19, 24, 30, 36 in CH₂Cl₂

Entry

Donor

Acceptor

Promotor

Equiv of TfOH ^a

Product

Isolated yield (%)

,

1

2

3

4

5

6

7

8

9

10

11

12

13

14

11

12

13

14

18

19

24

30

36

41

43

45

50

41

50

41

50

55

50

NIS, TfOH, MS-4 A

1.1

1

0.5

1.5

56

61

59

57

56

58

57

65

66

64

63

68

66

86

65

88

0

,

NIS, TfOH, MS-4 A

,

NIS, TfOH, MS-4 A

,

NIS, TfOH, MS-4 A

AgOTf

,

TMSOTf, MS-4 A

,

BF₃·Et₂O, MS-4 A

0

,

TMSOTf, MS-4 A

25

88

66

70

50

69

76

,

NIS, TfOH, MS-4 A

0.07

1

2.1

2

1

,

TfOH, MS-4 A

NIS, TfOH, MS-4 A

,

NIS, TfOH, MS-4 A

,

NIS, TfOH, MS-4 A

,

NIS, TfOH, MS-4 A

^aThe quantity of triﬂic acid (in equivalents referring to the donor) used in NIS–TfOH promoted glycosylations with

thioglycosides 11, 18, 24, 30, 36, and in TfOH-promoted glycosylation with oxazoline 19.

Scheme 6. Reagents and conditions: see Table 1; (i) O₃, 2:1 MeOH–CH₂Cl₂, then NaBH₄; (ii) MsCl, Et₃N, CH₂Cl₂; (iii) NaN₃,

18-crown-6, DMF, rt.

66% yields, respectively. In all these glycosyla-

tions, pure b-glycosides were obtained solely,

as judged by the value of J_1,2coupling con-

stant (ca. 8 Hz) of the N-trichloroacetyl glu-

cosamine residues (Table 2).

reaction gave acceptor trimethylsilyl ether as

the main product. The b conﬁguration of the

glucosamine residue in 56 was deduced from

C C

1, 2

the value of J

coupling constant 8 Hz, and

a anomer was not detected.

Glycosylation of 2-azidoethyl lactoside ac-

ceptor 50 with di-O-benzylated donor 18 pro-

Glycosylation with thioglycoside 11 could

be best performed using NIS, TfOH, and MS-

55

,

moted by NIS and TfOH afforded the

4 A in CH₂Cl₂at −20 °C. Under these

C C

1, 2

conditions, condensation of 11 with allyl lac-

toside 41 or its 2-azidoethyl congener 50 gave

trisaccharides 56 and 57 in 68 and 65% yields,

respectively. Similar glycosylation with 11 of

allyl galactoside 45 and 3^B,6^B-diol 43 afforded

di- and tetrasaccharides 59 and 61 in 86 and

b-linked trisaccharide 58 (J

7.9 Hz) in 88%

yield. As expected, benzyl protections in-

creased the reactivity of the donor 18 in com-

parison with peracetylated 11. Therefore, a

smaller amount of the acid could be used for

its activation (0.07 equiv for 18 vs. 1.5 equiv

20

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

Table 2

1

Chemical shifts (l, ppm) and coupling constants (J, Hz) for carbohydrate ring protons in H NMR spectra of compounds 1, 3,

5–7, 12, 15, 16, 18, 19, 23–25, 27, 29–31, 33, 35, 36, 41–43, 45, 49, 50, 53, 55, 56, 58, 59, 61, 63–65, 72, 75, 82 in the solvent

speciﬁed (solvent A, CDCl₃; B, D₂O; C, 5:1 CDCl₃–CD₃OD; D, 10:1 CDCl₃–CD₃OD)

Compound

(solvent)

Unit

H-1 (J_1,2

)

H-2 (J_2,3

)

H-3 (J_3,4

)

H-4 (J_4,5

)

H-5 (J_5,6a

)

H-6a (J_6a,6b

)

H-6b (J_6b,5)

1 (B)

3 (B)

Gal^A

4.41 (7.8)

3.56 (10.5)

3.70 (10.7)

3.33 (9.3)

3.59

3.72 (2.9)

3.54

3.62

3.73 (3.3)

3.57 (9.7)

3.67

3.73 (2.9)

3.72

3.67 (2.7)

3.66

3.72 (3.2)

3.85 (10)

3.64 (3.1)

3.70

4.12 (0)

3.43

3.62

4.14 (0)

3.47 (9.8)

3.66

4.16 (0)

3.72

3.92 (0)

3.65

4.17 (0)

3.59 (10)

3.91 (0)

3.70

4.17 (0)

3.73

3.92 (0)

5.28 (10.5)

3.49 (9.3)

3.67 (11.2)

5.19 (7.9)

4.93 (8.2)

3.75

5.33 (0)

4.87 (9.5)

5.26 (0)

3.29 (9.6)

5.27 (0)

5.26 (0)

5.83 (0)

5.98 (0)

4.21 (8.2)

5.77 (0)

5.98 (0)

3.76 (9.5)

5.36 (0)

3.88 (9)

5.36 (0)

3.82 (10.1)

5.36 (0)

4.23 (9.2)

5.50 (0)

4.06 (9.3)

5.46 (0)

4.19 (9.5)

5.27 (0)

5.81 (0)

4.28 (9.6)

5.63 (0)

4.21 (9.5)

5.51 (0)

4.08

3.68

3.73

3.72

3.76

3.80

3.75

3.78

3.83

GlcN^B4.67 (8.6)

3.41 (0)

3.59 (2)

3.68

3.45 (2)

3.61 (1)

3.68

3.59

3.72

3.64 (1.7)

3.69

3.49

3.88 (11.9)

3.97 (12.2)

3.75

3.90 (12.1)

3.97 (12.5)

Glc^A

Gal^B

4.52 (8)

4.43 (7.9)

GlcN^C4.70

3.77

5 (B)

6 (B)

7 (B)

Glc^A

Gal^B

4.54 (8)

4.43 (7.8)

3.38 (8.3)

3.58 (9.4)

3.80

3.53 (9.7)

3.38 (8.4)

3.60 (10)

3.88 (10)

3.52 (9.9)

3.78

3.80–3.72

GlcN^C4.70 (8.2)

3.95

3.86

3.80

3.78

3.82

3.86

Gal^D

Glc^A

Gal^B

4.48 (7.9)

4.53 (8)

4.44 (7.9)

3.80–3.72

3.98 (12.3)

3.79–3.72

GlcN^C4.75 (8.2)

3.89

3.96

3.93

Gal^D

GlcN^A4.58 (8.3)

Gal^B

4.48 (8)

GlcN^C4.70 (8.1)

4.43 (7.7)

3.71

3.61

3.70

3.60

3.79–3.72

3.70–3.80

3.59

3.80

3.71 (2.9)

3.73

Gal^D

4.49 (8)

6.58 (4)

4.78 (10.4)

4.79 (11)

5.17 (9)

3.54 (9.5)

4.25 (10.5)

3.61 (10)

3.81 (10.5)

3.75 (7.9)

4.47 (2.3) ^a

3.73 (9)

5.18 (10)

3.77 (10.5)

5.01 (10.4)

3.55

5.10 (10.5)

5.11 (10.6)

5.42 (10.5)

5.50 (10.4)

3.71 (8.9)

5.58 (10.5)

5.72 (9.9)

3.58 (9)

5.09 (9.5)

4.22 (9.5)

5.12 (8.1)

4.10 (10)

5.08 (10.4)

5.51 (9.2)

5.34 (9.8)

3.70 (9.3)

5.25 (9.6)

5.50 (9.8)

5.31 (10)

5.49 (10.6)

5.48 (9.6)

5.57 (10.4)

5.51 (9.5)

5.38 (9.9)

3.80

3.68 (3.2)

5.43 (10.5)

3.92 (9.4)

3.93 (11.2)

4.31 (7.9)

5.40 (2.3)

4.47 (9)

4.91 (3.3)

4.19 (9.5)

4.78 (3.6)

3.93

4.95 (3.4)

4.80 (3.3)

4.53 (3.5)

5.80 (3.2)

4.00 (8.6)

5.21 (2.5)

5.50 (3.4)

5.09 (9.5)

4.93 (3.2)

5.28 (9.7)

4.97 (3)

5.26 (10.1)

4.95 (3.2)

5.76 (9.2)

3.98 (3)

5.41 (9.4)

3.91 (3.2)

5.70 (9.5)

3.92 (3.3)

4.20 (3.4)

5.83 (9.6)

5.22 (3.4)

5.79 (9.5)

3.99 (2)

3.73

12 (A)

15 (C)

16 (D)

18 (A)

19 (A)

23 (A)

4.28 (4)

3.44 (4.7)

3.45 (5)

3.79 (5)

3.77 (3.2)

3.55 (4.8)

3.75

3.65 (5.2)

3.77 (0)

3.41 (\1)

3.86 (6.7)

3.93

4.34 (12.5)

4.26 (10.4)

4.26 (10.5)

3.68 (0)

4.28 (12.1)

4.35 (11)

4.07

4.15 (12.2)

4.10 (10.7)

4.12 (10.5)

4.06

4.13 (2)

3.59 (10.1)

3.70 (10.5)

3.68 (5)

4.18 (5.8)

3.77

4.07

4.10

4.00 (7)

3.55 (9.5)

4.06 (6.7)

4.05

6.34 (7.5)

GlcN^A5.05 (10)

Gal^B

GlcN^A4.69 (10.3)

Gal^B

4.55 (7.9)

4.76 (7.5)

24 (A)

25 (A)

GlcN^A4.68 (10.4)

Gal^B

Gal^C

4.50 (8)

4.51 (8)

5.21 (3.6)

6.92 (4)

4.05

4.55

27 (A)

29 (A)

30 (A)

4.43

4.41

4.82 (6.4)

3.37 (\1)

3.98 (6.9)

4.33 (6.5)

3.73

4.58 (11.5)

3.64 (10.5)

4.41 (11.2)

4.70 (11.2)

4.42

4.15

4.49 (14.7)

4.12

4.45 (6.4)

3.58 (\1)

4.23 (6.9)

4.45 (6.5)

4.06

GlcN^A4.79 (8.4)

Gal^B

4.83 (8)

4.87 (9.9)

31 (A)

33 (A)

GlcN^A5.51 (8.0)

Gal^B

GlcN^A5.80 (8.5)

Gal^B

4.51 (8)

GlcN^A4.58 (10.4)

4.46 (7.9)

3.87

4.15

35 (A)

36 (A)

41 (A)

42 (A)

43 (A)

3.75 (0)

3.92 (6.8)

3.61

3.89 (3.8)

3.87

3.77 (5.5)

3.72 (0)

3.75

3.82 (0)

3.44 (7)

4.18 (4.8)

3.85 (1)

3.84

4.13 (4.9)

4.12 (6.8)

4.11

4.09 (3.8)

4.58

3.50 (6.5)

4.50 (5.1)

3.73

4.55 (5)

2.53 (7)

4.22 (6.3)

4.49 (4.4)

3.78

4.52

4.09

4.62

Gal^B

Glc^A

Gal^B

Glc^A

Gal^B

Glc^A

Gal^B

4.49 (7.4)

4.78 (8)

4.77 (8)

3.84 (11)

4.61 (11.9)

3.79

4.66 (11.6)

2.88 (11.8)

4.41 (13.2)

4.65 (12.2)

3.78

4.46 (7.7)

4.73 (7.8)

4.75 (7.9)

4.70 (7.8)

4.80 (7.9)

4.80 (7.8)

4.86 (7.9)

4.91 (8.1)

4.89 (8.3)

45 (A)

49 (A)

Glc^A

Gal^B

Glc^A

Gal^B

50 (A)

53 (A)

3.88 (1.6)

3.68

3.76

4.66 (12)

3.49

4.53

4.58 (4.7)

3.49

4.53

GlcN^A4.69 (6.3)

4.09

5.33 (3.5)

Gal^B

4.82 (7.9)

5.61 (10.6)

5.79 (0)

4.02 (6.5)

4.45 (11.5)

4.29 (7)

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

21

Table 2 (Continued)

Compound

(solvent)

Unit

H-1 (J_1,2

)

H-2 (J_2,3

)

H-3 (J_3,4

)

H-4 (J_4,5

)

H-5 (J_5,6a

)

H-6a (J_6a,6b

)

H-6b (J_6b,5)

55 (A)

56 (A)

GlcN^A4.75 (6.2)

3.63 (7.6)

5.47 (9.7)

5.45 (9.8)

5.51 (10)

3.54 (11)

5.51 (9.4)

5.60 (10)

3.21 (9.5)

5.62 (10)

3.58 (9.5)

5.38 (9.5)

5.44 (10)

3.57

4.06

5.69 (0)

3.73

4.54

4.33

4.54

Gal^B

Glc^A

Gal^B

4.80 (8)

4.71 (8)

4.66 (8)

4.11 (3.5)

5.71 (9.5)

4.05 (3.2)

5.23 (10)

5.79 (9.4)

4.15 (3.2)

4.26 (9.5)

4.27 (3.5)

5.31 (10)

5.66 (9.5)

4.02 (4)

5.21 (10)

5.55 (10)

5.72 (9.4)

4.03 (3.3)

5.01 (8.75)

4.92 (3.4)

4.02

3.94 (6.6)

3.73 (3)

3.73 (5)

3.58 (3)

3.80 (3)

3.71 (5)

3.62 (5.6)

4.15

3.65

3.75

3.59 (6.5)

3.59

3.60

3.73 (0)

3.73

3.48 (1.7)

3.81

3.78

3.41

3.90

3.73

3.71 (5)

3.55

4.33 (6.6)

4.40 (4)

3.23 (7.9)

4.06 (4)

4.46 (3)

3.29

3.52 (3.6)

4.51

4.11

4.41

2.89 (6)

4.00

3.75

4.39 (4.3)

3.24

4.00 (8.1)

4.03

4.51

3.20

3.62

4.22

4.39

3.11 (8)

4.00

3.71

4.09 (9.5)

5.57 (0)

4.92 (10)

4.21 (9.4)

5.68 (0)

4.95 (9.2)

5.84 (0)

5.00 (9.5)

4.06 (9)

5.55 (0)

5.04 (10)

4.99 (10)

4.15 (9.3)

5.53 (0)

3.70 (9)

5.30 (0)

4.06

4.47 (12)

3.97 (12)

4.11 (11.5)

4.46

3.91 (11.6)

3.56 (10.3)

4.51

4.24

4.41

3.21 (11)

4.00

3.75

4.45 (12.1)

3.96

4.54 (12.2)

4.03

4.51

3.87

3.71

4.39

3.92 (12)

4.07

GlcN^C4.88 (8)

58 (A)

Glc^A

Gal^B

4.78 (7.8)

4.68 (7.8)

GlcN^C5.17 (7.9)

59 (A)

61 (A)

Gal^A

4.68 (8)

GlcN^B5.02 (8.2)

Glc^A

Gal^B

4.71 (7.9)

4.65 (8)

GlcN^C4.88 (8.3)

GlcN^D4.56 (8)

3.58

63 (A)

64 (A)

Glc^A

Gal^B

4.72 (7.7)

4.66 (8.3)

5.43 (9.5)

5.50 (10)

3.67 (9)

5.04 (10.5)

3.82

GlcN^C4.63 (8.5)

Gal^D

GlcN^A4.69 (5.6)

Gal^B

4.70 (7.6)

4.42 (7.6)

5.76 (9.6)

3.31

4.07

5.78(0)

GlcN^C5.13 (7.5)

4.05 (8.5)

5.22 (3.2)

5.70 (10)

4.04 (3)

4.37 (10)

3.55

3.59 (2.6)

3.46

4.74 (3.5)

5.72 (9.3)

4.05 (3)

3.98 (9.4)

5.74 (9.4)

4.09(2.6)

3.90 (10)

4.12 (8.3)

5.78 (0)

4.12 (10)

5.57 (0)

4.83 (9.5)

3.50

Gal^D

Glc^A

Gal^B

4.88 (8.4)

4.72 (8)

4.61 (8)

5.54 (9.9)

5.45 (9.5)

5.50 (10)

3.18 (10)

3.25 (8.6)

3.50

65 (A)

72 (B)

GlcN^C5.05 (8)

Glc^A

Gal^B

4.43 (8)

4.33 (7.9)

3.51

3.72

3.88

3.89

3.81

4.03 (0)

3.72

3.65

3.92

4.46 (0)

3.22 (3.9)

3.50 (10.6)

4.43 (4.3)

3.28

GlcN^C4.60 (8.6)

GlcN^D4.51 (8.5)

3.62

3.58

3.34–3.39

5.25 (0)

4.15 (9.5)

5.49 (0)

3.33 (9.5)

4.16 (9.4)

5.56 (0)

Gal^D

Glc^A

Gal^B

4.42 (8)

4.65 (7.9)

4.72 (7.8)

4.97 (10.5)

5.47 (9.8)

5.51 (9.7)

3.15 (9.4)

5.47 (9)

5.54 (9.9)

3.13 (10)

3.71

3.97

75 (A)

82 (A)

3.75 (0)

3.71 (5)

3.18 (5.2)

3.77 (4.3)

3.71

4.46 (0)

3.91 (11.5)

3.83 (10.6)

4.49

3.96

3.71 (10.9)

GlcN^C4.94 (8)

Glc^A

Gal^B

4.75 (7.7)

4.65 (8.1)

GlcN^C5.04 (7.9)

3.57 (8.8)

3.44

3.59 (5)

^aJ_2,41.2 Hz.

leading to substantial recovery of the unre-

acted acceptor and a low yield of the tetra-

saccharide product.

for 11), and a higher yield of the trisaccharide

58 (88% vs. 65% of 57) was obtained.

Glycosylations of 2-azidoethyl lactoside 50

and lactosaminide 55 with N-trichloroacetyl

lactosamine thioglycosides 36 and 30 pro-

moted by NIS and TfOH (afforded tetra-

saccharides 63 and 64 in 76 and 69% yields,

respectively (Scheme 7). The b conﬁguration

Attempts to glycosylate lactosides 41 or 50

with benzylidene protected iso-lactosamine

donor 23 were unsuccessful because of the

instability of the acetal protection in 41 and

50 in the medium which is necessary to acti-

vate the glycosylation by the corresponding

oxazoline intermediate formed from the donor

23. Therefore, compound 23 was ﬁrst con-

verted into peracetate 24 by hydrolysis with

aq CF₃CO₂H followed by acetylation. Glyco-

sylation of 41 (1.3 equiv) or 50 (1.16 equiv)

of the linkages formed was conﬁrmed by the

C C

1, 2

values of J

8.5 Hz for 63 and 7.5 Hz for 64,

and no a isomer was detected. If a smaller

quantity of the acid was used, the reaction

stopped at the stage of the transformation of

the donor into the corresponding oxazoline,

22

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

with 24 under the above mentioned conditions

or by adding more after the formation of the

oxazoline.

C C

afforded b-linked tetrasaccharides 65 (J

8

1, 2

C C

1, 2

Hz) and 66 (J

respectively.

8 Hz) in 70 and 50% yields,

Similar behavior was observed when glyco-

sylation of 41 with 11, promoted by MeOTf

,

The previous studies by Jacquinet et al. of

glycosylation with 2-deoxy-2-trichloroac-

and MS-4 A in CH₂Cl₂, was attempted (exper-

imental details are not presented). After stir-

ring overnight at rt, oxazoline 19 and

unreacted acceptor 41 were the only detectable

components in the reaction mixture. However,

they could be coupled into the trisaccharide 56

upon cooling to −20 °C and addition of 1

equiv of TfOH. Replacement of TfOH with

TMSOTf in this reaction gave the trimethylsi-

lyl ether of the acceptor 41 as the main

product. The use of the promoting system

etamido derivatives of

D

-glucose have shown

the oxazolinium cation to be the major reac-

tive intermediate.^32,36In complete agreement

with such a mechanism, treatment³⁶of thio-

glycoside 11 with NIS and a catalytic amount

,

of TfOH in the presence of MS-4 A gave

oxazoline 19,³¹isolated nearly quantitatively.

Furthermore, no glycosylation of 50 with 19

took place under such conditions, and efﬁcient

coupling of the oxazoline 19 and acceptor 50

required the presence of an equivalent amount

of TfOH to afford trisaccharide 57 in 66%

yield (Scheme 6).

,

CuBr₂–Bu₄NBr–AgOTf and MS-4 A in

56

MeNO₂in the glycosylation with 11 led only

to complete decomposition of the donor.

Thus, NIS–TfOH was found to be the promo-

tor of choice for the glycosylation with thio-

glycosides with the 2-deoxy-2-trichloroaceta-

mido moiety.

Conversion of the allyl glycosides 59 and 61

into the corresponding 2-azidoethyl glycosides

60 and 62 was performed by the ozonolysis–

reduction–mesylation–substitution sequence

as described for the transformation of allyl

lactoside 41 into 50 (Scheme 6).

As a general rule, in NIS–TfOH promoted

glycosylation with acetylated thioglycosides

11, 23, 24, 36, the use of triﬂic acid in catalytic

amount (ca. 0.1 equiv) led to quantitative

conversion of the donor into the correspond-

ing oxazoline within minutes, but only a small

amount (ꢀ20%) of the desired glycosylation

product was present in the reaction mixture,

together with the unconsumed acceptor (TLC

data). Much higher concentrations of TfOH

were necessary to bring the glycosylations to

completion, either by using the appropriate

amount of the acid from the very beginning,

Deprotection of di- (60), tri- (56, 57), and

tetrasaccharides 62–64, 66 was studied next

(Scheme 8). Previously, N-deacylation with

methanolic Ba(OH)₂or ammonia has been

Scheme 7. Reagents and conditions: see Table 1.

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

23

Scheme 8. Reagents and conditions: (i) NaOH, MeOH, then addition of Ac₂O; (ii) H₂, Pd–C, H₂O.

employed for N-dichloroacetyl,⁵⁷N-trichloro-

acetyl,^58,59and N-triﬂuoroacetyl⁵⁹derivatives

of 2-amino-2-deoxyglucose. Alternatively, re-

ductive free-radical dechlorination with

Bu₃SnH has been used^{32–34,36–38}for the direct

conversion of the N-trichloroacetyl moiety

into N-acetyl. However, the latter is incom-

patible with the presence of an azido function,

which undergoes reduction by this reagent.

Treatment of compounds 56, 57, 60, 62–64,

66 with sodium hydroxide in aqueous

methanol gave the expected aminopolyols,

which were N-acetylated by addition of acetic

anhydride to the reaction mixtures and af-

forded oligosaccharides 3, 67–72 in high

yields after gel-permeation chromatography.

Subsequent hydrogenation of the azido group,

with concomitant debenzylation in the case of

69, gave the spacer-armed derivatives 1, 2, and

4–7.

It is worth noting that alkaline hydrolysis of

the N-trichloroacetyl group in compounds 64

and 66, in which the neighboring to this func-

tion 3^C-hydroxyl is benzylated or glycosylated,

proceeded much more slowly and required

heating to 50 °C in comparison with 3^C-O-

acetylated derivatives 56, 57, 60, 62, 63. Simi-

lar observations were made during hydrolytic

removal of trichloroacetyl protection from the

pentasaccharides 79, 81, 83 (vide infra), and

by other authors.⁶⁰

In order to obtain sialyl-oligosaccharides

8–10 (Scheme 9), peracetylated sialyl-galacto-

syl trichloroacetimidate 73 was employed as a

common synthetic block. The ﬁve-step synthe-

sis of this compound from sialyl-a-(23%)-lac-

tose trisaccharide, using regioselective removal

of the glucose unit by acetolysis, will be pub-

lished elsewhere. Alternative preparation of

such disaccharide sialyl-galactosyl donors

24

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

from monosaccharides was elaborated by

Hasegawa et al.¹⁰This approach has been

used for the 13-step synthesis of compound

SOTf afforded, after deacetonation, penta-

saccharides 79 and 81 in 75 and 71% yields

based on the imidate, respectively. It is worth

73⁶¹from N-acetylneuraminic acid and

D

-

noting that in these reactions, the use of TM-

63

,

galactose, where the key reaction was glycosy-

lation of 2-trimethysilylethyl 4,6-O-benzyli-

SOTf pre-treated with MS-4 A improved the

coupling yields signiﬁcantly. We suppose that

such pre-treatment with molecular sieves re-

moves traces of the protic acid present in the

catalyst.

dene-b-

peracetylated

Neu5Ac methyl ester.

D

-galactopyranoside acceptor with the

2-phenylthioglycoside

of

For the synthesis of 1^D3^Clinked allyl and

2-aminoethyl glycosides 10 and 9, the trisac-

charides 56 and 57 were deacetylated using

acid-catalyzed methanolysis⁶²to give triols 74

(92%) and 76 (86%), which were then con-

verted into acetonides 75 and 77 in 77 and

90% yields, respectively. Glycosylation of

these acceptors (1.2 equiv) with sialyl-galacto-

syl trichloroacetimidate 73 promoted by TM-

In the H NMR spectra of the initially

1

obtained pentasaccharide acetonides 78 and

80, a substantial broadening of the signals of

Gal^Dresidue was observed. Therefore, com-

plete characterization and assignment of the

¹H NMR spectra was made for the diols 79

and 81 after removal of the acetonide protec-

D D

tions. In these compounds, the value of J

1, 2

coupling constant (7.8 Hz in both 79 and 81)

,

Scheme 9. Reagents and conditions: (i) AcCl, MeOH; (ii) 2,2-dimethoxypropane, 9CSA; (iii) TMSOTf, CH₂Cl₂, MS-4 A, rt; (iv)

90% aq CF₃CO₂H, CH₂Cl₂; (v) NaOH, MeOH, then addition of Ac₂O; (vi) H₂, Pd–C, H₂O; (vii) BF₃·Et₂O, CH₂Cl₂, MS

AW-300, −25 °C.

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

25

indicated the Gal^Danomeric conﬁguration to

be b, and a isomer was not detected.

benzyl ether 84 (91%) after N-acetylation,

which was then hydrogenated to give the

For the synthesis of 1^D4^Clinked pen-

tasaccharide 8, 4^C-hydroxy acceptor 82 was

prepared from the trisaccharide 58. Acid-cata-

lyzed deacetylation⁶²of 58 proceeded slowly,

and partial degradation of the target O-

deacetylated derivative 82 into the products

with much lower chromatographic mobility

occurred prior to complete consumption of

the starting 58. Therefore it was found beneﬁ-

cial to stop the reaction at the stage of ca.

70% of conversion of the starting 58, isolate

the readily separable 82, and repeat O-

deacetylation of the recovered 58. Such treat-

ment gave the requisite trisaccharide acceptor

82 in 87% yield after two cycles.

target 2-aminoethyl glycoside

quantitatively.

8

nearly

As illustrated by the syntheses of pentasac-

charides 8–10, N-trichloroacetyl protected

sialyl-oligosaccharides could be deblocked di-

rectly in a single step by treatment with alkali.

This is an obvious advantage over the widely

used phthalimido group, which can be re-

moved from sialyl-oligosaccharides only after

conversion of the sialic acid methyl ester into

a salt. This additional transformation, conven-

tionally performed by reﬂuxing with lithium

iodide in pyridine, complicates deprotection,

which proved to be troublesome in certain

cases.^64,65

In conclusion, a group of spacer-armed

oligosaccharide chains comprising di-, tri-,

tetra-, and pentasaccharides was synthesized

in order to investigate the carbohydrate spe-

ciﬁcity of galectin receptors. A systematic

study of mono- and disaccharide glycosyl

donors derived from N-trichloroacetyl glu-

cosamine revealed them to be very efﬁcient for

Glycosylation of 82 with sialyl-galactosyl

trichloroacetimidate 73 (2.1 equiv) could be

best performed by promotion with BF₃·Et₂O

(0.1 equiv with respect to the imidate) and

acid washed molecular sieves MS AW-300 in

CH₂Cl₂for 6 days at −27 °C to give the

D D

b-linked pentasaccharide 83 (J

8 Hz) in

1, 2

81% yield. The above mentioned pre-treat-

,

stereospeciﬁc incorporating a b- -GlcNAc

D

ment of the catalyst with MS-4 A gave at least

residue into an oligosaccharide chain, even for

glycosylation of low-reactive glycosyl accep-

tors with benzoyl-protected neighboring hy-

droxy groups. Among the various types of

such donors tested thioglycosides, activated by

NIS–TfOH, and glycosyl bromide, activated

with AgOTf, were found to be the most efﬁ-

cient. Removal of the N-trichloroacetyl group

by alkaline hydrolysis followed by N-acetyla-

tion proved, for base-stable substrates, a rea-

30% increase of the coupling yield. The quan-

tity of the promotor was also crucial in this

reaction, and the use of more BF₃·Et₂O under

the same conditions gave 83 in ca. 50% yield.

Therefore, acid-washed molecular sieves were

,

indispensable because the untreated MS-4 A

were found to be basic enough to consume all

the catalyst and stop the glycosylation.

Deblocking of the pentasaccharides 79 and

81, achieved by simultaneous alkaline hydrol-

ysis of methyl ester, O-acyl protections, and

trichloroacetyl group afforded after N-acety-

lation allyl glycoside 10 (86%) and its 2-azi-

sonable

alternative

to

free

radical

dechlorination.

doethyl

congener,

respectively.

These

compounds were stable as salts, but in acidic

form the sialic acid moiety was prone to par-

tial ab anomerisation. Therefore, allyl gly-

coside 10 was isolated as potassium salt by

Sephadex G-10 gel-permeation chromatogra-

phy in water, while its 2-azidoethyl analogue,

obtained as free acid after TSK HW-40S chro-

matography in 0.1 M aq acetic acid, was

immediately hydrogenated into the inner

amino acid salt 9 (93% overall yield from 81).

In a similar fashion, alkaline deprotection

of the pentasaccharide 83 afforded the di-O-

3. Experimental

General methods.—The reagents were pur-

chased from Fluka and E. Merck, all of the

highest grade available. Molecular Sieves were

activated by heating (180 °C) under vacuum

(0.1 mmHg) for 5–8 h. In glycosylation reac-

tions, freshly activated molecular sieve Union

,

Carbide type 4 A (Fluka), or molecular sieve

acid washed MSAW-300 (Fluka) were used.

The catalyst used for hydrogenolysis was 10%

Pd–C, oxide form, (E. Merck–Schuchardt).

26

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

Column chromatography was performed on

Silica Gel 60 (Fluka, 70–230 mesh), and TLC

was performed on Silica Gel 60 F₂₅₄(E.

Merck, Darmstadt, Germany). For TLC anal-

ysis of deblocked oligosaccharides, solvent

systems 1:2:1 n-butanol–n-propanol–0.1 M

aq HCl (BPHCl), 1:1:1 MeCN–MeOH–water

(AMW), and their combination was used. Op-

tical rotation was measured with JASCO DIP-

360 digital polarimeter at 26–30 °C. NMR

spectra were recorded at 27 °C with Bruker

—To a solution of 11 (5.38 g, 10.8 mmol) in

abs MeOH (15 mL) solid MeONa (54 mg, 1

mmol) was added, and the mixture was kept

for 3 h at rt, then neutralized with KU-2(H⁺)

cation-exchange resin, ﬁltered, concentrated,

and dried in vacuo to give the expected triol,

R_f0.3 (EtOAc), which was used without fur-

ther puriﬁcation. A mixture of the triol, Ph-

CH(OMe)₂(2.5 mL, 16.7 mmol), and

(9)-camphor-10-sulfonic acid (CSA) (30 mg)

in abs DMF (15 mL) was stirred for 2 h at

70 °C, neutralized with Et₃N (0.1 mL), and

evaporated at 80 °C/0.1 mmHg. The solid

residue was reﬂuxed for 1 min in i-PrOH (150

mL) until dissolution; the crystals formed

upon slow cooling were ﬁltered off, washed

with i-PrOH (50 mL), and dried to give 15

(4.2 g, 85%). Recrystallization of the mother

liquor afforded additional crop of 15 (463 mg,

9%): R_f0.5 (3:2 petroleum ether–EtOAc); [h]_D

−53° (c 0.9, 10:1 CH₂Cl₂–MeOH); mp 224–

1

DRX-500 instrument (500 MHz for H and

13

125 MHz for C), assignments were aided by

1

APT, COSY, TOCSY, and H–¹³C correla-

tion spectroscopy. tert-Butyl alcohol was used

as an internal standard for D₂O solutions

(1.24 ppm (¹H) and 30.29 ppm (¹³C)) and

Me₄Si for other ones. Superscript capital let-

ters are used to deﬁne the monosaccharide

residues starting from the reducing end of an

oligosaccharide, i.e. from right to left. Mass

spectra were recorded using either matrix-as-

sisted laser desorption-ionization (MALDI)-

time of ﬂight (TOF) or atmospheric pressure

chemical ionization (APCI) on VISION 2000

mass spectrometer. Melting points were deter-

mined with a Koﬂer apparatus and are

uncorrected.

1

226 °C; NMR (5:1 CDCl₃–CD₃OD): H, see

Table 2 for carbohydrate ring protons; l

7.40–7.25 (m, 5 H, Ph), 5.49 (s, 1 H, PhCH),

2.65 (m, 2 H, SꢀCH₂), 1.19 (t, J 7.4 Hz,

SꢀCH₂CH₃); ¹³C, see Table 4 for carbohydrate

ring carbons; l 162.6 (NꢀC(O)CCl₃), 136.8

(ipso Ph), 129.0, 128.0, 126.0 (Ph), 101.6

(PhCH), 93.0 (CCl₃), 24.2 (S-CH₂), 14.6 (S-

CH₂CH₃); APCI-MS: Calcd for [C₁₇H₂₀Cl₃-

NO₅S+H]⁺: 456.0. Found: 455.6. Anal.

Calcd for C₁₇H₂₀Cl₃NO₅S·0.5 i-PrOH: C,

45.64; H, 4.97; Cl, 21.85; N, 2.88; S, 6.59.

Found: C, 45.51; H, 4.74; Cl, 21.51; N, 3.18;

S, 6.48.

3,4,6-Tri-O-acetyl-2-deoxy-2-trichloroacet-

amido-h- -glucopyranosyl bromide (12).—To

D

a solution of 13 (663 mg, 1.34 mmol) in abs

CH₂Cl₂(4 mL), a solution of HBr in AcOH

(33% of HBr w/v, stabilized with 1% of Ac₂O,

5 mL) was added, and the tightly closed ﬂask

was kept for 15 h at −30 °C. The mixture

was allowed to attain rt, diluted with CH₂Cl₂

(50 mL), and poured into a separating funnel

containing crushed ice. The organic phase was

immediately separated and washed with ice-

cold satd aq NaHCO₃, dried by ﬁltration

through cotton wool, and concentrated to give

bromide 12 (678 mg, 95%) as a white foam: R_f

0.53 (3:2 petroleum ether–EtOAc); [h]_D120°

Ethyl 3-O-benzyl-4,6-O-benzylidene-2-de-

oxy-1-thio-2-trichloroacetamido-i- -glucopy-

D

ranoside (16).—NaH (60% suspension in

mineral oil, 3 g, 75 mmol) was added portion-

wise to abs DMF (150 mL) at −20 °C under

Ar (the solvent should be redistilled if any gas

evolution is observed at this stage). The mix-

ture was stirred until the homogeneous sus-

pension was formed and solid 15 (12.12 g,

26.5 mmol) was added portionwise during 15

min. The stirring was continued until gas evo-

lution ceased (ca. 1 h at −20 °C), BnBr (3.6

mL, 30 mmol) was added, and the mixture

was stirred for 1.5 h at −15 °C, then cooled

to −40 °C and glacial AcOH (7.5 mL, 125

mmol) was carefully added dropwise. The re-

action mixture was allowed to attain rt slowly,

1

(c 1, CHCl₃), lit.³²129°; NMR (CDCl₃): H,

the spectrum was identical to the published

one;³²see Table 2 for carbohydrate ring pro-

tons; l 7.09 (d, 1 H, J_N-H,28.5 Hz, N-H), 2.10,

2.07, 2.03 (3 s, 9 H, 3 OAc). Anal. Calcd for

C₁₄H₁₇BrCl₃NO₈: C, 32.74; H, 3.34; N, 2.73.

Found: C, 32.95; H, 3.50; N, 2.99.

Ethyl 4,6-O-benzylidene-2-deoxy-1-thio-2-

trichloroacetamido-i- -glucopyranoside (15).

D

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

27

137.7, 137.4 (2 ipso Ph), 128.3–127.6 (Ph),

92.2 (CCl₃), 74.3 (PhCH₂), 73.4 (PhCH₂), 24.6

(SꢀCH₂), 20.7 (OꢀC(O)CH₃), 15.1 (SꢀCH₂-

CH₃). Anal. Calcd for C₂₆H₃₀Cl₃NO₆S: C,

52.85; H, 5.12; Cl, 18.00; N, 2.37; S, 5.43.

Found: C, 53.04; H, 5.21; Cl, 17.79; N, 2.30;

S, 5.36.

diluted with EtOAc (500 mL), washed with

water, satd aq NaHCO₃, dried, and concen-

trated. Crystallization from i-PrOH (100 mL)

gave 16 (13.18 g, 91%) as ﬁne powder: R_f0.75

(3:2 petroleum ether–EtOAc); [h]_D−48° (c 1,

acetone); mp 245–247 °C; NMR (10:1

1

CDCl₃–CD₃OD): H, see Table 2 for carbo-

(3,4,6-Tri-O-acetyl-1,2-dideoxy-h- -gluco-

D

hydrate ring protons; l 7.40–7.12 (m, 10 H,

Ph), 5.50 (s, 1 H PhCH), 4.77 (d, 1 H, J 11.2

Hz, PhCH₂), 4.62 (d, 1 H, PhCH₂), 2.61 (m, 2

H, SꢀCH₂), 1.15 (t, 3 H, J 7.5 Hz,

SꢀCH₂CH₃); ¹³C, see Table 4 for carbohydrate

ring carbons; l 162.3 (NꢀC(O)CCl₃), 137.6,

136.9 (2 ipso Ph), 128.8–125.7 (Ph), 101.0

(PhCH), 74.4 (PhCH₂), 24.1 (S-CH₂), 14.6

(SCH₂CH₃); APCI-MS: Calcd for [C₂₄H₂₆Cl₃-

NO₅S]⁺: 545.1. Found: 544.8. Anal. Calcd for

C₂₄H₂₆Cl₃NO₅S·i-PrOH: C, 53.43; H, 5.65; N,

2.31; S, 5.28. Found: C, 53.45; H, 5.52; N,

2.15; S, 5.74.

pyranoso)4,5 - dihydro - 2 - trichloromethyl - [2,1-

d]2-oxazole (19).—A mixture of thioglycoside

,

11 (238 mg, 0.48 mmol) and MS-4 A (300 mg)

in abs CH₂Cl₂(5 mL) was stirred under Ar for

1 h, NIS (126 mg, 0.56 mmol) was added, and

the reaction mixture was cooled to −30 °C.

TfOH (0.003 mL, 0.034 mmol) was added,

and after stirring for 30 min at this tempera-

ture, the reaction was terminated with Et₃N

(0.1 mL); the mixture was ﬁltered through a

pad of Celite, diluted with CH₂Cl₂, washed

with satd aq NaHCO₃, 3 M aq Na₂S₂O₃,

dried, and concentrated. Chromatography

(petroleum ether–EtOAc) of the residue on a

column of silica gel (20 g) gave 19 (202 mg,

97%) as a syrup: R_f0.4 (3:1 toluene–EtOAc);

[h]_D20° (c 1, CHCl₃), lit.³²[h]_D22.5°; NMR

Ethyl 4-O-acetyl-3,6-di-O-benzyl-2-deoxy-

1-thio-2-trichloroacetamido-i- -glucopyrano-

D

side (18).—Me₃N·BH₃(3.79 g, 52 mmol) was

added with stirring under Ar to a solution of

16 (7.11 g, 13 mmol) in abs THF (195 mL,

freshly distilled from Na–Ph₂CO), followed

by anhyd AlCl₃(10.4 g, 78 mmol). After the

reagents had dissolved, water (0.47 mL, 26

mmol) was added dropwise and stirring was

continued for 6 h at rt until the complete

conversion of the starting 16 into the product

17 (R_f0.33 in 4:1 toluene–EtOAc). The reac-

tion was terminated by addition of water (100

mL) followed by 1 M aq HCl (100 mL) and

extracted with EtOAc (3×200 mL), the ex-

tracts were washed with brine, dried, concen-

trated, and dried in vacuo. The crude 17

obtained was acetylated with Ac₂O (10 mL) in

Py (20 mL) overnight at rt, then coevaporated

with toluene (4×50 mL). Crystallization from

i-PrOH (70 mL) gave 18 (6.38 g, 83%) as

needles: R_f0.5 (4:1 toluene–EtOAc); [h]_D

−15° (c 1, CHCl₃); mp 156–158 °C; NMR

1

(CDCl₃): H, the spectrum was identical to the

published one;³²see Table 2 for carbohydrate

ring protons; l 2.12 (s, 3 H, Ac), 2.09 (s, 3 H,

Ac), 2.07 (s, 3 H, Ac); ¹³C, l 170.4, 169.4,

168.9 (3 OC(O)CH₃), 163.1 (C-CCl₃), 103.1

(C-1), 68.8, 68.5, 67.5, 64.5, 63.4 (C-2–C-6),

20.8

(OC(O)CH₃).

Anal.

Calcd

for

C₁₄H₁₆Cl₃NO₈: C, 38.87; H, 3.73; Cl, 24.58; N,

3.24. Found: C, 38.94; H, 3.65; Cl, 24.79; N,

3.12.

Ethyl O-(2,3,4,6-tetra-O-acetyl-i-

topyranosyl) - (13) - 4,6 - O - benzylidene - 2-

deoxy-1-thio-2-trichloroacetamido-i- -gluco-

pyranoside (23) and ethyl O-(2,3,4,6-tetra-O-

acetyl-i- -galactopyranosyl)-(13)-O-[2,3,4,

6-tetra-O-acetyl-i- -galactopyranosyl-(1

6)]-2-deoxy-1-thio-2-trichloroacetamido-i-

D

-galac-

D

-glucopyranoside (25).—(a) A mixture of

acetobromogalactose 20 (671 mg, 1.63 mmol),

acceptor 15 (513 mg, 1.12 mmol), 2,4,6-col-

lidine (0.1 mL, 0.8 mmol), and MS-4 A (1.5 g)

1

(CDCl₃): H, see Table 2 for carbohydrate

ring protons; l 7.45–7.31 (m, 10 H, Ph), 7.12

(d, 1 H, J_N-H,210 Hz, N-H), 4.79 (d, 1 H, J 12

Hz, PhCH₂), 4.68 (d, 1 H, PhCH₂), 4.62 (s, 2

H, PhCH₂), 2.82 (m, 2 H, SꢀCH₂), 1.98 (s, 3

,

in abs CH₂Cl₂(25 mL) was stirred for 2 h

under Ar, then cooled to −30 °C and pow-

dered AgOTf (550 mg, 2.14 mmol) was added.

During 6 h of stirring, the mixture was al-

lowed to attain 0 °C, then terminated with

Et₃N (0.5 mL), diluted with CH₂Cl₂, ﬁltered

13

H, Ac), 1.40 (t, 3 H, J 6 Hz, SꢀCH₂CH₃); C,

see Table 4 for carbohydrate ring carbons; l

169.7 (OꢀC(O)CH₃), 161.7 (NꢀC(O)CCl₃),

28

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

NaHCO₃, dried, and concentrated. Chro-

matography (2:3 EtOAc–petroleum ether) of

the residue on a column of silica gel (20 g)

afforded thiogalactoside 22 (13 mg, 30%),

which was found to be identical in all respect

to the authentic sample obtained upon treat-

through a pad of Celite, washed with satd aq

NaHCO₃, 3 M aq Na₂S₂O₃, dried, and con-

centrated.

Chromatography

(2:33:2

EtOAc–petroleum ether) of the residue on a

column of silica gel (60 g) afforded (in order

of elution) disaccharide 23 (529 mg, 60%) and

trisaccharide 25 (124 mg, 11%).

ment of 1,2,3,4,6-penta-O-acetyl-b- -galacto-

D

pyranose with EtSH and ZnCl₂as described.⁶⁶

Data for disaccharide 23: white foam, R_f

0.21 (2:3 EtOAc–petroleum ether); [h]_D−28°

Next eluted was disaccharide 23 (61 mg, 70%).

1

(c 2, CH₂Cl₂); NMR (CDCl₃): H, see Table 2

Ethyl O-(2,3,4,6-tetra-O-acetyl-i- -galac-

D

for carbohydrate ring protons; l 7.31–7.50

(m, 5 H, Ph), 7.15 (d, 1 H, J_N-H,29 Hz, N-H),

5.54 (PhCH), 2.71 (m, 2 H, S-CH₂), 2.11, 2.03,

1.95, 1.89 (4 s, 12 H, 4 OAc), 1.25 (t, 3 H, J 6

topyranosyl)-(13)-4,6-di-O-acetyl-2-deoxy-

1-thio-2-trichloroacetamido-i- -glucopyrano-

D

side (24).—To a solution of 23 (225 mg, 0.29

mmol) in CH₂Cl₂(5 mL), 90% aq CF₃CO₂H

(0.4 mL) was added. After stirring for 1 h at

rt, the mixture was poured into satd aq

NaHCO₃and extracted with CH₂Cl₂. The ex-

tracts were concentrated, the residue was dis-

solved in pyridine (2 mL) and treated with

Ac₂O (1.5 mL) overnight at rt. Coevaporation

with toluene followed by chromatography

(benzene2:1 benzene–EtOAc) on a column

of silica gel (30 g) afforded 24 (182 mg, 81%)

as a white foam: R_f0.25 (1:2 EtOAc–ben-

zene); [h]_D−18° (c 2, CH₂Cl₂); NMR

13

Hz, SꢀCH₂CH₃); C, l 170.3 (4 OC(O)CH₃),

161.5 (NꢀC(O)CCl₃), 136.9 (ipso Ph), 129.2,

128.2, 126.0 (Ph), 101.1 (PhCH), 99.4 (C-1^B),

83.1 (C-1^A), 78.6, 77.1 (C-3^A, C-4^A), 61.1 (C-

6^B), 57.1 (C-2^A), 24.7 (SꢀCH₂), 20.6

(OC(O)CH₃), 14.9 (SꢀCH₂CH₃); APCI-MS:

Calcd for [C₃₁H₃₈Cl₃NO₁₄S+H₂O]⁺803.1.

Found 802.7. Calcd for [C₃₁H₃₈Cl₃NO₁₄Sꢀ

C₂H₅SH]⁺724.1. Found 723.8. Anal. Calcd

for C₃₁H₃₈Cl₃NO₁₄S: C, 47.31; H, 4.87; Cl,

13.51; N, 1.78; S, 4.07. Found: C, 47.26; H,

4.79; Cl, 13.20; N, 1.93; S, 3.99.

1

(CDCl₃): H, see Table 2 for carbohydrate

Data for trisaccharide 25: white foam, R_f

0.2 (3:2 EtOAc–petroleum ether); [h]_D−9° (c

ring protons; l 7.01 (d, J_N-H,28.7 Hz, NꢀH),

2.62 (m, 2 H, SꢀCH₂), 2.09 (s, 3 H, Ac), 2.01

(4 s, 12 H, 4 Ac), 1.84 (s, 3 H, Ac), 1.19 (t, 3

H, J 7.5 Hz, SꢀCH₂CH₃); ¹³C, l 170.7–169.2

(OC(O)CH₃), 161.5 (NꢀC(O)CCl₃), 100.3 (C-

1^B), 92.5 (CCl₃), 82.8 (C-1^A), 62.5, 60.9 (C-6^A,

C-6^B), 56.6 (C-2^A), 24.2 (SꢀCH₂), 20.7–20.4

(OC(O)CH₃), 14.9 (SꢀCH₂CH₃). Anal. Calcd

for C₂₈H₃₈Cl₃NO₁₆S: C, 42.95; H, 4.89; Cl,

13.58; N, 1.79; S, 4.09. Found: C, 43.16; H,

4.83; Cl, 13.26; N, 2.08; S, 4.0.

1

2, CH₂Cl₂); NMR (CDCl₃): H, see Table 2

for carbohydrate ring protons; l 7.18 (d, 1 H,

J_N-H,28.4 Hz, N-H), 2.54 (m, 2 H, SꢀCH₂),

2.07, 1.95, 1.86 (8 s, 24 H, 8 Ac), 1.15 (t, 3 H,

J 7.5 Hz, SꢀCH₂CH₃); ¹³C, l 170.4–169.5

(OC(O)CH₃), 161.7 (NꢀC(O)CCl₃), 101.6,

100.8 (C-1^B, C-1^C), 92.5 (CCl₃), 83.1 (C-1^A),

82.2 (C-3^A), 79.2 (C-5^A), 69.4 (C-6^A), 61.2,

61.1 (C-6^B, C-6^C), 56.0 (C-2^A), 24.1 (SꢀCH₂),

20.7-20.4 (OC(O)CH₃), 14.9 (SꢀCH₂CH₃).

Anal. Calcd for C₃₈H₅₂Cl₃NO₂₃S: C, 44.35; H,

5.09; N, 1.36. Found: C, 44.51; H, 4.97; N,

1.19.

Methyl 2,4,6-tri-O-benzoyl-h- -galactopy-

D

ranoside (27).—A mixture of diol 26⁴⁵(4.48 g,

11.1 mmol), PhC(OEt)₃(7.3 mL, 32.3 mmol)

and 9CSA (50 mg) in abs benzene (15 mL)

was stirred overnight at rt. Acetic acid (80%

aq, 100 mL) was added, and the biphasic

mixture was stirred vigorously for 1 h, then

diluted with CH₂Cl₂, washed with water, satd

aq NaHCO₃, dried, concentrated, and coevap-

orated with toluene. Chromatography (tolu-

ene1:1 toluene–EtOAc) of the residue on a

column of silica gel (150 g) gave 27 (5.6 g,

99%) as a white foam: R_f0.45 (4:1 toluene–

(b) A mixture of trichloroacetimidate 21 (52

mg, 0.11 mmol), acceptor 15 (83 mg, 0.18

,

mmol), and MS-4 A (300 mg) in abs CH₂Cl₂

(3 mL) was stirred for 1 h under Ar, then

cooled to −10 °C and neat TMSOTf (0.006

mL, 0.033 mmol) was added. After stirring for

0.5 h at −10 °C, the reaction was terminated

by addition of solid NaHCO₃(100 mg), the

mixture was ﬁltered through a pad of Celite,

diluted with CH₂Cl₂, washed with satd aq

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

29

(3 d, 2 H each, J 7.6 Hz, ortho protons of 3

Bz), 7.70–7.40 (m, 9 H, Ph), 1.87 (s, 3 H, Ac).

Anal. Calcd for C₂₉H₂₅BrO₉: C, 58.30; H,

4.22; Br, 13.37. Found: C, 58.44; H, 4.34; Br

13.39.

EtOAc); [h]_D120° (c 1, CHCl₃); NMR

1

(CDCl₃): H, see Table 2 for carbohydrate

ring protons; l 8.12–8.01 (3 d, 6 H, J 7.5 Hz,

ortho-protons of 3 Bz), 7.65–7.49 (m, 9 H,

Ph), 3.42 (s, 3 H, OMe), 2.85 (broaden s, 1 H,

OH). Anal. Calcd for C₂₈H₂₆O₉: C, 66.40; H,

5.17. Found: C, 66.44; H, 5.28.

Ethyl O-(3-O-acetyl-2,4,6-tri-O-benzoyl-i-

D

-galactopyranosyl)-(14)-3,6-di-O-benzyl-

2-deoxy - 1 - thio - 2 - trichloroacetamido - i -

glucopy-ranoside (30), ethyl 3-O-acetyl-2,4,6-

tri-O-benzoyl-1-thio-i- -galactopyranoside

(31), and ethyl O-(3-O-acetyl-2,4,6-tri-O-ben-

zoyl-i- -galactopyranosyl)-(14)-O-(3,6-di-

O-benzyl-2-deoxy-2-trichloroacetamido-i-

glucopyrano-syl)-(14)-O-3,6-di-O-benzyl-2-

deoxy-1-thio-2-trichloroacetamido-i- -gluco-

D

-

1,3-Di-O-acetyl-2,4,6-tri-O-benzoyl-h- -

D

galactopyranose (28).—Compound 27 (5.5 g,

10.9 mmol) was acetylated with Ac₂O (2 mL)

in Py (10 mL) for 2 days at rt. MeOH (5 mL)

was added, and the reaction mixture was kept

overnight at 0 °C, then coevaporated with tol-

uene and dried in vacuo to give the expected

3-O-acetyl derivative (5.9 g, quant.) as a white

foam: R_f0.3 (13:1 toluene–EtOAc); [h]_D113°

(c 1, CHCl₃). Anal. Calcd for C₃₀H₂₈O₁₀: C,

65.69; H, 5.17. Found: C, 65.38; H, 5.26.

To a cold (0 °C) solution of this compound

(1.5 g, 2.76 mmol) in 1:1 AcOH–Ac₂O (35

mL) was added a cold solution of concd

H₂SO₄(3.67 mL) in 1:1 AcOH–Ac₂O (35

mL). The reaction mixture was allowed to

attain rt slowly, and kept overnight. The mix-

ture was poured into crushed ice (500 g),

stirred for 2 h, and extracted with CH₂Cl₂

(3×50 mL). The extracts were washed with

water, satd aq NaHCO₃, and water, coevapo-

rated with toluene, and dried in vacuo. Chro-

matography (10:1 toluene–EtOAc) of the

residue on a short column of silica gel gave 28

(1.5 g, 96%) as a white foam: R_f0.27 (13:1

toluene–EtOAc); [h]_D98° (c 1, CHCl₃); NMR

D

-

D

pyranoside (37).—A mixture of bromide 29

(570 mg, 0.95 mmol), acceptor 17 (525 mg,

,

0.95 mmol), and MS-4 A (1 g) in abs CH₂Cl₂

(10 mL) was stirred under Ar for 1 h, then

cooled to −25 °C and powdered AgOTf (470

mg, 1.83 mmol) was added. Under stirring,

the reaction mixture was allowed to attain

0 °C during 1.5 h, then quenched with Et₃N (5

mL), ﬁltered through a pad of Celite, diluted

with CH₂Cl₂(150 mL), washed with satd aq

NaHCO₃, 3 M aq Na₂S₂O₃, dried, and con-

centrated. Chromatography (toluene3:1 tol-

uene–EtOAc) of the residue on a column of

silica gel (50 g) afforded, in order of elution,

thiogalactoside 31 (220 mg, 40%) and a mixed

fraction. It was subjected to gel-permeation

chromatography on a 3×70 cm column of

Bio-Beads SX3 in toluene to give lactosamine

30 (461 mg, 45%) and trisaccharide 37 (48 mg,

3.2%).

1

(CDCl₃): H, l 8.15 (d, 2 H, J 7.9 Hz, ortho

protons of 1 Bz), 8.00 (t, 4 H, J 7.7 Hz, ortho

protons of 2 Bz), 7.68–7.39 (m, 9 H, Ph), 6.70

(d, 1 H, J_1,23.4 Hz, H-1), 5.99 (d, 1 H, J_4,33.3

Hz, H-4), 5.74 (t, 2 H, H-2, H-3), 4.62 (m, 2

H, H-5, H-6a), 4.36 (dd, 1 H, J_6a,6b11, J_6b,56.5

Hz, H-6b), 2. 18 (s, 3 H, Ac), 1.96 (s, 3 H,

Ac). Anal. Calcd for C₃₁H₂₈O₁₁: C, 64.58; H,

4.89. Found: C, 64.67; H, 5.00.

Data for lactosamine 30: R_f0.43 (5:1 tolu-

ene–EtOAc); [h]_D−16° (c 1, CHCl₃); NMR

1

(CDCl₃): H, see Table 2 for carbohydrate

ring protons; l 8.09–7.96 (2 d, 6 H, ortho

protons of 3 Bz), 7.68-7.15 (m, 19 H, Ph), 6.96

(d, 1 H, J_N-H,29 Hz, N-H), 5.11, 4.79, 4.77,

4.40 (4 d, 1 H each, J 11 Hz, 4 PhCH₂), 2.60

(m, 2 H, SꢀCH₂), 1.89 (s, 3 H, Ac), 1.20 (t, 3

13

3-O-acetyl-2,4,6-tri-O-benzoyl-h- -galacto-

D

H, J 7.2 Hz, SꢀCH₂CH₃); C, see Table 4 for

pyranosyl bromide (29).—Treatment of diac-

etate 28 (1 g, 1.82 mmol) in abs CH₂Cl₂(2.5

mL) with HBr–AcOH (5 mL) for 3 h at rt

and subsequent aqueous workup as described

for the preparation of 12 gave 29 (1.012 g,

97%) as a white foam: R_f₁0.32 (13:1 toluene–

EtOAc); NMR (CDCl₃): H, see Table 2 for

carbohydrate ring protons; l 8.11, 8.04, 8.01

carbohydrate

ring

carbons;

l

170.3

(OC(O)CH₃), 165.9–165.1 (3 PhC(O)O), 161.7

(NꢀC(O)CCl₃), 138.2, 137.9 (2 ipso Bn),

133.7–127.8 (Ph), 74.5, 73.7 (2 PhCH₂), 24.6

(SꢀCH₂), 20.7 (OC(O)CH₃), 15.1 (Sꢀ

CH₂CH₃). Anal. Calcd for C₅₃H₅₂Cl₃NO₁₄S:

C, 59.75; H, 4.92; N, 1.31; S, 3.01. Found: C,

59.76; H, 5.15; N, 2.0; S, 2.66.

30

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

Ethyl O-(2,3,4,6-tetra-O-acetyl-i-

topyranosyl)-(14)-3,6-di-O-acetyl-2-deoxy-

1-thio-2-trichloroacetamido-i- -glucopyran-

D

-galac-

Data for thiogalactoside 31: R_f0.47 (5:1

toluene–EtOAc); [h]_D47° (c 1, CH₂Cl₂); mp

124–126 °C (from EtOH); NMR (CDCl₃): ¹H,

see Table 2 for carbohydrate ring protons; l

8.22 (d, 2 H, J 7.5 Hz, ortho protons of 1 Bz),

8.07 (2 d, 4 H, ortho protons of 2 Bz); 7.70–

7.35 (m, 9 H, Ph), 2.85 (m, 2 H, SꢀCH₂), 1.90

(s, 3 H, Ac), 1.35 (t, 3 H, J 7 Hz SꢀCH₂CH₃);

¹³C, see Table 4 for carbohydrate ring car-

bons; l 170.1 (OC(O)CH₃), 165.9–165.2 (3

PhC(O)O), 133.6–128.1 (Ph), 24.4 (SꢀCH₂),

20.4 (OC(O)CH₃), 14.9 (SꢀCH₂CH₃). Anal.

Calcd for C₃₁H₃₀O₉S: C, 64.35; H, 5.23; S,

5.54. Found: C, 64.65; H, 5.27; S, 5.13.

D

oside (36).—To a solution of azide 33 (420

mg, 0.64 mmol) and p-TsOH·H₂O (121 mg,

0.64 mmol) in THF (12 mL) Pd–C (40 mg)

was added, the mixture was degassed under

vacuum with stirring, reﬁlled with hydrogen,

and stirred at rt. After 6 h, TLC indicated

complete conversion into amine 34 (R_f0.37 in

50:3:2 CH₂Cl₂–MeOH–AcOH), and the reac-

tion mixture was cooled to 0 °C. Trichloro-

acetyl chloride (0.31 mL, 2.8 mmol) was

added, followed by Et₃N (0.58 mL, 4.2 mmol)

and after stirring for 1 h at 0 °C, the mixture

was ﬁltered through a pad of Celite, diluted

with CH₂Cl₂(50 mL), washed with satd aq

NaHCO₃, dried, and concentrated. The

residue was ﬁltered through a short column of

silica gel in 1:1 EtOAc–toluene to give 35 (375

mg, 76%) as a white foam: R_f0.44 (1:1

EtOAc–toluene); ¹H NMR (CDCl₃): see

Table 2 for carbohydrate ring protons; l 7.30

(d, 1 H, J_N-H,29 Hz, N-H), 2.16, 2.15, 2.10,

2.09, 2.07, 2.06, 1.98 (7 s, 21 H, 7 Ac); ¹³C

NMR (CDCl₃): l 170.7–169.1 (OꢀC(O)CH₃),

162.4 (NꢀC(O)CCl₃), 101.3 (C-1^B), 91.9 (C-

1^A), 75.7, 73.9, 71.7, 70.9, 70.8, 69.0, 66.6

(carbohydrate ring carbons), 61.8, 60.8 (C-

6^A,C-6^B), 54.5 (C-2^A), 20.7–20.4 (OꢀC(O)-

CH₃).

Data for trisaccharide 37: R_f0.42 (5:1 tolu-

ene–EtOAc); [h]_D−27° (c 1, CH₂Cl₂); NMR

1

(CDCl₃): H, l 8.10–7.90 (m, 6 H, ortho

protons of 3 Bz), 7.69–7.05 (m, 29 H, Ph),

6.81 (d, 1 H, J_N^B_A_−H,

7.8 Hz, NꢀH^B), 6.45

B

(d, 1 H, J_N−H

8.2²Hz, NꢀH^A), 5.74 (d, 1

A

,2

C C

4, 3

C C

2, 1

H, J

2, 3

3.3 Hz, H-4^C), 5.59 (dd, 1 H, J

8,

C C

J

10.2 Hz, H-2^C), 5.18 (dd, 1 H, H-3^C), 5.17

(d, 1 H, J 10.5 Hz, PhCH₂), 4.97 (d, 1 H, J

11.6 Hz, PhCH₂), 4.81 (d, 1 H, H-1^C), 4.74 (d,

B B

1, 2

A A

1, 2

J

6.7 Hz, H-1^B), 4.70 (d, J

7.5 Hz,

H-1^A), 2.70 (m, 2 H, SꢀCH₂), 1.88 (s, 3 H,

13

Ac), 1.33 (t, 3 H, J 7.3 Hz SꢀCH₂CH₃); C, l

170.2 (NꢀC(O)CH₃), 165.9–164.9 (3 PhC-

(O)O), 161.7 (2 NꢀC(O)CCl₃), 138.3–137.7 (4

ipso Bn), 133.8–127.5 (Ph), 100.0, 98.9 (C-1^C,

C-1^B), 82.9 (C-1^A), 61.4 (C-6^C), 57.8 (C-2^B),

56.2 (C-2^A), 24.5 (SꢀCH₂), 20.7 (OC(O)CH₃),

15.1 (SꢀCH₂CH₃). Anal. Calcd for C₇₅H₇₄Cl₆-

N₂O₁₉S: C, 58.04; H, 4.81; N, 1.80; S, 2.07.

Found: C, 58.09; H, 4.88; N, 1.66; S, 1.92.

1,3,6-Tri-O-acetyl-2-azido-2-deoxy-4-O-

To a solution of 35 (277 mg, 0.35 mmol)

and EtSH (0.044 mL, 0.6 mmol) in abs

CH₂Cl₂(5 mL) BF₃·Et₂O (0.067 mL, 0.53

mmol) was added. After stirring for 2 h at rt

the reaction mixture was poured into satd aq

NaHCO₃(30 mL) and extracted with CH₂Cl₂

(3×30 mL). The extracts were dried and con-

centrated, the residue was dissolved in EtOAc

(0.3 mL), i-PrOH (3 mL) was added, followed

by petroleum ether (3 mL), and the mixture

was kept for 3 days at +5 °C. The crystals

formed were ﬁltered off and washed with cold

i-PrOH to give 36 (225 mg, 80%): R_f0.28 (2:3

EtOAc–toluene); mp 196–198 °C; [h]_D−93°

(2,3,4,6-tetra-O-acetyl-i-

D

-galactopyranosyl)-

i-D

-glucopyranose (33).—A mixture of 32⁴⁷

(682 mg, 1 mmol) and Hg(OAc)₂(637 mg, 2

mmol) in glacial AcOH (10 mL) was stirred

for 17 h at rt, then diluted with CH₂Cl₂(100

mL), washed with satd aq KBr and water,

dried, and concentrated. Chromatography

(benzene2:1 benzene–EtOAc) of the residue

on a short column of silica gel afforded 33

(635 mg, 96%) as a white foam: R_f0.45 (1:1

EtOAc–toluene); [h]_D+4° (c 1, CH₂Cl₂);

1

(c 1, CH₂Cl₂); NMR (CDCl₃): H, see Table 2

1

for carbohydrate ring protons; l 7.19 (d,

J_N-H,29.4 Hz, NꢀH), 2.71 (m, 2 H, SꢀCH₂),

2.13 (s, 3 H, Ac), 2.10 (s, 3 H, Ac), 2.08 (s, 6

H, 2 Ac), 2.06 (s, 3 H, Ac), 1.95 (s 3 H, Ac),

1.27 (t, 3 H, J 7.5 Hz, SꢀCH₂CH₃); ¹³C, l

NMR (CDCl₃): H, see Table 2 for carbohy-

drate ring protons; l 2.18, 2.16, 2.13, 2.11,

2.08, 2.02, 1.96 (7 s, 21 H, 7 Ac). Anal. Calcd

for C₂₆H₃₅N₃O₁₇: C, 47.20; H, 5.33; N, 6.35.

Found: C, 47.15; H, 5.39; N, 6.31.

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

31

of elution) 2^A,3^B-diol 42 (549 mg, 5%) and

3^B,6^B-diol 43 (552 mg, 5%).

170.9–169.1 (OC(O)CH₃), 162.0 (NꢀC(O)-

CCl₃), 101.4 (C-1^B), 92.2 (CCl₃), 83.8 (C-1^A),

62.1, 60.7 (C-6^A, C-6^B), 54.4 (C-2^A), 24.1

(SꢀCH₂), 20.8–20.5 (OC(O)CH₃), 14.9

(SꢀCH₂CH₃). Anal. Calcd for C₂₈H₃₈Cl₃-

NO₁₆S: C, 42.95; H, 4.89; Cl, 13.58; N, 1.79;

S, 4.09. Found: C, 43.19; H, 4.94; Cl, 13.00;

N, 1.96; S, 3.92.

Data for monohydroxy derivative 41: R_f

0.18 (1:8 EtOAc–toluene); [h]_D4° (c 3,

1

CH₂Cl₂); NMR (CDCl₃): H, see Table 2 for

carbohydrate ring protons; l 8.15–7.85 (6 d,

12 H, J 7.5 Hz, 12 ortho protons of 6 Bz),

7.68–7.11 (m, 16 H, Ph), 7.02 (t, 2 H, J 8 Hz,

Ph), 5.77 (m, 2 H, H-3^A, CH₂CHꢁCH₂), 5.17

(dd, 1 H, J_trans17.5, J_gem1.5 Hz, CH₂CHꢁ

CH₂), 5.09 (dd, 1 H, J_cis10 Hz, CH₂CHꢁCH₂),

4.22 (m, 2 H, H-4^A, OCH₂CHꢁCH₂), 4.10 (dd,

J_gem14, J_vic6.5 Hz, OCH₂CHꢁCH₂), 2.80

(broad s, 1 H, OH); ¹³C, l 166.4–165.2 (6

PhC(O)O), 133.5–128.0 (Ph, CH₂CHꢁCH₂),

117.7 (CHꢁCH₂), 100.6, 99.7 (C-1^A, C-1^B),

75.9, 73.6, 73.0, 72.8, 71.8, 71.7, 71.6, 70.1

(carbohydrate ring carbons), 70.1 (OCH₂CHꢁ

CH₂), 62.7, 61.6 (C-6^A, C-6^B). Anal. Calcd for

C₅₇H₅₀O₁₇: C, 67.99; H, 5.00. Found: C, 67.82;

H, 4.91.

Allyl 2,3,6-tri-O-benzoyl-4-O-(2,4,6-tri-O-

benzoyl-i-

D

-galactopyranosyl)-i- -galactopy-

D

ranoside (41), allyl 3,6-di-O-benzoyl-4-O-

(2,4,6-tri-O-benzoyl-i- -galactopyranosyl)-

i- - galactopyranoside (42), and allyl 2,3,6-

tri-O-benzoyl-4-O-(2,4-di-O-benzoyl-i-

galactopyranosyl)-i- -galactopyranoside (43).

D

-

D

—A suspension of allyl b-lactoside⁵⁰(4.68 g,

12.25 mmol) and Bu₂SnO (4.52 g, 18.15

mmol) in abs MeOH (60 mL) was reﬂuxed

under Ar for 3 h until a homogeneous solu-

tion was formed. Under stirring, the pressure

was diminished to 10 mmHg, the solvent was

distilled off, and the solid residue was dried

for 1 h at 60 °C/0.1 mmHg. Absolute benzene

(150 mL) was added under Ar, followed by

4-methoxybenzyl chloride (2.5 mL, 18.31

mmol) and n-Bu₄NBr (5.93 g, 18.41 mmol),

and the mixture was stirred for 20 h at 50 °C.

The dark-brown mixture was poured into wa-

ter (300 mL) and extracted with CH₂Cl₂(3×

100 mL). The combined organic extracts,

containing bis-alkylated derivatives 39 and 40

were concentrated and treated as described

below. The aqueous phase, containing mono-

alkylated product 38 was concentrated, dried

in vacuo, the residue was dissolved in Py (15

mL), and treated with a solution of BzCl (10

mL, 86 mmol) in CH₂Cl₂(20 mL) dropwise at

0 °C. After stirring for 18 h at rt, the excess of

BzCl was decomposed with water (5 mL), the

mixture was diluted with CH₂Cl₂(300 mL),

washed with 1 M aq H₂SO₄(185 mL), water,

satd aq NaHCO₃, dried, and concentrated. In

order to remove 4-methoxybenzyl group, the

residue was dissolved in CH₂Cl₂(30 mL) and

treated with 90% aq CF₃CO₂H (17 mL) for 30

min at rt. Coevaporation with toluene fol-

lowed by chromatography (toluene3:1 tolu-

ene–EtOAc) on a column of silica gel (200 g)

afforded 41 (3.19 g, 26% overall) as a white

foam. The above mentioned organic extracts

were treated in the same way to give (in order

Data for 2^A, 3^B-diol 42: R_f0.7 (1:3 EtOAc–

toluene); [h]_D−18° (c 2, EtOAc); NMR

1

(CDCl₃): H, see Table 2 for carbohydrate

ring protons; l 8.05–7.89 (4 d, 8 H, J 7.6 Hz,

8 ortho protons of 4 Bz), 7.86 (d, 2 H, J 7.6

Hz, 2 ortho protons of 1 Bz), 7.66–7.26 (m,

13 H, Ph), 7.09 (t, 2 H, J 8 Hz, Ph), 5.84 (m,

1 H, CH₂CHꢁCH₂), 5.25 (d, 1 H, J_trans17.3

Hz, CH₂CHꢁCH₂), 5.12 (d, 1 H, J_cis10.5 Hz,

CH₂CHꢁCH₂), 4.27 (dd, 1 H, J_gem12.6, J_vic

5.1

Hz,

OCH₂CHꢁCH₂),

4.06

(dd,

OCH₂CHꢁCH₂), 2.80 (d, 1 H, J 5.1 Hz, 3^B-

OH), 2.48 (broad s, 1 H, 2^A-OH); ¹³C, l

166.3–165.9 (5 PhC(O)O), 133.4–128.1 (Ph,

CH₂CHꢁCH₂), 118.3 (CHꢁCH₂), 101.6, 100.3

(C-1^A, C-1^B), 70.5 (OCH₂CHꢁCH₂), 62.8, 61.8

(C-6^A, C-6^B). Anal. Calcd for C₅₀H₄₆O₁₆: C,

66.51; H, 5.14. Found: C, 66.38; H, 5.02.

Data for 3^B, 6^B-diol 43: R_f0.25 (1:3

EtOAc–toluene); [h]_D29° (c 2, CH₂Cl₂);

1

NMR (CDCl₃): H, see Table 2 for carbohy-

drate ring protons; l 8.15–7.85 (5 d, 10 H, J

7.6 Hz, 10 ortho protons of 5 Bz), 7.66–7.12

(m, 13 H, Ph), 7.00 (t, 2 H, J 8 Hz, Ph), 5.75

(m, 1 H, CH₂CHꢁCH₂), 5.19 (dd, 1 H, J_trans

17.3, J_gem1.5 Hz, CH₂CHꢁCH₂), 5.07 (dd, 1

H, J_cis10.5 Hz, CH₂CHꢁCH₂), 4.27 (dd, 1 H,

J_gem13.3, J_vic4.8 Hz, OCH₂CHꢁCH₂), 4.07

(dd, J_vic6.3 Hz, OCH₂CHꢁCH₂), 2.77

(broaden s, 1 H, OH), 2.48 (broad s, 1 H,

13

OH); C, l 166.9–165.2 (5 PhC(O)O), 133.8–

128.1 (Ph, CH₂CHꢁCH₂), 117.7 (CHꢁCH₂),

32

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

100.6, 99.5 (C-1^A, C-1^B), 69.9 (OCH₂CHꢁ

CH₂), 62.7 (C-6^A), 59.4 (C-6^B). Anal. Calcd

for C₅₀H₄₆O₁₆: C, 66.51; H, 5.14. Found: C,

66.64; H, 5.07.

(193 mg, 15%) which was recycled. A mixture

of mesylate 48 (1.05 g, 0.93 mmol), NaN₃

(0.65 g, 10 mmol) and 18-crown-6 (60 mg,

0.23 mmol) in abs DMF (8 mL) was stirred

for 96 h at rt, then diluted with EtOAc,

washed with water, dried, and concentrated.

Chromatography (3:1 EtOAc–toluene) of the

residue on a column of silica gel (50 g) gave

azide 49 (723 mg, 72%): as a white foam: R_f

0.52 in 9:1 toluene–acetone; [h]_D23° (c 1,

Allyl 2,4,6-tri-O-benzoyl-i- -galactopyran-

D

oside (45).—Ortho-esteriﬁcation of diol 44⁵⁰

(1.7 g, 4 mmol) followed by hydrolysis with

AcOH as described for the preparation of 27

and subsequent chromatography (1:52:1

EtOAc–petroleum ether) of the residue on a

column of silica gel (50 g) gave 45 (1.84 g,

87%) as a white foam: R_f0.75 (1:1 EtOAc–

petroleum ether); [h]_D1° (c 1, EtOAc); NMR

1

CHCl₃); NMR (CDCl₃): H, see Table 2 for

carbohydrate ring protons; l 1.8 (s, 3 H,

OAc), 3.23 (dd, 1 H, CH₂N₃), 3.34 (dd, 1 H,

CH₂N₃), 3.75 (m, OCH₂CH₂N₃), 4.02 (m, 1 H,

OCH₂CH₂N₃), 7.09–7.69 (m, 18 H, Ph), 7.91–

8.12 (m, 12 H, Ph); ¹³C, see Table 4 for

carbohydrate ring carbons; l 20.3 (CH₃CO),

50.4 (CH₂N₃), 69.8 (OCH₂CH₂N₃), 164.6–

165.7 (6 PhC(O)O), 169.9 (CH₃C(O)O). Anal.

Calcd for C₅₈H₅₁O₁₈N₃: C, 64.62; H, 4.77; N,

3.89. Found C, 64.68; H, 4.81; N, 3.97.

1

(CDCl₃): H, see Table 2 for carbohydrate

ring protons; l 8.19 (d 2 H, J 7.5 Hz, ortho

protons of 1 Bz), 8.09 (d, 4 H, J 7.8 Hz, ortho

protons of 2 Bz), 7.67–7.45 (m, 9 H, Ph), 5.89

(m, 1 H, OCH₂CHꢁCH₂), 5.29 (d, 1 H, J_trans

17.1 Hz, OCH₂CHꢁCH₂), 5.18 (d, 1 H, J_cis

10.5 Hz, OCH₂CHꢁCH₂), 4.63 (dd, 1 H, J_vic7,

J_gem11 Hz, OCH₂CHꢁCH₂), 4.46 (dd, 1 H,

J_vic5.9 Hz, OCH₂CHꢁCH₂), 3.15 (broaden s,

1 H, OH). Anal. Calcd for C₃₀H₂₈O₉: C, 67.66;

H, 5.30. Found: C, 67.50; H, 5.41.

2-Azidoethyl 2,4,6-tri-O-benzoyl-i-

topyranosyl-(14)-2,3,6-tetra-O-benzoyl-i-

-glycopyranoside (50).—The reagent was

D

-galac-

D

2-Azidoethyl 2,3,6-tri-O-benzoyl-4-O-(3-O-

prepared by dropwise addition, at 0 °C, of

acetyl chloride (2 mL, 28 mmol) to abs MeOH

(20 mL). After 10 min, the reagent was added

to a solution of compound 49 (2.29 g, 2.14

mmol) in abs CH₂Cl₂(10 mL). After 5 h at rt,

the mixture was poured into ice-cold water

and extracted with CH₂Cl₂(200 mL). The

organic phase was then washed with satd aq

NaHCO₃and water, dried, and concentrated.

Chromatography (toluene6:1 toluene–ace-

tone) of the residue on a column of silica gel

(200 g) afforded 50 (1.88 g, 86%) as a white

foam: R_f0.33 in 9:1 toluene–acetone; [h]_D5°

acetyl-2,4,6-tri-O-benzoyl-i-

D

-galactopyran-

osyl)-i-

D

-galactopyranoside (49).—Conven-

tional acetylation of allyl lactoside 41 with

Ac₂O in Py afforded 46 quantitatively. Ozone

was bubbled through a solution of 46 (1.29 g,

1.23 mmol) in 2:1 anhyd MeOH–CH₂Cl₂(75

mL) at −78 °C until a blue color persisted;

the excess of ozone was removed by a stream

of Ar; NaBH₄(467 mg, 12.35 mmol) was

added with vigorous stirring, and the mixture

was allowed to attain −5 °C over a period of

1.5 h. The next portion of NaBH₄(480 mg,

12.7 mmol) was added and the mixture was

stirred for 0.5 h at 0 °C. The reaction mixture

was neutralized with AcOH, diluted with

CH₂Cl₂, washed with water, satd aq NaHCO₃,

concentrated, and dried in vacuo. To a solu-

tion of the crude alcohol 47 in abs CH₂Cl₂(15

mL), Et₃N (0.36 mL, 2.6 mmol) was added at

0 °C, followed by methanesulfonyl chloride

(0.21 mL, 2.6 mmol). After stirring for 1 h at

0 °C, the reaction was diluted with CH₂Cl₂,

washed with satd aq NaHCO₃, dried, concen-

trated, and ﬁltered through a short column of

silica gel in 4:1 EtOAc–toluene to give mesy-

late 48 (1.05 g, 75%) and recovered alcohol 47

1

(c 1, CHCl₃); NMR (CDCl₃): H, see Table 2

for carbohydrate ring protons; l 2.9 (broad s,

1 H, OH), 3.28 (m, 1 H, CH₂N₃), 3.38 (m, 1

H, CH₂N₃), 3.67 (m, 1 H, OCH₂CH₂N₃), 3.99

(m, OCH₂CH₂N₃), 7.12–7.73 (m, 18 H, Ph),

13

7.88–8.09 (m, 12 H, Ph); C, l 50.5 (CH₂N₃),

61.6, 62.5 (C-6^A, C-6^B), 100.6, 101.1 (C-1^A,

C-1^B). Anal. Calcd for C₅₆H₄₉O₁₇N₃: C, 64.92;

H, 4.77; N, 4.06. Found C, 65.13; H, 4.73; N,

4.02.

Allyl 2-acetamido-6-O-benzoyl-3-O-benzyl-

2-deoxy-i-

D

-glucopyranoside (52).—To

a

cold (−5 °C) solution of diol 51⁴²(1.24 g,

3.53 mmol) in CH₂Cl₂(20 mL) and Et₃N (10

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

33

PhCH₂), 4.81 (d, 1 H, PhCH₂), 4.17 (dd, 1 H,

J_gem13.5, J_vic5.5 Hz, OCH₂CHꢁCH₂), 3.84

(dd, 1 H, J_vic6.5 Hz, OCH₂CHꢁCH₂), 2.02 (s,

3 H, Ac), 1.89 (s, 3 H, Ac); ¹³C, see Table 4

for carbohydrate ring carbons; 170.2 (2

C(O)CH₃), 165.9–164.9 (PhC(O)O), 138.2

(ipso Bn), 133.6–127.6 (Ph), 117.2 (OCH₂CHꢁ

CH₂), 73.3 (PhCH₂), 69.7 (OCH₂CHꢁCH₂),

23.4 (NꢀC(O)CH₃), 20.5 (OC(O)CH₃). Anal.

Calcd for C₅₄H₅₃NO₁₆: C, 66.73; H, 5.50; N,

1.44. Found: C, 66.38; H, 5.56; N, 1.43.

mL), BzCl (0.83 mL, 7.1 mmol) was added

dropwise, and the reaction mixture was kept

overnight at 0 °C. The mixture was diluted

with CH₂Cl₂, washed with satd aq NaHCO₃,

dried, and concentrated Crystallization from

EtOAc–petroleum ether afforded 52 (1.13 g,

70%): R_f0.55 (EtOAc); mp 209–211°C; [h]_D

5° (c 1, MeOH); NMR (10:1 CDCl₃–

1

CD₃OD): H, l 8.01 (d, 2 H, J 7.6 Hz, ortho

protons of Bz), 7.59–7.18 (m, 8 H, Ph), 5.70

(m, 1 H, OCH₂CHꢁCH₂), 5.19 (d, 1 H, J_trans

17.9 Hz, OCH₂CHꢁCH₂), 5.05 (d, 1 H, J_cis

10.8 Hz, OCH₂CHꢁCH₂), 4.83–4.55 (m, 5 H,

H-1, H-6a, H-6b, PhCH₂), 4.23 (dd, 1 H, J_gem

12.8, J_vic4.9 Hz, OCH₂CHꢁCH₂), 4.04 (dd, 1

H, J_vic6.8 Hz, OCH₂CHꢁCH₂), 3.89 (t, 1 H,

J_3,2=J_3,49.6 Hz, H-3), 3.64–3.41 (m, 3 H,

H-4, H-2, H-5), 1.83 (s, 3 H, Ac); ¹³C, see

Table 4 for carbohydrate ring carbons; l

171.1 (NꢀC(O)CH₃), 166.9 (PhC(O)O), 138.3

(ipso Bn), 133.1 (OCH₂CHꢁCH₂), 133.8–

127.7 (Ph), 117.4 (OCH₂CHꢁCH₂), 74.3

(PhCH₂), 69.8 (OCH₂CHꢁCH₂), 23.1 (Nꢀ

C(O)CH₃). Anal. Calcd for C₂₅H₂₉NO₇: C,

65.92; H, 6.42; N, 3.07. Found: C, 65.69; H,

6.25; N, 2.96.

2-Acetamido-2-azidoethyl

benzoyl-i- -galactopyranosyl)-(14)-6-O-

benzoyl-3-O-benzyl-2-deoxy-i- -glucopyrano-

O-(2,4,6-tri-O-

D

side (55).—Ozonolysis of 53 (1 g, 1.03 mmol)

in MeOH (120 mL) and CH₂Cl₂(60 mL),

followed by reduction with NaBH₄(1.56 g, 41

mmol), mesylation with MsCl (0.5 mL) and

Et₃N (2 mL) in abs CH₂Cl₂(120 mL) (0.89

g, 82% overall yield) and mesylateazide

substitution as described above for the prepa-

ration of 49 gave 2-azidoethyl glycoside 54

(0.79 g, 93% yield). Subsequent HCl-catalyzed

methanolysis of the acetate ester in 54 (0.79 g,

0.79 mmol) as described for the preparation of

50 afforded 55 (0.66 g, 87%) as a white foam:

R_f0.6 (3:2 toluene–acetone); [h]_D−6° (c 1,

Allyl O-(3-O-acetyl-2,4,6-tri-O-benzoyl-i-

1

D

-galactopyranosyl)-(14)-2-acetamido-6-O-

CHCl₃); NMR (CDCl₃): H, see Table 2 for

benzoyl-3-O-benzyl-2-deoxy-i-

D

-glucopyran-

carbohydrate ring protons; l 8.15–7.91 (4 d, 8

H, ortho protons of 4 Bz), 7.59–7.11 (m, 17

H, Ph), 5.97 (d, 1 H, J_NꢀH,27.8 Hz, NꢀH), 4.95

(d, 1 H, J 11.6 Hz, PhCH₂), 4.73 (2 d, 2 H,

H-1^A, PhCH₂), 3.84 (m, 1 H, OCH₂CH₂N₃),

3.44 (m, 1 H, OCH₂CH₂N₃), 3.35 (m, 1 H,

CH₂N₃), 3.15 (m, 1 H, CH₂N₃), 1.91 (s, 3 H,

Ac); ¹³C, l 170.6 (NꢀC(O)CH₃), 166.3–165.9

(4 PhC(O)O), 138.5 (ipso Bn), 133.6–127.6

(Ph), 100.4, 100.0 (C-1^A, C-1^B), 63.6, 62.0

(C-6^A, C-6^B), 54.7 (C-2^A), 50.5 (CH₂N₃), 23.4

(NꢀC(O)CH₃). Anal. Calcd for C₅₁H₅₀N₄O₁₅:

C, 63.88; H, 5.26; N, 5.84. Found: C, 63.79;

H, 5.32; N, 5.56.

oside (53).—A mixture of bromide 29 (1 g,

1.75 mmol), acceptor 52 (0.72 g, 1.58 mmol),

,

and MS-4 A (0.7 g) in abs CH₂Cl₂(40 mL)

was stirred under Ar at rt for 1 h, then cooled

to −15 °C and powdered AgOTf (0.64 g, 2.4

mmol) was added. After stirring for 4 h at

−5 °C, the reaction was terminated with Et₃N

(1 mL), diluted with CH₂Cl₂(100 mL), ﬁltered

through a pad of Celite, washed with satd aq

NaHCO₃, 3 M aq Na₂S₂O₃, dried, and con-

centrated. Chromatography (toluene1:2 tol-

uene–EtOAc) of the residue on a column of

silica gel (50 g) gave 53 (1.43 g, 93%) as a

white foam: R_f0.41 (3:2 toluene–EtOAc); [h]_D

Allyl

chloroacetamido-i-

O-(2,4,6-tri-O-benzoyl-i-

(14)-2,3,6-tri-O-benzoyl-i-

O-(3,4,6-tri-O-acetyl-2-deoxy-2-tri-

-glucopyranosyl)-(13)-

-galactopyranosyl)-

-glucopyran-

1

−4° (c 1, CH₂Cl₂); NMR (CDCl₃): H, see

D

Table 2 for carbohydrate ring protons; l

8.10–7.93 (m, 8 H, ortho protons of 4 Bz),

7.65–7.15 (m, 17 H, Ph), 6.02 (d, 1 H, J_NꢀH,2

8.8 Hz, NꢀH), 5.77 (m, 1 H, OCH₂CHꢁCH₂),

5.14 (dd, 1 H, J_trans18, J_gem1.6 Hz,

OCH₂CHꢁCH₂), 5.07 (dd, 1 H, J_cis10.5 Hz,

OCH₂CHꢁCH₂), 4.91 (d, 1 H, J 12 Hz,

D

oside (56).—(a) To a stirred solution of bro-

mide 12 (223 mg, 0.42 mmol) and acceptor 41

(235 mg, 0.23 mmol) in abs CH₂Cl₂(6 mL),

powdered AgOTf (117 mg, 0.46 mmol) was

added under Ar at −45 °C. After stirring for

34

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

(400 mg) in abs CH₂Cl₂(2.5 mL) was stirred

under Ar for 1 h; NIS (40 mg, 0.178 mmol)

was added, and the mixture was cooled to

−35 °C. TfOH was added in three equal

0.007 mL portions with 40 min intervals (in

total 0.021 mL, 0.237 mmol). The reaction

was terminated with Et₃N (0.1 mL), diluted

with CH₂Cl₂(30 mL), ﬁltered through a pad

of Celite, washed with satd aq NaHCO₃, 3 M

aq Na₂S₂O₃, dried, and concentrated. Chro-

matography (toluene1:1 toluene–EtOAc)

of the residue on a column of silica gel (20 g)

gave 57 (111 mg, 65%): R_f0.45 (2:1 toluene–

EtOAc); [h]_D17° (c 1, CH₂Cl₂); NMR

3 h at −20 °C, the reaction was terminated

by addition of satd aq NaHCO₃(20 mL) and

3 M aq Na₂S₂O₃(20 mL), and extracted with

CH₂Cl₂(50 mL); the extracts were dried and

concentrated. Chromatography (petroleum

ether6:4 EtOAc–petroleum ether) of the

residue on a column of silica gel (30 g) af-

forded 56 (296 mg, 88%) as transparent glass:

R_f0.24 (2:3 EtOAc–petroleum ether); [h]_D22°

1

(c 2, CH₂Cl₂); NMR (CDCl₃): H, see Table 2

for carbohydrate ring protons; l 8.15–7.80 (6

d, 12 H, J 7.9 Hz, ortho-protons of 6 Bz),

7.65–7.18 (m, 16 H, Ph), 6.91 (t, 2 H, J 8 Hz,

Ph), 6.45 (d, 1 H, J_NꢀH,28 Hz, NꢀH), 5.74 (m,

2 H, H-3^A, CH₂CHꢁCH₂), 5.15 (dd, 1 H, J_trans

17, J_gem1.5 Hz, CH₂CHꢁCH₂), 5.06 (dd, 1 H,

J_cis10 Hz, CH₂CHꢁCH₂), 4.22 (m, 1 H,

OCH₂CHꢁCH₂), 4.05 (m, OCH₂CHꢁCH₂),

1

(CDCl₃): H, the spectrum was identical to

that of 56 excepting the absence of the signals

of allyl moiety at l 5.74 (CH₂CHꢁCH₂), 5.15

(CH₂CHꢁCH₂), 5.06 (CH₂CHꢁCH₂), 4.22

(OCH₂CHꢁCH₂), 4.05 (OCH₂CHꢁCH₂), and

the presence of two one-proton multiplets at l

3.92, 3.64 (OCH₂CH₂N₃) and two one proton

multiplets at l 3.36 and 3.24 (OCH₂CH₂N₃);

¹³C, the spectrum was identical to that of 56

excepting the absence of the signal of allyl

moiety at l 117.6 (CHꢁCH₂), and the pres-

ence of the signals at l 69.4 (OCH₂CH₂N₃)

and 50.4 (CH₂N₃); Anal. Calcd for

C₇₀H₆₅Cl₃N₄O₂₅: C, 57.25; H, 4.46; N, 3.81.

Found: C, 56.96; H, 4.60; N, 3.49.

13

1.95, 1.93, 1.87 (3 s, 9 H, OAc); C, l 170.5,

170.1, 169.2 (3 OC(O)CH₃), 165.7–164.5 (6

PhC(O)O), 160.8 (NꢀC(O)CCl₃), 133.5–127.8

(Ph, CH₂CHꢁCH₂), 117.6 (CHꢁCH₂), 100.6,

99.7, 99.2 (3 C-1), 62.5, 61.9, 61.3 (3 C-6), 56.5

(C-2^C), 20.5 (3 OC(O)CH₃); APCI-MS: Calcd

for [C₇₁H₆₆Cl₃NO₂₅]⁻1437.3. Found 1437.8.

Calcd

for

[C₇₁H₆₆Cl₃NO₂₅+H₂O+H]⁺

1456.3. Found 1456.3. Anal. Calcd for

C₇₁H₆₆Cl₃NO₂₅: C, 59.24; H, 4.62; Cl, 7.39; N,

0.97. Found: C, 59.31; H, 4.59; Cl, 7.48; N,

1.03.

(b) A mixture of oxazoline 19 (109 mg,

(b) A mixture of thioglycoside 11 (33 mg,

0.067 mmol), acceptor 41 (51 mg, 0.05 mmol),

0.252 mmol), acceptor 50 (168 mg, 0.162

,

mmol), and MS-4 A (300 mg) in abs CH₂Cl₂

,

and MS-4 A (300 mg) was stirred in abs

(3 mL) was stirred under Ar for 1 h, then

cooled to −35 °C, and TfOH (0.022 mL,

0.252 mmol) was added. After stirring for 0.5

h at −20 °C, the reaction was terminated

with Et₃N (0.1 mL), diluted with CH₂Cl₂(30

mL), ﬁltered through a pad of Celite, washed

with satd aq NaHCO₃, dried, and concen-

trated. Chromatography of the residue as in

(a) gave 57 (157 mg, 66%): identical in all

respect to the material described in (a).

CH₂Cl₂(2 mL) under Ar for 1 h; NIS (15 mg,

0.067 mmol) was added, and the mixture was

cooled to −15 °C. TfOH (0.006 mL, 0.072

mmol) was added, and after stirring for 1 h at

−15 °C the reaction mixture was quenched

with Et₃N, diluted with CH₂Cl₂(30 mL),

ﬁltered through a pad of Celite, washed with

satd aq NaHCO₃, 3 M aq Na₂S₂O₃, dried, and

concentrated. Chromatography of the residue

as in (a) gave 56 (50 mg, 68%): identical in all

respect to the material described above.

2-Azidoethyl O-(4-O-acetyl-3,6-di-O-ben-

zyl-2-deoxy-2-trichloroacetamido-i-

pyranosyl)-(13)-O-(2,4,6-tri-O-benzoyl-i-

- galactopyranosyl) - (14) - 2,3,6 - tri - O-

benzoyl-i- -glucopyranoside (58).—A mix-

D

-gluco-

2-Azidoethyl

oxy - 2 - trichloroacetamido - i -

syl) -(13) - O - (2,4,6 - tri - O - benzoyl - i -

galactopyranosyl)-(14)-2,3,6-tri-O-benzoyl-

i- -glucopyranoside (57).—(a) A mixture of

thioglycoside 11 (78 mg, 0.154 mmol), accep-

O-(3,4,6-Tri-O-acetyl-2-de-

D

- glucopyrano-

D

-

D

ture of thioglycoside 18 (281 mg, 0.47 mmol),

D

,

acceptor 50 (467 mg, 0.45 mmol), and MS-4 A

,

tor 50 (121 mg, 0.117 mmol), and MS-4 A

(500 mg) in abs CH₂Cl₂(5 mL) was stirred

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

35

OCH₂CHꢁCH₂), 4.05 (m, OCH₂CHꢁCH₂),

2.01, 1.99, 1.92 (3 s, 9 H, OAc); APCI-MS:

Calcd for [C₄₄H₄₄Cl₃NO₁₇−H⁺]⁻: 962.2.

Found: 962.3. Anal. Calcd for C₄₄H₄₄Cl₃NO₁₇:

C, 54.75; H, 4.59; Cl, 11.02; N, 1.45. Found:

C, 54.50; H, 4.86; Cl, 11.32; N, 1.56.

under Ar for 1 h; NIS (120 mg, 0.53 mmol)

was added, and the mixture was cooled to

−20 °C. TfOH (0.003 mL, 0.034 mmol) was

added, and stirring was continued for 1 h. The

reaction was terminated with Et₃N (0.1 mL),

diluted with CH₂Cl₂(30 mL), ﬁltered through

a pad of Celite, washed with satd aq

NaHCO₃, 3 M aq Na₂S₂O₃, dried, and con-

centrated. Chromatography (toluene7:1 tol-

uene–acetone) of the residue on a column of

silica gel (50 g) gave 58 (623 mg, 88%): R_f0.39

(10:1 toluene–acetone); [h]_D19° (c 1, EtOAc);

2-Azidoethyl O-(3,4,6-tri-O-acetyl-2-deoxy-

2 - trichloroacetamido - i -

D

- glucopyranosyl)-

-galactopyran-

(13)-2,4,6-tri-O-benzoyl-i-

D

oside (60).—Ozonolysis of 59 (442 mg, 0.46

mmol) followed by reduction with NaBH₄,

mesylation, and mesylateazide substitution

as described above for the preparation of 49

and 54 gave 2-azidoethyl glycoside 60 (361

mg, 79% overall) as a white foam: R_f0.5 (2:3

EtOAc–toluene); [h]_D26° (c 1, EtOAc); NMR

1

NMR (CDCl₃): H, see Table 2 for carbohy-

drate ring protons; l 8.16, 8.12, 8.08 (3 d, 2 H

each, J 7.6 Hz, 6 ortho protons of 3 Bz), 7.99

(d, 4 H, J 7.7 Hz, 4 ortho protons of 2 Bz),

7.82 (d, 2 H, J 7.8 Hz, ortho protons of 1 Bz),

7.70–7.12 (m, 26 H, Ph), 6.95 (t, 2 H, J 7.8

Hz, Ph), 6.81 (d, 1 H, J_NꢀH,27 Hz, NꢀH^C),

4.52 (t, 2 H, J 10.5 Hz, PhCH₂), 4.43 (broad s,

2 H, PhCH₂), 3.97 (m, 1 H, OCH₂CH₂N₃),

3.68 (m, 1 H, OCH₂CH₂N₃), 3.40 (m, 1 H,

CH₂N₃), 3.29 (m, 1 H, CH₂N₃), 1.81 (s, 3 H,

1

(CDCl₃): H, the spectrum was identical to

that of 59, excepting the absence of the signals

of allyl moiety at l 5.73 (OCH₂CHꢁCH₂),

5.14 (CH₂CHꢁCH₂), 5.05 (CH₂CHꢁCH₂), 4.32

(OCH₂CHꢁCH₂), 4.05 (OCH₂CHꢁCH₂), and

the presence of four one-proton multiplets at

l 4.00, 3.69 (OCH₂CH₂N₃), 3.39, 3.27

(CH₂N₃); ¹³C, l 170.8, 170.3, 169.6 (3

OC(O)CH₃), 166.2, 165.6, 165.1 (3 PhC(O)O),

161.6 (NꢀC(O)CCl₃), 133.5–128.4 (Ph), 101.4,

99.3 (2 C-1), 62.9, 61.3 (2 C-6), 56.5 (C-2^B),

50.6 (CH₂N₃), 20.7, 20.6, 20.4 (3 OC(O)CH₃).

APCI-MS: Calcd for [C₄₄H₄₄Cl₃NO₁₇−H⁺]⁻:

991.2. Found: 991.1. Anal. Calcd for

C₄₃H₄₃Cl₃N₄O₁₇: C, 51.95; H, 4.36; Cl, 10.70;

N, 5.64. Found: C, 52.09; H, 4.72; Cl, 10.45;

N, 5.46.

13

Ac); C, l 169.5 (OC(O)CH₃), 165.8–164.6 (6

PhC(O)O), 161.6 (NꢀC(O)CCl₃), 138.9, 138.1

(2 ipso Bn), 137.8–127.4 (Ph), 101.0 (C-1^A),

100.8 (C-1^B), 98.3 (C-1^C), 62.3 (C-6^A), 61.9

(C-6^B), 59.0 (C-2^C), 50.5 (CH₂N₃), 20.6 (OC-

(O)CH₃). Anal. Calcd for C₈₀H₇₃Cl₃N₄O₂₃: C,

61.40; H, 4.70; N, 3.58. Found: C, 61.24; H,

4.93; N, 3.25.

Allyl

chloroacetamido-i-

2,4,6 - tri - O - benzoyl - i -

O-(3,4,6-tri-O-acetyl-2-deoxy-2-tri-

-glucopyranosyl)-(13)-

- galactopyranoside

D

Allyl

chloroacetamido-i-

O-[3,4,6-tri-O-acetyl-2-deoxy-2-trichloroacet-

amido-i- -glucopyranosyl-(16)]-O-(2,4-di-

O-benzoyl-i- -galactopyranosyl)-(14)-2,3,

6-tri-O-benzoyl-i- -glucopyranoside (61).—

O-(3,4,6-tri-O-acetyl-2-deoxy-2-tri-

(59).—Glycosylation of galactoside 45 (1.25 g,

2.37 mmol) with thioglycoside 11 (1.6 g, 3.22

mmol) in abs CH₂Cl₂(30 mL) promoted by

NIS (730 mg, 3.24 mmol), TfOH (0.142 mL,

D

-glucopyranosyl)-(13)-

D

,

1.61 mmol), and MS-4 A (1.5 g) at −20 °C

D

for 40 min as described above for the prepara-

tion of 56 and subsequent chromatography

(3:11:1 petroleum ether–EtOAc) afforded

59 (1.95 g, 86%) as a white foam: R_f0.41 (1:1

petroleum ether–EtOAc); [h]_D23° (c 1,

Bis-glycosylation of diol 43 (149 mg, 0.165

mmol) with thioglycoside 11 (248 mg, 0.5

mmol) in abs CH₂Cl₂(8 mL) promoted by

NIS (112 mg, 0.5 mmol), TfOH (0.044 mL,

,

0.5 mmol), and MS-4 A (2 g) at −15 °C for 2

1

EtOAc); NMR (CDCl₃): H, see Table 2 for

h as described above for the preparation of 56

and subsequent chromatography (benzene

2:3 benzene–EtOAc) afforded 61 (194 mg,

66%) as a white foam: R_f0.24 (2:3 EtOAc–

toluene); [h]_D18° (c 1, CH₂Cl₂); NMR

carbohydrate ring protons; l 8.17–8.01 (m, 6

H, ortho-protons of 3 Bz), 7.69–7.45 (m, 9 H,

Ph), 6.55 (d, 1 H, J_NꢀH,29 Hz, NꢀH^B), 5.73 (m,

1 H, OCH₂CHꢁCH₂), 5.14 (d, 1 H, J_trans18,

J_gem\1 Hz, CH₂CHꢁCH₂), 5.05 (m, 3 H,

CH₂CHꢁCH₂, H-1^B, H-4^B), 4.32 (m,

1

(CDCl₃): H, see Table 2 for carbohydrate

ring protons; l 8.10–7.88 (m, 8 H, ortho-pro-

36

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

acceptor 50 (200 mg, 0.193 mmol) with thio-

glycoside 36 (206 mg, 0.263 mmol) in abs

CH₂Cl₂(7 mL) promoted by NIS (65 mg, 0.29

mmol), TfOH (0.023 mL, 0.263 mmol), and

tons of 4 Bz), 7.82 (d, 2 H, J 7.9 Hz, ortho-

protons of 1 Bz), 7.65–7.18 (m, 13 H, Ph),

7.11 (m, 3 H, Ph, NꢀH^D), 6.51 (d, 1 H, J_NꢀH,2

9

Hz, NꢀH^C), 5.66 (m,

2

H, H-3^A,

,

MS-4 A (900 mg) for 1 h at −20 °C as

CH₂CHꢁCH₂), 5.15 (dd, 1 H, J_trans16.9, J_gem

described for the preparation of 56 and subse-

quent chromatography (petroleum ether1:1

petroleum ether–EtOAc) of the residue on a

column of silica gel (20 g) followed by rechro-

matography (toluene5:1 toluene–acetone)

gave 63 (259 mg, 76%): R_f0.17 (1:1 petroleum

ether–EtOAc); [h]_D10° (c 2, CH₂Cl₂); NMR

1.8 Hz, CH₂CHꢁCH₂), 5.06 (dd, 1 H, J_cis10

Hz, CH₂CHꢁCH₂), 4.22 (m,

1

H,

OCH₂CHꢁCH₂), 4.05 (m, OCH₂CHꢁCH₂),

13

2.11–1.84 (6 s, 18 H, Ac); C, l 171.1–169.2

(OC(O)CH₃), 165.9–164.6 (PhC(O)O), 162.0,

161.4 (2 NꢀC(O)CCl₃), 133.6–128.1 (Ph,

CH₂CHꢁCH₂), 117.7 (CHꢁCH₂), 100.9, 99.4

(2 C-1), 98.9 (2 C-1), 66.5 (C-6^B), 62.6, 61.8,

60.8 (C-6^A, C-6^C, C-6^D), 57.0 56.3 (C-2^C, C-

2^D), 20.8–20.4 (3 OCOCH₃). Anal. Calcd for

C₇₈H₇₈Cl₆N₂O₃₂: C, 52.98; H, 4.45; Cl, 12.03;

N, 1.58. Found: C, 52.86; H, 4.31; Cl, 11.71;

N, 1.33.

1

(CDCl₃): H, l see Table 2 for carbohydrate

ring protons; l 8.25–7.85 (5 d, 10 H, J 8 Hz,

10 ortho-protons of 5 Bz), 7.75 (d, 2 H, J 8

Hz, 2 ortho protons of 1 Bz), 7.65–7.18 (m,

16 H, Ph), 6.81 (t, 2 H, J 8 Hz, Ph), 6.40 (d,

1 H, J_NꢀH,28.8 Hz, NꢀH), 3.94 (m, 1 H,

OCH₂CH₂N₃), 3.62 (m, 1 H, OCH₂CH₂N₃),

3.34 (m, 1 H, CH₂N₃), 3.24 (m, 1 H, CH₂N₃),

2.19 (s, 3 H, Ac), 2.01 (3 s, 9 H, 3 Ac), 1.80 (s,

2-Azidoethyl O-(3,4,6-tri-O-acetyl-2-deoxy-

2 - trichloroacetamido - i -

D

- glucopyranosyl)-

(13)-O-[3,4,6-tri-O-acetyl-2-deoxy-2-tri-

chloroacetamido-i- -glucopyranosyl)-(16]-

O-(2,4-di-O-benzoyl-i- -galactopyranosyl)-

(14)-2,3,6-tri-O-benzoyl-i- -glucopyran-

13

3 H, Ac), 1.75 (s, 3 H, Ac); C, l 170.3–169.4

D

(CH₃C(O)O), 165.9–164.4 (PhC(O)O), 161.4

(NꢀC(O)CCl₃), 133.6–125.3 (Ph), 101.2,

101.0, 100.7, 99.9 (4 C-1), 91.7 (CCl₃), 62.4,

61.9, 61.1, 60.8 (4 C-6), 55.7 (C-2^C), 50.5

(CH₂N₃), 21.4–20.6 (OC(O)CH₃). Anal.

Calcd for C₈₂H₈₁Cl₃N₄O₃₃: C, 56.06; H, 4.65;

Cl, 6.05; N, 3.19. Found: C, 56.19; H, 4.81;

Cl, 5.73; N, 3.30.

D

o-side (62).—Ozonolysis of 61 (177 mg, 0.1

mmol) followed by reduction with NaBH₄,

mesylation, and mesylateazide substitution

as described above for the preparation of 49

and 54 gave 2-azidoethyl glycoside 62 (134

mg, 75% overall) as a white foam: R_f0.24 (4:1

toluene–acetone); [h]_D16° (c 1, acetone);

NMR (CDCl₃): ¹H, the spectrum was identical

to that of 61 excepting the disappearance of

the signals of the allyl moiety at l 5.66

(CH₂CHꢁCH₂), 5.15 (CH₂CHꢁCH₂), 5.06

(CH₂CHꢁCH₂), 4.22 (OCH₂CHꢁCH₂), 4.05

(OCH₂CHꢁCH₂) and the presence of four

2-Azidoethyl O-(3-O-acetyl-2,4,6-tri-O-ben-

zoyl-i- -galactopyranosyl)-(14)-O-(3,6-di-

D

O-benzyl-2-deoxy-2-trichloroacetamido-i-

glucopyranosyl)-(13)-O-(2,4,6-tri-O-ben-

zoyl - i - - galactopyranosyl) - (14) - 2 - acet-

amido-6-O-benzoyl-3-O-benzyl-2-deoxy-i-

D

-

D

-

glucopyranoside (64).—Glycosylation of lac-

tosamine acceptor 55 (150 mg, 0.16 mmol)

with lactosamine thioglycoside 30 (220 mg,

0.23 mmol) in abs CH₂Cl₂(5 mL) promoted

by NIS (70 mg, 0.31 mmol), TfOH (0.028 mL,

one-proton multiplets at

l

3.90, 3.45

(OCH₂CH₂N₃), 3.35, 3.20 (CH₂N₃). ¹³C, the

spectrum was identical to that of 61 excepting

the disappearance of the signal of the allyl

moiety at l 117.7 (CHꢁCH₂) and the presence

of the signal at l 50.5 (CH₂N₃). Anal. Calcd

for C₇₇H₇₇Cl₆N₅O₃₂: C, 51.46; H, 4.32; N,

3.90. Found: C, 51.40; H, 4.44; N, 3.70.

,

0.31 mmol), and MS-4 A (500 mg) for 3 h at

−20 °C as described for the preparation of 56

and subsequent chromatography (toluene

6:1 toluene–acetone) of the residue on a

column of silica gel (30 g) followed by gel-per-

meation chromatography on a 3×70 cm

column of Bio-Beads SX3 in toluene gave 64

(212 mg, 69%): R_f0.36 (3:1 toluene–acetone);

2-Azidoethyl O-(2,3,4,6-tetra-O-acetyl-i-

galactopyranosyl)-(14)-O-(3,6-di-O-acetyl-

2-deoxy-2-trichloroacetamido-i- -glucopyran-

osyl) - (13) - O - (2,4,6 - tri - O - benzoyl - i -

galactopyranosyl)-(14)-2,3,6-tri-O-benzoyl-

i- -glucopyranoside (63).—Glycosylation of

D

-

D

1

D

-

[h]_D11° (c 1, EtOAc); NMR (CDCl₃): H, see

Table 2 for carbohydrate ring protons; l

8.15–7.93 (m, 14 H, ortho protons of 7 Bz),

D

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

37

C

0.81. Found: C, 57.57; H, 5.00; Cl, 6.12; N,

1.09.

7.70–7.12 (m, 36 H, Ph), 6.70 (d, 1 H, J_N−H

,2

A

7.7 Hz, NꢀH^C), 6.06 (d, 1 H, J_N−H

8.3 Hz,

NꢀH^A), 5.09, 4.58 (2 d, 1 H each,^,2J 11 Hz,

PhCH₂), 4.86, 4.78 (2 d, 1 H each, J 11.9 Hz,

PhCH₂), 4.62, 4.30 (2 d, 1 H each, J 11.9 Hz,

PhCH₂), 3.71, 3.63 (2 m, OCH₂CH₂N₃), 3.50,

3.32 (2 m, CH₂N₃), 2.05 (s, 3 H, Ac), 1.92 (s,

3 H, Ac); ¹³C, l 170.6, 170.4 (C(O)CH₃),

166.2–165.1 (7 PhC(O)O), 161.8 (NꢀC(O)-

CCl₃), 138.5, 138.4, 138.2 (3 ipso Bn), 133.8–

127.5 (Ph), 100.5, 100.4, 100.2, 99.1 (4 C-1),

58.2 (C-2^C), 53.5 (C-2^A), 50.6 (CH₂N₃), 23.5

(NꢀC(O)CH₃), 20.7 (OC(O)CH₃). Anal. Calcd

for C₁₀₂H₉₆Cl₃N₅O₂₉: C, 62.43; H, 4.93; Cl,

5.43; N, 3.57. Found: C, 62.56; H, 5.40; Cl,

5.41; N, 3.45.

2-Azidoethyl O-(2,3,4,6-tetra-O-acetyl-i-

galactopyranosyl)-(13)-O-(4,6-di-O-acetyl-

2-deoxy-2-trichloroacetamido-i- -glucopyran-

osyl) - (13) - O - (2,4,6 - tri - O - benzoyl - i -

galactopyranosyl)-(14)-2,3,6-tri-O-benzoyl-

i- -glucopyranoside (66).—Glycosylation of

D

-

D

-

D

acceptor 50 (252 mg, 0.243 mmol) with thio-

glycoside 24 (164 mg, 0.209 mmol) in abs

CH₂Cl₂(7.5 mL) promoted by NIS (65 mg,

0.29 mmol), TfOH (0.035 mL, 0.4 mmol), and

,

MS-4 A (900 mg) for 1 h at −20 °C as

described for the preparation of 56 and subse-

quent chromatography (20:1 toluene–MeOH)

of the residue on a column of silica gel (30 g)

followed by rechromatography (toluene13:1

toluene–isopropanol) gave recovered acceptor

50 (143 mg, 57%) and tetrasaccharide 66 (184

mg, 50% based on the donor): R_f0.25 (20:1

toluene–MeOH); [h]_D15° (c 1, CH₂Cl₂);

NMR (CDCl₃): ¹H, the spectrum was identical

to that of 65, excepting the absence of the

signal of the allyl moiety at l 5.71 (CH₂CHꢁ

CH₂), 5.15 (CH₂CHꢁCH₂), 5.06 (CH₂CHꢁ

CH₂), 4.24 (OCH₂CHꢁCH₂), 4.05 (OCH₂CHꢁ

CH₂), and the presence of the multiplets at l

3.95, 3.59 (OCH₂CH₂N₃), 3.35, 3.22 (CH₂N₃).

Anal. Calcd for C₈₂H₈₁Cl₃N₄O₃₃: C, 56.06; H,

4.65; Cl, 6.05; N, 3.19. Found: C, 55.86; H,

4.91; Cl, 6.45; N, 2.96.

Allyl O-(2,3,4,6-tetra-O-acetyl-i-

pyranosyl)-(13)-O-(4,6-di-O-acetyl-2-de-

oxy-2-trichloroacetamido-i- -glucopyranosyl)-

(13)-O-(2,4,6-tri-O-benzoyl-i- -galacto-

pyranosyl)-(14)-2,3,6-tri-O-benzoyl-i-

D

-galacto-

D

-

glucopyranoside (65).—Glycosylation of ac-

ceptor 41 (182 mg, 0.18 mmol) with donor 24

(104 mg, 0.133 mmol) in abs CH₂Cl₂(5 mL)

promoted by NIS (36 mg, 0.16 mmol), TfOH

,

(0.024 mL, 0.28 mmol), and MS-4 A (500 mg)

for 1 h at −20 °C as described for the prepa-

ration of 56 and subsequent chromatography

(toluene5:1 toluene–acetone) of the residue

on a column of silica gel (30 g) gave recovered

acceptor 41 (73 mg, 40%) and tetrasaccharide

65 (156 mg, 70% based on the donor): R_f0.14

(8:1 toluene–acetone); [h]_D13° (c 2, CH₂Cl₂);

Allyl

trichloroacetamido-i-

3)-O-(2,4,6-tri-O-benzoyl-i-

syl)-(14)-2,3,6-tri-O-benzoyl-i-

O-(2-deoxy-4,6-O-isopropylidene-2-

-glucopyranosyl)-(1

-galactopyrano-

-glucopy-

D

1

NMR (CDCl₃): H, see Table 2 for carbohy-

D

drate ring protons; l 8.15–7.95 (3 d, 6 H, J 8

Hz, 6 ortho protons of 3 Bz), 7.90 (t, 4 H, J 8

Hz, 4 ortho protons of 2 Bz), 7.75 (d, 2 H, J

8 Hz, 2 ortho protons of 1 Bz), 7.65–7.18 (m,

16 H, Ph), 6.90 (m, 3 H, Ph, NꢀH), 5.71 (m, 2

H, H-3^A, CH₂CHꢁCH₂), 5.15 (dd, 1 H, J_trans

17, J_gem1.8 Hz, CH₂CHꢁCH₂), 5.06 (dd, 1 H,

J_cis10.5 Hz, CH₂CHꢁCH₂), 4.24 (m, 1 H,

OCH₂CHꢁCH₂), 4.05 (m, OCH₂CHꢁCH₂),

2.08 (s, 3 H, Ac), 1.95 (2 s, 6 H, 2 Ac), 1.89 (3

s, 9 H, 3 Ac); ¹³C, l 171.1–168.9 (6

OC(O)CH₃), 165.9–164.7 (5 PhC(O)O), 161.7

(NꢀC(O)CCl₃), 133.6–127.8 (Ph, CH₂CHꢁ

CH₂), 117.7 (CHꢁCH₂), 100.8, 99.7, 99.6, 98.0

(4 C-1), 62.5, 61.9, 61.6, 60.8, (4 C-6), 59.1

(C-2^C), 20.6 (OCOCH₃). Anal. Calcd for

C₈₃H₈₂Cl₃NO₃₃: C, 57.69; H, 4.78; Cl, 6.16; N,

D

ranoside (75).—The reagent was prepared by

dropwise addition, at 0 °C, of acetyl chloride

(0.4 mL, 5.6 mmol) to abs MeOH (10 mL).

After 10 min, the reagent was added to solid

56 (260 mg, 0.18 mmol) and the mixture was

kept for 26 h at rt. Solid NaHCO₃was added

in small portions until gas evolution ceased,

the mixture was poured into aq NaHCO₃and

extracted with CH₂Cl₂(200 mL). The extracts

were dried and concentrated to give triol 74

(219 mg, 92%) as transparent glass: R_f0.57

(EtOAc). A solution of triol 74 (203 mg, 0.154

mmol) and 9CSA (5 mg) in 2,2-

dimethoxypropane (2.5 mL) was stirred for 4

h at rt and then for 1 h at 50 °C, Et₃N

(0.05 mL) was added, and the mixture

38

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

the absence of the signals of allyl moiety at l

117.7 (CHꢁCH₂), 70.0 (OCH₂CHꢁCH₂), and

the presence of the signals at 68.5

(OCH₂CH₂N₃), 50.5 (CH₂N₃). Anal. Calcd for

C₆₇H₆₃Cl₃N₄O₂₂: C, 58.20; H, 4.59; Cl, 7.69;

N, 4.05. Found C, 58.37; H, 4.72; N, 3.84.

Allyl O-[methyl (5-acetamido-4,7,8,9-tetra-

was coevaporated with toluene (3×5 mL).

Crystallization from 3:1 acetone–petroleum

ether (8 mL) gave 75 (162 mg, 77%): R_f0.44

(1:1 EtOAc–petroleum ether); [h]_D7° (c 2,

1

CH₂Cl₂); mp 157–159 °C; NMR (CDCl₃): H,

see Table 2 for carbohydrate ring protons; l

8.20–7.75 (6 d, 12 H, J 8 Hz, 12 ortho pro-

tons of 6 Bz), 7.65–7.30 (m, 16 H, Ph), 6.93 (t,

2 H, J 8 Hz, Ph), 6.82 (d, 1 H, J_NꢀH,28 Hz,

NꢀH), 5.72 (m, 2 H, H-3^A, OCH₂CHꢁCH₂),

5.14 (dd, 1 H, J_trans18.2, J_gem1.4 Hz,

CH₂CHꢁCH₂), 5.05 (dd, 1 H, J_cis10.4 Hz,

O-acetyl-3,5-dideoxy-

non - 2 - ulopyranosyl)onate] - (23) - O - (2,4,6-

tri-O-acetyl-i- -galactopyranosyl)-(13)-O-

(2-deoxy-2-trichloroacetamido-i- -glucopyran-

osyl) - (13) - O - (2,4,6 - tri - O - benzoyl - i -

galactopyranosyl)-(14)-2,3,6-tri-O-benzoyl-

i- -glucopyranoside (79).—A 0.1 M solution

D

-glycero-h-

D

-galacto-

D

-

CH₂CHꢁCH₂), 4.25 (dd, 1 H, J_gem13.2, J_vic

5

Hz, OCH₂CHꢁCH₂), 4.05 (m, 2 H, H-3^B,

OCH₂CHꢁCH₂), 2.89 (broaden s, 1 H, OH),

1.39, 1.31 (2 s, 6 H, 2 CH₃); ¹³C, l 165.4–

162.4 (6 PhC(O)O), 160.9 (NꢀC(O)CCl₃),

133.6–127.8 (Ph), 117.7 (CHꢁCH₂), 100.6,

99.7, 98.7 (3 C-1), 99.7 (CH₃)₂C), 70.0

(OCH₂CHꢁCH₂), 62.6, 61.8, 61.5 (3 C-6), 59.9

(C-2^C), 28.8, 18.9 (2 CH₃). Anal. Calcd for

C₆₈H₆₄Cl₃NO₂₂: C, 60.34; H, 4.77; Cl, 7.86; N,

1.03. Found: C, 60.27; H, 4.79; Cl, 8.01; N,

0.96.

D

of TMSOTf in CH₂Cl₂was prepared as fol-

lows. Abs CH₂Cl₂(5 mL) was stirred under Ar

,

with MS-4 A (2.5 g) for 1 h, then TMSOTf

(0.09 mL, 0.5 mmol) was added, and the

mixture was stirred for 1 h. Sieves were al-

lowed to sediment, and 0.03 mL of this solu-

tion were added with a syringe to a mixture of

imidate 73 (21 mg, 0.023 mmol), acceptor 75

,

(41 mg, 0.03 mmol), and MS-4 A in abs

CH₂Cl₂(2 mL) under Ar at −20 °C. After

stirring overnight at 0 °C, the reaction was

terminated by addition of solid NaHCO₃(100

mg), the mixture was ﬁltered through a pad of

Celite, diluted with CH₂Cl₂(30 mL), washed

with satd aq NaHCO₃, dried, and concen-

trated. For deacetonation, a solution of the

residue in CH₂Cl₂(5 mL) was treated with

90% aq CF₃CO₂H (0.5 mL) for 0.5 h at rt,

then coevaporated with toluene (4×10 mL)

with the bath temperature 25 °C. Chromatog-

raphy (EtOAc) of the residue on a column of

silica gel (12 g) gave (in order of elution) triol

74 (17 mg, 41%) and pentasaccharide 79 (36

mg, 75% based on imidate): R_f0.29 (EtOAc);

2-Azidoethyl O-(2-deoxy-4,6-O-isopropyli-

dene-2-trichloroacetamido-i-

syl)-(13)-O-(2,4,6-tri-O-benzoyl-i-

topyranosyl)-(14)-2,3,6-tri-O-benzoyl-i-

D

-glucopyrano-

-galac-

D

-

glucopyranoside (77).—Deacetylation of 57

(251 mg, 0.17 mmol) with AcCl (0.2 mL, 2.8

mmol) in MeOH (5 mL) for 18 h at rt as

described for the preparation of 75 and subse-

quent chromatography (toluene8:1 tolu-

ene–MeOH) on a column of silica gel (20 g)

afforded triol 76 (197 mg, 86%) as a white

foam: R_f0.34 (7:1 toluene–MeOH). Acetona-

tion of 76 (176 mg, 0.131 mmol) with 2,2-

dimethoxypropane (5 mL) and TsOH (10 mg)

for 3 h at rt as described for the preparation

of 75 followed by chromatography (toluene

1:1 toluene–EtOAc) on a column of silica gel

(20 g) afforded 77 (162 mg, 90%) as a white

foam: R_f0.27 (5:2 toluene–EtOAc); [h]_D11°

1

[h]_D12° (c 1, CH₂Cl₂); NMR (CDCl₃): H, see

Table 3 for carbohydrate ring protons; l

8.12–8.03 (3 d, 6 H, J 7.9 Hz, ortho protons

of 3 Bz), 7.95 (2 d, 4 H, J 8 Hz, ortho protons

of 2 Bz), 7.75 (d, 2 H, J 8 Hz, ortho protons

of 1 Bz), 7.70–7.13 (m, 16 H, Ph), 6.89 (t, 2

H, J 8 Hz, Ph), 6.80 (d, 1 H, J 6.9 Hz,

1

(c 1, EtOAc); NMR (CDCl₃): H, the spec-

trum was identical to that of 75 excepting the

absence of the signals of the allyl moiety at l

5.72 (OCH₂CHꢁCH₂), 5.14, 5.05 (CH₂CHꢁ

CH₂), 4.25, 4.05 (OCH₂CHꢁCH₂) and the

presence of the signals at l 3.89, 3.63

(OCH₂CH₂N₃), 3.38, 3.24 (CH₂N₃); ¹³C, the

spectrum was identical to that of 75, excepting

N–H^C), 5.71 (m,

3

H, H-4^B, H-3^A,

OCH₂CHꢁCH₂), 5.16 (dd, 1 H, J_trans17.3 Hz,

CHꢁCH₂), 5.06 (d, 2 H, J 10.4 Hz, CHꢁCH₂,

NꢀH^E), 4.23 (dd, 1 H, J_vic4.8, J_gem13 Hz,

OCH₂CHꢁCH₂), 4.02 (m, OCH₂CHꢁCH₂),

3.79 (s, 3 H, OMe), 2.18, 2.13, 2.09 (3 s, 9 H,

Table 3

Chemical shifts (l, ppm) and coupling constants (J, Hz) for carbohydrate ring protons in H NMR spectra of compounds 8, 9, 79, 83 in the solvent speciﬁed

1

Compound Unit

(solvent)

H-1 (J_1,2

)

H-2 (J_2,3

)

H-3eq

(J_3eq,4

H-3ax

H-4 (J_4,5

)

H-5 (J_5,6a

)

H-6a

(J_6a,6b

H-6b

H-7 (J_7,8

)

H-8 (J_8,9a

)

H-9a

(J_9a,9b

H-9b

(J_9b,8)

)

(J_3ax,4

)

(J_6b,5

3.81

3.87

)

8

Glc^A

Gal^B

4.54 (7.8) 3.38 (8)

4.44 (7.9) 3.58

3.66

3.65

3.63 (1.9) 3.99

(D₂O)

3.74 (3.3) 4.16 (0)

3.73

4.11 (3)

3.71

3.58

3.71

3.81

3.71–3.78

3.96

3.71–3.78

3.64

GlcN^C4.7 (8.3)

3.80

3.57

3.74

3.94 (0)

Gal^D

Neu^E

Glc^A

Gal^B

4.56 (7)

2.76 (4.4) ^a1.80 (12.1) 3.69

3.58

3.67

3.88

3.84

3.87

3.82

4.10

3.65

3.61

3.96

9

4.51 (7.9) 3.35 (8.3)

4.41 (7.9) 3.58

3.64

3.69 (3)

3.77

3.62

4.11 (0)

3.56

3.59 (\1) 3.94 (10.9) 3.77

(D₂O)

3.67

3.44

3.65

3.81

3.75–3.69

3.87

3.75–3.69

3.62

4.40 (0)

GlcN^C4.72 (8.3) 3.83

3.75

/

Gal^D

Neu^E

Glc^A

Gal^B

4.47 (7.8) 3.52 (9.7)

4.05 (2.9) 3.91 (0)

2.73 (4.4) ^b1.75 (12.1) 3.56

79

(CDCl₃)

4.70 (7.9) 5.46 (9.3)

4.63 (7.8) 5.52 (8.1)

5.70 (9.6) 4.14 (9.5) 3.69 (2)

3.95

4.11

4.40 (2)

5.75 (0)

3.30 (7.1) 3.53

3.69 (5.6) 3.73 (10.9) 3.30

GlcN^C5.21 (8.2) 2.99

3.80

4.04

3.80

4.04

Gal^D

Neu^E

Glc^A

Gal^B

4.56 (7.8) 4.92 (7.0)

4.50 (3.2) 4.81 (0)

3.89

2.53 (4.4) ^c1.60 (12.6) 4.88

3.96 (10.2) 3.57 ^d

5.31 (9.5) 5.26

83

(CDCl₃)

4.63 (7.8) 5.36 (9.4)

4.53 (7.8) 5.48 (10.3)

5.65 (9.4) 4.04 (9.4) 3.68 (\1) 4.40 (11)

3.97 (3.8) 5.50 (0)

3.84 3.86

4.32

3

3.57

3.50

3.85 (11.5) 3.05 (8)

(

GlcN^C4.92 (6.9) 3.21

3.63–3.72

Gal^D

Neu^E

4.67 (8)

4.82 (10)

4.45 (3.3) 4.74 (0)

3.60 (6.2) 3.82

3.95

3.54 (6.2)

2.47 (4.3) ^e1.61 (12.4) 4.80

3.55 ^f

5.28 (9.1) 5.49 (2.2) 4.24 (12.4) 3.89 (6.1)

1

4

^aJ_3eq,3ax12.1 Hz.

^bJ_3eq,3ax12.1 Hz.

^cJ_3eq,3ax12.6 Hz.

^dJ_6,72 Hz.

^eJ_3eq,3ax12.4 Hz.

^fJ_6,72 Hz.

40

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

and 4-OH derivative 82 (337 mg, 66%) as a

white foam. Recycling of recovered 58 (156

mg, 0.1 mmol) gave an additional amount of

82 (101 mg, 65%). Total yield 438 mg, 87%: R_f

0.59 (3:1 toluene–EtOAc); [h]_D33° (c 1,

3 Ac), 2.04, 2.02 (2 s, 12 H, 4 Ac), 1.98 (s, 3

H, Ac). Anal. Calcd for C₉₇H₁₀₃Cl₃N₂O₄₂: C,

56.14; H, 5.00; Cl, 5.13; N, 1.35. Found C,

56.13; H, 4.92; Cl, 5.29; N, 1.17.

2-Azidoethyl O-[methyl (5-acetamido-4,7,

1

EtOAc); NMR (CDCl₃): H, see Table 2 for

8,9-tetra-O-acetyl-3,5-dideoxy-

D

-glycero-h- -

D

carbohydrate ring protons; l 8.11, 8.08, 8.01

(3 d, 2 H each, J 7.5 Hz, 6 ortho protons of 3

Bz), 7.92 (d, 4 H, J 7.5 Hz, 4 ortho protons of

2 Bz), 7.78 (d, 2 H, J 7.6 Hz, ortho protons of

1 Bz), 7.65–7.12 (m, 26 H, Ph), 6.90 (t, 2 H, J

7.5 Hz, Ph), 6.68 (d, 1 H, J_NꢀH,27 Hz, NꢀH^C),

4.68, 4.58 (2 d, 1 H each, J 11.2 Hz, 2

PhCH₂), 4.46–4.41 (m, 4 H, 2 PhCH₂, H-6a^A,

galacto-non-2-ulopyranosyl)onate]-(23)-O-

(2,4,6 - tri - O - acetyl - i - - galactopyranosyl)-

(13)-O-(2-deoxy-2-trichloroacetamido-i-

-glucopyranosyl)-(13)-O-(2,4,6-tri-O-ben-

zoyl-i- -galactopyranosyl)-(14)-2,3,6-tri-

O-benzoyl-i- -glucopyranoside (81).—Glyco-

D

sylation of acceptor 77 (108 mg, 0.078 mmol)

with imidate 73 (60 mg, 0.065 mmol) in

CH₂Cl₂(5 mL) promoted by TMSOTf (0.264

H-6b^A), 3.90 (m,

3

H, H-6a^B, H-3^C,

,

mL of 0.1 M solution in CH₂Cl₂) and MS-4 A

OCH₂CH₂N₃), 3.63 (m, 1 H, OCH₂CH₂N₃),

3.37 (m, 1 H, CH₂N₃), 3.26 (m, 2 H, H-6b^B,

CH₂N₃); ¹³C, see Table 4 for carbohydrate

ring carbons; l 165.8–164.6 (6 PhC(O)O),

161.6 (NꢀC(O)CCl₃), 139.1, 138.5 (2 ipso Bn),

133.4–127.6 (Ph), 74.6, 73.7 (PhCH₂), 68.4

(OCH₂CH₂N₃), 50.5 (CH₂N₃). Anal. Calcd for

C₇₈H₇₁Cl₃N₄O₂₂: C, 61.52; H, 4.70; N, 3.68.

Found C, 61.94; H, 5.01; N, 3.56.

followed by deacetonation with CF₃CO₂H

was performed as described for the prepara-

tion of 79. Chromatography (toluene1:2

toluene–acetone) of the residue on a column

of silica gel followed by gel-permeation chro-

matography in toluene on a 1×50 cm column

of Bio-Beads SX3 gel gave 81 (91 mg, 71%

based on imidate): R_f0.45 (1:1 toluene–ace-

tone); [h]_D13° (c 1, EtOAc); NMR (CDCl₃):

¹H, the spectrum was identical to that of 79,

excepting disappearance of the signals of allyl

moiety at l 5.71 (OCH₂CHꢁCH₂), 5.16, 5.06

(CHꢁCH₂), 4.23, 4.02 (OCH₂CHꢁCH₂) and

the presence of four one-proton multiplets at

l 3.80, 3.55 (OCH₂CH₂N₃), 3.25, 3.15

(CH₂N₃); ¹³C, l 170.8ꢀ169.4 (OC(O)CH₃),

167.8 (C-1^E), 165.8–164.8 (6 PhC(O)O), 161.6

(NꢀC(O)CCl₃), 133.8–127.9 (Ph), 101.0,

100.6, 99.8, 98.9 (4 C-1), 96.6 (C-1^E), 58.7

(C-2^C), 53.2 (OMe), 50.5 (CH₂N₃), 49.1 (C-

5^E), 37.7 (C-3^E), 23.1 (NꢀC(O)CH₃), 21.4–

2-Azidoethyl O-[methyl (5-acetamido-4,7,8,

9-tetra-O-acetyl-3,5-dideoxy-

D

-glycero-h- -

D

galacto-non-2-ulopyranosyl)onate]-(23)-O-

(2,4,6 - tri - O - acetyl - i - - galactopyranosyl)-

(14)-O-(3,6-di-O-benzyl-2-deoxy-2-tri-

chloroacetamido-i- -glucopyranosyl)-(13)-

O-(2,4,6-tri-O-benzoyl-i- -galactopyranosyl)-

(14)-2,3,6-tri-O-benzoyl-i- -glucopyra-

D

noside (83).—Abs CH₂Cl₂(5 mL) was stirred

,

under Ar with MS-4 A (2.5 g) for 1 h, then

BF₃·Et₂O (0.063 mL, 0.5 mmol) was added,

and the mixture was stirred for 1 h. Sieves

were allowed to sediment, and 0.1 M solution

of BF₃·Et₂O in CH₂Cl₂thus obtained was

used in this reaction. This solution was always

freshly prepared, because it lost catalytic ac-

tivity within 1–2 days.

20.5

(OC(O)CH₃).

Anal.

Calcd

for

C₉₆H₁₀₂Cl₃N₅O₄₂: C, 54.80; H, 4.89; N, 3.33.

Found C, 54.75; H, 4.93; N, 2.98.

2-Azidoethyl O-(3,6-di-O-benzyl-2-deoxy-2-

trichloroacetamido-i-

3)-O-(2,4,6-tri-O-benzoyl-i-

osyl)-(14)-2,3,6-tri-O-benzoyl-i-

D

-glucopyranosyl)-(1

-galactopyran-

-glucopy-

To a stirred mixture of acceptor 82 (102 mg,

0.067 mmol) and MS AW-300 in abs CH₂Cl₂

(5 mL), three equal portions of imidate 73 (in

total 132 mg, 0.143 mmol) and BF₃·Et₂O (in

total 0.141 mL of the above described 0.1 M

solution in CH₂Cl₂) were added under Ar at

−27 °C with 48 h intervals. The reaction mix-

ture was diluted with CH₂Cl₂(30 mL), ﬁltered

through a pad of Celite, washed with satd aq

NaHCO₃, dried, and concentrated. Chro-

D

ranoside (82).—Deacetylation of 58 (520 mg,

0.33 mmol) in MeOH (10 mL) with AcCl (0.4

mL) for 18 h at rt as described for the prepa-

ration of 77 and subsequent chromatography

(toluene1:1 toluene–EtOAc) on a column

of silica gel (20 g) gave (in order of elution)

recovered starting material 58 (156 mg, 30%)

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

41

Table 4

Chemical shifts (l, ppm) for carbohydrate ring carbons in ¹³C NMR spectra of compounds 1, 3, 5–9, 15, 16, 18, 30, 31, 49, 52,

53, 72, 82, 83 in the solvent speciﬁed

Compound (solvent)

1 (D₂O)

Unit

C-1

C-2

C-3

C-4

C-5

C-6

C-7

C-8

C-9

Gal^A

GlcN^B

Glc^A

103.7

102.2

104.1

103.9

103.1

104.1

103.9

104.0

103.0

104.0

103.5

104.5

102.1

104.0

103.9

104.0

103.1

104.1

103.9

103.7

174.9

103.0

104.0

103.5

104.5

175.0

83.8

70.7

83.0

74.6

74.7

83.1

75.5

75.3

83.2

73.3

73.6

75.3

83.1

83.3

73.6

73.4

83.2

73.3

73.7

75.4

83.2

73.3

76.7

40.8

75.4

83.0

83.3

76.8

41.3

71.2

81.9

79.0

79.2

70.9

72.1

72.8

71.0

80.6

77.1

70.6

75.5

82.8

75.0

74.7

72.6

76.1

78.8

72.5

76.3

76.2

71.1

37.4

69.3

70.8

79.6

69.5

70.9

79.4

69.4

79.3

69.7

79.5

69.3

69.6

79.5

69.1

79.4

69.7

79.5

69.4

79.3

68.6

69.4

79.5

69.4

69.6

68.4

69.2

81.4

78.1

71.4

75.9

68.0

68.1

75.9

67.4

70.9

75.8

67.6

80.1

69.5

71.0

71.1

75.4

69.6

73.4

75.3

69.4

75.3

67.3

69.2

75.8

76.7

75.9

76.0

76.8

75.9

76.0

75.7

76.5

75.9

76.0

76.3

75.8

76.0

75.7

76.5

75.9

76.1

75.7

76.3

52.9

75.9

76.0

76.4

76.2

52.8

70.4

70.1

77.5

78.9

71.2

74.9

73.1

71.3

73.8

71.4

72.7

75.8

74.6

77.0

76.8

73.1

71.9

73.4

73.0

71.9

75.0

70.4

48.8

62.0

61.5

61.3

62.1

61.7

61.0

62.1

61.1

62.2

61.1

62.0

61.7

62.1

61.0

62.1

61.0

62.1

61.1

62.2

61.0

62.2

74.1

61.1

62.1

61.7

62.1

73.9

68.3

69.6

67.8

61.6

62.2

61.0

63.9

63.7

61.5

61.2

69.7

61.9

61.7

62.3

61.9

70.6

62.3

62.0

68.7

61.3

71.9

56.7

73.9

71.1

56.8

73.8

71.1

56.3

72.1

73.8

71.1

55.8

71.8

56.0

71.1

56.3

72.1

73.8

71.1

56.4

70.5

101.0

73.8

71.1

55.7

70.2

100.8

57.2

56.2

57.5

56.7

70.2

68.2

71.6

69.7

56.3

53.4

69.9

74.0

70.9

56.8

56.6

71.5

71.7

58.6

71.3

71.5

53.0

70.4

96.7

3 (D₂O)

5 (D₂O)

Gal^B

GlcN^C

Glc^A

Gal^B

GlcN^C

Gal^D

Glc^A

6 (D₂O)

7 (D₂O)

8 (D₂O)

Gal^B

GlcN^C

Gal^D

GlcN^A

Gal^B

GlcN^C

Gal^D

Glc^A

Gal^B

GlcN^C

Gal^D

Neu^E

Glc^A

69.3

69.4

72.9

63.8

63.7

9 (D₂O)

Gal^B

GlcN^C

Gal^D

Neu^E

15 (5:1 CDCl₃–CD₃OD)

16 (10:1 CDCl₃–CD₃OD)

18 (CDCl₃)

83.6

82.3

82.5

100.1

84.3

101.2

100.9

99.2

30 (CDCl₃)

GlcN^A

Gal^B

31 (CDCl₃)

49 (CDCl₃)

Glc^A

Gal^B

52 (10:1 CDCl₃–CD₃OD)

53 (CDCl₃)

GlcN^A

Gal^B

98.9

100.3

103.2

104.1

103.7

102.1

101.0

100.8

98.4

100.9

100.7

98.7

99.7

167.7

72 (D₂O)

Glc^A

Gal^B

GlcN^C

GlcN^D

Glc^A

82 (CDCl₃)

83 (CDCl₃)

Gal^B

GlcN^C

Glc^A

Gal^B

GlcN^C

Gal^D

Neu^E

67.0

67.6

62.3

matography (toluene1:2 toluene–acetone)

of the residue on a column of silica gel (20 g)

gave pentasaccharide 83 (124 mg, 81% based

on acceptor): R_f0.46 (1:1 toluene–acetone);

42

A.A. Sherman et al. / Carbohydrate Research 336 (2001) 13–46

1

ring, reﬁlled with H₂, and stirred for 0.5 h at

rt. The mixture was ﬁltered through a pad of

Celite, the pad was washed thoroughly with

water, and the combined ﬁltrate and washings

were concentrated. The residue was subjected

to gel-permeation chromatography on a 2.5×

100 cm column of Sephadex G-10 gel by

elution with water to give after freeze-drying 1

(63 mg, 95%) as amorphous powder: R_f0.12

(BPHCl); [h]_D−124° (c 1, water); NMR

[h]_D14° (c 1, EtOAc); NMR (CDCl₃): H, see

Table 3 for carbohydrate ring protons; l 7.99,

7.96, 7.91 (3 d, 2 H each, J 7.7 Hz, 6 ortho

protons of 3 Bz), 7.83 (d, 4 H, J 7.7 Hz, 4

ortho protons of 2 Bz), 7.66 (d, 2 H, J 7.7 Hz,

2 ortho protons of 1 Bz), 7.57–7.05 (m, 26 H,

Ph), 6.79 (t, 2 H, J 7.6 Hz, Ph), 6.70 (d, 1 H,

J^C_{N−H, 2}7.4 Hz, NꢀH^C), 5.08 (d, 1 H,

C

J_{N−H , 5}10.2 Hz, NꢀH^E), 4.70 (d, 1 H, J 11

E

Hz, PhCH₂), 4.32 (s, 2 H, PhCH₂), 4.27 (d, 1

H, PhCH₂), 3.82 (m, 6 H, H-9b^E, H-4^C, H-6a^B,

H-3^C, OCH₂CH₂N₃, H-6a^D), 3.72 (s, 3 H,

OMe), 3.52 (m, 4 H, H-5^B, H-6^E, H-6b^D,

OCH₂CH₂N₃), 3.28 (m 1 H, CH₂N₃), 3.14 (m,

CH₂N₃), 2.11, 2.05, 2.01, 1.91, 1.88, 1.85, 1.79,

1

(D₂O): H, see Table 2 for carbohydrate ring

protons; l 4.09 (m, 1 H, OCH₂CH₂NH₂), 3.93

(m, 1 H, OCH₂CH₂NH₂), 3.24 (t, 2 H, J 5 Hz,

OCH₂CH₂NH₂), 2.00 (s, 3 H, Ac); ¹³C, see

Table 4 for carbohydrate ring carbons; l

176.0 (NꢀC(O)CH₃), 66.8 (OCH₂CH₂NH₂),

40.5 (CH₂NH₂), 23.2 (NꢀC(O)CH₃). MALDI-

TOF-MS: Calcd for [C₁₆H₃₀N₂O₁₁+H]⁺:

427.2. Found: 427.5.

13

1.77 (8 s, 3 H each, 8 Ac); C, see Table 4 for

carbohydrate ring carbons; l 170.7–169.5

(OC(O)CH₃), 165.7–164.5 (PhC(O)O), 161.3

(NꢀC(O)CCl₃), 138.4, 137.9 (2 ipso Bn),

133.2–126.8 (Ph), 68.3 (OCH₂CH₂N₃), 52.9

(OMe), 50.3 (CH₂N₃), 23.0 (NꢀC(O)CH₃),

21.2–20.4 (OC(O)CH₃). Anal. Calcd for

C₁₁₀H₁₁₄Cl₃N₅O₄₂: C, 57.83; H, 5.03; N, 3.07.

Found C, 58.09; H, 5.23; N, 2.76.

2-Aminoethyl O-(2-acetamido-2-deoxy-i-

glucopyranosyl)-(13)-O-(i- -galactopyra-

nosyl)-(14)-i- -glucopyranoside (2).—

D

-

D

Deacylation of 57 (44 mg, 0.03 mmol) fol-

lowed by N-acetylation as described for the

preparation of 1 and subsequent gel-perme-

ation chromatography on a 2×20 cm column

of Sephadex G-10 gel by elution with water

gave 70 (16.7 mg, 93%) after freeze-drying: R_f

0.26 (BPHCl); [h]_D3° (c 1, water).

2-Aminoethyl O-(2-deoxy-2-acetamido-i-

glucopyranosyl)-(13)-i- -galactopyranoside

D

-

D

(1).—To a solution of 60 (245 mg, 0.247

mmol) in abs MeOH (14 mL), solid MeONa

(187 mg, 3.46 mmol) was added, and the

mixture was stirred for 18 h at rt. At this

point, TLC indicated total O-deacylation and

some N-detrichloroacetylation. In order to

complete the latter, water (1 mL) was added,

and stirring was continued for another 18 h.

Ac₂O (0.5 mL) was added dropwise at 0 °C,

and after 18 h at rt, the mixture was concen-

trated. A solution of the residue in water was

treated with KU-2 (H⁺) cation-exchange

resin, the resin was ﬁltered off, and the ﬁltrate

was concentrated. The solid residue was ex-

tracted with EtOAc (3×2 mL) and then sub-

jected to gel-permeation chromatography on a

2.5×100 cm column of Sephadex G-10 gel by

elution with water, followed by rechromatog-

raphy by elution with 0.5% aq NH₃to give

after freeze-drying 67 (104 mg, 94%) as trans-

parent glass: R_f0.32 (BPHCl); [h]_D−5° (c 1,

water).

Hydrogenation of 70 (16 mg, 0.026 mmol)

as described for the preparation of 1 and

subsequent gel-permeation chromatography

on a 1.5×100 cm column of TSK HW-40S

gel by elution with 0.1 M aq AcOH gave 2

(14.4 mg, 94%) after freeze-drying: [h]_D3° (c

1

1, water); NMR (D₂O): H, the spectrum was

identical to that of 3 (see below), excepting the

disappearance of the signals of the allyl moi-

ety at

l

5.99 (OCH₂CHꢁCH₂), 5.37

(OCH₂CHꢁCH₂), 5.28 (OCH₂CHꢁCH₂), 4.39

(OCH₂CHꢁCH₂), 4.23 (OCH₂CHꢁCH₂), and

the presence of two one-proton multiplets at l

4.12, 3.96 (OCH₂CH₂NH₂) and two-proton

13

triplet at l 3.27 (CH₂NH₂); C, the spectrum

was identical to that of 3 (see below), except-

ing the disappearance of the signals of allyl

moiety at l 134.5 (OCH₂CHꢁCH₂), 119.8

(OCH₂CHꢁCH₂), 71.8 (OCH₂CHꢁCH₂), and

the presence of the signals at l 67.0 (OCH₂-

CH₂NH₂) and 40.5 (CH₂NH₂). MALDI-TOF-

To a solution of 67 (70 mg, 0.16 mmol) in

water (3 mL), Pd–C (5 mg) was added, the

mixture was degassed under vacuum with stir-

Article Doi

Study of glycosylation with N-trichloroacetyl-D-glucosamine derivatives in the syntheses of the spacer-armed pentasaccharides sialyl lacto-N-neotetraose and sialyl lacto-N-tetraose, their fragments, and analogues

DOI: 10.1016/S0008-6215(01)00213-0

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Authors:

Article abstract of DOI:10.1016/S0008-6215(01)00213-0

Full text of DOI:10.1016/S0008-6215(01)00213-0

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