The Baylis-Hillman reaction: a strategic tool for the synthesis of higher-carbon sugars

Article abstract of DOI:10.1016/j.tetlet.2007.07.067

The Baylis-Hillman reaction of acyclic sugar-derived aldehydes is invoked as an attractive synthetic strategy for ready access to higher-carbon sugars.

Full text of DOI:10.1016/j.tetlet.2007.07.067

Tetrahedron Letters 48 (2007) 6466–6470
The Baylis–Hillman reaction: a strategic tool for the synthesis
of higher-carbon sugarsI
Palakodety Radha Krishna,a,* P. V. Narasimha Reddy,a A. Sreeshailam,a
M. Uday Kiranb and B. Jagdeeshb
aD-206/B, Discovery Laboratory, Organic Chemistry Division-III, Indian Institute of Chemical Technology, Hyderabad 500 007, India
bNMR Center Indian Institute of Chemical Technology, Hyderabad 500 007, India
Received 11 May 2007; revised 3 July 2007; accepted 11 July 2007
Available online 17 July 2007
Abstract—The Baylis–Hillman reaction of acyclic sugar-derived aldehydes is invoked as an attractive synthetic strategy for ready
access to higher-carbon sugars.
Ó 2007 Published by Elsevier Ltd.
Higher-carbon sugars are carbohydrates containing
seven or more consecutive carbon atoms and are
frequently encountered as subunits in a number of
natural products of biological significance and have
found important use as chiral synthons.1 They often
play a major role in cell–cell recognition, consequently,
their synthesis has been a challenge in carbohydrate
chemistry for more than a century and assumes ever
increasing significance.2 The addition of more carbon
atoms to unprotected pentoses and hexoses is often
plagued by low yields, poor diastereoselectivity and
troublesome isolation of the products.3 The general
method for accessing them involves olefination of the
C1 or C5 aldehyde and subsequent cis-dihydroxylation.4
However, the yield in the Wittig reaction using
Ph3P@CHCO2Et was moderate (30–60%) due to a con-
comitant intramolecular Michael addition occurring in
the products.5 The Michael addition side reaction is a
well-known problem in Wittig reactions on pentofura-
noses and on hexopyranoses with methyl or ethyl ester
stabilized phosphoranes. As part of our research on
the Baylis–Hillman reaction,6 herein we report a novel
Baylis–Hillman reaction based synthetic protocol for
ready access of diverse and rare heptanoates and oct-
anoates in their protected form. Towards this endeav-
our, we examined 2,3-O-isopropylidene D-ribose 5 and
diacetone D-mannose 13 as starting materials to perform
the Baylis–Hillman reaction on their acyclic derivatives
for the first time and elaborated the resulting adducts
into polyhydroxylated seven- and eight-carbon-contain-
ing higher sugars with a terminal ester moiety (com-
pounds 1–4 and 9–12).
Initially, 2,3-O-isopropylidene D-ribose (5) was selected
to test the efficacy of the proposed methodology. Thus,
5 was treated with LAH in dry THF to give triol 6
(75%). Triol 6 was treated with 2,2-DMP in the presence
of a catalytic amount of PTSA in CH2Cl2 to furnish the
diacetonide protected primary alcohol 7 (85%). Alcohol
7 was oxidized under Swern conditions and the ensuing
aldehyde was subjected to a Baylis–Hillman reaction
with ethyl acrylate under standard conditions (DAB-
CO/DMSO/rt) to afford a separable mixture of Bay-
lis–Hillman adducts 8a and 8b (6.5:3.5). Following
separation of the diastereomers, our next task was to
assign the stereochemistry at the newly created stereogenic
centres. Earlier, we demonstrated that the Baylis–Hill-
man reaction of sugar-derived aldehydes gave the anti-
product as the major diastereomer.6c,g,k By analogy,
the stereochemistry at the newly created centres of com-
pounds 8a and 8b was assigned (Scheme 1). Compound
8a was identified as the major product where the C3 ste-
reochemistry was assigned as anti to C4 (J3,4 = 9.6 Hz).
Likewise, in the minor product 8b the C3 stereochemis-
try was assigned syn (J3,4 = 3.0 Hz). Next, these two
adducts were independently subjected to ozonolysis
followed by reduction with NaBH4 in MeOH at 0 °C
Keywords: Acyclic sugar-derived aldehydes; Baylis–Hillman reaction;
Ozonolysis; Reduction; Higher-carbon sugars.
q IICT Communication No. 070513.
*
Corresponding author. Tel.: +91 40 27160123x2651; fax: +91 40
27160387; e-mail: prkgenius@iict.res.in
0040-4039/$ - see front matter Ó 2007 Published by Elsevier Ltd.
doi:10.1016/j.tetlet.2007.07.067

P. Radha Krishna et al. / Tetrahedron Letters 48 (2007) 6466–6470
6467
O
OH
OH
O
HO
HO
O
OH
a
b
O
c
OH
O
COOEt
OH
O
O
O
O
+
O
O
O
O
5
6
7
8a (65%)
O
OH
O
COOEt
O
O
8b (35%)
O
OH
O
OH
O
O
OH
COOEt
O
d
COOEt
O
COOEt
+
O
O
O
O
OH
O
O
OH
8a
1 (80%)
2 (20%)
O
OH
O
OH
O
OH
O
O
O
COOEt
COOEt
COOEt
d
+
O
O
OH
O
O
OH
O
O
4 (20%)
3 (80%)
8b
Scheme 1. Reagents and conditions: (a) LAH, THF, 0 °C–rt, 5 h, (75%); (b) 2,2-DMP, PTSA, CH2Cl2, 0 °C–rt, 6 h, (85%); (c) (i) (COCl)2, DMSO,
Et3N, ꢀ78 °C; (ii) ethyl acrylate, DABCO, DMSO, 0 °C–rt, 36 h, (60% over two steps); (d) (i) O3, CH2Cl2, ꢀ78 °C; (ii) NaBH4, MeOH, 0 °C–rt, 0.5 h
(65% over two steps).
to afford all four possible diastereomers 1–4 (1:2 and 3:4
in 8:2 ratios, respectively). To determine the absolute
stereochemistry at C2, diastereomers 1–4 were converted
into their respective cyclic carbonate derivatives 1a–4a
(Fig. 1) using triphosgene in the presence of Et3N in
CH2Cl2.7 A comparative NMR study of compounds
1a–4a helped in the unambiguous determination of the
absolute stereochemistries at C2 and C3. For example,
biguously determined for 1/1a (as depicted in Fig. 1)
taking into account that C3 was already assigned for
adduct 8a. Likewise the C2 and C3 stereochemistry for
compounds 2/2a was also established based on the
1
1
above H NMR data. Analogously, the H NMR spec-
trum of 3a showed the H2 proton as a doublet at d 5.01
(J = 8.0 Hz) and H3 as a double doublet at d 4.80
(J = 8.0, 9.2 Hz) indicative of a C2/C3-syn relationship,
while the 1H NMR spectrum of 4a revealed H2 as a dou-
blet at d 4.98 (J = 4.5 Hz) and H3 as double doublet at d
4.95 (J = 2.2, 4.5 Hz) being indicative of a C2/C3-anti
relative arrangement. From these data the absolute con-
figurations of C2 and C3 were assigned for compounds
3/3a and 4/4a. The relative spatial arrangements of the
C2–C3 and C2–C4 protons in 3a and 4a were examined
through 1D-NOESY studies, and the results supported
the above conclusions. Thus, it is clear that reduction
after ozonolysis afforded the major products as C2/C3-
syn isomers (1 and 3) and the minor products as C2/
C3-anti isomers (2 and 4).
1
the H NMR spectrum of 1a, derived from the major
adduct 8a, revealed both the H2 and H3 protons at d
5.05 as a pair of doublets (J = 9.4 Hz) integrating for
2H, while in 2a, H2 appeared as a doublet at d 5.03
(J = 4.1 Hz) and H3 appeared as a double doublet at d
1
4.90 (J = 2.8, 4.1 Hz). These H NMR values indicated
that C2 and C3 in 1 were syn and in 2 were anti.8 Thus
the absolute stereochemistry at C2 and C3 was unam-
O
O
H
O
O
O
O
3
H
O
O
3
O
O
2
Similarly, diol 14 obtained from diacetone D-mannose9
(13, Scheme 2) was protected as its benzoate ester (benz-
oyl chloride/Et3N/CH2Cl2) and the secondary hydro-
xyl group as its TBS ether with TBSOTf, 2,6-lutidine
in CH2Cl2 to afford 15 (80% over two steps). Compound
15, on methanolysis with excess K2CO3 in MeOH gave
primary alcohol 16 (95%). Alcohol 16 on oxidation
under Swern conditions followed by Baylis–Hillman
reaction with ethyl acrylate under standard conditions
(DABCO/DMSO/rt) yielded the corresponding adduct
+
H
2
H
O
O
COOEt
O
O
COOEt
2a
1a
O
O
O
O
O
O
H
H
3
O
3
O
O
O
2
2
H
+
H
O
O
O
O
COOEt
COOEt
3a
4a
Figure 1. Cyclic carbonates of heptonoates 1–4.

6468
P. Radha Krishna et al. / Tetrahedron Letters 48 (2007) 6466–6470
O
O
OH
OTBS
O
OH
Ref. 9
a
OH
b
OBz
O
O
O
O
O
O
O
O
O
O
14
13
15
OTBS
OH
OTBS
OAc
OTBS
COOEt
OH
COOEt
COOEt
c
d
O
O
O
O
O
O
O
O
O
+
O
O
O
O
16
(70%)
OAc
17
18a
OTBS
O
O
O
18b(30%)
OAc
OTBS
O
OH
OTBS
OH
OTBS
O
COOEt
COOEt
COOEt
e
O
+
O
O
O
O
O
O
OH
O
O
OH
O
9 (75%)
(25%)
10
18a
OH
OTBS
O
OAc
OH
OTBS
OTBS
COOEt
COOEt
COOEt
e
O
+
O
O
O
OH
O
O
O
O
O
OH
O
O
12 (25%)
11 (75%)
18b
Scheme 2. Reagents and conditions: (a) (i) benzoyl chloride, Et3N, CH2Cl2, 0 °C–rt, 8 h. (ii) TBSOTf, 2,6-lutidine, CH2Cl2, 0 °C–rt, 3 h, (80% over
two steps); (b) K2CO3, MeOH, 0 °C–rt, 2 h, (95%); (c) (i) (COCl)2, DMSO, Et3N, CH2Cl2, ꢀ78 °C; (ii) ethyl acrylate, DABCO, DMSO, 0 °C–rt,
24 h, (65%); (d) Ac2O, Et3N, CH2Cl2, 0 °C–rt, (95%); (e) O3, CH2Cl2, ꢀ78 °C, 0.5 h, (ii) NaBH4, MeOH, 0 °C, (70% over two steps).
17 in 65% yield as a mixture of inseparable diastereo-
O
O
mers. The mixture was acetylated (Ac2O/Et3N/CH2Cl2)
to afford the separable diastereomers 18a as the major
(70%) and 18b as the minor (30%) products, respec-
tively. Based on our previous results6c,g,k and on 1H
NMR spectral analysis of adducts 18a and 18b, wherein
H3 (allylic proton) appeared at d 5.77 (J = 5.9 Hz) in
18a and at d 5.78 (J = 2.3 Hz) in 18b, the stereochemis-
try of the allylic hydroxyl group was tentatively assigned
as depicted (Scheme 2). Later, both the major (18a) and
minor (18b) acetate derivatives were independently sub-
jected to ozonolysis followed by reduction with NaBH4
in MeOH. As expected two sets of diastereomers 9–12
were formed. However, during this reaction, the acetate
group was cleaved and the products were obtained as
diols. Due to the overlap of the diagnostic H2 and H3
protons in all the 1H NMR spectra of diols 9–12, the ste-
reochemistry was established from their corresponding
carbonate derivatives. Thus, diols 9 and 10 obtained
from major isomeric adduct 18a, when independently
treated with triphosgene in the presence of Et3N in
CH2Cl2, afforded cyclic carbonates 9a and 10a (Fig. 2)
while 18b gave 11a and 12a. 1H NMR analysis of 9a re-
vealed the H2 proton as a doublet at d 5.01 (J = 8.2 Hz)
and H3 as a double doublet at d 4.7 (J = 8.2, 9.5 Hz).
O
OTBS
O
O
OTBS
O
O
O
+
+
O
O
O
O
O
O
O
COOEt
O
O
O
COOEt
O
O
O
10a
9a
O
OTBS
O
O
OTBS
O
O
O
O
COOEt
COOEt
12a
11a
Figure 2. Cyclic carbonates of octanoates 9–12.
doublet at d 4.89 (J = 4.0, 5.1 Hz). These results for 9a
and 10a were very similar to those of 3a and 4a, which
suggests that 9a is C2/C3-syn and 10a is C2/C3-anti.
Likewise, the minor Baylis–Hillman adduct 18b, follow-
ing ozonolysis-reduction, furnished two products 11 and
12 whose structures were determined using the above
analogy. Based on carbohydrate nomenclature,10 com-
pound 1 was named as the D-glycero-D-altro heptose
derivative and compound 9 as the D-erythro-L-altro
octose derivative. On closer inspection of compounds
2–4 and 10–12, it was apparent that in general, the
D-ribose derivative furnished the D-series while the
D-mannose derivative gave the L-series. Thus, heptanoates
1
Similarly, the H NMR spectrum of 10a revealed H2
as a doublet at d 4.95 (J = 4.0 Hz) and H3 as a double

P. Radha Krishna et al. / Tetrahedron Letters 48 (2007) 6466–6470
6469
7. Kang, S.-K.; Jeon, J.-Ho.; Nam, K.-S.; Park, C.-H.; Lee,
H.-W. Synth. Commun. 1994, 24, 305–312.
1–4 and octanoates 9–12 were synthesized and their
structures assigned.11
8. (a) Rama Rao, A. V.; Murali Dhar, T. G.; Chakraborty,
T. K.; Gurjar, M. K. Tetrahedron Lett. 1988, 29, 2069–
2072; (b) Contelles, J. M.; de Opazo, E.; Arroyo, N.
Tetrahedron 2001, 57, 4729–4739.
9. Bird, J. W.; Jones, J. K. N. Can. J. Chem. 1963, 41, 1877–
1881.
In summary, we have reported a novel synthetic proto-
col for the construction of higher-carbon sugars through
the elaboration of Baylis–Hillman adducts of acyclic
sugar-derived aldehydes. This protocol should prove
useful to access other members of this class of com-
pounds. These products should find wide use in the syn-
thesis of bio-conjugates.
10. McNaught, A. D. Pure Appl. Chem. 1996, 68, 1919–2008.
11. Spectral data of selected compounds: Compound 8a: White
25
syrup; ½aꢁD +13.8 (c 1.5, CHCl3); 1H NMR (300 MHz,
CDCl3); d 6.30 (s, 1H), 5.86 (s, 1H), 4.62 (d, 1H,
J = 9.6 Hz), 4.26–4.18 (m, 2H), 4.11–3.99 (m, 3H), 3.96–
3.90 (m, 2H), 2.89 (d, 1H, J = 9.4 Hz), 1.43–1.40 (m, 15H).
13C NMR (100 MHz, CDCl3); d 166.1, 140.3, 125.9, 109.7,
81.4, 77.4, 76.9, 69.2, 67.5, 60.7, 27.1, 26.8, 26.5, 26.4, 25.2,
14.0. IR (thin film) 3473, 2987, 2934, 1716, 1631,
1376 cmꢀ1; ESIMS; 331 (M++1) 353 (M+Na)+. Anal.
Calcd for C16H26O7: C, 58.17; H, 7.93. Found: C, 58.19;
Acknowledgements
The authors (P.V.N.R., A.S. and M.U.K.) thank CSIR,
New Delhi for financial assistance in the form of fellow-
ships. Financial assistance from the Department of Sci-
ence and Technology, New Delhi, India is gratefully
acknowledged.
25
H, 7.88. Compound 8b: White syrup; ½aꢁD +63.3 (c 1.5,
CHCl3); 1H NMR (300 MHz, CDCl3); d 6.26 (s, 1H), 5.91
(s, 1H), 4.55 (dd, 1H, J = 3.0, 6.0 Hz), 4.22 (q, 2H,
J = 7.55 Hz), 4.14–4.06 (m, 1H), 4.01–3.87 (m, 2H), 3.79
(dd, 1H, J = 6.7, 8.3 Hz), 3.45 (d, 1H, J = 3.0 Hz), 1.38–
1.30 (m, 15H). 13C NMR (100 MHz, CDCl3); d 166.2,
139.4, 126.2, 109.9, 82.2, 79.5, 75.7, 68.2, 67.6, 60.6, 58.3,
28.3, 26.8, 26.1, 25.1, 14.0. IR (thin film) 3477, 2929, 2910,
References and notes
1. (a) Secrist, J. A., III; Barnes, K. D.; Wu, S.-R. In Trends in
Synthetic Carbohydrate Chemistry; Horton, D., Hawkins,
L. D., McGarvey, G. J., Eds.; ACS Symposium Series 386;
American Chemical Society: Washington, DC, 1989; p 93;
(b) Danishefsky, S. J.; DeNinno, M. P. Angew. Chem., Int.
Ed. Engl. 1987, 26, 15–23; (c) Lundt, I. Top. Curr. Chem.
1997, 187, 117; (d) Casiraghi, G.; Zanardi, F.; Rassu, G.;
Spanu, P. Chem. Rev. 1995, 95, 1677–1716; (e) Fleet, G.
W. J. In Antibiotics and Antiviral Compounds—Chemical
Synthesis and Modification; Krohn, K., Kirst, H. A.,
Maag, H., Eds.; VCH: Weinheim, 1993; p 333; (f)
Hanessian, S. Total Synthesis of Natural Products: The
‘Chiron’ Approach; Pergamon Press: Oxford, 1983.
1730, 1216, 1067 cmꢀ1
;
ESIMS; 331 (M++1) 353
(M+Na)+. Anal. Calcd for C16H26O7: C, 58.17; H, 7.93.
Found: C, 58.21; H, 7.90. Compound 1a: White syrup;
25
½aꢁD +45.7 (c 0.25, CHCl3); 1H NMR (200 MHz, CDCl3);
d 5.13–5.00 (2d, 2H, J = 9.4 Hz each), 4.37–4.20 (m, 2H),
4.15–4.09 (m, 2H), 4.03–3.91 (m, 3H), 1.41–1.25 (m, 15H).
13C NMR (100 MHz, CDCl3); d 165.7, 152.3, 110.8, 109.9,
77.6, 77.2, 75.6, 73.9, 67.9, 62.1, 27.2, 26.9, 26.2, 25.3, 14.1.
IR (thin film) 2986, 2931, 1800, 1760, 1376, cmꢀ1; ESIMS;
361 (M++1) 378 (M+NH4)+. Anal. Calcd for C16H24O9:
C, 53.33; H, 6.71. Found: C, 53.00; H, 6.80. Compound
´
´
2. Gyo¨rgydeak, Z.; Pelyvas, I. F. Monosaccharide Sugars–
Chemical Synthesis by Chain Elongation. In Degradation
and Epimerization; Academic Press: San Diego, 1998.
3. (a) Dromowicz, M.; Ko¨ll, P. Carbohydr. Res. 1998, 308,
169; (b) Bell, A. A.; Nash, R. J.; Fleet, G. W. J.
Tetrahedron: Asymmetry 1996, 7, 595–606; (c) Lundt, I.;
Madsen, R. Synthesis 1995, 787; (d) Sato, K.-I.; Miyata,
T.; Tanai, I.; Yonezawa, Y. Chem. Lett. 1994, 129–132.
4. Kochetkov, N. K.; Dmitriev, B. A. Tetrahedron 1965, 21,
803–815.
25
3a: White syrup; ½aꢁD +9.3 (c 0.5, CHCl3); 1H NMR
(300 MHz, CDCl3); d 5.03 (d, 1H, J = 8.0 Hz), 4.79 (dd,
1H, J = 8.0, 9.2 Hz), 4.34–4.23 (m, 3H), 4.10–4.01 (m,
2H), 4.00–3.88 (m, 2H), 1.42–1.25 (m, 15H). 13C NMR
(100 MHz, CDCl3); d 165.3, 155.2, 111.4, 110.0, 79.8, 77.1,
74.9, 66.6, 62.4, 31.9, 26.6, 27.4, 26.5, 25.1, 22.6, 13.9. IR
(thin film) 2975, 2923, 1825, 1756, 1392, cmꢀ1; ESIMS;
361 (M++1) 378 (M+NH4)+. Anal. Calcd for C16H24O9:
C, 53.33; H, 6.71. Found: C, 53.36; H, 6.68. Compound
25
4a: White syrup; ½aꢁD +23.2 (c 0.2, CHCl3); 1H NMR
5. (a) Mootoo, D. R.; Fraser-Reid, B. J. Org. Chem. 1987,
52, 4511–4517; (b) Mootoo, D. R.; Fraser-Reid, B. J. Org.
Chem. 1989, 54, 5548–5550.
(200 MHz, CDCl3); d 4.94 (d, 1H, J = 4.5 Hz), 4.86 (dd,
1H, J = 2.2, 4.5 Hz), 4.36–4.25 (m, 3H), 4.18–3.89 (m,
3H), 3.63 (t, 1H, J = 7.9 Hz), 1.43–1.25 (m, 15H). 13C
NMR (100 MHz, CDCl3); d 165.8, 153.2, 110.2, 109.9,
80.2, 77.5, 76.9, 66.9, 61.9, 31.2, 26.0, 27.8, 26.7, 25.0, 22.1,
14.1. IR (thin film) 2960, 2955, 1830, 1745, 1380, cmꢀ1
ESIMS; 361 (M++1) 378 (M+NH4)+. Anal. Calcd for
C16H24O9: C, 53.33; H, 6.71. Found: C, 53.30; H, 6.70.
6. (a) Radha Krishna, P.; Kannan, V.; Ilangovan, A.;
Sharma, G. V. M. Tetrahedron: Asymmetry 2001, 12,
829–837; (b) Radha Krishna, P.; Raja Sekhar, E.; Kan-
nan, V. Tetrahedron Lett. 2003, 44, 4973–4975; (c) Radha
Krishna, P.; Kannan, V.; Sharma, G. V. M.; Ramana
Rao, M. H. V. Synlett 2003, 888–890; (d) Radha Krishna,
P.; Kannan, V.; Sharma, G. V. M. Synth. Commun. 2004,
34, 55–64; (e) Radha Krishna, P.; Raja Sekhar, E.;
Kannan, V. Synthesis 2004, 857–860; (f) Radha Krishna,
P.; Kannan, V.; Narasimha Reddy, P. V. Adv. Synth.
Catal. 2004, 346, 603–606; (g) Radha Krishna, P.;
Narsingam, M.; Kannan, V. Tetrahedron Lett. 2004, 45,
4773–4775; (h) Radha Krishna, P.; Krishnarao, Lopinti;
Kannan, V. Tetrahedron Lett. 2004, 45, 7847–7850; (i)
Radha Krishna, P.; Rachna Sachwani; Kannan, V. Chem.
Commun. 2004, 2580–2581; (j) Radha Krishna, P.; Kan-
nan, V.; Sharma, G. V. M. J. Org. Chem. 2004, 69, 6467–
6469; (k) Radha Krishna, P.; Manjuvani, A.; Kannan, V.
Tetrahedron: Asymmetry 2005, 16, 2691–2703.
25
Compound 18a: Yellowish syrup; ½aꢁD ꢀ23.6 (c 1.5,
CHCl3); 1H NMR (300 MHz, CDCl3); d 6.40 (s, 1H),
5.88 (s, 1H), 5.77 (d, 1H, J = 5.9 Hz), 4.33–4.08 (m, 4H),
3.97–3.77 (m, 3H), 3.73 (dd, 1H, J = 2.9, 5.1 Hz), 2.08 (s,
3H), 1.42–1.25 (m, 15H), 0.90 (s, 9H), 0.11 (s, 6H). 13C
NMR (75 MHz, CDCl3); d 169.1, 165.0, 137.5, 128.1,
110.0, 108.4, 79.9, 72.6, 71.4, 66.1, 61.1, 31.8, 29.6, 29.3,
27.2, 27.1, 26.4, 26.0, 24.9, 22.6, 20.9, 18.3, 14.0. IR (thin
film) 2984, 2929, 1752, 1723, 1465, 1220 cmꢀ1; ESIMS;
517 (M++1), 534 (M+NH4)+, 539 (M+Na)+. Anal. Calcd
for C25H44O9Si: C, 58.11; H, 8.58; Si, 5.44. Found: C,
58.18; H, 8.59; Si, 5.42. Compound 18b: Yellowish syrup;
25
½aꢁD +21.0 (c 1.5, CHCl3); 1H NMR (200 MHz, CDCl3); d

6470
P. Radha Krishna et al. / Tetrahedron Letters 48 (2007) 6466–6470
6.35 (s, 1H), 5.85 (s, 1H), 5.78 (d, 1H, J = 2.3 Hz), 4.28–
(c 0.5, CHCl3); 1H NMR (300 MHz, CDCl3); d 5.06 (d, 1H
J = 8.2 Hz), 4.69 (dd, 1H, J = 8.2, 9.5 Hz), 4.31–4.19 (m,
3H), 4.12–4.06 (m, 2H), 3.96 (dd, 1H, J = 6.2, 8.2 Hz),
3.89–3.80 (m, 2H), 1.40–1.31 (m, 15H), 0.90 (s, 9H), 0.11
(s, 6H). 13C NMR (100 MHz, CDCl3); d 165.1, 152.0,
110.6, 108.8, 82.5, 78.3, 76.8, 75.2, 72.5, 72.1, 66.4, 62.3,
27.4, 26.8, 26.6, 26.1, 25.2, 18.5, 14.0. IR (thin film) 2986,
2931, 1826, 1755, 1376, 1214 cmꢀ1; ESIMS; 505 (M++1),
522 (M+NH4)+. Anal. Calcd for C23H40O10Si: C, 54.74;
H, 7.99; Si, 5.57. Found: C, 54.70; H, 8.00; Si, 5.55.
4.17 (m, 3H), 4.08 (t, 1H, J = 4.5 Hz), 3.97–3.76 (m, 4H),
2.12 (s, 3H), 1.39–1.25 (m, 15H), 0.90 (s, 9H), 0.11 (s, 6H).
13C NMR (75 MHz, CDCl3); d 169.3, 165.1, 137.4, 127.2,
109.9, 108.7, 78.9, 77.5, 72.9, 70.2, 66.2, 61.1, 29.8, 27.4,
26.9, 26.5, 26.0, 25.1, 22.8, 21.0, 18.5, 14.2. IR (thin film)
2972, 2936, 1758, 1742, 1470, 1155 cmꢀ1; ESIMS; 517
(M++1), 534 (M+NH4)+, 539 (M+Na)+. Anal. Calcd for
C25H44O9Si: C, 58.11; H, 8.58; Si, 5.44. Found: C, 58.09;
25
H, 8.60; Si, 5.45. Compound 9a: White syrup; ½aꢁD ꢀ11.1