(S)-Camphorsulfonic acid catalyzed highly stereoselective synthesis of pseudoglycosides

Article abstract of DOI:10.1016/j.bmcl.2009.04.003

A mild and efficient synthesis of pseudoglycosides has been developed using metal free (S)-camphorsulfonic acid. (S)-CSA acts as an excellent catalyst for conversion of 2,4,6-tri-O-acetyl-d-glucal to 2,3-unsaturated O-glycosides. A wide range of biologically active natural products, alcohols and thiols could be coupled with glucal to give the desired pseudoglycosides in good to excellent yields with exclusive α-stereoselectivity.

Full text of DOI:10.1016/j.bmcl.2009.04.003

Bioorganic & Medicinal Chemistry Letters 19 (2009) 3093–3095
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
(S)-Camphorsulfonic acid catalyzed highly stereoselective synthesis
of pseudoglycosides
*
Bala Kishan Gorityala, Shuting Cai, Jimei Ma, Xue-Wei Liu
Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
a r t i c l e i n f o
a b s t r a c t
Article history:
A mild and efficient synthesis of pseudoglycosides has been developed using metal free (S)-camphorsul-
Received 8 January 2009
Revised 31 March 2009
Accepted 2 April 2009
Available online 8 April 2009
fonic acid. (S)-CSA acts as an excellent catalyst for conversion of 2,4,6-tri-O-acetyl-
urated O-glycosides. A wide range of biologically active natural products, alcohols and thiols could be
coupled with glucal to give the desired pseudoglycosides in good to excellent yields with exclusive
stereoselectivity.
D-glucal to 2,3-unsat-
a-
Ó 2009 Elsevier Ltd. All rights reserved.
Keywords:
Glycosylation
Ferrier rearrangement
a-Selectivity
2,3-Unsaturated glycosides
Nowadays the diversity oriented synthesis (DOS) for synthesiz-
ing small molecule libraries with definite stereoselectivity has in-
creased.1 A variety of biologically active natural products are
oxygen rich and synthesized from combinatorial libraries.2
Attracted by these facts we began to develop oxygen rich small
molecule libraries and natural products connected to sugar skele-
tons with the aid of Ferrier rearrangement. The primordial work
of Ferrier and Prasad resulted in Ferrier rearrangement,3 an acid
catalyzed reaction between glucal and an alcohol,4 is an old and
reliable procedure for the formation of 2,3-unsaturated O-glyco-
sides. This rearrangement is believed to proceed through a cyclic
allylic oxocarbonium intermediate that is formed via displacement
of the C-3 substituent in a glucal, followed by the preferential
attack of a nucleophile from the quasi-equatorial orientation.5
2,3-Unsaturated O-glycosides are known to play a vital role in
the synthesis of antibiotics,6 oligosaccharides,7 uronic acids,8 com-
plex carbohydrates9 and various natural products10 and they are
important building blocks in many bioactive molecules.11
and usage of excess catalyst. And moreover, the strong acidic con-
ditions could result in undesired side products, hence a mild, inex-
pensive and metal free catalyst which would deliver the desired
pseudoglycosides with high anomeric selectivity and yield is
highly desirable.
The usage of organic acids in glycosylation is strictly limited
and, therefore, we set out to explore the catalytic potential of or-
ganic acids in the Ferrier rearrangement. The treatment of glucal
with propargyl alcohol in the presence of acetic acid (pKa 4.76)
to obtain desired 2,3-unsaturated glycoside was unsuccessful.
Then we tested the activity of racemic camphorsulfonic acid (pKa
1.17) under the same conditions, which gave the desired pseudo-
glycoside with good anomeric selectivity (78% yield,
a/b 5:1) in
1 h. Attracted by this result, optically pure camphorsulfonic acids
(both R and S) were used to test the effect of chirality on anomeric
selectivity. To our interest, both (R) and (S)-CSA furnished the de-
sired 2,3-unsaturated glycosides in good to excellent yields (80
and 92%, respectively) with predominant
a-selectivity (a/b 10:1)
Moreover, the unsaturated part in sugar moiety allows many
modifications such as hydroxylation, epoxidation, hydrogenation
and aminohydroxylation which contribute their complexities and
diversities. Over the decades Ferrier rearrangement has seen
extensive development as this rearrangement could be undergone
by various Lewis acids and oxidants.12 However the metal catalysts
and metal triflates used in this transformation are highly expensive
and most of the other catalysts suffer from drawbacks such as air
sensitivity, strong oxidizing conditions, low anomeric selectivity
in 1 h. The reactions involving (R)-CSA delivered higher yields if
the reaction time is prolonged to 2 h, hence we used (S)-CSA rather
than (R)-CSA. To the best of our knowledge, (S)-camphorsulfonic
acid has not been used in this area. Camphorsulfonic acid has got
importance in organic synthesis as this catalyst is used in the
O
AcO
AcO
O
OR
(S)-CSA
AcO
AcO
+
ROH
CH2Cl2, rt
1-4 hrs
OAc
1
2 or 3
* Corresponding author. Tel.: +65 6316 8901; fax: +65 67911961.
E-mail address: xuewei@ntu.edu.sg (X.-W. Liu).
Scheme 1. A synthetic model for the Ferrier rearrangement.
0960-894X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2009.04.003

3094
B. K. Gorityala et al. / Bioorg. Med. Chem. Lett. 19 (2009) 3093–3095
synthesis of ligands,13 chromans,14 as an auxillary,15 in some poly-
merization reactions16 and it is extensively used in the optical res-
olution of amines.17
In the present study, we describe the successful implementa-
tion of (S)-camphorsulfonic acid as a catalyst in the Ferrier rear-
rangement for the synthesis of 2,3-unsaturated O-glycosides
(Scheme 1). In view of atom economy low amount of catalyst
was used. Typically, (S)-CSA was added to the mixture of glucal
and alcohol in dichloromethane at room temperature. When the
reaction was complete, simple aqueous work up and subsequent
purification of the crude product by column chromatography gave
the desired glycosides. The structure and stereochemistry of the
glycosylated products were elucidated from 1H, 13C and 2D NMR
spectroscopic data. To further establish the scope of the reaction,
a variety of O and S pseudoglycosides were synthesized in good
to excellent yields (68–92%) and most of the glycosylation prod-
ucts were obtained in exclusively pure diastereomers as resulted
in Table 1. Based on the anomeric ratios obtained from 1H NMR
spectra, it is evident that catalytic reactions using all nucleophiles
(Table 1, entries 2–9) except propargyl alcohol and O-methoxy
Table 1
Ferrier reaction of 2,3-tri-O-glucal with alcohols and thiols in the presence of (S)-
camphorsulfonic acid
Entry
1
Product
Time (h)
Yield (%)
92
a
/ba
OAc
O
AcO
1
10:112k
O
2a
OAc
O
AcO
AcO
2
3
4
1
90
83
85
a12n
benzenethiol (Table 1, entries 1 and 10) gave exclusive
a-selectiv-
O
ity. The predominant formation of the
thermodynamic anomeric effect.
a-anomer may arise from a
2b
OAc
O
Encouraged by these results, we next explored the scope of this
route for the synthesis of pseudoglycals connected to various bio-
1.5
a22
logically important natural products such as citronellol,18
L-men-
O
O
2c
thol,19 borneol,19 endo-fenchol and preglenolone20 glycosides,
these all have served as challenging targets to study and transform
because of their diversity of the biological activities and their
structural complexity. Some of them were generally synthesized
by enzymatic21 as well as Koenigs–Knorr–Zemplen19 methods,
which are expensive, lengthy and tedious. We used our catalytic
system to synthesize sugar-containing natural products with
OAc
O
AcO
AcO
1
a12o
O
2d
OAc
O
exclusive
a-anomeric selectivity in 120–180 min of reaction time
(Table 2). Pregnenolone glycoside, which was first isolated from
Nerium Odorum,20 operates as a powerful neurosteroid in the brain,
modulating the transmission of messages from neuron to neuron
5
1
82
a12n
O
Table 2
2e
Ferrier reaction of 2,3-tri-O-acetyl-D-glucal with various natural products alcohols in
the presence of (S)-CSA
OAc
O
AcO
AcO
Entry
Natural product alcohols
HO
Product
Time (h)
Yield (%)
a/b
6
7
1.5
1.5
82
85
a12k
O
H
2f
1
3a
3
80
a24
OAc
O
S-(-)-β-Citronellol
a
O
2g
2
3b
2.5
88
a25
OH
L-Menthol
OAc
O
AcO
AcO
8
9
2
2
68
75
a
a
S
3
4
3c
3
3
85
84
a26
2h
OH
OAc
O
(+)-Borneol
S
3d
a27
2i
HO
(+)-endo-Fenchol
OAc
O
O
AcO
10
2
78
20:123
S
H
5
3e
4
78
a28
OMe
H
H
2j
HO
The a
/b ratio was determined from the anomeric proton ration in the 1H NMR
a
Pregnenolone
spectra.

B. K. Gorityala et al. / Bioorg. Med. Chem. Lett. 19 (2009) 3093–3095
3095
22. To a mixture of 2,4,6-tri-O-acetyl-
D
-glycal (100 mg, 0.37 mmol) and 2-allyloxy
and strongly influencing learning and memory. The synthesis of
pregnenolone 2,3-unsaturated glycoside achieved by employing
ethanol (1 equiv) in dichloromethane (5 ml) was added 0.5 equiv of (S)-
camphorsulfonic acid at room temperature. The mixture was stirred for the
appropriate amount of time (Table 1, entry 3), and the extent of reaction was
monitored by TLC analysis. When the reaction was complete, aqueous work up
and subsequent purification of the crude compound by silica gel column
chromatography by hexane, ethyl acetate solvent system, gave the desired 2,3-
unsaturated glycoside..
(S)-CSA with
a-selectivity (78% yield). The biological evaluation
of the compounds 3a–e is under way.
In summary, we have demonstrated a new protocol for forming
glycosidic linkage in high distereoselective fashion. Many complex
natural products, alcohols and thiols could be incorporated with
glucal donor in a single process. The main advantage of this meth-
od concern about high anomeric selectivity, low cost reagents and
friendly environmental conditions.
2-(Allyloxy)ethanyl 4,6-di-O-acetyl-2,3-dideoxy-
a
-
D-erythro-hex-2-enopyranoside
(2c): ½a 2D4
ꢀ
+272.2 (c 0.4, CHCl3); 1H NMR (500 MHz, CDCl3) d 5.90 (ABX system,
JAX = 17.2 Hz, JBX = 9.6 Hz, JAB = 5.4 Hz, 1H), 5.85 (br s, 2H), 5.30 (d, J = 9.7 Hz,
1H) 5.26 (dd, J = 17.2, 1.6 Hz, 1H), 5.16 (d, J = 9.5 Hz, 1H), 5.06 (s, 1H), 4.23 (dd,
J = 12.1, 5.2 Hz, 1H), 4.15 (dd, J = 12.1, 2.3 Hz, 1H), 4.12–4.10 (m, 1H), 4.0 (d,
J = 5.0 Hz, 2H), 3.89 (dt, J = 11.0, 4.5 Hz, 1H), 3.72–3.68(m, 1H), 3.61 (t,
J = 4.8 Hz, 2H), 2.07 (s, 3H), 2.05 (s, 3H); 13C NMR (125 MHz, CDCl3) d 170.7,
170.2, 134.6, 129.1, 127.7, 117.1, 94.6, 72.1, 69.2, 67.8, 66.8, 65.2, 62.9, 20.9,
Acknowledgements
20.7; IR (NaCl neat)
m
1743, 1317, 1234, 1047 cmꢁ1; HRMS (ESI) m/z [M+Na]+
calcd for C15H22O7Na 337.1263, found 337.1252.
We gratefully thank Nanyang Technological University and the
Ministry of Education, Singapore for the financial support.
23. 2-Methoxybenzenethainyl 4,6-di-O-acetyl-2,3-dideoxy-a-D-erythro-hex-2-enopyr-
?tjl?>anoside (2j): ½a D24
ꢀ
+262.6 (c 0.5, CHCl3); 1H NMR (500 MHz, CDCl3) d 7.42
(dd, J = 7.5, 1.6 Hz,1H), 7.24 (m, 1H), 6.8 (m, 1H), 6.40 (d, J = 5.8 Hz, 1H), 5.13 (dd,
J = 10.1, 4.5 Hz, 1H), 4.94 (t, J = 5.8 Hz, 1H), 4.54 (m, 2H), 4.38 (dd, J = 12.2, 4.4 Hz,
1H), 4.32 (dd, J = 12.2, 2.1 Hz, 1H),3.88 (s, 1H), 2.06 (s, 6H), 1.47 (s, 3H); 13C NMR
(125 MHz, CDCl3) d 170.7, 169.8, 158.7, 144.7, 133.6, 129.1, 122.9, 120.8, 111.0,
References and notes
98.7, 70.8, 69.8, 62.3, 55.8, 40.4, 20.7, 19.8; IR (NaCl neat)
m 1743, 1370, 1232,
1. (a) Stockwell, B. Nat. Rev. Genet. 2000, 1, 116; (b) Schreiber, S. L. Bioorg. Med.
Chem. 1998, 6, 1127.
1037 cmꢁ1; HRMS (ESI) m/z [M+Na]+ calcd for C17H20O6SNa 375.0878, found
375.0871.
2. Feher, M.; Schmidt, J. M. J. Chem. Inf. Comput. Sci. 2003, 43, 218.
3. Ferrier, R. J.; Prasad, N. J. Chem. Soc. C. 1969, 570.
4. Ferrier, R. J. J. Chem. Soc., Perkin Trans. 1 1979, 1455.
5. (a) Ferrier, R. J.; Sankey, G. H. J. Chem. Soc. C 1966, 2345; (b) Wieczorek, B.;
Thiem, J. J. Carbohydr. Chem. 1998, 17, 785; (c) Levy, D. E.; Tang, C. The Chemistry
of C-Glycosides; Pergamon Press: Tarrytown, NY, 1995; (d) Postema, M. H. D. C-
Glycosides Synthesis; CRC Press: Boca Raton, FL, 1995; (e) Csuk, R.; Shaade, M.;
Krieger, C. Tetrahedron 1996, 52, 6397.
24. (S)-(ꢁ)-b-Citronellol 4,6-di-O-acetyl-2,3-dideoxy-
a-D-erythro-hex-2-enopyrano-
side (3a):
½ ꢀ
a 2D4
+41.5 (c 0.5, CHCl3); 1H NMR (500 MHz, CDCl3) 5.86 (d,
J = 10.4 Hz, 1H), 5.82 (d, J = 10.4 Hz, 1H), 5.29 (dd, J = 9.6, 1.1 Hz, 1H), 5.08 (t,
J = 7.0 Hz, 1H), 5.01 (s, 1H), 4.23 (dd, J = 12.1, 5.4 Hz, 1H), 4.16 (dd, J = 12.1,
2.2 Hz, 1H), 4.10–4.07 (m, 1H), 3.82 (dd, J = 7.4, 2.2 Hz, 1H), 3.55–3.50 (m, 1H),
2.08 (s, 3H), 2.07 (s, 3H), 1.99–1.93 (m, 2H), 1.67–1.65 (m, 4H), 1.59–1.55 (m,
4H), 1.41–1.30 (m, 2H), 1.17–1.12 (m, 1H), 0.88 (d, J = 6.6 Hz, 3H); 13C NMR
(125 MHz, CDCl3) d 170.8, 170.3, 131.2, 128.9, 127.9, 124.7, 94.3, 67.0, 66.9,
6. Williams, N. R.; Wander, J. D. The Carbohydrates in Chemistry and Biochemistry;
Academic Press: New York, 1980. 761 pp.
65.3, 63.1, 37.2, 36.5, 29.4, 25.7, 25.4, 20.9, 20.8, 19.3, 17.6; IR (NaCl neat) m
1743, 1371, 1232, 1035 cmꢁ1; HRMS (ESI) m/z [M+Na]+ calcd for C20H32O6Na
7. Bussolo, V. D.; Kim, Y. J.; Gin, D. Y. J. Am. Chem. Soc. 1998, 120, 13515.
8. (a) Schmidt, R. R.; Angerbauer, R. Carbohydr. Res. 1981, 89, 159; (b) Angerbauer,
R.; Schmidt, R. R. Carbohydr. Res. 1981, 89, 193.
391.2097, found 391.2089.
25.
L
-Menthyl 4,6-di-O-acetyl-2,3-dideoxy-
a-D-erythro-hex-2-enopyranoside (3b):
½ ꢀ
a 2D4 +142.5(c 0.5, CHCl3); 1H NMR (500 MHz, CDCl3) d 5.85 (s, 2H), 5.26 (d,
9. Schmidt, R. R.; Angerbauer, R. Angew. Chem., Int. Ed. 1977, 16, 783.
10. Tolstikov, A. G.; Tolstikov, G. A. Russ. Chem. Rev. 1993, 62, 579.
11. (a) Fraser-Reid, B. Acc. Chem. Res. 1985, 18, 347; (b) Ferrier, R. J. Adv. Carbohydr.
Chem. Biochem. 1969, 24, 199; (c) Toshima, K.; Tatsuda, K. Chem. Rev. 1993, 93,
1503; (d) Nicolaou, K. C.; Mitchell, H. J. Angew. Chem., Int. Ed. 2001, 40, 1576; (e)
Feher, M.; Schmidt, J. M. J. Chem. Inf. Comput. Sci. 2003, 43, 218; (f) Dorgan, B. J.;
Jackson, R. F. W. Synlett 1996, 859; (g) Schmidt, R. R.; Angerbauer, R. Carbohydr.
Res. 1981, 89, 193; (h) Schmidt, R. R.; Angerbauer, R. Carbohydr. Res. 1979, 72,
272; (i) Danishefsky, S. J.; Bilodeau, M. T. Angew. Chem., Int. Ed. 1996, 35, 1380;
(j) Liu, Z. J. Tetrahedron: Asymmetry 1999, 10, 2119.
12. (a) Descotes, G.; Martin, J. C. Carbohydr. Res. 1977, 56, 168; (b) Klaffke, W.;
Pudlo, P.; Springer, D.; Thiem, J. L. Ann. Chem. 1991, 6, 509; (c) Bhate, P.; Harton,
D.; Priebe, W. Carbohydr. Res. 1985, 144, 331; (d) Babu, B. S.; Balsubramanian, K.
K. Tetrahedron Lett. 2000, 41, 1271; (e) Das, S. K.; Reddy, K. A.; Roy, J. Synlett
2003, 1607; (f) Takhi, M.; Rahman, A.; Schmidt, R. R. Tetrahedron Lett. 2001, 42,
4053; (g) Masson, C.; Soto, J.; Besodes, M. Synlett 2000, 1281; (h) Yadav, J. S.;
Reddy, B. V. S.; Chandraiah, L.; Reddy, K. S. Carbohydr. Res. 2001, 332, 221; (i)
Swamy, N. R.; Venkateswarlu, A. Synthesis 2002, 598; (j) Bettadaiah, B. K.;
Srinivas, P. Tetrahedron Lett. 2003, 44, 7257; (k) Yadav, J. S.; Reddy, B. V.; Reddy,
J. S. J. Chem. Soc. Perkin Trans. 1 2002, 2390; (l) Yadav, J. S.; Reddy, B. V.; Murthy,
C. V.; Kumar, G. M. Synlett 2000, 1450; (m) Smitha, G.; Reddy, S. C. Synthesis
2004, 834; (n) Gorityala, B. K.; Cai, S.; Lorpitthaya, R.; Ma, J.; Pasunooti, K. K.;
Liu, X. W. Tetrahedron Lett. 2009, 50, 676; (o) Zhang, G.; Liu, Q.; Shi, L.; Wang, J.
Tetrahedron 2008, 64, 339; (p) Yadav, J. S.; Reddy, B. V. S.; Geetha, V. Synth.
Commun. 2003, 33, 717; (q) Rafiee, E.; Tangestaninejad, S.; Habibi, M. H.;
Mirkhani, V. Bioorg. Med. Chem. Lett. 2004, 14, 3611.
13. Gayet, A.; Bolea, C.; Andersson, P. G. Org. Biomol. Chem. 2004, 2, 1887.
14. Makoto, M.; Yamamoto, H. Bull. Chem. Soc. Jpn. 1995, 68, 2657.
15. Barrett, A. G. M.; Braddock, D. C.; Christian, P. W. N.; Pilipauskas, D.; White, A. J.
P.; Williams, D. J. J. Org. Chem. 1998, 63, 5818.
16. Sejin, O.; Gijung, K.; Narae, K.; Shim, S. E.; Soonja, C. Macromol. Res. 2005, 13,
187.
17. Richard, M. K.; Jose, W. N. K.; Pouwer, T. R.; Vries, Q. B. Synthesis 2003, 10, 1626.
18. Mastalic, J.; Jerkovic, I.; Vinkovic, M.; Dzolic, Z.; Vikic-Topic, D. Crotica. Chem.
Acta 2004, 77, 491.
19. Noguchi, K.; Nakagawa, H.; Yoshiyama, M.; Shimura, S.; Kirimura, K.; Usami, S.
J. Ferment. Bioeng. 1998, 85, 436.
J = 10 Hz, 1H), 5.08 (s,1H), 4.18 (dd, J = 12.3, 6.7 Hz, 1H), 4.17–414 (m, 2H), 3.39
(dt, J = 10.6, 4.4 Hz, 1H), 2.17 (d, J = 4.0 Hz, 1H), 2.09 (s, 3H), 2.08 (s, 3H), 1.67–
1.59 (m, 2H), 1.44–1.37 (m, 1H), 1.25–1.20 (m,1H), 1.03 (dd, J = 23.2, 12.2 Hz,
1H), 0.95 (dd, J = 12.1, 3.0 Hz, 1H), 0.92–0.87 (m, 7H), 0.85–0.79 (m, 1H), 0.75
(d, J = 7.0 Hz, 3H); 13C NMR (125 MHz, CDCl3) d 170.8, 170.3, 128.5, 128.0, 96.1,
81.0, 66.6, 65.3, 63.3, 48.8, 43.3, 34.2, 31.7, 25.6, 23.1, 22.3, 21.1, 20.9, 20.8,
16.2; IR (NaCl neat)
calcd for C20H32O6Na 391.2097, found 391.2089.
26. (+)-Borneol 4,6-di-O-acetyl-2,3-dideoxy- -erythro-hex-2-enopyranoside (3c):
+72.6 (c 0.8, CHCl3); 1H NMR (500 MHz, CDCl3) d 5.84–5.79 (m, 2H),
m
1743, 1369, 1234, 1035 cmꢁ1; HRMS (ESI) m/z [M+Na]+
a-D
½ ꢀ
a 2D4
5.27 (d, J = 9.8 Hz, 1H), 4.99 (s, 1H), 4.21 (dd, J = 12.2, 5.6 Hz, 1H), 4.12 (dd,
J = 12.2, 2.2 Hz, 1H), 4.10–4.09 (m, 1H), 3.82 (dt, J = 6.6, 2.1 Hz, 1H), 2.24–2.22
(m, 1H), 2.07 (s, 3H), 2.06 (s, 3H), 1.96–1.90 (m, 1H), 1.70–1.64 (m, 2H), 1.59 (t,
J = 4.5 Hz, 1H), 1.23–1.17 (m, 2H), 0.94–0.82 (s, 3H), 0.81(s, 3H), 0.80 (s, 3H);
13C NMR (125 MHz, CDCl3) d 170.7, 170.2, 128.4, 128.2, 96.1, 85.8, 66.8, 66.7,
64.1, 48.8, 47.7, 46.6, 38.9, 28.2, 28.2, 26.6, 20.9, 20.7, 19.7, 13.6; IR (NaCl neat)
m
1747, 1369, 1230, 1041 cmꢁ1; HRMS (ESI) m/z [M+Na]+ calcd for C20H30O6Na
389.1940, found 389.1938.
27. (+)-Endo-fenchyl 4,6-di-O-acetyl-2,3-dideoxy-a-D-erythro-hex-2-enopyranoside
(3d): ½a 2D4
ꢀ
+48.7 (c 0.5, CHCl3); 1H NMR (500 MHz, CDCl3) d 5.83 (s, 2H), 5.25
(d, J = 10 Hz, 1H), 4.95(s, 1H), 4.20 (dd, J = 12.2, 5.2 Hz, 1H), 4.13–4.09 (m, 2H),
3.42 (d, J = 1.5 Hz, 1H), 2.06 (s, 3H), 2.05 (2, 3H), 1.65–1.61 (m, 3H), 1.45 (dd,
J = 10.1, 1.5 Hz, 1H), 1.38–1.36 (m, 1H), 1.08 (s, 3H), 1.07–1.06 (m, 1H), 1.01 (s,
3H), 0.96–0.94 (m, 1H), 0.85 (s, 3H); 13C NMR (125 MHz, CDCl3) d 170.8, 170.2,
128.5,127.9, 94.1, 90.1, 66.8, 65.2, 63.1, 48.8, 48.7, 41.3, 39.4, 31.8, 25.9, 21.1,
20.9, 20.8, 19.7; IR (NaCl neat)
[M+Na]+ Calcd for C20H30O6Na 389.1940, found 389.1935.
28. Pregnenolonyl 4,6-di-O-acetyl-2,3-dideoxy- -erythro-hex-2-enopyranoside (3e):
+162.4 (c 0.5, CHCl3); 1H NMR (500 MHz, CDCl3) d 5.85 (d, J = 10.4 Hz, 1H),
m
1732, 1456, 1259, 1064 cmꢁ1; HRMS (ESI) m/z
a-D
½ ꢀ
a 2D4
5.78 (d, J = 10.4 Hz, 1H), 5.32 (s, 1H), 5.26 (d, J = 10.0 Hz, 1H), 5.14 (s, 1H), 4.20 (dd,
J = 12.2, 5.9 Hz,1H), 4.17–413 (m, 2H), 3.57–3.51 (m, 1H), 2.50 (t, J = 8.0 Hz, 1H),
2.38–2.34 (m, 1H), 2.32 (d, J = 11.0 Hz, 1H), 2.19–2.14 (m, 1H), 2.09 (s, 3H), 2.06 (s,
3H), 2.05 (s, 3H), 2.02 (d, J = 9.5 Hz,1H), 1.99–1.95 (m, 1H), 1.88–1.83 (m, 2H),
1.60–1.42 (m, 8H), 1.24–1.18 (m, 1H), 1.17–1.12 (m, 1H), 1.06–1.03 (m, 1H), 0.98–
0.95 (m, 4H), 0.60 (s, 3H); 13C NMR (125 MHz, CDCl3) d 209.5, 170.8, 170.3, 140.7,
128.9, 128.3, 121.5, 92.8, 78.0, 66.8, 65.3, 63.6, 63.1, 56.8, 49.9, 43.9, 40.3, 38.8,
37.1, 36.6, 31.8, 31.7, 31.5, 28.1, 24.4, 22.8, 21.0, 20.9, 20.8, 19.3, 13.2; IR (NaCl
20. Yamauchi, T.; Hara, M.; Mihashi, K. Phytochemistry 1972, 1, 3345.
21. Hotha, S.; Tripathi, V. Tetrahedron Lett. 2005, 61, 4555.
neat)
C31H44O7Na 551.2985, found: 551.2994.
m
1745, 1699, 1371, 1228, 1035 cmꢁ1; HRMS (ESI) m/z [M+Na]+ calcd for