Stereoselective β-mannosylation via anomeric O-Alkylation: Concise synthesis of β-D-Xyl-(l→2)-β-D-Man-(1→4)-α-D-Glc-OMe, a trisaccharide oligomer of the hyriopsis schlegelii glycosphingolipid

Article abstract of DOI:10.1080/07328303.2017.1390579

Synthesis of ?-D-Xyl-(l→2)-?-D-Man-(1→4)-α-D-Glc-OMe (1), a trisaccharide oligomer of the Hyriopsis schlegelii glycosphingolipid is described. The synthesis involves a key ?-mannosylation via cesium carbonate-mediated anomeric O-alkylation for direct synt

Full text of DOI:10.1080/07328303.2017.1390579

Journal of Carbohydrate Chemistry
ISSN: 0732-8303 (Print) 1532-2327 (Online) Journal homepage: http://www.tandfonline.com/loi/lcar20
Stereoselective β-mannosylation via anomeric O-
Alkylation: Concise synthesis of β-D-Xyl-(l→2)-β-D-
Man-(1→4)-α-D-Glc-OMe, a trisaccharide oligomer
of the hyriopsis schlegelii glycosphingolipid
Bishwa Raj Bhetuwal, Justin Woodward, Xiaohua Li & Jianglong Zhu
To cite this article: Bishwa Raj Bhetuwal, Justin Woodward, Xiaohua Li & Jianglong Zhu (2017):
Stereoselective β-mannosylation via anomeric O-Alkylation: Concise synthesis of β-D-Xyl-(l→2)-β-
D-Man-(1→4)-α-D-Glc-OMe, a trisaccharide oligomer of the hyriopsis schlegelii glycosphingolipid,
Journal of Carbohydrate Chemistry, DOI: 10.1080/07328303.2017.1390579
To link to this article: http://dx.doi.org/10.1080/07328303.2017.1390579
Published online: 14 Nov 2017.
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Date: 17 November 2017, At: 11:56

JOURNAL OF CARBOHYDRATE CHEMISTRY
, VOL. , NO. , –
https://doi.org/./..
Stereoselective β-mannosylation via anomeric O-Alkylation:
Concise synthesis of β-D-Xyl-(l→)-β-D-Man-(→)-
α-D-Glc-OMe, a trisaccharide oligomer of the hyriopsis
schlegelii glycosphingolipid
Bishwa Raj Bhetuwala, Justin Woodwardb, Xiaohua Lib, and Jianglong Zhua
aDepartment of Chemistry and Biochemistry and School of Green Chemistry and Engineering, The
University of Toledo, Toledo, Ohio, United States; bDepartment of Natural Sciences, University of
Michigan-Dearborn, Dearborn, Michigan, United States.
ABSTRACT
ARTICLE HISTORY
Received  August 
Revised  September 
Accepted  October 
Synthesis of β-D-Xyl-(l→2)-β-D-Man-(1→4)-α-D-Glc-OMe (1), a tr-
isaccharide oligomer of the Hyriopsis schlegelii glycosphingolipid
is described. The synthesis involves a key β-mannosylation via
cesium carbonate-mediated anomeric O-alkylation for direct syn-
thesis of partially protected disaccharide β-D-Man-(1→4)-α-D-
KEYWORDS
β-mannosylation; lactol;
anomeric O-alkylation;
glycosylation
–
Glc-OMe (4) bearing a free C2 OH in the mannose moiety. In addi-
tion, a silver triflate-promoted glycosylation of 4 with 2,3,4-tri-O-
benzoyl-α-D-xylopyranosyl bromide (5) followed by deprotection
affords the desired trisaccharide component (1) of the Hyriopsis
schlegelii glycosphingolipid.
GRAPHICAL ABSTRACT
CONTACT X. Li
Evergreen Road, Dearborn, Michigan , United States. J. Zhu
shannli@umich.edu
Department of Natural Sciences, University of Michigan-Dearborn, 
Jianglong.Zhu@Utoledo.edu Department of
Chemistry and Biochemistry and School of Green Chemistry and Engineering, The University of Toledo,  W. Bancroft
Street, Toledo, Ohio , United States.
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/lcar.
©  Taylor & Francis Group, LLC

2
B. R. BHETUWAL ET AL.
Introduction
Stereoselective construction of biologically significant β-mannopyranosides has
been a long-standing synthetic challenge in carbohydrate chemistry, due to steric
effect of the axial C2-substituents as well as the absence of anomeric effect and
anchimeric assistance (also known as neighbouring group participation (NGP)).[1]
Consequently, tremendous efforts have been devoted to solving this difficulty for
the synthesis complex carbohydrates bearing β-mannosidic linkage. Thus far, typ-
ical efforts include: 1) direct β-mannosylation using non-participating protecting
group[2] for O2 and insoluble silver salts for activation of mannosyl halides;[2a-d]
2) inversion of the C2 stereochemistry of β-glucosides[3] or stereoselective reduc-
tionof β-2-ulosyl glycosides;[4] 3) de novo synthesis of β-mannopyranosides via α-
selective quenching of C1-alkoxy radicals by suitable hydrogen atom donors;[5] 4)
synthesis of β-mannopyranosides involving intramolecular aglycone delivery;[6,7,8]
5) use of 4,6-O-benzylidene,[9] 4,6-O-arylboronate,[10] or 4,6-O-silylene[11] pro-
tected α-mannopyranosyl triflates; 6) use of hydrogen-bond-mediated aglycone
delivery mediated by a remote 3- and/or 6-O-picoloyl group;[12] 7) use of glycosyl-
acceptor-derived borinic ester[13] or boronic ester[14] as catalysts for activation of
1,2-anhydromannose donors; 8) use of mannosyl donors bearing 2,6-[15] or 3,6-
lactone moieties;[16] 9) β-selective anomeric O-alkylation of mannose-derived lac-
tols[17] or 1,2-O-dibutylstannylenes.[18]
Early in 2016, we reported an efficient β-mannosylation method involving
cesium carbonate-mediated anomeric O-alkylation of D-mannose-derived 1,2-diols
with primary or secondary electrophiles.[17c] This β-mannosylation was developed
based on our previous experiences in the stereoselective synthesis of 2-deoxy-β-
glycosides[19] or 2-deoxy-α-glycosides[20] via anomeric O-alkylation. In particu-
lar, this easily operable β-mannosylation directly affords the desired β-mannosides
Scheme . Previous synthesis of β-D-Xyl-(l→)-β-D-Man-(→)-α-D-Glc-OMe (1) and our strategy.

JOURNAL OF CARBOHYDRATE CHEMISTRY
3
Figure . The structure of β-D-Xyl-(l→)-β-D-Man-(→)-α-D-Glc-OMe (1), a trisaccharide oligomer
of the Hyriopsis schlegelii Glycosphingolipid.
–
with a free C2 OH at the mannose residue (cf. 4, Scheme 1). The free C2-alcohol
can be directly subjected to the next chemical transformation, such as acylation
and glycosylation, without the necessity of additional deprotection steps. Recently,
this β-mannosylation was successfully employed in a highly efficient formal syn-
thesis of potent calcium signal modulator acremomannolipin A,[17d] in which the
–
free C2 OH of corresponding mannose residue was directly subjected to acylation.
In this Communication, we would like to demonstrate its application to the synthe-
sis of β-D-Xyl-(l→2)-β-D-Man-(1→4)-α-D-Glc-OMe (1, Figure 1), a trisaccha-
ride oligomer of the Hyriopsis schlegelii glycosphingolipid. In this synthesis the free
–
C2 OH at the mannose residue of the disaccharide 4 is directly subjected to another
glycosylation with protected xylosyl bromide donor 5 to furnish the corresponding
trisaccharide (cf. 14).
The trisaccharide oligomer of the Hyriopsis schlegelii glycosphingolipid, β-
D-Xyl-(l→2)-β-D-Man-(1→4)-α-D-Glc-OMe (1),[21] has been previously
synthesized independently by two groups (Scheme 1). The first synthesis of 1
was reported by Lichtenthaler and co-workers in 1994.[22] In their synthesis, ulosyl
bromide 2 reacted with acceptor 3 in the presence of excess silver aluminosilicate
promoter to afford the corresponsing β-uloside (87% yield) which was subsequently
reduced by sodium borohydride to furnish β-mannoside 4 (81% yield overall for
two steps). This β-mannoside 4 was then subjected to glycosylation with xylosyl
bromide donor 5[23] followed by removal of the protecting group afforded desired
trisaccharide oligomer 1. A few years later, Crich and Dai disclosed the second
synthesis of trisaccharide 1 employing so-called “Crich β-mannosylation”.[24] As
shown in Scheme 1, 4,6-O-benzylidene-protected D-mannosyl sulfoxide donor 6
reacted with acceptor 3 in the presence of triflic anhydride/DTBMP to afford cor-
responding desired β-mannoside (β/α = 12/1, 87% yield) which was subjected to
a two-step de-allylation to give rise to the β-mannoside 7 (60% yield for two steps).
Similarly, glycosylation of β-mannoside 7 with xylosyl bromide donor 5 followed
by removal of the protecting group afforded desired trisaccharide oligomer 1. In
addition, Takeda and co-workers synthesized the protected form of 1[25] and incor-
porated it into a more complex octasaccharide in the same glycosphingolipid.[26]
Obviously, the Lichtenthaler approach required additional steps, i.e. oxidation of the
C2-alcohol of the glycosyl donor to the ketone (2-oxo) and reduction of the 2-oxo
to the C2-axial alcohol after glycosylation. It is worth noting that the sodium boro-
hydride reduction may result in lower diastereoselectivites.[27] The Crich synthesis
required an additional two-step deprotection of the O-2 allyl protecting group in the

4
B. R. BHETUWAL ET AL.
Scheme . Concise Synthesis of β-D-Xyl-(l→)-β-D-Man-(→)-α-D-Glc-OMe (1) involving
β-mannosylation via CsCO-mediated anomeric O-alkylation.
mannose moiety to free the C2-alcohol (cf. 7) for subsequent glycosylation with
xylosyl bromide donor 5. In this report, we will describe the synthesis of trisac-
charide oligomer of the Hyriopsis schlegelii glycosphingolipid, β-D-Xyl-(l→2)-β-
D-Man-(1→4)-α-D-Glc-OMe (1) in which the key intermediate β-mannoside 4
–
bearing a free C2 OH at the mannose moiety is directly prepared from known D-
mannose-derived lactol 8[28] and methyl α-D-galactoside-derived axial C4-triflate
9 via cesium carbonate-mediated anomeric O-alkylation (Scheme 1).
Results and Discussion
Our preparation of the known methyl α-D-galactoside-derived C4-axial tri-
flate 9[29] commenced with the 4,6-O-benzylidenation of commercially available
methyl α-D-galactoside 10. As depicted in Scheme 2, standard acid-catalyzed
4,6-O-benzylidenation of methyl α-D-galactoside 10 using benzaldehyde dimethyl
acetal in DMF afforded methyl 4,6-O-benzylidene-α-D-galactoside 11 (65% yield)
and subsequently the 2,3-diol of 11 underwent double benzylation to furnish methyl
2,3-di-O-benzyl-4,6-O-benzylidene-α-D-galactoside 12 (82% yield). Regioselective
reductive opening of the 4,6-O-benzylidene of 12 using sodium cyanoborohydride
in the presence of acid provided methyl 2,3,6-tri-O-benzyl-α-D-galactoside 13
(81% yield) bearing an axial free C4-alcohol. Next, this C4-alcohol in 13 under-
went standard triflation to give rise to axial C4-triflate 9 in 80% yield. Under our
previously reported optimal condition, cesium carbonate-mediated stereoselective
anomeric O-alkylation of known D-mannose-derived lactol 8 with C4-triflate 9
afforded desired key intermediate β-mannoside 4 in 85% yield (β only) which
contains a free C2-alcohol ready for next glycosylation with xylosyl bromide
donor 5.

JOURNAL OF CARBOHYDRATE CHEMISTRY
5
Previously, Lichtenthaler and co-workers described that treatment of β-
mannoside 4 (1 eq.) with xylosyl bromide donor 5 (1.5 eq.) in the presence of silver
triflate (ca. 2.0 eq.) in the absence of base at −40 °C for 30 minutes gave desired
trisaccharide 14 in 71% yield (experimental section).[22] However, in our hands
applying the exactly same reaction condition reported by Lichtenthaler et al[22] to
β-mannoside 4 and xylosyl bromide donor 5 only afforded desired trisaccharide
14 in low conversion. We then turned our attention to the experimental proce-
dure reported by Crich et al for glycosylation of a similar substrate β-mannoside
7 with xylosyl bromide donor 5 in which a general bulky base 2,6-di-tert-butyl-
4-methylpyridine (DTBMP) was used.[24b] Indeed, under the exactly same condi-
tion reported by Crich et al (4 (1 eq.), 5 (1.15 eq.), AgOTf (2.1 eq.), DTBMP (3.25
˚
eq.), 4A molecular sieves), desired trisaccharide 14 was obtained in 43% yield (84%
based on recovered disaccharide 4). After extensive studies, finally we found out
that treatment of β-mannoside 4 (1 eq.) with xylosyl bromide donor 5 (3.5 eq.) in
˚
the presence of silver triflate (4.0 eq.), DTBMP (5.0 eq.), and 4A molecular sieves
from –40 to 0°C gave desired trisaccharide 14 in 84% yield. Next, standard global
de-benzoylation of 14 followed by Pd/C-catalyzed global hydrogenolysis of remain-
ing benzyl groups produced the β-D-Xyl-(l→2)-β-D-Man-(1→4)-α-D-Glc-OMe
(1) in 81% yield over two steps.[22]
In conclusion, we have described a concise synthesis of β-D-Xyl-(l→2)-β-D-
Man-(1→4)-α-D-Glc-OMe (1), a trisaccharide oligomer of the Hyriopsis schlegelii
glycosphingolipid. The synthesis involves a key stereoselective β-mannosylation
via cesium carbonate-mediated anomeric O-alkylation for the preparation of par-
tially protected disaccharide β-D-Man-(1→4)-α-D-Glc-OMe (4). Application of
this Cs2CO3-mediated β-mannosylation to the synthesis of other biologically sig-
nificant oligosaccharides and glycoconjugates is in progress.
Experimental
Materials and methods
Proton and carbon nuclear magnetic resonance spectra (1H NMR and 13C NMR)
were recorded on either Bruker 600 (1H NMR-600 MHz; 13C NMR 150) or INOVA
600 (1H NMR-600 MHz; 13C NMR-150 MHz) at ambient temperature with CDCl3
as the solvent unless otherwise stated. Chemical shifts are reported in parts per mil-
lion relative to residual protic solvent internal standard CDCl3: 1H NMR at δ 7.26,
13C NMR at δ 77.36. Data for 1H NMR are reported as follows: chemical shift, inte-
gration, multiplicity (app = apparent, par obsc = partially obscure, ovrlp = overlap-
ping, s = singlet, d = doublet, dd = doublet of doublet, t = triplet, q = quartet, m =
multiplet) and coupling constants in Hertz. All 13C NMR spectra were recorded with
complete proton decoupling. Low resolution mass spectra (LRMS) were acquired
on a Waters Acuity Premiere XE TOF LC-MS by electrospray ionization. Optical
rotations were measured with Autopol-IV digital polarimeter; concentrations are
expressed as g/100 mL.

6
B. R. BHETUWAL ET AL.
All reagents and chemicals were purchased from Acros Organics, Sigma Aldrich,
Fisher Scientific, Alfa Aesar, and Strem Chemicals and used without further purifi-
cation. THF, methylene chloride, toluene, and diethyl ether were purified by passing
through two packed columns of neutral alumina (Innovative Technology). Anhy-
drous DMF and benzene were purchased from Acros Organics and Sigma-Aldrich
and used without further drying. All reactions were carried out in oven-dried glass-
ware under an argon atmosphere unless otherwise noted. Analytical thin layer chro-
matography was performed using 0.25 mm silica gel 60-F plates. Flash column chro-
matography was performed using 200–400 mesh silica gel (Scientific Absorbents,
Inc.). Yields refer to chromatographically and spectroscopically pure materials,
unless otherwise stated.
Methyl ,,-tri-O-benzyl-β-D-mannopyranosyl-(→)-,,-tri-O-benzyl-α-D-glu-
copyranoside ()
To a mixture of 3,4,6-tri-O-benzyl-D-mannopyranose 8 (45 mg, 0.1 mmol), D-
galactose-derived C4-triflate 9 (119 mg, 0.2 mmol), and cesium carbonate (81.5 mg,
0.25 mmol), was added 1,2-dichloroethane (1.0 mL). The reaction mixture was
stirred at 40˚C for 12 hours. The crude reaction mixture was diluted with
dichloromethane and purified by preparative thin layer chromatography (hexanes:
EtOAc: methanol = 2:1:1%) to furnish 77 mg (85% yield) of β-mannose 4. The β-
configuration of the mannosidic linkage in 4 was assigned by measuring the J(C, H)
21
of anomeric carbon of the mannose moiety (159 Hz). [α]D = + 14.3˚ (c = 1.0,
CHCl3). 1H NMR (600 MHz, CDCl3) δ 2.62 (br, s, 1 H), 3.27 – 3.31 (m, 2 H), 3.34 –
3.37 (m, 1 H), 3.40 – 3.42 (m, 5 H), 3.55 (dd, J = 9.4, 3.6 Hz, 2 H), 3.61 (d, J = 4.6 Hz,
1 H), 3.63 (d, J = 4.6 Hz, 1 H), 3.65 – 3.66 (m, 1 H), 3.67 – 3.69 (m, 1 H), 3.69 – 3.71
(m, 1 H), 3.79 (d, J = 3.3 Hz, 1 H), 3.80 – 3.84 (m, 2 H), 3.88 (t, J = 9.5 Hz, 2 H), 3.96
– 4.00 (m, 3 H), 4.04 (t, J = 9.3 Hz, 2 H), 4.48 (s, 1 H) 4.49 – 4.51 (m, 5 H), 4.53 (d,
J = 6.1 Hz, 2 H), 4.55 (s, 1 H), 4.59 (d, J = 11.9 Hz, 2 H), 4.62 – 4.65 (m, 4 H), 4.65
– 4.68 (m, 2 H), 4.81 (d, J = 12.1 Hz, 2 H), 4.88 (d, J = 10.8 Hz, 1 H), 4.94 (d, J =
11.0 Hz, 2 H), 5.02 (d, J = 11.0 Hz, 2 H), 7.21 – 7.24 (m, 3 H), 7.25 – 7.31 (m, 14 H),
7.31 – 7.37 (m, 30 H), 7.41 (d, J = 7.3 Hz, 3 H). 13C NMR (150 MHz, CDCl3):
δ 55.27, 67.87, 68.73, 69.00, 69.57, 71.09, 73.44, 73.55, 73.95, 75.18, 75.59, 75.65,
75.77, 76.91, 77.12, 77.33, 79.55, 80.74, 81.57, 98.19, 99.98, 127.47, 127.67, 127.73,
127.77, 127.79, 127.82, 127.89, 127.96, 128.09, 128.14, 128.21, 128.30, 128.38, 128.46,
128.49, 128.52, 128.57, 137.86, 137.96, 138.12, 138.34, 138.42, 139.00. FT-IR (thin
flim): 3468, 3035, 2880, 1728, 1501, 1456, 1053, 751, 695 cm−1. ESILRMS[M+Na]+
calculated C55H60O11Na 919.40, found 919.50.
Methyl ,,-tri-O-benzoyl-β-D-xylopyranosyl-(→)-,,-tri-O-benzyl-β-D-mann-
opyranosyl-(→)-,,-tri-O-benzyl-α-D-glucopyranoside ()
To β-mannoside acceptor 4 (90 mg, 0.1 mmol) in dry CH2Cl2 (5 mL) were added
powdered molecular sieves (100 mg) and DTBMP (102 mg, 0.5 mmol). The reac-
tion mixture was cooled to -40˚C and stirred for 0.5 h under argon. A solution of

JOURNAL OF CARBOHYDRATE CHEMISTRY
7
xylosyl bromide donor 5 (183 mg, 0.35 mmol) in CH2Cl2 (2.3 mL) was added fol-
lowed by dropwise addition of AgOTf (103 mg, 0.4 mmol) in toluene (1.6 mL). The
reaction mixture was stirred at -40˚C for 0.5 h and then warmed up to 0˚C and
stirred for another 1 h before being filtered through a pad of celite. The combined
organic solutions were washed with 10% aq. Na2SO3 and brine, dried over anhy-
drous sodium sulfate, filtered, and concentrated. The residue was purified by silica
gel column chromatography (Toluene: EtOAc = 15:1) to afford 113 mg (84%) of
21
trisaccharide 14. [α]D = −41.6˚ (c = 1.0, CHCl3). 1H NMR (600 MHz, CDCl3) δ
3.25 – 3.31 (m, 3 H), 3.32 (d, J = 2.9 Hz, 1 H), 3.42 – 3.47 (m, 1 H), 3.54 – 3.58 (m,
1 H), 3.59 – 3.68 (m, 4 H), 3.70 – 3.76 (m, 2 H), 3.87 (t, J = 9.5 Hz, 1 H), 4.00 (t, J
= 9.3 Hz, 1 H), 4.11 (d, J = 2.9 Hz, 1 H), 4.15 (d, J = 12.1 Hz, 1 H), 4.36 – 4.42 (m,
3 H), 4.42 – 4.46 (m, 2 H), 4.54 – 4.60 (m, 3 H), 4.63 (d, J = 12.1 Hz, 1 H), 4.70 –
4.74 (m, 2 H), 4.75 (d, J = 2.8 Hz, 1 H), 4.81 (dd, J = 13.0, 2.6 Hz, 1 H), 4.84 (s, 1 H),
5.14 (d, J = 11.4 Hz, 1 H), 5.19 (q, J = 3.1 Hz, 1 H), 5.43 (d, J = 2.2 Hz, 1 H), 5.49 –
5.51 (m, 1 H), 5.56 (t, J = 4.0 Hz, 1 H), 7.12 – 7.16 (m, 3 H), 7.18 (dd, J = 7.3, 1.8 Hz,
2 H), 7.19 – 7.22 (m, 2 H), 7.23 – 7.27 (m, 10 H), 7.29 – 7.30 (m, 4 H), 7.31 – 7.35
(m, 10 H), 7.37 – 7.41 (m, 5 H), 7.48 – 7.52 (m, 2 H), 7.57 – 7.61 (m, 1 H), 7.98 – 8.01
(m, 2 H), 8.05 – 8.10 (m, 4 H). 13C NMR (151 MHz, CDCl3) δ 55.28, 71.69, 73.34,
73.66, 74.98, 75.13, 75.27, 76.83, 77.05, 77.26, 80.01, 98.56, 126.81, 127.22, 127.56,
127.58, 127.62, 127.68, 127.71, 127.82, 127.92, 128.14, 128.19, 128.22, 128.33, 128.37,
128.39, 128.49, 128.57, 130.02, 130.08, 133.29, 133.31, 138.04, 138.74. FT-IR (thin
flim): 3056, 2915, 1721, 1452, 1252, 1093, 700 cm−1. ESILRMS [M+Na]+ calcu-
lated C81H80O18Na, 1363.52 observed 1363.80.
Methyl β-D-xylopyranosyl-(→)-β-D-mannopyranosyl-(→)-α-D-glucopyrano-
side ()
To trisaccharide 14 (17 mg, 0.012 mmol) in methanol (0.26 mL) was added a small
drop of sodium methoxide solution (ca. 3 μL, 5.4 M in methanol). The resulting
mixture was stirred at room temperature overnight and then neutralized by acidic
ion exchange resin (Dowex H+ resin). The mixture was filtered and the filtrate was
concentrated. The residue was purified by silica gel column chromatography with
CH2Cl2: MeOH (20:1) to afford a syrup (11.1 mg) which was directly subjected to
hydrogenolysis over Pd/C (1 mg) in methanol (1 mL) for 24 h. Filtration and removal
21
of the solvent furnished 1 as a white solid (5 mg, 81% for two steps). [α]D = + 19.3˚
(c = 0.15, H2O). 1H NMR (600 MHz, D2O) δ ppm 3.14 (s, 1 H), 3.23 – 3.29 (m, 2 H),
3.30 (s, 3 H), 3.32 (d, J = 9.2 Hz, 2 H), 3.46 (s, 1 H), 3.47 – 3.50 (m, 2H), 3.50 – 3.55
(m, 3 H), 3.66 (s, 3 H), 3.71 (s, 1 H), 3.74 (s, 1 H), 3.82 (s, 1 H), 4.13 (d, J = 3.3 Hz,
1 H), 4.38 (d, J = 7.7 Hz, 1 H), 4.69 (br, s, 1 H). 13C NMR (151 MHz, D2O) δ ppm
54.96, 55.09, 60.09, 60.42, 64.98, 66.80, 69.19, 70.05, 70.84, 71.56, 71.74, 73.17, 75.30,
76.36, 77.75, 78.73, 98.93, 100.11, 104.01, 128.49, 129.25, 189.71, 195.62, 204.99,
208.78, 210.50, 211.63. FT-IR (thin flim): 3227, 29256, 1728, 1382, 1156, 1038,
525 cm−1. ESILRMS [M + Na]+ C55H60O11Na, Calculated 511.16, found 511.10.

8
B. R. BHETUWAL ET AL.
Acknowledgements
We are grateful to National Science Foundation (CHE-1464787), The University of Toledo, and
University of Michigan-Dearborn for supporting this research.
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