Total synthesis of batatoside L

Article abstract of DOI:10.1021/jo101231r

The total synthesis of batatoside L (1), a resin glycoside possessing cytotoxicity against laryngeal carcinoma cells, has been completed in a highly convergent manner. The most crucial step in this total synthesis was the efficient construction of the 18-membered macrolactone framework through the Corey-Nicolaou macrolactonization approach.

Full text of DOI:10.1021/jo101231r

pubs.acs.org/joc
such as cytotoxic activity against human cancer cell lines,3
Total Synthesis of Batatoside L
antibacterial,3a,4 purgative,3b,5 and ionophoretic activity,6 as
wellasplant growth controlling effects.3a,b,7 It has beenshown
that all the bioactivities of these lipo-oligosaccharides are
associated with their macrocyclic structures. Cleavage of the
lactone bond by saponification destroys the activity.1a
Lin Xie, San-Yong Zhu, Xiao-Qiu Shen, Li-Li He, and
Jin-Song Yang*
Key Laboratory of Drug Targeting and Delivery Systems,
Ministry of Education, and Department of Chemistry of
Medicinal Natural Products, School of Pharmacy, Sichuan
University, Chengdu 610041, People’s Republic of China
Batatoside-type resin glycosides were isolated by Kong
and co-workers from the tuber of Ipomoea batatas (L.) Lam.
(Convolvulaceae),8 a plant with the common name of sweet
potato. In Chinese traditional medicine, the tubers of
I. batatas have been used as a medicinal herb for promoting
hemostasis and eliminating abnormal secretions. Bioassays
proved that batatosides L (1, Scheme 1) and O exhibited
significant cytotoxic activity against laryngeal carcinoma
yjs@scu.edu.cn
Received June 23, 2010
(Hep-2) cells with ED50 values at 3.5 and 2.0 μg mL-1
,
3
respectively.8b
Because of their appealing structural and bioactive fea-
tures, several total syntheses of resin glycosides have been
accomplished.9 Producing the unique macrolactone frame-
work in these natural products has been considered a major
synthetic challenge, in which two cyclization strategies have
been applied so far. One is a macrolactonization approach10
used by Schmidt and co-workers for their pioneering synth-
esis of calonyctin A1.10a Later, the effectiveness of this
method was further demonstrated by the Heathcock,10c-e
Yu,10f,g and Sakairi10b laboratories, respectively, in the syn-
thesis of several other resin glycosides. The other strategy is
The total synthesis of batatoside L (1), a resin glycoside
possessing cytotoxicity against laryngeal carcinoma cells,
has been completed in a highly convergent manner. The
most crucial step in this total synthesis was the efficient
construction of the 18-membered macrolactone frame-
work through the Corey-Nicolaou macrolactonization
approach.
an olefin ring closing metathesis (RCM) method,11 by which
11a
€
the Furstner group formed the macrolidic systems
and
succeededin synthesizing tricolorins,11b woodrosin I,11c-e and
ipomoeassins.11f,g Recently, the same strategy was employed
(5) Noda, N.; Ono, M.; Miyahara, K.; Kawasaki, T.; Okabe, M. Tetra-
hedron 1987, 43, 3889–3902.
(6) Kitagawa, I.; Ohashi, K.; Kawanishi, H.; Shibuya, H.; Shinkai, K.;
Akedo, H. Chem. Pharm. Bull. 1989, 37, 1679–1681.
Resin glycosides, mainly isolated from the morning glory
family (Convolvulaceae) of plants, are a class of amphiphilic
glycolipids with a characteristic macrolactone skeleton.1 The
hydrophobic aglycons commonly found in these constituents
are optically active 11-hydroxyaliphatic acids, namely, jala-
pinolic acid (11(S)-hydroxyhexadecanoic acid) and convol-
vulinolic acid (11(S)-hydroxytetradecanoic acid).2 While the
hydrophilic carbohydrate sections consist typically of four
or five monosaccharide units mainly including D-glucose,
D-fucose, L-rhamnose, and D-quinovose, and these sugar
residues are usually modified with some fatty acyl substitu-
ents. The carboxyl group of aglycon esterifies intramolecu-
larly with one hydroxyl group of the complex oligosaccharide
chain to form the macrocycle. Besides, resin glycosides are
reported to have a wide range of promising bioactivities
ꢀ
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(8) (a) Yin, Y.-Q.; Li, Y.; Kong, L.-Y. J. Agric. Food Chem. 2008, 56,
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Angew. Chem., Int. Ed. Engl. 1995, 34, 2520–2524. (b) Furukawa, J.;
Kobayashi, S.; Nomizu, M.; Nishi, N.; Sakairi, N. Tetrahedron Lett. 2000,
41, 3453–3457. Tricolorins: (c) Larson, D. P.; Heathcock, C. H. J. Org.
Chem. 1996, 61, 5208–5209. (d) Larson, D. P.; Heathcock, C. H. J. Org.
Chem. 1997, 62, 8406–8418. (e) Brito-Arias, M.; Pereda-Miranda, R.; Heath-
cock, C. H. J. Org. Chem. 2004, 69, 4567–4570. (f) Lu, S.-F.; O’Yang, Q.-Q.;
Guo, Z.-W.; Yu, B.; Hui, Y.-Z. Angew. Chem., Int. Ed. Engl. 1997, 36, 2344–
2346. (g) Lu, S.-F.; O’Yang, Q.-Q.; Guo, Z.-W.; Yu, B.; Hui, Y.-Z. J. Org.
Chem. 1997, 62, 8400–8405.
(11) For the RCM method in total synthesis of resin glycosides, see:
€
€
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Furstner, A.; Muller, T. J. Am. Chem. Soc. 1999, 121, 7814–7821. Woodrosin
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131. (b) Lu, Sh.-F.; Guo, Z.-W.; O’yang, Q.-Q.; Hui, Y.-Z. Youji Huaxue,
1997, 17, 488-497 and references cited therein.
(2) Ono, M.; Yamada, F.; Noda, N.; Kawasaki, T.; Miyahara, K. Chem.
Pharm. Bull. 1993, 41, 1023–1026.
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Eur. J. 2003, 9, 307–319. (d) Furstner, A.; Jeanjean, F.; Razon, P.; Wirtz, C.;
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Razon, P. Angew. Chem., Int. Ed. 2002, 41, 2097–2101. Ipomoeassins: (f)
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Furstner, A.; Nagano, T. J. Am. Chem. Soc. 2007, 129, 1906–1907. (g)
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Hernandez-Carlos, B.; Bye, R.; Pereda-Miranda, R. J. Nat. Prod. 1999, 62,
1096–1100. (c) Gaspar, E. M. M. Eur. J. Org. Chem. 2001, 369–373.
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5764 J. Org. Chem. 2010, 75, 5764–5767
Published on Web 07/28/2010
DOI: 10.1021/jo101231r
r
2010 American Chemical Society

Xie et al.
JOCNote
SCHEME 1. Retrosynthetic Analysis
SCHEME 2. Preparation of Monosaccharide Building Blocks
stereoselectivity of each glycosylation. Additionally, the
p-methoxybenzyl (PMB) group was chosen as the sole per-
manent hydroxyl-protecting group, thus reducing the need
for functional group transformations and facilitating the
final deprotection manipulation.
by a team from the Eisai Research Institute, which completed
a synthesis of ipomoeassin F.11h During our continuing efforts
in the synthesis of resin glycosides,12 we developed a new and
efficient synthetic route to chiral methyl 11(S)-jalapinolate
(5) using commercially available (R)-glycidol as starting
material,12a,13 and then by taking advantage of the Corey-
Nicolaou macrolactonization reaction14 as a key step, we
realized the construction of the 20- and 21-membered cyclic
lactones that represent the core structures of merremoside-type
resin glycosides.12a In this paper, we report the total synthesis of
the tetrasaccharidic glycolipid batatoside L (1).
As is shown in our retrosynthetic analysis (Scheme 1),
batatoside L can be obtained in a highly convergent manner
by glycosidic coupling reaction between heterodisaccharide
macrolactone 2 and exocyclic dirhamnose trichloroacetimi-
date 3. To get the synthetically challenging subunit 2, we
planned to adopt the Corey-Nicolaou macrolactonization
method to form the macrocyclic ring from glycosidic acid
precursor 4. For the synthesis of the intermediates 3 and 4,
several suitably functionalized monosaccharide modules
were needed including four glycosyl trichloroacetimidate
donors 6, 7, 13, and 15, and one L-rhamnosyl acceptor 18
(Scheme 2). The acyl groups serving as the necessary neigh-
boring participating groups were incorporated at the
2-OH position of each donor to ensure the desired 1,2-trans
The glucose derivatives 6 and 7 were prepared according to
the literature procedures.15 The preparation of building
blocks 13, 15, and 18 was carried out as outlined in Scheme 2.
Reaction of the known allyl 3-O-PMB-R-L-rhamnopyrano-
side (8)16 with acetyl chloride (CH3COCl) and trans-cinna-
moyl chloride (Cna-Cl) via a Ag2O-mediated regioselective
monoacylation methodology17 developed by our group pro-
vided exclusively C-2 acetate 9 and cinnamate 10, respec-
tively, in 68% and 76% yield. Protection of the remaining
4-OH in 9 with tert-butyldiphenylsilyl (TBDPS) and tert-
butyldimethylsilyl (TBS) groups secured silyl ethers 11 and
12 in 90% and 82% yield, respectively. The anomeric center
of 11 was then unmasked by a PdCl2-catalyzed deallylation18
of the allyl ether. Activation of the obtained crude hemi-
acetal for glycoside formation was performed by treatment
with trichloroacetonitrile (CCl3CN) and 1,8-diazabicyclo-
[5.4.0]undec-7-ene (DBU),19 giving rise to the R-L-rhamno-
pyranosyl trichloroacetimidate 13 in 65% yield over the two
steps from 11. Conversion of 10 to the required 15 involved
(i) 4-O-n-dodecanoylation of 10 with n-dodecanoyl chloride
(Dodeca-Cl), forming 14 (92%), and (ii) installation of the
(12) (a) Zhu, X.-M.; He, L.-L.; Yang, G.-L.; Lei, M.; Yang, J.-S. Synlett
2006, 3510–3512. (b) Shen, X.-Q.; Xie, L.; Gao, L.; He, L.-L.; Yang, Q.;
Yang, J.-S. Carbohydr. Res. 2009, 344, 2063–2068.
(15) Schmidt, R. R. Liebigs Ann. Chem. 1987, 10, 825–831.
(16) Mulard, L. A.; Clement, M. J.; Imberty, A.; Delepierre, M. Eur. J.
Org. Chem. 2002, 2486–2498.
(13) 11(S)-Hydroxyhexadecanoic acid (jalapinolic acid) is available by
hydrolysis of the crude convolvulaceous resins (ref 1a) and also by total
synthesis, see: refs 10b-g and: Kitagawa, I.; Baek, N. I.; Kawashima, K.;
Yokokawa, Y.; Yoshikawa, M.; Ohashi, K.; Shibuya, H. Chem. Pharm. Bull.
1996, 44, 1680–1692.
(17) Yang, Q.; Lei, M.; Yin, Q.-J.; Yang, J.-S. Carbohydr. Res. 2007, 342,
1175–1181.
(18) Zhang, J.-J.; Zhu, Y.-L.; Kong, F.-Z. Carbohydr. Res. 2001, 336,
229–235.
(19) Schmidt, R. R.; Jung, K.-H. In Preparative Carbohydrate Chemistry;
Hanessian, S., Ed.; Dekker: New York, 1997; pp 283-312.
(14) Corey, E. J.; Nicolaou, K. C. J. Am. Chem. Soc. 1974, 96, 5614–5616.
J. Org. Chem. Vol. 75, No. 16, 2010 5765

Xie et al.
JOCNote
SCHEME 3. Formation of Macrolactone Framework
SCHEME 4. Completion of Total Synthesis of Batatoside L (1)
leaving group following the same two-step sequence as
described above at the anomeric carbon of 14, giving the
corresponding imidate 15 (57% for two steps). In addition,
the preparation of the rhamnose unit 18 began with metha-
nolysis of sugar 12 with sodium methoxide/methanol at low
temperature (-15 °C) to provide alcohol 16 in a yield of
95%. Esterification of 16 with 2(S)-methylbutyric anhydride
((Mba)2O) in pyridine gave 17 (79%), which was easily
desilylated with tetrabutylammonium fluoride (TBAF) to
afford 18 in 79% yield.
Then, compound 22 was saponifiedwithpotassiumhydroxide
(KOH) in a CH3OH/tetrahydrofuran/water (9:9:1) cosolvent
at 55 °C to release the 20-OH and the aglycon carboxyl groups,
affording the acid 4 in 82% yield.
The efficient construction of the 18-membered macrocycle
core must be the most critical step for this total synthesis.
With the key precursor 4 in hand, we then centered on the
ring-closing reaction using the Corey-Nicolaou method.14
After screening several conditions, we found that the desired
cyclized product 23 was obtained efficiently (88% yield)
under the typical Corey-Nicolaou’s lactonization protocol
using 2,20-pyridyl disulfide ((PyS)2) and triphenylphosphine
(Ph3P) in highly dilute toluene (7.5 ꢀ 10-4 M) upon heating
to reflux for 5 days. The resulting 23 was then exposed to
fluoride ion at 35 °C to remove the silyl moiety, which yielded
the lactone alcohol 2 in 65% yield without damaging the
macrolactone ring (Scheme 3).
The next task was to prepare the exocyclic dirhamno-
pyranose fragment. The imidate donor 15 was readily re-
acted with the L-rhamnose building block 18 by means of a
similar TMSOTf-catalyzed glycosylation procedure to fur-
nish disaccharide glycoside 24 (92% yield) with R-anomeric
configuration at the new glycosidic linkage (Scheme 4). After
subjecting 24 again to the same series of transformations as
that used for 11 f 13, we obtained the corresponding imidate
3 (50% yield over the two steps).
Finally, we investigated the methods for connecting the
macrocycle acceptor 2 and the fully elaborated disaccharide
donor 3 (Scheme 4). Although this coupling reaction using
the similar glycosylation conditions outlined above afforded
our desired product 25, the lability of the donor 3 in the
presence of the Lewis acid (TMSOTf) resulted in low yield
(only 40%). Alternatively, we turned to the “inverse glyco-
sylation” procedure developed by Schmidt et al.,23 with the
goal of minimizing the exposure of the glycosyl donor to the
Lewis acidic solutions. In such an experiment, premixing the
acceptor 2 with catalytic amounts of TMSOTf (0.38 equiv)
and 4 A molecular sieves in anhydrous CH2Cl2, followed
by slow addition of a CH2Cl2 solution of excess donor 3
For the total synthesis of batatoside L (1), our first task
was the preparation of the macrolactone 2 (Scheme 3).
Under the standard Schmidt glycosylation conditions,19,20
the chiral hydroxyl ester 512a was glycosylated with D-gluco-
syl donors 6 and 7 in methylene chloride (CH2Cl2) activated
by a catalytic amount of trimethylsilyl trifluoromethanesul-
fonate (TMSOTf) to deliver β-D-glucopyranosides 19 and 20,
respectively, in 73% and 93% yield. In the glycosylation of 5
with the C-2 acetate donor 6, the possible orthoester by-
product formed by participation of the acetyl moiety was not
detected. At this junction, we encountered difficulties in
selectively cleaving the C-2 ester functionalities from 19
and 20 under various hydrolysis conditions. Initial attempts
employing NaOCH3/CH3OH for 19 and 20 and CH3COCl/
CH3OH21 for 19 were found to be ineffective and no reac-
tions were realized. This is probably because of the steric
hindrance around the secondary 2-OH position that resulted
from the bulkiness of the anomeric substituent and the PMB
group at C-3. Gratifyingly, dissolution of the conjugate 19 in
a solvent mixture of CH3OH/CH2Cl2 (7:1), addition of 7.0
equiv of DBU,22 and heating to 40 °C effected 2-O-deacety-
lation, and thus the hydrolyzed product 21 bearing the point
for the next glycosylation step was obtained as a sole pro-
duct (91% yield). Subsequent coupling of 21 and donor 13
(2.0 equiv) took place smoothly in the presence of TMSOTf as
the promoter at -78f0 °C, providing the lipo-disaccharide
22 in a good yield and with complete R-stereoselectivity.
(20) Schmidt, R. R. Angew. Chem., Int. Ed. Engl. 1986, 25, 212–235.
(21) Byramova, N. E.; Ovchinnikov, M. V.; Backinowsky, L. V.; Ko-
chetkov, N. K. Carbohydr. Res. 1983, 124, c8–c10.
(22) Baptistella, L. H. B.; dos Santos, J. F.; Ballabio, K. C.; Marsaioli,
A. J. Synthesis 1989, 436–438.
(23) Schmidt, R. R.; Behrendt, M.; Toepfer, A. Synlett 1990, 694–696.
5766 J. Org. Chem. Vol. 75, No. 16, 2010

Xie et al.
JOCNote
(3.0 equiv) at -78 °C, did bring about a considerably
improved 82% yield of 25. Then, under the influence of 8.0
equiv of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)
in aqueous CH2Cl2 at ambient temperature, exhaustive
oxidation cleavage of PMB-ether functions in 25 produced
the target molecule 1 in 81% yield. Synthetic batatoside L (1)
was found to be identical with the natural isolate8b on the
basis of 1H and 13C NMR spectra and specific rotation
comparisons (see the Supporting Information).
In summary, we have reported the total synthesis of
architecturally novel resin glycoside batatoside L (1). The
use of the trichloroacetimidate glycosylation method pro-
vided an entry to the oligosaccharide motif, and application
of the Corey-Nicolaou macrolactonization method allowed
an efficient formation of the key 18-membered lactone ring.
The attachment of the disaccharide donor 3 to the macro-
cycle acceptor 2 was conducted through an “inverse glyco-
sylation” technique in order to prevent the hydrolysis of the
donor,24 thus generating the fully protected product 25 in
good yield. The final removal of all PMB protecting groups
in 25 finished the total synthesis of 1.
1615, 1515, 1254 cm-1; HR ESIMS calcd for C76H100O15Si [M þ
Na]þ 1303.6729, found m/z 1303.6743.
Synthesis of Compound 25. The donor 3 (51 mg, 0.047 mmol)
and the acceptor 2 (12.9 mg, 0.016 mmol) were dried separately
under high vacuum for 3 h. Then, compound 2 was dissolved in
CH2Cl2 (184 μL) followed by addition of freshly activated 4 A
molecular sieves (70 mg). The resulting slurry was stirred
at room temperature for 15 min, after which it was cooled to
-78 °C and a solution of TMSOTf (1.14 μL, 0.006 mmol) in
CH2Cl2 (356 μL) was added. After 5 min, a solution of 3 in CH2Cl2
(131 μL) was added dropwise at -78 °C. After being stirred for 1 h
at the same temperature, the reaction was gradually warmed to
ambient temperature, and then was quenched with triethylamine
and filtered. The filtrate was concentrated in vacuo to give
a residue, which was purified by column chromatography (7:1,
petroleum ether-EtOAc) to afford 25 as a colorless syrup (20 mg,
82%). Rf 0.48 (3:1, petroleum ether-EtOAc). [R]20D þ2.8 (c 1.0,
CHCl3); 1H NMR (400 MHz, CDCl3) δ 7.71 (d, 1H, J = 16.0 Hz),
7.54 (m, 2H), 7.40 (t, 3H, J= 3.2 Hz), 6.70-7.37 (m, 24H), 6.52 (d,
1H, J = 16.0 Hz), 5.60 (s, 1H), 5.49 (s, 1H), 5.42 (s, 1H), 5.39 (s,
1H), 5,19 (s, 1H), 5.11 (s, 1H), 5.06 (t, 1H, J = 9.6 Hz), 4.84 (d, 1H,
J = 10.8 Hz), 4.81 (d, 1H, J = 9.2 Hz), 4.72 (d, 1H, J = 10.4 Hz),
4.68 (d, 1H, J = 11.6 Hz), 4.65 (d, 1H, J = 7.2 Hz), 4.63 (d, 1H,
J = 10.0 Hz), 4.61 (d, 1H, J = 10.0 Hz), 4.52 (d, 1H, J = 9.6 Hz),
4.72 (d, 1H, J = 10.8 Hz), 4.37 (d, 1H, J = 11.2 Hz), 4.34 (d, 1H,
J = 9.6 Hz), 4.32 (d, 1H, J = 8.8 Hz), 4.14 (d, 1H, J = 10.0 Hz),
3.49-3.89 (m, 33H), 2.42-2.48 (m, 1H), 2.28-2.33 (m, 2H),
2.23-2.28 (m, 2H), 1.68-1.71 (m, 1H), 1.20-1.50 (m, 1H),
1.18-1.40 (m, 51H), 1.04 (d, 3H, J = 6.8 Hz), 0.80-0.88 (m,
6H), 0.78 (t, 3H, J = 7.6 Hz); 13C NMR (100 Hz, CDCl3) δ 11.4,
14.1, 16.3, 17.4, 18.4, 18.9, 19.7, 22.2, 22.7, 24.7, 24.9, 25.0, 26.6,
27.1, 27.4, 27.8, 29.2, 29.3, 29.35, 29.4, 29.5, 29.6, 29.7, 29.9,
31.87, 31.9, 32.1, 33.5, 33.9, 34.3, 40.8, 54.8, 55.1, 55.2, 67.2,
67.3, 67.6, 67.7, 68.4, 69.1, 70.1, 70.8, 72.1, 73.1, 74.5, 75.7, 75.8,
76.4, 77.2, 77.3, 77.8, 78.1, 82.2, 82.6, 83.8, 98.1, 99.0, 99.1,
103.1, 113.5, 113.69, 113.7, 113.9, 117.8, 128.2, 128.5, 128.8,
129.2, 129.4, 129.5, 129.6, 129.7, 130.1, 130.2, 130.25, 130.3,
130.5, 134.3, 145.5, 158.9, 159.0, 159.1, 159.2, 165.8, 172.75,
172.8, 175.3; IR (KBr) νmax 3453, 2923, 1738, 1614, 1513, 1461
cm-1; HR ESIMS calcd for C114H154O28 [M þ Na]þ 1994.0524,
found m/z 1994.0533.
Experimental Section
Synthesis of Compound 23. A solution of 4 (110 mg,
0.09 mmol), (PyS)2 (99.8 mg, 0.47 mmol), and Ph3P (119 mg,
0.47 mmol) in deoxygenated anhydrous toluene (2.37 mL) was
stirred at 25 °C for 5 h. The mixture was diluted with deoxyge-
nated anhydrous toluene (7.87 mL) and then the resulting
solution was added dropwise by a syringe pump to refluxing
dry deoxygenated toluene (109 mL) over 10 h. The solution was
refluxed under nitrogen for 5 days. After removal of toluene
under reduced pressure, the residue was purified by column
chromatography (10:1, petroleum ether-EtOAc) to afford 23 as
a white amorphous solid (95.5 mg, 88%). Rf 0.34 (5:1, petroleum
ether-EtOAc). [R]20 -5.34 (c 6.25, CHCl3); 1H NMR
D
(400 MHz, CDCl3) δ 6.34-7.57 (m, 26H), 5.30 (s, 1H), 5.07 (s,
1H), 4.90 (d, 1H, J = 11.6 Hz), 4.87 (d, 1H, J = 11.6 Hz), 4.69
(d, 1H, J = 10.4 Hz), 4.54 (d, 1H, J = 12.0 Hz), 4.51 (d, 1H, J =
10.8 Hz), 4.49 (d, 1H, J = 11.2 Hz), 4.46 (d, 1H, J = 5.6 Hz),
4.46 (d, 1H, J = 10.8 Hz), 4.01 (m, 1H), 3.88 (d, 1H, J = 10.0
Hz), 3.80 (s, 6H), 3.75 (s, 3H), 3.66 (s, 3H), 3.47-3.80 (m, 9H),
2.07-2.09 (m, 2H), 1.23-1.50 (m, 27H), 0.90 (s, 9H), 0.87 (s,
3H); 13C NMR (100 Hz, CDCl3) δ 14.1, 19.1, 19.7, 22.7, 24.3,
24.5, 24.8, 27.1, 27.3, 27.4, 27.8, 29.4, 31.9, 32.2, 32.8, 34.0,
55.07, 55.16, 67.1, 68.5, 69.1, 69.9, 73.1, 74.2, 74.5, 74.6,
74.8, 76.7, 82.4, 84.0, 97.9, 103.4, 112.8, 113.7, 113.8, 125.0,
127.0, 127.1, 128.3, 129.0, 129.2, 129.3, 129.6, 129.7,
130.0, 130.2, 130.3, 130.8, 133.1, 134.5, 135.7, 136.3, 158.4,
158.6, 158.9, 159.2, 172.4; IR (KBr) νmax 3439, 2925, 1728,
Acknowledgment. We appreciate the NSF of China
(20672074), the National Basic Research Program of China
(973 Program; 2010CB833200973), PCSIRT (IRT0846),
Ministry of Education (NCET-08-0377), and Sichuan Province
(08ZQ026-029) of P. R. China for financial support. We thank
Prof. Ling-Yi Kong, China Pharmaceutical University, for
providing NMR spectra of natural batatoside L.
Supporting Information Available: Experimental proce-
dures, compound characterization data, and copies of H and
1
13C NMR spectra. This material is available free of charge via
the Internet at http://pubs.acs.org.
(24) An inverse Schmidt glycosylation has also played a key role in
Furstner’s total synthesis of woodrosin I, see refs 11d and 11e.
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J. Org. Chem. Vol. 75, No. 16, 2010 5767