Efficient synthesis of man2, man3, and man 5 oligosaccharides, using mannosyl iodide donors

Article abstract of DOI:10.1021/jo051360d

A highly efficient protocol for making Man₃ and Man₅ oligosaccharides with use of orthogonally protected glycosyl iodide donors has been developed. Glycosylation of a C-2-O-acetyl mannosyl iodide donor in the presence of silver trifl

Full text of DOI:10.1021/jo051360d

Efficient Synthesis of Man2, Man3, and Man5 Oligosaccharides,
Using Mannosyl Iodide Donors1
Son N. Lam† and Jacquelyn Gervay-Hague*
Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616
gervay@chem.ucdavis.edu
Received June 30, 2005
A highly efficient protocol for making Man3 and Man5 oligosaccharides with use of orthogonally
protected glycosyl iodide donors has been developed. Glycosylation of a C-2-O-acetyl mannosyl iodide
donor in the presence of silver triflate at -40 °C initially gave a mixture of the desired R-linked
mannoside and an orthoacetate resulting from attack at the C-2 acetate. However, upon warming
to room temperature the orthoacetate quantitatively rearranged to the desired oligosaccharide.
Employing a 3,6-dihydroxy acceptor and subjecting it to double glycosidation quickly afforded high
mannose sugars in nearly quantitative yields. Glycosyl iodide donors offer advantages over
previously reported chloride donors as the reactions are faster, proceed in higher yields, and are
not diminished in higher order constructs. These studies continue to dispel the notion that glycosyl
iodides are too reactive to be of synthetic utility.
Introduction
1 and 2, respectively. Polyvalent presentation appears
to be an important factor in this recognition process as
the disaccharide alone is 100 times less effective in
binding to CVN than either 1 or 2. These same high
mannose structures are required for recognition of 2G12,
an HIV-associated neutralizing antibody.7 Moreover,
investigations in our own laboratory have led to the
hypothesis that carbohydrate/carbohydrate interactions
may mediate adhesion processes required for sexual
transmission of the virus.8 To probe this hypothesis, we
have targeted the synthesis of high-mannose oligosac-
charides. Here we disclose a highly efficient synthesis of
Man5 corresponding to the C-6 branch of Man9 (Figure
1).
The HIV-1 envelope is highly glycosylated with N-
linked high-mannose oligosaccharides that play critical
roles in the pathology of the disease.2 For example,
mannose undecasaccharide 1 (Man9) and decasaccharide
2 (Man8) are primary targets for cyanovirin-N (CVN),
which is a multivalent anti-HIV lectin isolated from
cyanobacterium Nostoc ellipsosporum.3-6 CVN targets a
disaccharide (3), which is triply and doubly displayed on
* Address correspondence to this author. Phone: +1-530-754-9577.
Fax: +1-530-752-8995.
† Current address: National Institutes of Health, 9000 Rockville
Pike, Bethesda, MD 20892.
(1) Taken in part from the dissertation of Son Lam, University of
California, Davis, 2003.
(7) Scanlan, C. N.; Pantophlet, R.; Wormald, M. R.; Ollmann
Saphire, E.; Stanfield, R.; Wilson, I. A.; Katinger, H.; Dwek, R. A.;
Rudd, P. M.; Burton, D. R. J. Virol. 2002, 76 (14), 7306-7321.
(8) (a) McReynolds, K. D.; Hadd, M. J.; Gervay-Hague, J. Bioconj.
Chem. 1999, 10, 1021-1031. (b) McReynolds, K. D.; Bhat, A.; Conboy,
J. C.; Saavedra, S. S.; Gervay-Hague, J. Bioorg., Med. Chem. 2002,
10, 625-637. (c) Conboy, J. C.; McReynolds, K. D.; Gervay-Hague, J.;
Saavedra, S. S. J. Am. Chem. Soc. 2002, 124, 968-977. (d) Conboy, J.
C.; McReynolds, K. D.; Gervay-Hague, J.; Saavedra, S. S. Angew.
Chem., Int. Ed. 2000, 39, 2882-2884. (e) Nolting, B. N.; Yu. J.-J.; Liu,
G.-Y.; Cho, S.-J.; Kauzlarich, S.; Gervay-Hague, J. Langmuir 2003,
19, 6465-6473.
(2) Yeh, J. C.; Seals, J. R.; Murphy, C. I.; van Halbeek, H.;
Cummings, R. D. Biochemistry 1993, 32, 11087-99.
(3) Boyd, M. R.; Gustafson, K. R.; McMahon, J. B.; Shoemaker, R.
H.; O’Keefe, B. R.; Mori, T. Antimicrob. Agents Chemother. 1997, 41,
1521-1530.
(4) Bewley, C. A.; Kiyonaka, S.; Hamachi, I. J. Mol. Biol. 2002, 322,
881-889.
(5) Bewley, Ca.; Otero-Quintero, S. J. Am. Chem. Soc. 2001, 123,
3892-3902.
(6) Barrientos, L. G.; Gronenborn, A. M. Mini-Rev. Med. Chem. 2005,
5, 21-31.
10.1021/jo051360d CCC: $30.25 © 2005 American Chemical Society
Published on Web 09/27/2005
8772
J. Org. Chem. 2005, 70, 8772-8779

Synthesis of High-Mannose Oligosaccharides
FIGURE 1. Representative high-mannose oligosaccharides of HIV-1 gp120.
FIGURE 2. Retrosynthesis of Man3 and Man5 methyl paraben glycoconjugates.
We have recently demonstrated that mannosyl iodides
efficiently undergo R glycosidation under in situ anomer-
ization conditions.9 The reaction is essentially quantita-
tive, but purification is impeded by the formation of a
glycal byproduct that coelutes with the product. We were
able to scavenge the glycal by reacting it with dimethyl
dioxirane to form the 1,2 anhydrosugar, which was
trapped by norbornene-2-methanol and subjected to
ROMP producing a polymer that could be filtered from
the desired material. While we were happy to retrieve
greater than 70% yield of the product, we decided to
explore alternative methods for activation of the glycosyl
iodide in hopes of avoiding glycal formation and improv-
ing upon the overall yields.
donor substrate (II) to yield trisaccharide III, which could
be further extended to arrive at the target molecule IV
(Figure 2). We chose to incorporate methyl paraben (X)
at the reducing end of Man5 to facilitate purification and
provide a handle for conjugation to various supports for
biological analyses. These studies led to a highly efficient
synthesis of HIV-1 gp120 mannose di-, tri-, and pen-
tasaccharides.
Results and Discussion
The synthesis of the core reducing sugar began with
commercially available and readily synthesized10 3,4,6-
tri-O-benzyl mannosyl ortho ester 4 (Scheme 1). HOAc
mediated hydrolysis of the ortho ester quickly afforded
2-O-acetyl-3,4,6-tri-O-benzyl-D-mannose 5.11 After acety-
The retrosynthetic analysis shown in Figure 2 begins
with a 3,6-orthogonally protected mannose derivative (I)
serving as an acceptor for the selectively protected C-2
(10) Millar, A.; Kim, K. H.; Minster, D. K.; Ohgi, T.; Hecht, S. M. J.
Org. Chem. 1986, 51, 189-196.
(9) Lam, S. N.; Gervay-Hague, J. J. Org. Chem. 2005, 70, 2387-90.
J. Org. Chem, Vol. 70, No. 22, 2005 8773

Lam and Gervay-Hague
SCHEME 1. Synthesis of p-Methoxycarbonylphenyl Mannopyranoside
SCHEME 2. Synthesis of Man2 (12)
1
lation, the 1,2-diacetate 612 was used as a glycosyl donor
via Lewis acid assisted O-arylation to provide the R-O-
aryl mannopyranoside 7 in 92% isolated yield. Quantita-
tive C-2 deacetylation of 7 with NaOMe in MeOH
provided 8. Compound 4 was also used for the formation
of glycosyl iodide 9 in a one-pot procedure employing
iodotrimethylsilane (TMSI).
In a model study, AgOTf activation of mannosyl iodide
donor 9 at -40 °C and subsequent addition of acceptor 8
provided the R-(1f2)-linked disaccharide 10a (Scheme
2) as confirmed by the J coupling (1JH1,C1 ) 175.8 Hz,
1JH1′,C1′ ) 170.9 Hz). However, the 1,2-disaccharide ortho
ester 10b was also observed (a separable 3:1 mixture).
This did not prove problematic as BF3‚Et2O mediated
rearrangement13 of 10b to 10a proceeded quantitatively
upon warming to 0 °C. C-2′ deacetylation gave 11 and
catalytic hydrogenation at an elevated pressure supplied
p-methoxycarbonylphenyl D-mannopyranosyl-R-(1f2)-R-
D-mannopyranoside 12. These preliminary studies dem-
onstrated that AgOTf mediated glycosidations with 9
were identical with analogous reactions utilizing glycosyl
chloride donors with respect to yields.14 However, the
(11) Schmidt, R. R.; Effenberger, G. Liebigs Ann. Chem. 1987, 825-
831.
(12) Mayer, T. G.; Schmidt, R. R. Eur. J. Org. Chem. 1999, 1153-
1165.
(13) Kong, F.; Zhu, Y. Carbohydr. Res. 2001, 332, 1-21.
8774 J. Org. Chem., Vol. 70, No. 22, 2005

Synthesis of High-Mannose Oligosaccharides
SCHEME 3. Synthesis of 3,6-Diol Core Acceptor 18
advantage of glycosyl iodides was clear as reaction times
were significantly reduced, from >16 to 3 h. Acid catalysis
also proved more efficient than in situ anomerization as
no glycal was observed.9
borates in vacuo, and flash chromatography. Satisfactory
results (70% yield) were achieved on large scales (10 g
of sugar) while quantitative transformations were achieved
with small amounts (1 g of sugar). Through this two-step
protocol, we prepared large quantities of 15. Although
only 13-endo was needed in this situation to provide the
desired 3,6-diol 6, 13-exo was not discarded as it is also
an important building block for numerous other natural
products and oligomers.25-27 This protocol essentially
bypasses the need for tin reagents and proved more
attractive than alternative methods employed by Ogawa
and co-workers.28-30 The 3,6-diol 15 was quantitatively
acetylated providing 16 and subsequent acetolysis pre-
sented 1,3,6-tri-O-acetyl-2,4-di-O-benzyl-D-mannopyra-
nose 17.28 Treatment of 17 with BF3‚Et2O in the presence
of methyl paraben with concomitant deacetylation af-
forded 18. The core diol acceptor was repeatedly prepared
in high yields over multiple successive chromatography-
free steps, 88% from 16 and 91% from 17.
With the orthogonally protected diol acceptor (18) in
hand, the double glycosidation was pursued. Reaction of
18 with 9 using AgOTf activation provided trisaccharide
19 in 91% yield after chromatography, Scheme 4. Instead
of adding BF3‚OEt2 to effect the orthoacetate rearrange-
ment, we simply let the reaction warm to room temper-
ature from -40 °C over 3 h. After the usual workup, no
ortho ester formation was detected as evidenced by NMR;
JC1,H1 coupling constants revealed only R-mannosyl link-
ages (1JH1′′3,C1′′3 ) 172.0 Hz, 1JH1′′6,C1′′6 ) 171.0 Hz, 1JH1′,C1′
) 170.5 Hz). In comparison to double glycosidations in
Encouraged by these results, we set out to prepare a
3,6 orthogonally protected sugar to serve as the core
acceptor 18 (Scheme 3). Acid-catalyzed acetal transfer
to R-methyl-D-mannopyranoside afforded dibenzylidene
mannose 13 as a mixture of isomers that could be
separated by crystallization.15 Numerous methods exist
to regioselectively open the acetal giving orthogonally
4-O-benzyl16-20 or 6-O-benzyl20-23 sugars. When reacted
with borane‚tetrahydrofuran complex in the presence of
dibutylborotriflate 13-exo quantitatively afforded methyl
3,4-di-O-benzyl-R-D-mannopyranoside 14 while 13-endo
generated methyl 2,4-di-O-benzyl-R-D-mannopyranoside
15.24 In our hands, this reduction was conducted cleanly
and smoothly within 1 h under strict anhydrous condi-
tions. However, longer reaction times were required in
situations where rigorous exclusion of water was not met.
Upon completion of the reaction, the workup simply
required quenching with methanol, removal of the methyl
(14) Ogawa, T.; Katano, K.; Sasajima, K.; Matsui, M. Tetrahedron
1981, 37, 2779-2786.
(15) Ferro, V.; Mocerino, M.; Stick, R. V.; Tilbrook, M. G. Aust. J.
Chem. 1988, 41, 813-815.
(16) Bhattacharjee, S. S.; Gorin, P. A. Can J. Chem. 1969, 47, 1195-
1206.
(17) Liptak, A.; Imre, J.; Harangi, J.; Nanasi, P. Tetrahedron 1982,
38, 3721-3729.
(18) Garegg, P. J. Pure Appl. Chem. 1984, 56, 845-858.
(19) Johansson, R.; Samuelsson, B. J. Chem. Soc., Perkin Trans. 1
1984, 2371-2374.
(20) Oikawa, M.; Liu, W. C.; Nakai, Y.; Koshida, S.; Fukase, K.;
Kusumoto, S. Synlett 1996, 1179-1180.
(25) Alker, D.; Jones, D. N.; Taylor, G. M.; Wood, W. W. Tetrahedron
Lett. 1991, 32, 1667-1670.
(26) Handa, S.; Tsang, R.; McPhail, A. T.; Fraser-Reid, B. J. Org.
Chem. 1987, 52, 3489-3491.
(27) Klemer, A.; Rodemeyer, G. Chem. Ber. 1974, 107, 2612-2614.
(28) Ogawa, T.; Sasajima, K. Tetrahedron 1981, 37 (16), 2787-2792.
(29) Ogawa., T.; Matsui, M. Carbohydr. Res. 1978, 62, C1-C4.
(30) Ogawa, T.; Katano, K.; Sasajima, K.; Matsui, M. Tetrahedron
1981, 37, 2779-2786.
(21) Garegg, P. J.; Hultberg, H.; Wallin, S. Carbohydr. Res. 1982,
108, 97-101.
(22) DeNino, M. P.; Etienne, J. B.; Duplantier, K. C. Tetrahedron
Lett. 1995, 36, 669-672.
(23) Ek, M.; Garegg, P. J.; Hultberg, H.; Oscarson, S. J. Carbohydr.
Chem. 1983, 2, 305-311.
(24) Lu, J.; Chan, T.-H. Tetrahedron Lett. 1998, 39, 355-358.
J. Org. Chem, Vol. 70, No. 22, 2005 8775

Lam and Gervay-Hague
SCHEME 4. Syntheses of Man3 (21) via Double Glycosidation
SCHEME 5. Synthesis of Man5 (23) via Double Glycosidation
the glycosyl chloride work, this double glycosidation
showed tremendous reduction in time (2 days to 3 h) and
a slight enhancement of isolated yield (79 to 91%).14
Global deprotection via deacetylation (to give 20) and
hydrogenation afforded trisaccharide 21 in 82% purified
yield.
donor 9 in the rapid construction of Man2, Man3, and
Man5 oligosaccharides. These represent the first cases
where a C-2 participating group was employed in the
formation of glycosidically linked oligosaccharides using
glycosyl iodides. Although ortho ester formation posed a
problem in initial glycosidations, simply allowing the
reaction to warm to room temperature remedied the
problem. AgOTf mediated glycosidations proved facile
and efficient, as the transformations were often nearly
quantitative. This process complements in situ anomer-
ization glycosidations in demonstrating that a glycosyl
iodide with a C-2 participating group is equally efficient
and ameliorates problems associated with glycal forma-
tion. Glycosyl iodides were once thought too reactive to
be of synthetic utility, these studies continue to dispel
that notion. Overall, the use of glycosyl iodides toward
oligosaccharide synthesis has proven extremely success-
ful.
Further extension of this methodology led to the
efficient synthesis of Man5 (23) with similar savings in
required time. In the event, action of 9 with AgOTf in
the presence of acceptor 20 supplied pentasaccharide 22
1
1
(1JH1,C1 ) 173.0 Hz, JH1,C1 ) 171.0 Hz, JH1,C1 ) 171.0
1
1
Hz, JH1,C1 ) 172.5 Hz, JH1,C1 ) 170.5 Hz) without
complication in 91% purified yield, Scheme 5. Global
deprotection yielded the pentasaccharide 23 in pure form,
86% yield. Contrary to what is generally accepted,31
glycosyl acceptor size in these studies does not appear
to affect the efficiency of mannosyl donor 9. However,
screening a larger array of higher ordered glycosyl
acceptors is necessary before any conclusions as to the
generality of 9 as a glycosyl donor for R-(1f2)-linked
mannosides can be made.
Experimental Section
Synthesis of 2-O-Acetyl-3,4,6-tri-O-benzyl-R-D-man-
nopyranosyl iodide (9). 3,4,6-Tri-O-benzyl-manno-ortho es-
ter (4, 587 mg, 1.12 mmol) was dissolved in dry CH2Cl2 (12
mL) and cooled to 0 °C under an inert atmosphere. The stirring
mixture was treated with TMSI (192 µL, 1.41 mmol) and
allowed to stir at 0 °C for 50 min, after which time, TLC
revealed complete conversion to 9 (Rf 0.54, 30% EtOAc/
hexanes) and dry PhMe was added. The reaction was concen-
Conclusion
In the course of these studies, we have clearly dem-
onstrated the viability of C-2 O-acetyl mannosyl iodide
(31) Toshima, K.; Tatsuta, K. Chem. Rev. 1993, 93, 1503-1531 and
references therein.
8776 J. Org. Chem., Vol. 70, No. 22, 2005

Synthesis of High-Mannose Oligosaccharides
trated in vacuo on a rotary evaporator. The evacuated system
was purged with argon upon completion. The mixture was
continuously azeotroped from dry PhMe until a clear distillate
persisted. Mannosyl iodide 9 was redissolved in CH2Cl2 and
used without further manipulation. 1H NMR (C6D6, 500 MHz)
δ 7.36-7.15 (15H, PhH), 6.83 (s, 1H, H-1), 5.84 (d, 1H, J )
1.8 Hz, H-2), 5.02 (d, 1H, J ) 10.8 Hz, PhCH2), 4.67 (m, 2H,
H-3, PhCH2), 4.62 (d, 1H, J ) 11.4 Hz, PhCH2), 4.65 (d, 1H, J
) 12.0 Hz, PhCH2), 4.40 (d, 1H, J ) 11.4 Hz, PhCH2), 4.36 (t,
1H, J ) 9.6 Hz, H-4), 4.31 (d, 1H, J ) 12.0 Hz, PhH), 3.88
(apparent d, 1H, J ) 9.6 Hz, H-5), 3.80 (dd, 1H, J ) 3.6 Hz,
11.4 Hz, H-6), 3.51 (d, 1H, J ) 11.4 Hz, H-2), 1.71 (s, 3H, OAc).
13C NMR (C6D6, 125 MHz) δ 169.2 (CdO), 139.0 (Ph-C), 138.6
(Ph-C), 138.1 (Ph-C), 128.61 (Ph-CH), 128.58 (Ph-CH), 128.52
(Ph-CH), 128.48 (Ph-CH), 128.44 (Ph-CH), 128.40 (Ph-CH),
128.3 (Ph-CH), 128.2 (Ph-CH), 128.09 (Ph-CH), 128.08 (Ph-
CH), 128.06 (Ph-CH), 128.00 (Ph-CH), 127.94 (Ph-CH), 127.91
(Ph-CH), 127.87 (Ph-CH), 127.83, 127.78 (Ph-CH), 127.74 (Ph-
CH), 127.69 (Ph-CH), 79.2 (C-5), 77.7 (C-3), 75.4 (OBn), 74.0
(C-4), 73.5 (OBn), 73.0 (C-2), 72.4 (C-1), 72.1 (OBn), 68.0 (C-
6), 20.2 (OAc). HRFABMS m/z [M - I]+ calcd for C29H31O6
475.2121, found 475.2123.
was revealed through TLC analyses (40% EtOAc/hexanes). The
reaction was quenched with Dowex H+ resin until neutral and
the resin was filtered off. The resin was washed with copious
amounts of MeOH/CH2Cl2 and the mother liquor was concen-
trated in vacuo to provide 318 mg of 11. [R]25 +41 (c 1.0,
D
1
CHCl3). H NMR (C6D6, 600 MHz) δ 8.18 (d, 2H, J ) 8.5 Hz,
PhH), 7.41 (t, 4H, J ) 8.4 Hz, PhH), 7.36 (d, 2H, J ) 7.2 Hz,
PhH), 7.33-7.10 (m, 28H, PhH), 6.38 (s, 1H, H-1), 5.42 (s, 1H,
H-1′), 5.11 (d, 1H, J ) 11.4 Hz, PhCH2), 4.93 (d, 1H, J ) 11.4
Hz, PhCH2), 4.80 (d, 1H, J ) 11.4 Hz, PhCH2), 4.65 (d, 1H, J
) 11.4 Hz, PhCH2), 4.62-4.52 (m, 4H, PhCH2, PhCH2, PhCH2,
H-5′), 4.49-4.46 (m, 3H, PhCH2, PhCH2, H-4), 4.39 (apparent
d, 2H, H-2′, PhCH2), 4.36-4.29 (m, 4H, PhCH2, H-3, PhCH2,
H-2), 4.14 (dd, 1H, J ) 3.6 Hz, 9.0 Hz, H-3′), 4.00 (apparent
dd, 1H, J ) 2.4 Hz, 9.6 Hz, H-5), 3.94 (t, 1H, J ) 9.6 Hz, H-4′),
3.91 (apparent d, 1H, J ) 11.4 Hz, H-6′), 3.89 (dd, 1H, J ) 3.6
Hz, 11.4 Hz, H-6), 3.78 (dd, 1H, J ) 7.2 Hz, 11.4 Hz, H-6′),
3.61 (m, 1H, H-6), 3.59 (s, 3H, OMe), 2.50 (br, 1H, OH). HSQC
(C6D6, 500 MHz) without 1H-decoupling: JH1,C1 ) 175.8 Hz,
JH1′,C1′ ) 169.8. 13C NMR (C6D6, 125 MHz) δ 166.3 (CdO), 160.1
(Ph-C), 139.4 (Ph-C), 139.2 (Ph-C), 139.0 (Ph-C), 138.9 (Ph-
C), 138.67 (Ph-C), 138.65 (Ph-C), 131.9 (Ph-CH), 128.7 (Ph-
CH), 128.6 (Ph-CH), 128.52 (Ph-CH), 128.50 (Ph-CH), 128.4
(Ph-CH), 128.3 (Ph-CH), 128.19 (Ph-CH), 128.15 (Ph-CH),
128.1 (Ph-CH), 128.0 (Ph-CH), 127.9 (Ph-CH), 127.8 (Ph-CH),
127.72 (Ph-CH), 127.68 (Ph-CH), 127.62 (Ph-CH), 127.60 (Ph-
CH), 127.5 (Ph-CH), 124.8 (Ph-CH), 116.5 (Ph-CH), 102.6 (C-
1′), 97.1 (C-1), 80.8 (C-3′), 79.6 (C-3), 76.3 (C-2), 75.3 (OBn,
OBn, C-4′), 74.7 (C-4), 73.5 (OBn, OBn, C-5), 72.6 (C-5′), 72.4
(OBn), 71.9 (OBn), 70.3 (C-6′), 69.2 (C-6), 68.9 (C-2′), 51.4
(OMe). MALDI-HRMS m/z [M + Na]+ calcd for C62H64NaO13
1039.4244, found 1039.4248.
Preparation of p-Methoxycarbonylphenyl 2-O-Acetyl-
3,4,6-tri-O-benzyl-D-mannopyranosyl-R-(1f2)-3,4,6-tri-O-
benzyl-R-D-mannopyranoside (10a). A mixture of acceptor
(8, 264 mg, 0.46 mmol), AgOTf (434 mg, 1.69 mmol), and 4 Å
MS (480 mg) was suspended in dry CH2Cl2 (3 mL) under argon,
kept in the dark, and cooled to -40 °C. Glycosyl iodide (9, 1.12
mmol) was dissolved in CH2Cl2 (2 mL) and cooled to -60 °C.
Into the stirring acceptor mixture was cannulated the donor
solution. The reaction was allowed to gradually warm to -10
°C over 3 h, after which Et3N (2 mL) was added and the
mixture wasstirred for 5 min. The heterogeneous mixture was
filtered over a pad of Celite. The solid mass was washed with
copious amounts of EtOAc. The filtrate was extracted with
saturated aq NaHCO3 (2 × 75 mL) and brine. The organic
layer was dried over MgSO4 and concentrated in vacuo. The
crude material was chromatographed via a flash silica gel
column with use of 25% EtOAc/hexanes as the eluent to
provide 341 mg of 10a, 70% yield. Data for 10a: [R]25D +57 (c
Preparation of p-Methoxycarbonylphenyl d-Mannopy-
ranosyl-R-(1f2)-R-D-mannopyranoside (12). Benzylated
disaccharide (11, 287 mg, 0.28 mmol) was dissolved in 10%
HOAc/EtOH (10 mL). To the solution was added 10% Pd/C
dry (162 mg). The mixture was degassed under vacuum to -10
mmHg and repressurized to 60 psi of H2. This routine was
repeated twice more and the mixture was shaken overnight
at 60 psi of H2. The heterogeneous mixture was filtered over
a pad of Celite and the solid mass was washed with copious
amounts of MeOH. Following concentration of the mother
liquor in vacuo, the mass was redissolved in H2O and passed
through a C8 plug. The mother liquor was lyophilized to yield
a white foamy solid, 122 mg. [R]25D +27 (c 1.0, CHCl3). 1H NMR
(D2O, 500 MHz) δ 7.76 (d, 2H, J ) 9.0 Hz, PhH), 7.02 (d, 2H,
J ) 9.0 Hz, PhH), 5.89 (s, 1H, H-1′), 4.97 (s, 1H, H-1′′), 4.06-
4.01 (m, 3H, H-5′, H-2′, H-2′′), 3.83-3.77 (m, 3H, H-6′′, H-3′,
H-3′′), 3.74 (s, 3H, OMe), 3.70 (t, 1H, J ) 10.0 Hz, H-4′′), 3.65-
3.60 (m, 4H, H-5′′, H-6′, H-6′, H-6′′), 3.54-3.50 (m, 2H, H-4′,
1
1.0, CHCl3). H NMR (C6D6, 500 MHz) δ 8.20 (d, 2H, J ) 8.5
Hz, PhH), 7.54 (d, 2H, J ) 7.5 Hz, PhH), 7.42-7.35 (m, 9H,
PhH), 7.31-7.11 (m, 21H, PhH), 6.35 (s, 1H, H-1′), 6.00 (s,
1H, H-2′′), 5.31 (s, 1H, H-1′′), 5.09 (t, 2H, J ) 10.5 Hz, PhCH2,
PhCH2), 4.79 (d, 1H, J ) 11.0 Hz, PhCH2), 4.68-4.44 (m, 8H,
PhCH2, PhCH2, PhCH2, PhCH2, H-5′, PhCH2, H-4′′, PhCH2),
4.42-4.34 (m, 4H, PhCH2, PhCH2, H-3′, H-3′′), 4.30 (d, 1H, J
) 11.0 Hz, PhCH2), 4.26 (s, 1H, H-2′), 4.07 (t, 1H, J ) 9.5 Hz,
H-4′), 4.03 (m, 1H, H-5′′), 3.91 (apparent d, 1H, J ) 10.5 Hz,
H-6′), 3.87 (dd, 1H, J ) 4.0 Hz, 11.5 Hz, H-6′′), 3.81 (dd, 1H,
J ) 6.5 Hz, 10.5 Hz, H-6′), 3.62 (apparent d, 1H, J ) 11.5 Hz,
H-6′′), 3.59 (s, 3H, OMe), 1.78 (s, 3H, OAc). HSQC (C6D6, 500
MHz) without 1H-decoupling: JH1,C1 ) 175.8 Hz, JH1′,C1′ ) 170.9
Hz. 13C NMR (C6D6, 500 MHz) δ 169.8 (CdO), 166.2 (Ph-C),
160.1 (Ph-C), 139.4 (Ph-C), 139.2 (Ph-C), 139.04 (Ph-C), 138.95
(Ph-C), 138.7 (Ph-C), 138.7 (Ph-C), 131.9 (Ph-CH), 129.2 (Ph-
CH), 128.8 (Ph-CH), 128.6 (Ph-CH), 128.49 (Ph-CH), 128.47
(Ph-CH), 128.4 (Ph-CH), 128.34 (Ph-CH), 128.29 (Ph-CH),
128.2 (Ph-CH), 128.1 (Ph-CH), 128.0 (Ph-CH), 127.81 (Ph-CH),
127.75 (Ph-CH), 127.7 (Ph-CH), 127.63 (Ph-CH), 127.60 (Ph-
CH), 127.5 (Ph-CH), 124.9 (Ph-CH), 116.5 (Ph-CH), 101.0 (C-
1′), 97.0 (C-1), 79.6 (C-3′), 78.8 (C-3), 76.7 (C-2), 75.5 (OBn),
75.4 (OBn), 75.3 (C-4), 74.5 (C-4′), 73.5 (OBn), 73.43 (OBn),
73.42 (C-5′), 72.8 (C-5), 72.4 (OBn), 71.9 (OBn), 70.2 (C-6), 69.3
(C-2′), 69.1 (C-6′), 51.4 (OMe), 20.5 (OAc). MALDI-HRMS m/z
[M + Na]+ calcd for C64H66NaO14 1081.4350, found 1081.4391.
1
H-5′′). HSQC (D2O, 500 MHz) without H-decoupling: JH1,C1
) 175.8 Hz, JH1′,C1′ ) 169.8. 13C NMR (D2O, 125 MHz) δ 169.0
(CdO), 159.9 (Ph-C), 131.7 (Ph-CH), 123.7 (Ph-C), 116.6 (Ph-
CH), 116.5 (Ph-CH), 102.8 (C-1′′), 96.3 (C-1′), 79.2 (C-2′), 73.8
(C-5′′), 73.7 (C-3′′), 70.6 (C-3′), 70.21 (C-2′′), 70.16 (C-5′), 67.2
(C-4′′), 66.9 (C-4′), 61.5 (C-6′′), 60.8 (C-6′), 52.7 (OMe). MALDI-
HRMS m/z [M + Na]+ calcd for C20H28NaO13 499.1428, found
499.1455.
Preparation of p-Methoxycarbonylphenyl 2,4-Di-O-
benzyl-R-D-mannopyranoside (18). A solution of 1,3,6-tri-
O-acetyl mannose14 (17, 473 mg, 0.97 mmol) and methyl
p-hydroxybenzoate (765 mg, 4.87 mmol) was dissolved in dry
CH2Cl2 (10 mL) and cooled to 0 °C under an inert atmosphere.
The solution was treated with BF3‚Et2O (247 µL, 2.75 mmol)
and stirred for 10 min at 0 °C. The reaction was then removed
from the bath and allowed to warm to room temperature over
4 h, after which, TLC (30% EtOAc/hexanes) revealed the
complete consumption of the starting material and the pres-
ence of a major spot (Rf 0.49). The reaction was then diluted
with CH2Cl2 (50 mL) and washed with saturated aq K2CO3 (3
× 50 mL). The organic layer was dried over MgSO4 and
concentrated in vacuo. 1H NMR revealed only the presence of
Preparation of p-Methoxycarbonylphenyl 3,4,6-Tri-O-
benzyl-D-mannopyranosyl-R-(1f2)-3,4,6-tri-O-benzyl-R-D-
mannopyranoside (11). 2-Acetoxy-disaccharide (10a, 383
mg, 0.36 mmol) was dissolved in dry MeOH (25 mL) and CH2-
Cl2 (5 mL) under argon. The solution was treated with 30 wt
% NaOMe/MeOH (100 µL) for 1.5 h. A new spot with Rf 0.27
J. Org. Chem, Vol. 70, No. 22, 2005 8777

Lam and Gervay-Hague
the R-linked product. As the acceptor could not be separated
from the desired product, the crude mixture was redissolved
in dry MeOH (20 mL) and treated with 30 wt % NaOMe/MeOH
(1 mL) for 40 min. TLC (30% EtOAc/Hexanes) revealed
complete deacetylation to afford 18 (Rf 0.08). The mixture was
neutralized with Dowex 50WX8 H+ resin. After removal of the
resin, the mother liquor was concentrated in vacuo and
purified via silica gel column chromatography (30% EtOAc/
hexanes) to provide 435 mg of the desired diol 18, 91% over 2
steps. [R]25D +59 (c 1.0, CHCl3). 1H NMR (CDCl3, 500 MHz) δ
7.97 (d, 2H, J ) 8.5 Hz, PhH), 7.41-7.29 (m, 10H, PhH), 7.00
(d, 1H, J ) 8.4 Hz, PhH), 5.63 (s, 1H, H-1), 4.91 (d, 1H, J )
11.0 Hz, PhCH2), 4.78 (d, 1H, J ) 11.0 Hz, PhCH2), 4.70 (d,
2H, J ) 11.0 Hz, PhCH2, PhCH2), 4.20 (dt, 1H, J ) 5.0 Hz,
9.5 Hz, H-3), 3.95 (m, 1H, H-2), 3.88 (s, 3H, OMe), 3.84 (t, 1H,
J ) 9.5 Hz, H-4), 3.76 (m, 2H, H-6, H-6), 3.64 (m, 1H, H-5),
2.39 (d, 1H, J ) 9.5 Hz, C3-OH), 1.85 (t, 1H, J ) 6.5 Hz, C6-
MALDI-HRMS m/z [M + Na]+ calcd for C86H90NaO20 1465.5922,
found 1465.5843.
Preparation of p-Methoxycarbonylphenyl (3,4,6-Tri-
O-benzyl-D-mannopyranosyl-R-(1f3))-(3,4,6-tri-O-benzyl-
D-mannopyranosyl-R-(1f6))-2,4-di-O-benzyl-R-D-mannopy-
ranoside (20). The trisaccharide 19 was dissolved in dry
MeOH (25 mL) and dry CH2Cl2 (5 mL) under argon at room
temperature and treated with 30 wt % NaOMe/MeOH (100
µL) for 1 h. TLC (40% EtOAc/hexanes) revealed complete
deacetylation of 19 to afford 20 (Rf 0.12) and Dowex 50WX8
H+ resin was added to neutralize the mixture. Following
removal of the resin, the mother liquor was concentrated in
vacuo, and flash silica gel column chromatography with 40%
EtOAc/hexanes provided the trisaccharide diol, 220 mg, 93%
1
yield. [R]25 +61 (c 1.0, CHCl3). H NMR (C6D6, 500 MHz) δ
D
8.29 (d, 2H, J ) 8.5 Hz, PhH), 7.50 (d, 2H, J ) 8.5 Hz), 7.46-
7.35 (m, 14H, PhH), 7.30-7.05 (m, 26H, PhH), 5.63 (s, 1H,
H-1′′3), 5.61 (s, 1H, H-1′), 5.22 (s, 1H, H-1′′6), 5.10 (d, 1H, J )
11.0 Hz, PhCH2), 4.98 (d, 1H, J ) 11.0 Hz, PhCH2), 4.89 (d,
1H, J ) 11.0 Hz, PhCH2), 4.73 (d, 2H, J ) 11.0 Hz, PhCH2,
PhCH2), 4.68 (d, 1H, J ) 11.0 Hz, PhCH2), 4.65-4.52 (m, 8H,
PhCH2, PhCH2, PhCH2, PhCH2, PhCH2, C-3′, PhCH2, PhCH2),
4.48-4.43 (m, 5H, PhCH2, PhCH2, PhCH2, H-2′, H-4′′6), 4.27-
4.13 (m, 6H, H-4′, H-2′′3, H-5′′,6 H-5′′3, H-3′′3, H-2′′6), 4.04-
3.91 (m, 6H, H-4′′3, H-3′′,6 H-6′′,6 H-5′, H-6′′3, H-6′), 3.85-3.81
(m, H-6′′3, H-6′), 3.55 (s, 3H, OMe), 2.48 (br, 2H, OH, OH).
1
OH). HSQC (CDCl3, 500 MHz) without H-decoupling: JH1,C1
) 175.8 Hz, JH1′,C1′ ) 169.8. 13C NMR (CDCl3, 125 MHz) δ 166.6
(CdO), 159.5 (Ph-C), 138.1 (Ph-C), 137.4 (Ph-C), 131.6 (Ph-
CH), 128.7 (Ph-CH), 128.5 (Ph-CH), 128.3 (Ph-CH), 128.0 (Ph-
CH), 127.9 (Ph-CH), 124.3 (Ph-CH), 125.7 (Ph-CH), 95.2 (C-
1), 77.8 (C-2), 75.7 (C-4), 75.0 (OBn), 73.5 (OBn), 72.5 (C-5),
71.5 (C-3), 61.8 (C-6), 52.0 (OMe). MALDI-HRMS m/z [M +
Na]+ calcd for C28H30NaO8 517.1838, found 517.1813.
Preparation of p-Methoxycarbonylphenyl (2-O-Acetyl-
3,4,6-tri-O-benzyl-D-mannopyranosyl-R-(1f3))-(2-O-acetyl-
3,4,6-tri-O-benzyl-D-mannopyranosyl-R-(1f6))-2,4-di-O-
benzyl-R-D-mannopyranoside (19). A mixture of diol
monosaccharide acceptor (18, 110 mg, 0.22 mmol), AgOTf (429
mg, 1.67 mmol), and 4 Å MS (464 mg) was suspended in dry
CH2Cl2 (3 mL) under argon, kept in the dark, and cooled to
-40 °C. Mannosyl iodide (9, 1.11 mmol) was dissolved in CH2-
Cl2 (2 mL) and cooled to -60 °C. Into the stirring acceptor
mixture was cannulated the donor solution. The reaction was
allowed to gradually warm to room temperature over 3 h, after
which Et3N (2 mL) was added and the mixture was stirred
for 5 min. TLC analyses (40% EtOAc/hexanes) showed the
presence of a new spot, Rf 0.37. The heterogeneous mixture
was filtered over a pad of Celite. The solid mass was washed
with copious amounts of EtOAc (100 mL). The filtrate was
extracted with saturated aq NaHCO3 (2 × 50 mL) and brine.
The organic layer was dried over MgSO4 and concentrated in
vacuo. The crude material was chromatographed via a flash
HSQC (C6D6, 500 MHz) without 1H-decoupling: JH1′′
)
3
3
,C1′′
171.5 Hz, JH1′′
) 170.0 Hz, JH1′,C1′ ) 171.0 Hz. 13C NMR
6
6
,C1′′
(C6D6, 125 MHz) δ 166.4 (CdO), 160.3 (Ph-C), 139.5 (Ph-C),
139.3 (Ph-C), 139.2 (Ph-C), 138.9 (Ph-C), 138.82 (Ph-C), 138.75
(Ph-C), 138.7 (Ph-C), 138.6 (Ph-C), 132.0 (Ph-CH), 128.74 (Ph-
CH), 128.70 (Ph-CH), 128.64 (Ph-CH), 128.60 (Ph-CH), 128.54
(Ph-CH), 128.52 (Ph-CH), 128.50 (Ph-CH), 128.4 (Ph-CH),
128.3 (Ph-CH), 128.2 (Ph-CH), 128.1 (Ph-CH), 128.0 (Ph-CH),
127.9 (Ph-CH), 127.8 (Ph-CH), 127.7 (Ph-CH), 127.62 (Ph-CH),
127.56 (Ph-CH), 127.5 (Ph-CH), 124.8 (Ph-CH), 116.5 (Ph-CH),
102.0 (C-1′′3), 99.8 (C-1′′6), 95.7 (C-1′), 80.7 (C-3′′3), 80.6 (C-
3′′6),78.1 (C-4′′6), 75.4 (OBn, C-4′), 75.2 (OBn, C-4′′3), 75.0 (OBn,
C-3′, C-5′′6), 73.8 (OBn), 73.53 (OBn), 72.95 (C-2′), 72.23 (C-
5′), 72.7 (OBn), 72.1 (C-5′′3), 72.0 (OBn), 71.7 (OBn), 70.5 (C-
6′), 69.7 (C-6′′3), 69.1 (C-2′′3), 68.4 (C-2′′6), 66.0 (C-6′′6), 51.5
(OMe). MALDI-HRMS m/z [M + Na]+ calcd for C82H86NaO18
1381.5712, found 1381.5735.
Preparation of p-Methoxycarbonylphenyl (D-Man-
nopyranosyl-R-(1f3))-(D-mannopyranosyl-R-(1f6))-R-D-
mannopyranoside (21). Benzylated trisaccharide (20, 94 mg,
0.07 mmol) was dissolved in 10% HOAc/EtOH (10 mL). To the
solution was added 10% Pd/C dry (102 mg). The mixture was
degassed under vacuum to -10 in Hg and repressurized to 60
psi of H2. This routine was repeated twice more and the
mixture was shaken overnight at 60 psi of H2. The heteroge-
neous mixture was filtered over a pad of Celite and the solid
mass was washed with copious amounts of MeOH. Following
concentration of the mother liquor in vacuo, the mass was
redissolved in H2O and passed through a C8 plug. The mother
liquor was lyophilized to yield a white foamy solid. HPLC
purification was performed with a C18 Vydac prep column at
a flow rate of 5 mL/min with a linear gradient from 100% H2O
to 100% over 60 min. Fully deprotected trisaccharide 21 was
silica gel column, using 25% EtOAc/hexanes as the eluent to
1
provide 19, 293 mg (91% yield). [R]25 +31 (c 1.0, CHCl3). H
D
NMR (C6D6, 500 MHz) δ 8.29 (d, 2H, J ) 8.5 Hz, PhH), 7.52-
7.07 (m, 42H, PhH), 5.98 (s, 1H, H-2′′3), 5.78 (s, 1H, H-2′′6),
5.67 (s, 1H, H-1′), 5.61 (s, 1H, H-1′′3), 5.23 (d, 1H, J ) 11.0
Hz, PhCH2), 5.12 (d, 1H, J ) 11.0 Hz, PhCH2), 5.11 (s, 1H,
H-1′′6), 5.06 (d, 1H, J ) 11.0 Hz, PhCH2), 4.80-4.61 (m, 10H,
10 PhCH2, H-3′), 4.53-4.50 (m, 5H, 4 PhCH2, H-5′′3), 4.47-
4.31 (m, 4H, H-3′′,3 H-5′′,6 H-4‘′,6 H-4′), 4.26-4.25 (m, 2H, H-2′,
H-3′′6), 4.15 (t, 1H, J ) 9.5 Hz, H-4′′3), 4.00 (apparent d, 2H,
J ) 9.0 Hz, H-6′′,6 H-5′), 3.94 (apparent d, 2H, J ) 11.0 Hz,
H-6′, H-6′′3), 3.87 (dd, 1H, J ) 6.0 Hz, 11.0 Hz, H-6′), 3.80 (d,
1H, J ) 11.0 Hz, H-6′′3), 3.67 (d, 1H, J ) 9.0 Hz, H-6′′6), 3.56
(s, 3H, OMe), 1.81 (s, 6H, 2 OAc). HSQC (C6D6, 500 MHz)
without 1H-decoupling: JH1′′3,C1′′3 ) 172.0 Hz, JH1′′6,C1′′6 ) 171.0
Hz, JH1′,C1′ ) 170.5 Hz. 13C NMR (C6D6, 125 MHz) δ 169.8 (2
CdO), 166.3 (CdO), 160.2 (Ph-C), 139.5 (Ph-C), 139.2 (Ph-C),
138.9 (Ph-C), 138.8 (Ph-C), 138.6 (Ph-C), 138.5 (Ph-C), 132.1
(Ph-CH), 128.9 (Ph-CH), 128.7 (Ph-CH), 128.6 (Ph-CH), 128.54
(Ph-CH), 128.48 (Ph-CH), 128.4 (Ph-CH), 128.2 (Ph-CH), 128.1
(Ph-CH), 127.8 (Ph-CH), 127.6 (Ph-CH), 124.9 (Ph-CH), 116.5
(Ph-CH), 100.6 (C-1′′3), 98.4 (C-1′′6), 95.6 (C-1′), 78.9 (C-3′), 78.6
(C-3′′3), 78.4 (C-3′′6), 77.9 (C-4′′6), 75.5 (OBn), 75.34 (OBn),
75.27 (OBn, C-5′′6), 75.2 (C-4′′3), 75.0 (C-4′), 73.7 (OBn), 73.5
(OBn), 73.2 (C-5′′3), 73.0 (C-5′), 72.8 (OBn), 72.4 (C-2′), 72.0
(OBn), 71.7 (OBn), 70.3 (C-6′), 69.6 (C-6′′3), 69.2 (C-2′′3), 68.7
(C-2′′6), 66.3 (C-6′′6), 51.5 (OMe), 20.6 (OAc), 20.5 (OAc).
provided in 82% isolated yield (37 mg) after lyophilization.
1
[R]25 +48 (c 1.0, CHCl3). H NMR (D2O, 500 MHz) δ 7.92 (d,
D
2H, J ) 9.0 Hz, PhH), 7.12 (d, 2H, J ) 9.0 Hz), 5.62 (s, 1H,
H-1′), 5.09 (s, 1H, H-1′′3), 4.63 (s, 1H, H-1′′6), 4.25 (s, 1H, H-2′),
4.08 (dd, 1H, J ) 4.5 Hz, 9.5 Hz, H-3′), 4.00 (s, 1H, H-2′′3),
3.84-3.52 (m, 18H). Estimated 1H chemical shifts from HSQC
(D2O, 500 MHz) data of 3.84-3.52 region: 3.85 (H-4′), 3.84
(H-6′′3, H-3′′3), 3.83 (OMe), 3.80 (H-6′), 3.78 (H-6′′3), 3.75 (H-
3′′6), 3.74 (H-4′′6), 3.71 (H-6′′6), 3.65 (H-6′′6), 3.63 (H-5′′3), 3.61
(H-2′′6), 3.60 (H-6′, H-4′′3), 3.55 (H-5′′6), 3.54 (H-5′). HSQC
(D2O, 500 MHz) without 1H-decoupling: JH1′′
) 172.0 Hz,
3
3
,C1′′
JH1′′
) 171.0 Hz, JH1′,C1′ ) 174.5 Hz. 13C NMR (D2O, 125
MHz) δ 169.2 (CdO), 159.5 (Ph-C), 131.8 (Ph-CH, Ph-CH),
6
6
,C1′′
8778 J. Org. Chem., Vol. 70, No. 22, 2005

Synthesis of High-Mannose Oligosaccharides
124.0 (Ph-C), 116.6 (Ph-CH, Ph-CH), 102.7 (C-1′′3), 99.1 (C-
1′′6), 97.5 (C-1′), 78.3 (C-3′), 73.7 (C-4′′6), 72.9 (C-5′′6), 71.8
(C-3′′6), 70.8 (C-2′′6), 70.6 (C-3′′3), 70.3 (C-2′′3), 70.1 (C-5′′3),
69.5 (C-2′), 67.0 (C-4′′3), 66.9 (C-5′), 66.0 (C-4′), 65.3 (C-6′),
61.23 (C-6′′6), 61.16 (C-6′′3), 52.8 (OMe). MALDI-HRMS m/z
[M + Na]+ calcd for C26H38NaO18 661.1956, found 661.1954.
Preparation of p-Methoxycarbonylphenyl (2-O-Acetyl-
3,4,6-tri-O-benzyl-D-mannopyranosyl-R-(1f2)-3,4,6-tri-O-
benzyl-D-mannopyranosyl-R-(1f3))-(2-O-acetyl-3,4,6-tri-
O-benzyl-D-mannopyranosyl-R-(1f2)-3,4,6-tri-O-benzyl-
D-mannopyranosyl-R-(1f6))-2,4-di-O-benzyl-R-D-mannopy-
ranoside (22). A mixture of diol trisaccharide acceptor (20,
113 mg, 0.08 mmol), AgOTf (116 mg, 0.23 mmol), and 4 Å MS
(356 mg) was suspended in dry CH2Cl2 (2 mL) under argon,
kept in the dark, and cooled to -40 °C. Mannosyl iodide (9,
0.42 mmol) was dissolved in CH2Cl2 (1.5 mL) and cooled to
-60 °C. The donor solution was cannulated into the stirring
acceptor mixture. The reaction was allowed to gradually warm
to room temperature over 7 h, after which TLC (40% EtOAc/
hexanes) analyses revealed a major spot (Rf 0.40). After
stirring with Et3N (2 mL) for 5 min, the heterogeneous mixture
was filtered over a pad of Celite. The solid mass was washed
with copious amounts of EtOAc (50 mL). The filtrate was
extracted with saturated aq NaHCO3 (2 × 25 mL) and brine.
The organic layer was dried over MgSO4 and concentrated in
vacuo. The crude material was chromatographed via a flash
silica gel column with 25% EtOAc/hexanes as the eluent to
provide 175 mg (91% yield) of pentasaccharide 22. [R]25D +29
CH), 102.2 (C-1), 100.7 (C-1), 99.3 (C-1), 95.7 (C-1), 80.2 (C-
3), 79.9 (C-3), 78.8 (C-3), 78.8 (C-3), 78.4 (C-3), 77.0, 76.4, 75.6,
75.42, 75.36, 75.24, 75.17, 75.1, 73.7, 73.5, 73.4, 73.1, 72.8,
72.71, 72.66, 72.6, 72.4, 71.9, 71.8, 70.5, 69.9 (C-6), 69.6 (C-6),
69.5 (C-6), 69.30 (C-6), 69.28 (C-6), 66.8 (C-6), 51.5 (OMe), 30.2
(OAc), 20.6 (OAc). MALDI-HRMS m/z [M + Na]+ calcd for
C140H146NaO30 2329.9796, found 2329.9753.
Preparation of p-Methoxycarbonylphenyl (D-Manno-
pyranosyl-R-(1f2)-D-mannopyranosyl-R-(1f3))-(D-manno-
pyranosyl-R-(1f2)-D-mannopyranosyl-R-(1f6))-R-D-mannopy-
ranoside (23). Benzylated pentasaccharide (22, 175 mg, 0.08
mmol) was dissolved in 10% HOAc/EtOH (10 mL). To the
solution was added 10% Pd/C dry (112 mg). The mixture was
degassed under vacuum to -10 in Hg and repressurized to 60
psi of H2 (g). This routine was repeated twice more and the
mixture was shaken overnight at 60 psi of H2 (g). The
heterogeneous mixture was filtered over a pad of Celite and
the solid mass was washed with copious amounts of MeOH.
The mother liquor was concentrated, redissolved in H2O, and
lyophilized to yield a yellowish-white foamy solid. The deben-
zylated pentasaccharide was redissolved in MeOH (50 mL) and
treated with 5 mL of 30 wt % NaOMe/MeOH for 1 day.
Following concentration of the mother liquor in vacuo, the
mass was redissolved in H2O and passed through a C8 plug.
The concentrated fully deprotected pentasaccharide was puri-
fied with HPLC under conditions reported for 21. After
concentration of fractions 22 and 23, 23 was isolated in 86%
yield (66 mg) over 2 steps. [R]25D +37 (c 0.8, CHCl3). 1H NMR
(D2O, 500 MHz) δ 7.88 (d, 2H, J ) 8.5 Hz, PhH), 7.09 (d, 2H,
J ) 8.5 Hz, PhH), 5.59 (s, 1H, H-1′), 5.35 (s, 1H, H-1), 4.96 (s,
1H, H-1), 4.88 (s, 1H, H-1), 4.65 (s, 1H, H-1), 4.23 (s, 1H, H-2′),
4.03 (s, 2H, J ) 9.5 Hz, H-3′, H-2), 3.98 (s, 1H, H-2′′3), 3.92 (d,
1 H, J ) 9.5 Hz, H-3), 3.89 (s, 1H, H-2), 3.85-3.45 (m, 24H).
HSQC (D2O, 500 MHz) without 1H-decoupling: JH1,C1 ) 171.5
Hz, JH1,C1 ) 170.0 Hz, JH1,C1 ) 172.0 Hz, JH1,C1 ) 171.0 Hz,
JH1,C1 ) 174.5 Hz. 13C NMR (D2O, 125 MHz) δ 169.2 (CdO),
159.5 (Ph-C), 131.9 (Ph-CH, Ph-CH), 124.0 (Ph-C), 116.7 (Ph-
CH, Ph-CH), 102.6 (C-1), 102.5 (C-1), 101.1 (C-1), 98.0 (C-1),
97.5 (C-1), 79.0 (C-3), 78.8 (C-3), 78.7 (C-3), 73.7, 73.6, 73.4,
73.04, 73.01, 72.7, 72.2, 71.0, 70.7, 70.59, 70.55, 70.44, 70.37,
70.3, 70.24, 70.20, 69.6, 67.30, 67.27, 67.2, 67.14, 67.10, 67.02,
66.98, 66.1, 66.0, 61.44 (C-6), 61.39 (C-6), 61.36 (C-6), 61.30
(C-6), 61.25 (C-6), 52.8 (OMe). MALDI-HRMS m/z [M + Na]+
calcd for C38H58NaO28 985.3012, found 985.3038.
1
(c 0.8, CHCl3). H NMR (C6D6, 500 MHz) δ 8.28 (d, 2H, J )
8.5 Hz, PhH), 7.59 (m, 4H, PhH), 7.47 (m, 9H, PhH), 7.41 (m,
16H, PhH), 7.34-7.04 (m, 111H, PhH), 6.02 (s, 1H, C-2′′′3),
5.99 (s, 1H, C-2′′′6), 5.95 (s, 1H, H-1), 5.70 (s, 1H, H-1), 5.49
(s, 1H, H-1), 5.31 (s, 1H, H-1), 5.28 (S, 1H, H-1), 5.23 (d, 1H,
J ) 11.0 Hz, PhCH2), 5.14 (d, 1H, J ) 11.0 Hz, PhCH2), 5.11
(d, 1H, J ) 11.0 Hz, PhCH2), 5.10 (d, 1H, J ) 11.0 Hz, PhCH2),
5.09 (d, 1H, J ) 11.0 Hz, PhCH2), 5.02 (d, 1H, J ) 11.0 Hz,
PhCH2), 4.84 (d, 1H, J ) 11.0 Hz, PhCH2), 4.80 - 4.73 (m,
4H, PhCH2, PhCH2, PhCH2, PhCH2), 4.70-4.64 (m, 8H), 4.63-
4.47 (m, 12H), 4.45-4.51 (m, 4H), 3.36-3.34 (m, 2H), 4.31-
4.19 (m, 9H), 4.09 (dd, 1H, J ) 5.0, 10.5 Hz, H-6), 4.04-3.98
(m, 2H, H-6, H-6), 3.96-3.90 (m, 3H, H-6, H-6, H-6), 3.86-
3.79 (m, 4H), 3.68 (d, 1H, J ) 10.0 Hz, H-6), 3.57 (OMe), 1.83
(s, 3H, OAc), 1.82 (s, 3H, OAc). HSQC (C6D6, 500 MHz) without
1H-decoupling: JH1,C1 ) 173.0 Hz, JH1,C1 ) 171.0 Hz, JH1,C1
)
171.0 Hz, JH1,C1 ) 172.5 Hz, JH1′,C1′ ) 170.5 Hz. 13C NMR (C6D6,
125 MHz) δ 169.8 (CdO), 169.7 (CdO), 166.3 (CdO), 160.4
(Ph-C), 139.6 (Ph-C), 139.4 (Ph-C), 139.3 (Ph-C), 139.2 (Ph-
C), 139.12 (Ph-C), 139.07 (Ph-C), 139.05 (Ph-C), 139.0 (Ph-C),
138.92 (Ph-C), 138.89 (Ph-C), 138.87 (Ph-C), 138.8 (Ph-C),
138.6 (Ph-C), 132.1 (Ph-CH), 128.81 (Ph-CH), 128.77 (Ph-CH),
128.7 (Ph-CH), 128.60 (Ph-CH), 128.58 (Ph-CH), 128.55 (Ph-
CH), 128.53 (Ph-CH), 128.50 (Ph-CH), 128.48 (Ph-CH), 128.44
(Ph-CH), 128.42 (Ph-CH), 128.38 (Ph-CH), 128.36 (Ph-CH),
128.3 (Ph-CH), PhCH2, 128.2 (Ph-CH), 128.01 (Ph-CH), 127.94
(Ph-CH), 127.9 (Ph-CH), 127.8 (Ph-CH), 127.70 (Ph-CH),
127.67 (Ph-CH), 127.64 (Ph-CH), 127.61 (Ph-CH), 127.56 (Ph-
CH), 127.5 (Ph-CH), 127.4 (Ph-CH), 124.9 (Ph-CH), 116.6 (Ph-
Acknowledgment. This work was supported by
National Science Foundation CHE-0210807. NSF CRIF
program (CHE-9808183), NSF Grant OSTI 97-24412,
and NIH Grant RR11973 provided funding for the NMR
spectrometers used on this project.
Supporting Information Available: General experimen-
1
tal details, experimental data for 7 and 8, and H NMR and
13C NMR spectra for all new compounds. This material is
available free of charge via the Internet at http://pubs.acs.org.
JO051360D
J. Org. Chem, Vol. 70, No. 22, 2005 8779