Gold-catalyzed glycosidations: Unusual cleavage of the interglycosidic bond while studying the armed/disarmed effect of propargyl glycosides

Article abstract of DOI:10.1016/j.tetlet.2010.07.157

Armed/disarmed effect of propargyl glycosides in the presence of AuBr ₃ is studied. Observed that oxophilic AuBr₃ cleaves interglycosidic bond of an armed disaccharide resulting in the formation of a disaccharide and a 1,6-anhydro sugar. Trisaccharides were obtained after fine tuning the reactivity of the glycosyl donor with different protecting groups.

Full text of DOI:10.1016/j.tetlet.2010.07.157

Tetrahedron Letters 51 (2010) 5269–5272
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Tetrahedron Letters
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Gold-catalyzed glycosidations: unusual cleavage of the interglycosidic bond
while studying the armed/disarmed effect of propargyl glycosides
*
Abhijeet K. Kayastha, Srinivas Hotha
Division of Organic Chemistry, Combi Chem-BioResource Center, National Chemical Laboratory (CSIR), Dr. Homi Bhabha Road, Pune 411 008, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Armed/disarmed effect of propargyl glycosides in the presence of AuBr3 is studied. Observed that oxo-
philic AuBr3 cleaves interglycosidic bond of an armed disaccharide resulting in the formation of a disac-
charide and a 1,6-anhydro sugar. Trisaccharides were obtained after fine tuning the reactivity of the
glycosyl donor with different protecting groups.
Received 22 May 2010
Revised 22 July 2010
Accepted 27 July 2010
Available online 1 August 2010
Ó 2010 Elsevier Ltd. All rights reserved.
Oligosaccharides and glycoconjugates are implicated in various
intracellular and extracellular molecular recognition events.1 In this
regard, several strategies were developed for the synthesis of oligo-
saccharides; Fraser-Reid pioneered strategy of armed/disarmed n-
pentenyl glycosides that exploits differential reactivity of protecting
groups is one of the most significant advancements in the annals of
oligosaccharide synthesis.2a,3 Ethers at the C-2 position of alkyl gly-
cosides (armed) electronically facilitate the departure of the alkyl-
leaving group at the anomeric position favoring the formation of
oxocarbenium ion and thus transglycosides are easily formed.2a,s
Whereas, C-2 esters (disarmed) make the anomeric carbon electron
deficient and as a consequence, the alkyl-leaving group at the C-1
position does not depart quickly and hence do not facilitate transgly-
coside formation.2a,s
We have recently identified propargyl glycosides as glycosyl
donors in the presence of catalytic amount of Au(III) salts.4a–c
Subsequently, propargyl 1,2-orthoesters were reported for the
1,2-trans selective glycosidation under AuBr3/CH2Cl2/rt.4d Further-
more, gold-catalyzed activation was found to activate the propar-
gyl moiety of 1,2-orthoesters in the presence of aglycones having
propargyl group to obtain propargyl disaccharides.4e In all these
studies, we observed that alkyl glycosides get disarmed when the
protecting group at the C-2 position is an ester and armed to par-
ticipate in the glycosidation when the protecting group at the C-2
position is a benzyl ether.4f In continuation of our efforts on the
development of novel strategies for the glycoconjugate synthesis,4
we got interested in the study of armed/disarmed effects for prop-
argyl glycosides to enable sequential glycosylations.
1,2-trans stereoselectivity in the resulting disaccharide.4a,h Accord-
ingly, armed glycosyl donor 1 was allowed to react with aglycone 2
in the presence of AuBr3 in CH3CN at 70 °C for 8 h and obtained the
anticipated disaccharide 3a in 68% (Scheme 1).4a,5,6a The disarmed
disaccharide was then converted to an armed disaccharide 3b in
two steps involving Zemplén debenzoylation (NaOMe/MeOH/rt)
followed by benzylation using NaH and benzyl bromide in DMF.
In continuation, the armed disaccharide 3b6c was allowed to react
with disarmed aglycone 2 in anticipation of a trisaccharide 5,
resulting in the isolation of two compounds. Purification by con-
ventional silica gel column chromatography enabled us to charac-
terize the major component not as the trisaccharide
5 but
surprisingly as 3a.5,6b For instance, only two anomeric protons
were noticed at d 5.26(d, 1H, J = 1.8 Hz), 5.68 (dd, 1H, J = 1.8,
2.9 Hz) in the 1H NMR spectrum instead of three if it were 5. The
13C NMR spectrum of 3a revealed that there are two mannose res-
idues with 1,2-trans configuration as their anomeric carbons were
noticed at d 96.2 (1JC–H = 175.5 Hz) and 98.2 (1JC–H = 170.9 Hz) ppm
and the molecular weight was found to be 1075.3889 (C64H60O14N-
a).5,6b These observations and matching of the data with that of 3a
previously synthesized led us to assign the structure of the major
component (53%) to be propargyl 2,3,4-tri-O-benzoyl-6-(2,3,4,6-
tetra-O-benzyl
a-D-mannopyranosyl)-a-D-manno-pyranoside 3a.
The minor component (16%) was identified to be 1,6-anhydro
derivative 4.4h,5,6e
The formation of disaccharide 3a and the 1,6-anhydro sugar for-
mation can be rationalized by a double activation of the armed gly-
cosyl donor 3b in the presence of AuBr3 (Fig. 1). Initially, oxophilic
AuBr3 cleaved the interglycosidic bond leaving the intermediate
oxocarbenium ion (A) with the extrusion of propargyl mannoside
B. Intermediate A was then attacked by the disarmed aglycone 2
resulting in disaccharide 3a whereas the ejected product B led to
the second oxocarbenium ion C which is trapped intramolecularly
by the 6-OH group to give 1,6-anhydro derivative 4. The sequence
of events could not be established. Similar reaction on disaccharide
Initial set of experiments were planned with propargyl 2,3,4,6-
tetra-O-benzyl
a-
D-mannopyranoside (1) as the armed glycosyl do-
nor and the propargyl 2,3,4-tri-O- benzoyl
a
-D
-mannopyranoside
(2) as the disarmed aglycone mainly due to the prospect of
* Corresponding author. Tel.: +91 20 2590 2401; fax: +91 20 2590 2624.
E-mail address: s.hotha@ncl.res.in (S. Hotha).
0040-4039/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2010.07.157

5270
A. K. Kayastha, S. Hotha / Tetrahedron Letters 51 (2010) 5269–5272
OBn
OBn
OBn
OBn
OH
OBz
O
BnO
BnO
O
O
BnO
BnO
BzO
BzO
O
i
+
OR
O
O
O
2
1
RO
RO
Armed
Disarmed
O
3a R = -COPh
3b R = -CH2Ph
3c R = -CH3
OBn
ii, iii
ii, iv
OBn
O
BnO
BnO
OBn
OBn
O
O
OBn
OBn
OBn
O
BnO
BnO
BnO
BnO
O
BnO
BnO
O
O
OBn
O
O
3b
Armed
OBn
O
O
OBn
BnO
BnO
OBz
O
i
+
+
OBn
+
BzO
BzO
4
(20%)
O
OBz
O
OH
OBz
O
O
BzO
BzO
3a (53%)
BzO
BzO
O
5
(0%)
O
2
Disarmed
Scheme 1. A study on the armed-disarmed effect of propargyl glycosides. Regents and conditions: (i) AuBr3, CH3CN, 70 °C, 8 h, 68%; (ii) NaOMe, MeOH, rt,, 0.5 h, 95%; (iii)
NaH, DMF, 0 °C to rt, 0.5 h, then BnBr, 0 °C to rt, 4 h, 94%; (iv) KOH, DMSO, 0 °C to rt, 0.5 h then CH3I, 0 °C to rt, 3 h, 96%.
OBn
OBn
O
BnO
BnO
BnO
BnO
OBz
O
HO
+
O
O
BnO
OBn
OBn
BzO
BnO
OBz
BzO
O
O
A
BzO
BzO
O
BnO
BnO
2 Disarmed
AuBr3
O
3a
O
OBn
O-
BnO
O
OH
O
OBn
O
OBn
O
BnO
BnO
BnO
BnO
+
O
BnO
BnO
OBn
O
3b
Armed
O
OBn
B
C
4
Figure 1. Mechanistic rationale.
OBn
O
BnO
BnO
Armed
OBn
O
OBn
BnO
OBn
OBn
O
BnO
BnO
O
BnO
O
OBn
O
OBn
O
OBn
O
α:β=4:1
O
α:β=4:1 BnO
BnO
6
BnO
OBn
O
HO
BnO
O
O
OBn
AuBr3, CH3CN
70oC, 8h
OBz
O
OBz
+
+
+
O
OBn
BzO
BzO
BzO
BzO
OH
9
(21%)
OBz
O
O
O
BzO
BzO
7 (15%)
8
(46%)
O
2
Disarmed
OR
OR
OR
OR
O
O
RO
RO
OR
RO
RO
OR
OH
O
O
OMe
O
RO
RO
OMe
OBz
O
O
MeO
MeO
O
+
O
AuBr3, CH3CN MeO
MeO
+
BzO
BzO
2
+
OMe
O
70oC, 8h
O
O
O
MeO
MeO
11
(16%)
OBz
R = Bn (3a) 51%
Me(14) 54%
O
O
Armed
BzO
BzO
3c
R = Bn
(
)
10
O
R = Bn ( ) 16%
12
Me (
)
13
Me( ) 14%
Scheme 2. Study of armed/disarmed effect for the trisaccharide synthesis.

A. K. Kayastha, S. Hotha / Tetrahedron Letters 51 (2010) 5269–5272
5271
66f resulted in the identification of trisaccharide 7,6g disaccharide
8,6h and ejected out monosaccharide 96i but not the anhydro sugar
due to the unfavorable spatial separation (Scheme 2).
Udodong, U. E.; Wu, Z.; Ottosson, H.; Merritt, J. R.; Rao, C. S.; Roberts, C.; Madsen,
R. Synlett 1992, 927–942; (i) Schmidt, R. R. Angew. Chem., Int. Ed. Engl. 1986, 25,
212–235; (j) Paulsen, H. Angew. Chem., Int. Ed. Engl. 1982, 21, 155–173; (k)
Pougny, J.-R.; Jacquinet, J.-C.; Nassr, M.; Duchet, D.; Milat, M.-L.; Sinaÿ, P. J. Am.
Chem. Soc. 1977, 99, 6762–6763.
Replacement of benzoyl groups of disaccharide 3a by methyl
groups via a two-step procedure gave armed disaccharide 3c6d
with less-directing methyl groups on the sugar at the reducing
end. AuBr3- catalyzed glycosidation gave us the trisaccharide
10,6j disaccharide 3a6b, and propargyl 2,3,4-tri-O-methyl manno-
side 116k in 16%, 51%, and 16%, respectively. Similar observations
were noticed with the per O-methylated disaccharide 126l to give
the trisaccharide 13,6m disaccharide 146n, and the monosaccharide
116k (Scheme 2). The foregoing studies led us to understand that
the propargyl glycosides are highly dependent on the electronic ef-
fect of the protecting groups.
4. (a) Hotha, S.; Kashyap, S. J. Am. Chem. Soc. 2006, 128, 9620–9621; (b) Kashyap, S.;
Hotha, S. Tetrahedron Lett. 2006, 47, 2021–2023; (c) Kashyap, S.; Vidadala, S. R.;
Hotha, S. Tetrahedron Lett. 2007, 48, 8960–8962; (d) Sureshkumar, G.; Hotha, S.
Tetrahedron Lett. 2007, 48, 6564–6568; (e) Sureshkumar, G.; Hotha, S. Chem.
Commun. 2008, 4282–4284; (f) Vidadala, S. R.; Hotha, S. Chem. Commun. 2009,
4282–4284; (g) Vidadala, S. R.; Thadke, S. A.; Hotha, S. J. Org. Chem. 2009, 74,
9233–9236; Some selected references on gold catalyzed glycosylations (h)
Götze, S.; Fitzner, R.; Kunz, H. Synlett 2009, 3346–3348; (i) Mamidyala, S. K.;
Finn, M. G. J. Org. Chem. 2009, 74, 8417–8420; (j) Li, Y.; Tank, P.; Chen, Y.; Yu, B. J.
Org. Chem. 2008, 73, 4323–4325; (k) Li, Y.; Yang, X.; Liu, Y.; Zhu, C.; Yang, Y.; Yu,
B. Chem. Eur. J. 2010, 16, 1871–1882.
5. All products gave satisfactory 1H, 13C, DEPT NMR and HRMS (MALDI-TOF)
analysis. See Supplementary data.
6. (a) General procedure for glycosylations using propargyl glycosides as glycosyl
donor: To a solution of glycosyl donor (0.1 mmol) and aglycone (0.12 mmol) in
anhydrous acetonitrile (5 mL) was added a solution of 5 mol% of AuBr3 in
anhydrous acetonitrile (2 mL) under argon atmosphere at room temperature.
The resulting mixture was heated to 70 °C and stirred till the completion of the
reaction as judged by TLC analysis. The reaction mixture was concentrated in
vacuo to obtain a crude residue which was purified by conventional silica gel
column chromatography using ethyl acetate/petroleum ether (ratio?) as mobile
phase.
In conclusion, armed/disarmed effects of propargyl glycosides
in the presence of catalytic amount of AuBr3 were studied. The
cleavage of interglycosidic bond was noticed in the presence of
armed-protecting groups due to the double activation and the
resulting oxocarbenium ion is attacked by the aglycone giving,
respectively, disaccharide and 1,6-anhydro sugar as major and
minor products. Fine tuning of protecting groups led to the synthe-
sis of trisaccharides albeit in poor yields. The unusual cleavage of
the interglycosidic bond can be circumvented if the glycosidations
were conducted at room temperature. Efforts in this direction are
currently underway and results will be reported in future. Applica-
tion of these results for the synthesis of significant carbohydrate
epitopes is currently underway.
(b) Compound characterization data for disarmed disaccharide 3a:
½
a 2D5
ꢀ
= ꢁ23.3°(CHCl3,
c d 2.50 (t, 1H,
1.0); 1H NMR (200.13 MHz, CDCl3):
J = 2.4 Hz), 3.53–3.78 (m, 4H), 3.84 (dd, 1H, J = 3.3, 9.2 Hz), 3.88–4.05 (m, 2H),
4.22 (m, 1H), 4.31 (d, 2H, J = 2.4 Hz), 4.37 (d, 2H, J = 4.5 Hz), 4.43 (s, 2H) 4.49
(ABq, 2H, J = 12.3 Hz), 4.63 (s, 2H), 4.86 (d, 1H, J = 10.9 Hz), 4.96 (d, 1H,
J = 1.8 Hz), 5.26 (d, 1H, J = 1.8 Hz), 5.68 (dd, 1H, J = 1.8, 2.9 Hz), 5.89 (m, 2H),
7.10–7.56 (m, 29H), 7.75–8.11 (m, 6H); 13C NMR (50.32 MHz, CDCl3): d 55.1,
66.6, 67.1, 69.0, 69.7, 69.8, 70.4, 71.8, 71.9, 72.5, 73.2, 74.7, 74.8, 74.9, 75.7, 78.1,
80.1, 96.2, 98.2, 127.3–128.9, 133.1, 133.3, 133.5, 138.3, 138.4, 138.5, 138.6,
165.3, 165.4, 165.4; HRMS (MALDI-TOF) calcd for C64H60O14Na, 1075.3881;
found, 1075.3889.
Acknowledgments
(c)
Compound
= +31.4°(CHCl3,
characterization
c
data
for
armed
disaccharide
3b:
½
a 2D5
ꢀ
1.0); 1H NMR (200.13 MHz, CDCl3):
d
2.37 (t, 1H,
S.H. thanks the financial support from CSIR (NWP0036-B) and
Director NCL for LC-MS facility. A.K.K. acknowledges the fellowship
from UGC, New Delhi.
J = 2.4 Hz), 3.58–4.07 (m, 12H), 4.10 (dd, 2H, J = 0.7, 2.4 Hz), 4.42–4.71 (m,
8H), 4.61 (s, 2H), 4.68 (s, 2H), 4.87 (d, 2H, J = 10.8 Hz), 4.99 (d, 1H, J = 1.6 Hz),
5.11 (d, 1H, J = 1.6 Hz), 7.10–7.45 (m, 35H); 13C NMR (100.61 MHz, CDCl3): d
54.1, 65.9, 69.1, 71.5, 71.8, 72.0, 72.1, 72.4, 72.9, 73.2, 74.4, 74.6, 74.7, 74.7, 74.9,
74.9, 75.0, 78.8, 79.3, 80.0, 96.5, 98.1, 127.3–128.4, 138.1, 138.4(ꢂ4), 138.6,
Supplementary data
138.7; Mol. HRMS (MALDI-TOF) calcd for
1033.4510.
C64H66O11Na, 1033.4503; found,
(d) Compound characterization data for compound 3c: ½a D25
= +56.6°(CHCl3, c 1.0);
ꢀ
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tetlet.2010.07.157.
1H NMR (200.13 MHz, CDCl3): d 2.42 (t, 1H, J = 2.4 Hz), 3.44, 3.46, 3.48 (3s, 9H),
3.46 (m, 2H), 3.55 (td, 1H, J = 2.4, 11.5 Hz), 3.63–4.02 (m, 9H), 4.14 (t, 2H,
J = 2.4 Hz), 4.60 (ABq, 2H, J = 12.0 Hz), 4.61 (s, 2H), 4.70 (ABq, 2H, J = 10.9 Hz),
4.73 (s, 2H), 5.02 (d, 1H, J = 1.5 Hz), 5.09 (d, 1H, J = 1.3 Hz), 7.04–7.45 (m, 20H);
13C NMR (50.32 MHz, CDCl3): d 54.1, 57.9, 58.9, 60.8, 65.8, 69.2, 71.7, 71.8, 71.8,
72.3, 73.2, 74.7, 74.8, 74.9, 74.9, 75.9, 76.8, 78.7, 79.7, 81.1, 95.2, 98.0, 127.3-
128.3, 138.3, 138.4, 138.5, 138.6; HRMS (MALDI-TOF) calcd for C46H54O11Na,
805.3564; found, 805.3560.
References and notes
1. (a) Rudd, P. M.; Elliott, T.; Cresswell, P.; Wilson, I. A.; Dwek, R. A. Science 2001,
291, 2370–2376; (b) McAuliffe, J. C.; Hindsgaul, O. Front. Mol. Biol. 2000, 30, 249–
280; (c) Rademacher, T. W. Curr. Opin. Biotechnol. 1998, 9, 74–79; (d) Varki, A.
Glycobiology 1993, 3, 97–130.
(e) Compound characterization data for 1,6-anhydro sugar 4: ½a D25
= ꢁ16.6°(CHCl3,
ꢀ
c 1.0); 1H NMR (200.13 MHz, CDCl3): d 3.47 (t, 1H, J = 1.8 Hz), 3.58 (dd, 1H,
J = 1.8, 5.4 Hz), 3.73 (dd, 1H, J = 6.0, 7.1 Hz), 3.81 (qd, 1H, J = 1.6, 3.1, 5.0 Hz), 4.25
(dd, 1H, J = 0.9, 7.1 Hz), 4.43–4.57 (m, 5H), 4.52 (ABq, 2H, J = 12.4 Hz), 5.46 (s,
1H), 7.20–7.38 (m, 15H); 13C NMR (50.32 MHz, CDCl3): d 65.0, 71.3, 71.4, 73.4,
74.1, 74.4, 74.5, 76.5, 100.1, 127.7–128.5, 137.6, 137.9, 137.9; HRMS (MALDI-
TOF) calcd for C27H28O5Na, 455.1834; found, 455.1830.
2. For armed-disarmed strategy (a) Mootoo, D. R.; Konradsson, P.; Udodong, U.;
Fraser-Reid, B. J. Am. Chem. Soc. 1988, 110, 5583–5584; (b) Fraser-Reid, B.; Wu,
Z.; Udodong, U. E.; Ottosso, H. J. Org. Chem. 1990, 55, 6068–6070; (c) Burgeym, C.
S.; Vollerthun, R.; Fraser-Reid, B. Tetrahedron Lett. 1994, 35, 2637–2640; (d)
Tsukida, T.; Yoshida, M.; Kurokawa, K.; Nakai, Y.; Achiha, T.; Kiyoi, T.; Kondo, H.
J. Org. Chem. 1997, 62, 6876–6881; (e) Hashimoto, S.-I.; Sakamoto, H.; Honda, T.;
Abe, H.; Nakamura, S.-I.; Ikegami, S. Tetrahedron Lett. 1997, 38, 8969–8972; (f)
Fraser-Reid, B.; Burgey, C. S.; Vollerthun, R. Pure Appl. Chem. 1998, 70, 285–288;
(g) Yoshida, M.; Kiyoi, T.; Tsukida, T.; Kondo, H. J. Carbohydr. Chem. 1998, 17,
673–681; (h) Chiba, H.; Funasaka, S.; Kiyota, K.; Mukaiyama, T. Chem. Lett. 2002,
746–747; (i) Demchenko, A. V.; DeMeo, C. Tetrahedron Lett. 2002, 43, 8819–
8822; (j) Kamath, M. N.; Demchenko, A. V. Org. Lett. 2005, 7, 3215–3218; (k)
Demchenko, A. V. Lett. Org. Chem. 2005, 2, 580–589; (l) Smoot, J. T.;
Pornsuriyasak, P.; Demchenko, A. V. Angew. Chem., Int. Ed. 2005, 44, 7123–
7126; (m) Pornsuriyasak, P.; Demchenko, A. V. Chem. Eur. J. 2006, 12, 6630–
6646; (n) Li, Z.; Gildersleeve, J. C. Tetrahedron Lett. 2007, 48, 559–562; (o)
Schmidt, T. H.; Madsen, R. Eur. J. Org. Chem. 2007, 3935–3941; (p) Crich, D.; Li, M.
Org. Lett. 2007, 9, 4115–4118; (q) Mydock, L. K.; Demchenko, A. V. Org. Lett.
2008, 10, 2107–2110; (r) Smoot, J. T.; Demchenko, A. V. J. Org. Chem. 2008, 73,
8838–8850; (s) Fraser-Reid, B.; Lopez, J. C.; Radhakrishnan, K. V.; Mach, M.;
Schlueter, U.; Gomez, A. M.; Uriel, C. J. Am. Chem. Soc. 2002, 124, 3198–3199.
3. Strategies for oligosaccharide synthesis: (a) Zhu, X.; Schmidt, R. R. Angew. Chem.,
Int. Ed. 2009, 48, 1900–1934; (b) Kim, J. H.; Yang, H.; Boons, G.-J. Angew. Chem.,
Int. Ed. 2005, 44, 947–949; (c) Garegg, P. J. Adv. Carbohydr. Chem. Biochem. 1997,
52, 179–205; (d) Danishefsky, S. J.; Bilodeau, M. T. Angew. Chem., Int. Ed. Engl.
1996, 35, 1380–1419; (e) Boons, G.-J. Tetrahedron 1996, 52, 1095–1121; (f)
Schmidt, R. R.; Kinzy, W. Adv. Carbohydr. Chem. Biochem. 1994, 50, 21–123; (g)
Toshima, K.; Tatsuta, K. Chem. Rev. 1993, 93, 1503–1531; (h) Fraser-Reid, B.;
(f) Compound characterization data for disaccharide 6: ½a D25
= +5.3°(CHCl3, c 1.0);
ꢀ
1H NMR (200.13 MHz, CDCl3): d 2.44 (t, 1H, J = 2.4 Hz), 3.25–4.05 (m, 12H), 4.28
(ABq, 2H, J = 11.8 Hz), 4.40 (m, 3H), 4.48–4.65 (m, 3H), 4.62–4.83 (m, 7H), 4.97
(ABq, 2H, J = 9.1 Hz), 4.98 (ABq, 1H, J = 12.8 Hz), 7.10–7.42 (m, 35H); 13C NMR
(50.32 MHz, CDCl3): d 55.8, 68.0, 68.1, 72.5, 72.9, 73.0, 73.3, 73.5, 74.7, 74.8,
74.9, 75.1, 75.2, 75.4, 77.2, 79.0, 79.9, 81.4, 82.4, 82.8, 101.3, 102.7, 127.0-128.4,
138.0, 138.2, 138.5, 138.6, 138.7, 139.0, 139.1; HRMS (MALDI-TOF) calcd for
C
64H66O11Na, 1033.4503; found, 1033.4509.
(g) Compound characterization data for compound 7: Overall
a/b = 9:1; Data for
the major isomer: ½a D25
ꢀ
= ꢁ5.9°(CHCl3, c 1.0); 1H NMR (500.13 MHz, CDCl3): d
2.52 (t, 1H, J = 2.4 Hz), 3.43–3.78 (m, 10H), 3.83–3.98 (m, 4H), 4.02 (dd, 1H,
J = 3.7, 9.8 Hz), 4.16 (t, 1H, J = 6.7 Hz), 4.29–5.00 (m, 17H), 5.29 (m, 1H), 5.74 (dd,
1H, J = 1.8, 3.1 Hz), 5.88 (m, 1H), 5.96 (t, 1H, J = 10.2 Hz), 7.10–7.55 (m, 44H),
7.78–8.14 (m, 6H); 13C NMR (125.76 MHz, CDCl3): d 54.9, 66.7, 67.1, 68.9, 69.2,
69.6, 70.1, 70.2, 70.2, 70.3, 70.8, 72.8, 72.9, 73.3, 73.5, 73.6, 74.6, 74.7, 75.2, 75.8,
76.6, 78.2, 78.7, 79.7, 81.3, 91.9, 96.1, 97.3, 127.4–130.1, 133.1, 133.4, 133.5,
137.9, 138.0, 138.2, 138.3, 138.5, 138.6, 138.9, 165.4, 165.4, 165.6; HRMS
(MALDI-TOF) calcd for C91H88O19Na, 1508.5851; found, 1508.5855.
(h) Compound characterization data for compound 8: Overall
a/b = 3:1; Data for
the major isomer: ½a D25
ꢀ
= ꢁ19.2°(CHCl3, c 1.0); 1H NMR (200.13 MHz, CDCl3): d
2.31–2.48 (m, 1H), 3.36–5.12 (m, 21H), 5.26 (m, 1H), 5.72 (m, 1H), 5.81–5.98 (m,
1H), 7.09–7.63 (m, 29H), 7.76–8.12 (m, 6H); 13C NMR (50.32 MHz, CDCl3): d
54.7, 66.9, 67.1, 68.6, 69.1, 70.1, 70.1, 70.2, 72.9, 73.0, 73.1, 74.7, 75.0, 75.8, 77.2,

5272
A. K. Kayastha, S. Hotha / Tetrahedron Letters 51 (2010) 5269–5272
1H NMR (200.13 MHz, CDCl3): d 2.46 (t, 1H, J = 2.4 Hz), 3.4, 3.5, 3.5, 3.5, 3.5, 3.5,
78.1, 78.7, 95.8, 97.9, 127.3–130.0, 133.1, 133.4, 133.4, 138.0, 138.6, 138.7,
138.9, 165.4, 165.4, 165.8; HRMS (MALDI-TOF) calcd for
1075.3881; found, 1075.3889.
C
64H60O14Na,
3.5 (7s, 21H), 3.42 (m, 1H), 3.50–3.72 (m, 10H), 3.92 (dd, 1H, J = 3.7, 11.5 Hz),
4.22 (t, 2H, J = 2.4 Hz), 5.07 (d, 1H, J = 1.5 Hz), 5.09 (d, 1H, J = 1.8 Hz); 13C NMR
(50.32 MHz, CDCl3): d 54.2, 57.6, 57.6, 58.7, 58.8, 59.1, 60.6, 60.8, 65.8, 71.2,
71.6, 71.9, 74.8, 75.7, 76.3, 76.8, 76.8, 78.6, 81.1, 81.1, 95.3, 97.0; HRMS (MALDI-
TOF) calcd for C22H38O11Na, 501.2312; found, 501.2318.
(i) Compound characterization data for compound 9: ½a D25
= ꢁ11.0°(CHCl3, c 1.0);
ꢀ
1H NMR (200.13 MHz, CDCl3): d 2.47 (t, 1H, J = 2.4 Hz), 2.51 (br s, 1H), 3.38–3.82
(m, 6H), 4.43 (t, 2H, J = 2.4 Hz), 4.58 (d, 2H, J = 1.8 Hz), 4.63–4.76 (m, 3H), 4.90-
5.03 (m, 2H), 7.23–7.44 (m, 15H); 13C NMR (50.32 MHz, CDCl3): d 56.0, 70.0,
71.2, 73.7, 74.1, 74.7, 75.0, 75.3, 78.9, 81.4, 83.9, 101.5, 127.5–128.6, 137.9,
(m) Compound characterization data for compound 13: ½a D25
= ꢁ7.1°(CHCl3, c 1.0);
ꢀ
1H NMR (200.13 MHz, CDCl3): d 2.57 (t, 1H, J = 2.3 Hz), 3.34, 3.37, 3.38, 3.38,
3.44, 3.49, 3.52 (7s, 21H), 3.38–3.59 (m, 8H), 3.69 (m, 3H), 3.78 (dd, 1H, J = 3.3,
4.8 Hz), 3.9 (dd, 1H, J = 3.5, 11.1 Hz), 4.14–4.36 (m, 2H), 4.40 (d, 2H, J = 2.3 Hz),
4.92 (d, 1H, J = 1.3 Hz), 4.94 (d, 1H, J = 1.3 Hz), 5.29 (d, 1H, J = 1.5 Hz), 5.69 (dd,
1H, J = 1.8, 3.2 Hz), 5.88 (dd, 1H, J = 3.2, 10.1 Hz), 6.02 (t, 1H, J = 9.9 Hz), 7.20–
7.71 (m, 9H), 7.75–8.18 (m, 6H); 13C NMR (100.61 MHz, CDCl3): d 55.3, 57.4,
57.6, 58.6, 58.6, 59.1, 60.6, 60.8, 65.6, 66.1, 67.3, 69.9, 69.9, 70.5, 71.1, 71.5, 71.6,
75.6, 75.7, 76.3, 76.6, 77.2, 78.1, 81.2, 81.2, 96.5, 96.9, 96.9, 128.2–130.0, 133.2,
133.5, 133.6, 165.3, 165.4, 165.4; HRMS (MALDI-TOF) calcd for C49H60O19Na,
975.3627; found, 975.3631.
138.3, 138.6; HRMS (MALDI-TOF) calcd for
511.2090.
C30H32O6Na, 511.2097; found,
(j) Compound characterization data for 10: ½a D25
ꢀ
= ꢁ11.1°(CHCl3, c 1.0); 1H NMR
(200.13 MHz, CDCl3): d 2.50 (t, 1H, J = 2.4 Hz), 3.30, 3.36, 3.46 (3s, 9H), 3.45 (m,
4H), 3.58–4.09 (m, 10H), 4.24 (m, 1H), 4.35 (d, 2H, J = 2.4 Hz), 4.43–4.71 (m, 7H),
4.86 (dd, 2H, J = 4.8, 6.2 Hz), 4.99 (d, 1H, J = 1.7 Hz), 5.26 (d, 1H, J = 1.7 Hz), 5.67
(dd, 1H, J = 1.7, 3.2 Hz), 5.86 (dd, 1H, J = 3.2, 10.2 Hz), 6.03 (t, 1H, J = 10.2 Hz),
7.09–7.66 (m, 29H), 7.75–8.17 (m, 6H); 13C NMR (125.76 MHz, CDCl3): d 55.4,
57.4, 58.7, 60.7, 65.6, 66.1, 67.3, 69.3, 69.9, 69.9, 70.5, 71.6, 71.7, 71.8, 72.3, 73.3,
74.8, 75.0, 75.0, 75.6, 75.8, 76.7, 78.2, 79.9, 81.2, 96.6 (1JC–H = 170.5 Hz), 97.1
(1JC–H = 169.7), 98.1 (1JC–H = 174.2), 127.3–130.2, 133.1, 133.4, 133.6, 138.5,
138.5, 138.7, 138.7, 165.3, 165.4, 165.4; HRMS (MALDI-TOF) calcd for
(n) Compound characterization data for compound 14: ½a D25
= ꢁ144.3°(CHCl3, c
ꢀ
1.0); 1H NMR (200.13 MHz, CDCl3): d 2.56 (t, 1H, J = 2.4 Hz), 3.21, 3.36, 3.36, 3.50
(4s, 12H), 3.18–3.59 (m, 6H), 3.71 (dd, 1H, J = 3.7, 11.1 Hz), 3.96 (dd, 1H, J = 3.8,
11.1 Hz), 4.29 (td, 1H, J = 3.6, 7.3, 9.8 Hz), 4.40 (d, 2H, J = 2.4 Hz), 4.94 (s, 1H),
5.31 (d, 1H, J = 1.5 Hz), 5.69 (dd, 1H, J = 1.8, 3.1 Hz), 5.87 (dd, 1H, J = 3.3, 10.1 Hz),
6.02 (t, 1H, J = 9.9 Hz), 7.21–7.68 (m, 9H), 7.79–8.14 (m, 6H); 13C NMR
(50.32 MHz, CDCl3): d 55.3, 57.5, 58.8, 58.9, 60.6, 66.1, 67.2, 69.8, 69.9, 70.4,
71.2, 71.3, 75.6, 76.2, 76.7, 78.1, 80.9, 96.4, 97.0, 128.2–129.9, 133.1, 133.3,
133.6, 165.3, 165.4, 165.4; HRMS (MALDI-TOF) calcd for C40H44O14Na, 771.2629;
found, 771.2620.
C
73H76O19Na, 1279.4879; found, 1279.4870.
(k) Compound characterization data for 11: ½a 2D5 = +75.5°(CHCl3, c 1.0); 1H NMR
ꢀ
(200.13 MHz, CDCl3): d 2.18 (br s, 1H), 2.47 (t, 1H, J = 2.4 Hz), 3.50, 3.51, 3.55 (3s,
9H), 3.52 (m, 3H), 3.62 (m, 1H), 3.71–3.90 (m, 2H), 4.23 (d, 2H, J = 2.4 Hz), 5.09
(d, 1H, J = 1.7 Hz); 13C NMR (50.32 MHz, CDCl3): d 54.3, 57.7, 59.1, 60.8, 62.1,
72.4, 74.9, 76.3, 76.9, 78.6, 80.9, 95.6 HRMS (MALDI-TOF) calcd for C12H20O6Na,
283.1158; found, 283.1164.
(l) Compound characterization data for compound 12: ½a D25
= +106.9°(CHCl3, c 1.0);
ꢀ