C-glycosyl aldehydes: Synthons for C-linked disaccharides

Full text of DOI:10.1021/jo9517095

1894
J . Org. Chem. 1996, 61, 1894-1897
Sch em e 1
C-Glycosyl Ald eh yd es: Syn th on s for
C-Lin k ed Disa cch a r id es
William R. Kobertz,*,† Carolyn R. Bertozzi, and
Mark D. Bednarski‡
Department of Chemistry, University of California,
Berkeley, California 94720
Received September 19, 1995
The emerging role of carbohydrate molecules as central
determinants of biological function has stimulated tre-
mendous interest in the synthesis of carbohydrate ana-
logs with therapeutic potential. Carbon-linked glycosides
(C-glycosides) are a particularly interesting class of
derivatives by virtue of their resistance to chemical and
enzymatic hydrolysis of the glycosidic linkage and their
ability to interact with protein receptors similarly to their
O-linked counterparts.1,2 In our efforts to construct
C-glycosyl analogs of biologically active glycoconjugates,
we developed an expedient synthesis of C-glycosyl alde-
hydes such as compound 1.3 These versatile synthons
are constructed in three steps from simple monosaccha-
rides and are available in both R- and â-linked forms.
Aldehyde 1 proved to be extremely useful in the synthesis
of C-linked glycopeptides4 and C-linked glycolipids.5
Here we extend the utility of compound 1 in a general
method for the synthesis of C-linked disaccharides.
F igu r e 1.
ization of pyranose units with mutually reactive centers,
which are often incompatible with neighboring alkoxy
substituents.
Martin and Lai have taken advantage of a mild nitro-
aldol (Henry) condensation in their synthesis of (1,6)- and
(1,1)-linked C-disaccharides.8 For example, C-glycosyl
nitrate 2 was condensed with a second pyranose func-
tionalized with a C-6 aldehyde (3) (Scheme 1). The
resulting adduct 4 was then converted to the target
C-disaccharide. The low pKa of the proton adjacent to
the nitro group (ca. 10) allows formation of the nitronate
anion under mildly basic conditions (KF in CH3CN),
avoiding concurrent â-elimination of the neighboring
alkoxy group. We reasoned that aldehyde 1 could be
utilized in a similar approach, in which the polarity of
the nitro-aldol reaction is the reverse of that employed
by Martin and Lai. The target C-disaccharide in this
study possesses a 1,6 linkage. However, the nitro group
can be installed at any position in a monosaccharide
unit,9 thereby generalizing this method to other disac-
charide linkages.
Current strategies for the synthesis of C-disaccharides
fall largely into two categories: those in which an acyclic
precursor is appended to a pyranose unit and later
cyclized to form the second pyranose of the C-disaccha-
ride6 and those in which two intact pyranose units are
coupled directly to afford the C-disaccharide.7 The intel-
lectual appeal of the latter approach derives from the
availability of monosaccharide starting materials with
the desired hydroxyl group stereochemistry already in
place. However, this strategy requires the functional-
The utility of aldehyde 1 was demonstrated in the
synthesis of a C-linked analog of a biologically active
disaccharide, allolactose (galâ1,6glc, 5, Figure 1). Allolac-
tose is a potent inducer of the lac repressor protein, which
exerts negative control over the expression of the lactose
operon.10-12 The operon comprises several genes encod-
ing proteins involved in galactose metabolism, such as
â-galactosidase. The lac operon has been used exten-
sively for the control of gene expression in bacterial
cloning systems. Allolactose is susceptible to rapid
enzymatic hydrolysis by â-galactosidase, rendering this
molecule unusable in cloning systems.13 In contrast,
C-allolactose could serve as a potent inducer of the lac
repressor protein.
* Author to whom correspondence should be addressed.
† Present address: Department of Chemistry, Massachusetts Insti-
tute of Technology, Cambridge, Massachusetts 02139.
‡ Present address: Lucas MRS Research Center, Stanford Univer-
sity School of Medicine, Stanford, California 94305.
(1) Postema, M. H. D. C-Glycoside Synthesis; CRC Press: London,
1995.
(2) Bertozzi, C. R.; Bednarski, M. D. Synthesis of C-Glycosides:
Stable Mimics of O-Glycosidic Linkages In Modern Methods in
Carbohydrate Synthesis; Harwood Academic Publishers, Gmbh, in
press.
(3) Kobertz, W. R.; Bertozzi, C. R.; Bednarski, M. D. Tetrahedron
Lett. 1992, 33, 737.
(4) Bertozzi, C. R.; Hoeprich, P. D., J r.; Bednarski, M. D. J . Org.
Chem. 1992, 57, 6092.
(5) Bertozzi, C. R.; Cook, D. G.; Kobertz, W. R.; Gonzalez-Scarano,
F.; Bednarski, M. D. J . Am. Chem. Soc. 1992, 114, 10639.
(6) (a) Reviewed in ref. 1. (b) Wang, Y.; Babirad, S. A.; Kishi, Y. J .
Org. Chem. 1992, 57, 468. (c) Goekjian, P. G.; Wu, T.-C.; Kang, H.-Y.;
Kishi, Y. J . Org. Chem. 1991, 56, 6422. (d) Dyer, U. C.; Kishi, Y. J .
Org. Chem. 1988, 53, 3383. (e) Armstrong, R. W.; Sutherlin, D. P.
Tetrahedron Lett. 1994, 35, 7743.
(7) (a) Rouzaud, D.; Sinay¨, P. J . Chem. Soc., Chem. Commun. 1983,
1353. (b) Schmidt, R. R.; Preuss, R. Tetrahedron Lett. 1989, 30, 3409.
(c) Preuss, R.; Schmidt, R. R. J . Carbohydr. Chem. 1991, 10, 887. (d)
Giese, B.; Witzel, T. Angew. Chem. 1986, 98, 459. (e) Giese, B.; Hoch,
M.; Lamberth, C.; Schmidt, R. R. Tetrahedron Lett. 1988, 29, 1375. (f)
Haneda, T.; Goekjian, P. G.; Kim, S. H.; Kishi, Y. J . Org. Chem. 1992,
57, 490.
(8) Martin, O. R.; Lai, W. J . Org. Chem. 1990, 55, 5188.
(9) (a) Nielsen, A. T. Nitronic Acids and Esters. In The Chemistry
of the Nitro and Nitroso Groups; Feuer, H., Ed.; Wiley-Interscience:
London, 1969; Part I. (b) Colvin, E. W.; Beck, A. K.; Seebach, D. Helv.
Chim. Acta 1981, 64, 2264. (c) Baer, H. H. Adv. Carbohydr. Chem.
Biochem. 1969, 24, 67.
(10) J obe, A.; Bourgeois, S. J . Mol. Biol. 1972, 69, 397.
(11) Chakerian, A. E.; Olson, J . S.; Matthews, K. S. Biochemistry
1987, 26, 7250.
(12) J acob, F.; Monod, J . J . Mol. Biol. 1961, 3, 318.
0022-3263/96/1961-1894$12.00/0 © 1996 American Chemical Society

Notes
J . Org. Chem., Vol. 61, No. 5, 1996 1895
Sch em e 2
this stage, removal of the hydroxyl and nitro groups can
be accomplished in the same manner as previously
reported.8 We explored an alternative approach utilizing
a radical-promoted elimination reaction.15 The hydroxyl
group in compound 10 was converted to the correspond-
ing phenyl thiocarbonate ester 11 by treatment with 2
equiv of n-BuLi followed by phenyl chlorothionocarbonate
(PTC-Cl) (Scheme 4).16 Treatment with Bu3SnH and a
radical initiator effected the elimination reaction, yielding
only trans olefin 12. The overall yield for these two steps
was ∼10% unoptimized.17 The limiting step is the
conversion of the alcohol into the phenyl thionocarbonate
ester whereas the radical-promoted elimination reaction
proceeds in good yield. In spite of the low yield, this two-
step, one-pot procedure has the advantage of only one
purification step. Once conditions are optimized for these
two steps, this method will facilitate the conversion of
Henry condensation products into their fully reduced
form. Finally, the olefin was reduced with diimide
(generated in situ) and the benzyl ethers were removed
by dissolving metal reduction to afford target disaccha-
ride 14.18
Sch em e 3
In summary, a new method for the synthesis of
C-disaccharides has been presented that utilizes a nitro-
aldol condensation between readily available C-glycosyl
aldehydes and nitro sugars. Evaluation of the generality
of this method by extension to (1,2)-, (1,3)-, and (1,4)-
linked C-disaccharides will come in due course.
Exp er im en ta l Section
Gen er a l P r oced u r es. Unless otherwise noted, materials
were obtained from commercial suppliers and were used without
further purification. Melting points (Pyrex capillary) are uncor-
rected. The silica gel used in column chromatography was
Universal Adsorbents DCC. 1H NMR spectra were determined
at 400 or 500 MHz. 13C NMR spectra were proton decoupled
and measured at 100.6 or 125.7 MHz. Chemical shifts are
reported in δ values, positive values indicating shifts downfield
of tetramethylsilane. Coupling constants are in hertz. Fast
atom bombardment (FAB+) mass spectra were recorded at the
U.C. Berkeley Mass Spectral Laboratory.
The nitro sugar coupling partner was synthesized as
depicted in Scheme 2. Selective acetoxylation of methyl
2,3,4,6-tetra-O-benzyl-R-D-glucopyranoside (6)14 followed
by deacetylation afforded compound 7, which was con-
verted to azido sugar 8 using standard methods. The
azide was reduced to the amine by hydrogenation over
Lindlar’s catalyst and then oxidized with m-CPBA to
afford nitro sugar 9.
Meth yl 2,3,4-Tr i-O-ben zyl-r-D-glu cop yr a n osid e (7).
A
solution of 27.4 g (49.4 mmol) of methyl 2,3,4,6-tetra-O-benzyl)-
R-D-glucopyranoside (6) in 230 mL of acetic anhydride and 230
mL of dry CH2Cl2 was cooled to -61 °C under a N2 atmosphere.
A solution of 11.7 g (49.4 mmol) of trimethylsilyl trifluo-
romethanesulfonate in 15 mL of dry CH2Cl2 was then added over
a 45-min period. The resulting orange solution was stirred for
90 min, and then the reaction was quenched with saturated
Aldehyde 1 was condensed with compound 9 using the
conditions reported by Martin and Lai8 to afford the
adduct 10 as a mixture of diastereomers (Scheme 3). At
Sch em e 4

1896 J . Org. Chem., Vol. 61, No. 5, 1996
Notes
NaHCO3. The solution was diluted with CH2Cl2, washed with
water, and dried over MgSO4. The crude product was dissolved
in 500 mL of methanol with a catalytic amount of sodium
methoxide. After 3 h, the reaction was neutralized with acidic
methanol. Purification of the crude product by silica gel
chromatography eluting with 5:1 cyclohexane/ethyl acetate
afforded 12.7 g (55%) of a thick syrup: IR (thin film) 3473, 2931,
1652, 1497, 1455, 1363, 1211, 1195, 1162, 1074, 1027, 912, 735,
697 cm-1; 1H NMR (400 MHz, CDCl3) δ 3.40 (s, 3 H), 3.53-3.60
(m, 2 H), 3.67-3.82 (m, 3 H), 4.06 (app t, 1 H, J ) 9.2), 4.61 (d,
1 H, J ) 3.5), 4.68 (d, 1 H, J ) 5.4), 4.70 (d, 1 H, J ) 6.5), 4.82-
4.94 (m, 3 H), 5.03 (d, 1 H, J ) 11.9), 7.28-7.40 (m, 15 H); 13C
NMR δ 55.05, 61.64, 70.60, 73.28, 74.90, 75.61, 77.27, 79.85,
81.82, 98.03, 127.50, 127.73, 127.82, 127.84, 127.89, 127.99,
128.28, 128.35, 137.99, 138.03, 138.61; mass spectrum (FAB+)
471 (M + Li)+.
eluting with a gradient of 2:1 ethyl acetate/cyclohexane to ethyl
acetate (2% Et3N) affording 7.28 g (88%) of a colorless syrup
which solidified upon standing: mp 86-89 °C; IR (thin film)
3387, 3031, 2908, 1643, 1495, 1453, 1358, 1069, 735, 696 cm-1
;
1H NMR (400 MHz, CDCl3) δ 2.70 (dd, 1 H, J ) 6.5, 13.4), 2.97
(dd, 1 H, J ) 2.7, 13.4), 3.31-3.36 (m, 1 H), 3.36 (s, 3 H), 3.49
(dd, 1 H, J ) 3.6, 9.6), 3.53-3.58 (m, 1 H), 3.99 (app t, 1 H, J )
9.2), 4.55 (d, 1 H, J ) 3.5), 4.60 (d, 1 H, J ) 11.1), 4.66 (d, 1 H,
J ) 12.1), 4.78-4.84 (m, 2 H), 4.87 (d, 1 H, J ) 11.1), 4.99 (d, 1
H, J ) 10.9), 7.27-7.40 (m, 15 H); 13C NMR δ 42.7, 55.0, 71.6,
73.3, 74.8, 75.6, 78.5, 80.0, 82.0, 97.8, 127.5, 127.8, 127.8, 127.9,
128.0, 128.0, 128.3, 128.4, 138.0, 138.0, 138.6; high-resolution
mass spectrum (FAB+) calcd for C28H34NO5 (MH)+ 464.2437,
found 464.2431.
Meth yl 6-Deoxy-6-n itr o-2,3,4-tr i-O-ben zyl-r-D-glu cop y-
r a n osid e (9). A stirring solution of 50% m-chloroperbenzoic
acid (m-CPBA) (19.7 g, 62.8 mmol) in 300 mL of 1,2-dichloro-
ethane was heated to reflux under a N2 atmosphere. A solution
of compound 8a (7.28 g, 15.7 mmol) in 50 mL of 1,2-dichloro-
ethane was added to the solution over a 30-min period, and the
reaction was stirred for an additional 2 h at reflux. The solution
was cooled to room temperature, the reaction was quenched with
a saturated NaHCO3, and the solution was diluted with CH2-
Cl2. The organic layer was washed repeatly with saturated
NaHCO3 until all of the m-chlorobenzoic acid was removed. The
acid free organic layer was dried over MgSO4, and the solvents
were removed in vacuo. Purification of the crude product by
silica gel chromatography eluting with 15:1 cyclohexane/ethyl
acetate afforded 5.32 g (69%) of a waxy solid. Recrystallization
from hexanes/ethyl acetate afforded white needles: mp 62-63
°C; IR (thin film) 3072, 3024, 2937, 1726, 1558, 1497, 1454, 1362,
Meth yl 6-O-Meth a n esu lfon yl-2,3,4-tr i-O-ben zyl-r-D-glu -
cop yr a n osid e (7a ). A solution of 8.95 g (19.3 mmol) of
compound 7 in 40 mL of dry CH2Cl2 was cooled to 0 °C under a
N2 atmosphere after which 4.1 mL (29 mmol) of Et3N was added.
After 10 min, methanesulfonyl chloride (1.7 mL, 21 mmol) was
added dropwise via syringe and the solution was stirred for 1 h.
The reaction was quenched with saturated NH4Cl, and the
solution diluted with CH2Cl2, washed with water, and dried over
MgSO4. Removal of solvents afforded a yellow syrup which was
used in the next step without further purification: IR (thin film)
3032, 2919, 1497, 1455, 1359, 1178, 1087, 966, 930, 819, 698
1
cm-1; H NMR (400 MHz, CDCl3) δ 2.98 (s, 3 H), 3.38 (s, 3 H),
3.47-3.54 (m, 2 H), 3.82-3.87 (m, 1 H), 4.02 (app t, 1 H, J )
9.3), 4.35-4.37 (m, 2 H), 4.59-4.68 (m, 3 H), 4.78-4.85 (m, 2
H), 4.91 (d, 1 H, J ) 10.8), 5.00 (d, 1 H, J ) 10.9), 7.26-7.40
(m, 15 H); 13C NMR δ 37.5, 55.4, 68.3, 68.6, 73.4, 75.1, 75.7,
76.9, 79.7, 81.7, 98.1, 127.7, 127.9, 128.0, 128.0, 128.4, 128.5,
128.5, 137.7, 137.9, 138.4; high-resolution mass spectrum (FAB+)
calcd for C29H34O8SLi (M + Li)+ 549.2134, found 549.2143.
1221, 908, 740, 699 cm-1 1H NMR (400 MHz, CDCl3) δ 3.33
;
(app t, 1 H, J ) 9.9), 3.37 (s, 1 H), 3.52 (dd, 1 H, J ) 3.5, 9.6),
4.07 (app t, 1 H, J ) 9.2), 4.20 (dd, 1 H, J ) 9.3, 12.6), 4.37 (dt,
1 H, J ) 2.5, 9.8), 4.48 (d, 1 H, J ) 2.6), 4.51-4.53 (m, 1 H),
4.58 (d, 1 H, J ) 11.3), 4.65 (d, 1 H, J ) 12.0), 4.79-4.86 (m, 1
H), 4.93 (d, 1 H, J ) 11.3), 5.04 (d, 1 H, J ) 10.8), 7.22-7.37
(m, 15 H); 13C NMR δ 55.58, 67.38, 73.41, 74.84, 75.81, 76.10,
77.66, 79.71, 81.71, 97.90, 127.76, 127.97, 128.05, 128.09, 128.12,
128.20, 128.44, 128.50, 128.61, 137.40, 137.77, 138.30; high-
resolution mass spectrum (FAB+) calcd for C28H31NO7Li (M +
Li)+ 500.2261, found 500.2271.
Meth yl 6-Azid o-6-d eoxy-2,3,4-tr i-O-ben zyl-r-D-glu cop y-
r a n osid e (8). To a stirring solution of 10.5 g (19.3 mmol) of
compound 7a in 40 mL of dry CH3CN was added 6.6 g (23 mmol)
19
of Bu4NN3 under a nitrogen atmosphere. The solution was
heated at reflux for 8 h and cooled to room temperature, and
the solvent was removed in vacuo. Purification of the crude
product by silica gel chromatography eluting with 5:1 cyclohex-
ane/ethyl acetate afforded 8.7 g (92% from alcohol 7) of a
colorless syrup: IR (thin film) 3089, 3065, 3032, 2924, 2246,
2100, 1497, 1454, 1360, 1290, 1286, 1193, 1158, 1077, 1001, 910,
736, 698, 647 cm-1; 1H NMR (400 MHz, CDCl3) δ 3.33 (dd, 1 H,
J ) 5.6, 13.0), 3.41 (s, 3 H), 3.41-3.47 (m, 2 H), 3.55 (dd, 1 H,
J ) 3.6, 9.6), 3.77-3.82 (m, 1 H), 4.00 (app t, 1 H, J ) 9.2), 4.59
(d, 1 H, J ) 11.0), 4.62 (d, 1 H, J ) 3.5), 4.68 (d, 1 H, J ) 12.1),
4.79-4.84 (m, 2 H), 4.92 (d, 1 H, J ) 11.0), 5.01 (d, 1 H, J )
11.0), 7.22-7.40 (m, 15 H); 13C NMR δ 51.31, 55.30, 69.87, 73.36,
75.08, 75.71, 78.27, 79.90, 81.77, 97.96, 127.62, 127.90, 128.03,
128.38, 128.44, 137.87, 137.96, 138.53; high-resolution mass
spectrum (FAB+) calcd for C28H31N3O5Li (M + Li)+ 496.2424,
found 496.2415.
Meth yl 6-Am in o-6-d eoxy-2,3,4-tr i-O-ben zyl)-r-D-glu cop y-
r a n osid e (8a ). To a stirring solution of compound 8 (8.71 g,
17.8 mmol) in 180 mL of EtOH was added 2.61 g (30% by weight)
of Pd/CaCO3 poisoned with PbO (Lindlar’s catalyst). Hydrogen
gas was bubbled through the solution for 1 h, and the reaction
was stirred under a H2 atmosphere for an additional 12-h period.
The mixture was filtered through Celite, and the catalyst was
rinsed with ethyl acetate. The filtrate was concentrated, and
the crude product was purified by silica gel chromatography
Anal. Calcd for C28H31NO7: C, 68.14; H, 6.33; N, 2.84.
Found: C, 68.34; H, 6.42; N, 2.67.
Met h yl 6-C-(2,6-An h yd r o-3,4,5,7-t et r a -O-b en zyl-d -gly-
cer o-L-ma n n o-h eptitol-1-yl)-6-deoxy-6-n itr o-2,3,4-tr i-O-ben -
zyl-r-D-glu cop yr a n osid e (10). To a stirring solution of 1.80
g (3.62 mmol) of compound 9 in 15 mL of dry CH3CN were added
2.20 g (3.98 mmol) of (2,3,4,6-tetra-O-benzyl-â-D-galactopyrano-
syl)methanal (1), 0.23 g (4.0 mmol) of KF, and 0.21 g (0.80 mmol)
of 18-crown-6 under a N2 atmosphere. The solution was stirred
at room temperature for 7 h, and the solvent was removed in
vacuo. Purification of the crude product by silica gel chroma-
tography eluting with 5:1 pentane/ether afforded 1.97 g (52%)
of a thick syrup, which consisted of an inseparable mixture of
1
four diastereomers as determined by H and 13C NMR spectro-
scopy. The mixture was characterized by IR spectroscopy and
mass spectrometry: IR (thin film) 3442, 3090, 3064, 3033, 2924,
2871, 1548, 1498, 1452, 1362, 1212, 1087, 1047, 1029, 999, 911,
736, 698 cm-1; high-resolution mass spectrum (FAB+) calcd for
C
63H67NO13Li (M + Li)+ 1052.4772, found 1052.4793.
Met h yl 6-C-(2,6-An h yd r o-1-O-(p h en ylt h ion oca r b on yl)-
3,4,5,7-t et r a -O-b en zyl-D-glycer o-L-m a n n o-h ep t it ol-1-yl)-6-
d eoxy-6-n itr o-2,3,4-tr i-O-ben zyl-r-D-glu cop yr a n osid e (11).
A solution of 37 mg (0.35 mmol) of compound 10 in 3.5 mL of
THF was placed in a flame-dried flask under a N2 atmosphere.
The solution was cooled to -78 °C, and 280 µL (0.70 mmol) of a
2.5 M solution of n-BuLi in hexanes was added slowly. The
resulting yellow solution was stirred for 15 min, after which 60
µL (0.42 mmol) of phenyl chlorothionocarbonate was added
dropwise. The reaction mixture was warmed to -42 °C for 45
min and then to room temperature for 5 min. The reaction was
quenched with saturated NH4Cl, and the solution was diluted
with ether, washed with water and brine, and dried over MgSO4.
Removal of the solvents afforded a yellow syrup which decom-
posed readily upon exposure to silica gel. The crude product
was therefore used in the next step without further purification;
mass spectrum (FAB+) 1182.6 (MH)+.
(13) Miller, J . H.; Reznikoff, W. S. The Operon; Cold Spring Harbor
Laboratory: New York, 1980.
(14) Angibeaud, P.; Utille, J .-P. Synthesis 1991, 737.
(15) A similar reaction has been used for the conversion of â-nitro
sulfides and sulfones to the corresponding olefins: Ono, N.; Kaji, A.
Synthesis 1986, 693.
(16) Robins, M. J .; Wilson, J . S.; Hansske, F. J . Am. Chem. Soc.
1983, 105, 4059.
(17) Unfortunately, optimization of this step was not possible due
to closure of the laboratory.
(18) Compound 12 was refractory to hydrogenation of both the olefin
and the benzyl ethers.
(19) Brandstrøm, A.; Lamm, B.; Palmertz, I. Acta Chem. Scand. B
1974, 28, 699.

Notes
Meth yl 6-C-(2,6-An h ydr o-1-deoxy-1-deh ydr o-3,4,5,7-tetr a-
J . Org. Chem., Vol. 61, No. 5, 1996 1897
4.56 (d, 1 H, J ) 10.8), 4.62 (d, 1 H, J ) 11.2), 4.64 (d, 1 H, J )
13.0), 4.68 (app d, 2 H, J ) 11.9), 4.76 (d, 1 H, J ) 11.7), 4.80
(d, 1 H, J ) 12.2), 4.81 (d, 1 H, J ) 10.8), 4.84 (d, 1 H, J ) 10.8),
4.93 (d, 1 H, J ) 10.9), 4.96 (d, 1 H, J ) 11.7), 4.97 (d, 1 H, J )
10.8), 7.25-7.38 (m, 35 H); 13C NMR δ 27.77, 29.60, 54.80, 68.82,
70.38, 72.07, 73.14, 73.42, 73.65, 74.37, 75.13, 75.36, 75.64, 76.82,
79.25, 79.85, 80.07, 82.00, 82.26, 84.82, 97.60, 127.39, 127.42,
127.48, 127.65, 127.75, 127.80, 127.92, 127.98, 128.09, 128.20,
128.27, 128.31, 128.34, 137.88, 138.19, 138.28, 138.35, 138.44,
138.77; high-resolution mass spectrum (FAB+) calcd for C63H68O10-
Li (M + Li)+ 991.4973, found 991.4973.
O-ben zyl-D-glycer o-L-m a n n o-h ep titol-1-yl)-6-d eoxy-6-d eh y-
d r o-2,3,4-tr i-O-ben zyl-r-D-glu cop yr a n osid e (12). To a stir-
ring, degassed solution of crude 11 (41 mg, 0.35 mmol) in 3.5
mL of dry, degassed toluene were added 280 µL (1.1 mmol) of
tributyltin hydride and 114 mg (0.70 mmol) of AIBN. The
solution was heated at reflux for 1 h, cooled to room temperature,
and then concentrated in vacuo. The resulting syrup was
dissolved in acetonitrile and washed extensively with pentane.
The acetonitrile layer was concentrated, and the crude product
was purified by silica gel chromatography eluting with 15:1
cyclohexane/ethyl acetate to afford an amorphous gel. Subse-
quent treatment with pentane resulted in the formation of white
crystals. Isolation by vacuum filtration afforded 33 mg of the
desired product in an overall yield of 10% based on compound
10. The product was exclusively in the trans configuration as
determined by an olefin coupling constant of 15.5 Hz: mp 95-
97 °C; IR (KBr) 3097, 3064, 3031, 2913, 2863, 1453, 1360, 1266,
1212, 1094, 1072, 1052, 1031, 913, 740, 696 cm-1; 1H NMR (500
MHz, CDCl3) δ 3.18 (app t, 1 H, J ) 9.3), 3.32 (s, 3 H), 3.50 (dd,
1 H, J ) 3.6, 9.6), 3.55-3.60 (m, 4 H), 3.67-3.71 (m, 1 H), 3.74
(dd, 1 H, J ) 5.8, 9.2), 3.95 (app t, 1 H, J ) 9.3), 3.99 (d, 1 H, J
) 2.7), 4.09 (dd, 1 H, J ) 5.9, 9.8), 4.37-4.44 (m, 2 H), 4.46-
4.52 (m, 2 H), 4.58-4.72 (m, 7 H), 4.77-4.83 (m, 2 H), 4.91-
4.96 (m, 2 H), 5.90 (dd, 1 H, J ) 6.2, 15.5), 5.98 (dd, 1 H, J )
6.1, 15.5), 7.15-7.40 (m, 35 H); 13C NMR δ 55.14, 68.78, 70.71,
72.41, 73.35, 73.52, 74.00, 74.57, 74.99, 75.17, 75.80, 79.25, 79.59,
79.82, 81.66, 82.22, 84.18, 98.04, 127.47, 127.54, 127.75, 127.84,
127.92, 127.95, 127.96, 128.04, 128.07, 128.11, 128.18, 128.25,
128.34, 128.38, 128.42, 130.31, 130.76, 137.85, 138.16, 138.23,
138.42, 138.48, 138.85, 138.87; high-resolution mass spectrum
(FAB+) calcd for C63H66O10Li (M + Li)+ 989.4816, found 989.4828.
Meth yl 6-C-(2,6-An h yd r o-1-d eoxy-3,4,5,7-tetr a -O-ben zyl-
D-glycer o-L-ma n n o-h eptitol-1-yl)-6-deoxy-2,3,4-tr i-O-ben zyl-
r-D-glu cop yr a n osid e (13). A solution of 29 mg (0.029 mmol)
of alkene 12 and 16 mg (0.087 mmol) of (p-toluenesulfonyl)-
hydrazine in 3 mL of dimethoxyethane was heated to reflux. A
solution of 7.1 mg (0.087 mmol) of NaOAc in 1.5 mL of H2O was
then added to the solution via syringe pump over a 12-h period.
The reaction was stirred at reflux for an additional 12 h and
cooled to room temperature. The solution was diluted with
ether, washed with water and brine, and dried over MgSO4. The
solution was concentrated and coevaporated twice with ethanol
to afford a fluffy white solid (28 mg, 98%) that was used in the
next step without further purification: 1H NMR (500 MHz,
CDCl3) δ 1.40-1.53 (m, 4 H), 3.16 (app t, 1 H, J ) 9.4), 3.20 (m,
1 H), 3.30 (s, 3 H), 3.49-3.60 (m, 6 H), 3.67 (app t, 1 H, J )
9.3), 3.94 (app t, 1 H, J ) 9.3), 4.01 (app d, 1 H, J ) 2.5), 4.40
(d, 1 H, J ) 11.7), 4.46 (d, 1 H, J ) 11.7), 4.54 (d, 1 H, J ) 3.6),
Met h yl 6-C-(2,6-An h yd r o-1-d eoxy-D-glycer o-L-m a n n o-
h ep titol-1-yl)-6-d eoxy-r-D-glu cop yr a n osid e (14). Compound
13 was dissolved in 1.5 mL of dry dimethoxyethane and cooled
to -78 °C under a N2 atmosphere. Ammonia (5 mL) was
condensed into the reaction flask, and the solution was warmed
to -33 °C. Sodium metal was added to the stirring solution until
a dark blue color persisted. The reaction mixture was stirred
for an additional 15 min, and then the reaction was quenched
with solid NH4Cl. The resulting suspension was concentrated
and diluted with ethanol, and the insoluble salts were filtered.
The filtrate was concentrated and passed down a column of Bio-
Rad AG501-X8 (D) resin (mixed bed desalting resin), and the
eluate was concentrated to afford 11 mg (100%) of a white solid.
The product was further purified by reversed-phase HPLC
eluting with H2O: 1H NMR (400 MHz, D2O) δ 1.29-1.33 (m, 2
H), 1.89-1.94 (m, 2 H), 3.00-3.06 (m, 2 H), 3.21 (s, 3 H), 3.24
(app t, 1 H, J ) 9.5), 3.34-3.43 (m, 6 H), 4.38 (dd, 1 H, J ) 4.3,
11.6), 3.55 (dd, 1 H, J ) 8.1, 11.7), 3.74 (d, 1 H, J ) 3.2); 13C
NMR δ 29.48, 30.04, 57.90, 64.30, 72.08, 73.81, 74.25, 74.27,
75.94, 76.25, 76.92, 81.39, 82.72, 101.95; high-resolution mass
spectrum (FAB+) calcd for C14H26O10Li (M + Li)+ 361.1686, found
361.1706.
Ack n ow led gm en t. This research was supported by
the Director, Office of Energy Research, Office of Basic
Energy Sciences, Division of Materials Sciences, and by
the Division of Energy Biosciences of the U.S. Depart-
ment of Energy, DE-AC03-76SF0098.
Su p p or tin g In for m a tion Ava ila ble: 1H NMR spectra for
compounds 7-10 and 12-14; 13C NMR specta for compounds
7-9 and 12-14 (17 pages). This material is contained in
libraries on microfiche, immediately follows this article in the
microfilm version of the journal, and can be ordered from the
ACS; see any current masthead page for ordering information.
J O9517095