Synthesis of a (2R,6R)-2-(hydroxymethyl)-6-propa-1,2-dienyl-2H-pyran-3(6H)-one derivative, a new enone for the convergent construction of C-glycosides of C-disaccharides

Article abstract of DOI:10.1055/s-2001-9699

The previously unknown (2R,6R)-2[(tert-butyl)diphenylsilyloxy]-6-propa-1,2-dienyl-2H-pyran-3(6H)-one (16) was derived from tri-O-acetylglucal. Conjugate addition of PhSAlMe₂ to 16 followed by enolate trapping with 1,2-O-isopropylidene-3-O-methyl-α-D-xylo-pentodialdo-1,4-furanose and NaBH₄ reduction of the intermediate aldol furnished a new C-glycoside of a C-disaccharide: 4,8-anhydro-9-O-[(tert-butyl)diphenylsilyl]-6-[(5R)-1,2-O-isopropylidene-3-O- methyl-α-D-xylo-furanos-5-C-yl]-5-S-phenyl-1,2,3,6-tetradeoxy-5-thio-D- glycero-L-gulo-nona-1,2-dienitol (24). Similarly, conjugate addition of PhMe₂SiZnMe₂Li to 16, followed by cross-aldol reaction with 2,6-anhydro-1,3,4,5-tetra-O-[(tert-butyl)dimethylsilyl]-D-glycero-L-manno-hep tose (27), and reduction gave either 4,8-anhydro-6-{(1S)-2,6-anhydro-3,4,5,7-tetra-O-[(tert-butyl)dimethylsilyl-D- glycero-L-manno-heptitol-1-C-yl}-9-O-[tert-butyl)diphenylsilyl]-1,2,3,5,6-pen tadeoxy-5-phenyldimethylsilyl-D-glycero-D-manno-(29) or L-gulo-nona-1,2-dienitol (30).

Full text of DOI:10.1055/s-2001-9699

82
LETTER
Synthesis of a (2R,6R)-2-(Hydroxymethyl)-6-propa-1,2-dienyl-2H-pyran-
3(6H)-one Derivative, a New Enone for the Convergent Construction of
C-Glycosides of C-Disaccharides
Yao-Hua Zhu, Pierre Vogel*
Section de Chimie de l'Université, BCH, CH-1015 Lausanne-Dorigny, Switzerland
Fax +41 21 692 39 75; E-mail: pierre.vogel@ico.unil.ch
Received 22 September 2000
O
O
Abstract:
The
previously
unknown
(2R,6R)-2[(tert-
butyl)diphenylsilyloxy]-6-propa-1,2-dienyl-2H-pyran-3(6H)-one
(16) was derived from tri-O-acetylglucal. Conjugate addition of
PhSAlMe2 to 16 followed by enolate trapping with 1,2-O-isopropy-
lidene-3-O-methyl-a-D-xylo-pentodialdo-1,4-furanose and NaBH4
reduction of the intermediate aldol furnished a new C-glycoside of
a C-disaccharide: 4,8-anhydro-9-O-[(tert-butyl)diphenylsilyl]-6-
[(5R)-1,2-O-isopropylidene-3-O-methyl-a-D-xylo-furanos-5-C-yl]-
5-S-phenyl-1,2,3,6-tetradeoxy-5-thio-D-glycero-L-gulo-nona-1,2-
dienitol (24). Similarly, conjugate addition of PhMe2SiZnMe2Li to
16, followed by cross-aldol reaction with 2,6-anhydro-1,3,4,5-tetra-
O-[(tert-butyl)dimethylsilyl]-D-glycero-L-manno-heptose (27), and
reduction gave either 4,8-anhydro-6-{(1S)-2,6-anhydro-3,4,5,7-tet-
ra-O-[(tert-butyl)dimethylsilyl-D-glycero-L-manno-heptitol-1-C-
yl}-9-O-[tert-butyl)diphenylsilyl]-1,2,3,5,6-pentadeoxy-5-phe-
nyldimethylsilyl-D-glycero-D-manno-(29) or L-gulo-nona-1,2-di-
enitol (30).
O
O
O
O
1
2
Nu-M+
O
Nu-M+
O
O
O
MO
OM
Nu
Nu
3
4
CHO
H
Z
5 (R-CHO)
Z = O, NBoc
O
O
Key words: aldol reaction, carbohydrate-derived enone, conjugate
addition, C-disaccharides, C-glycosides, glycal, C-silyl substituted
carbohydrate
O
O
H
HO
R
OH
H
O
Nu
O
Nu
R
6
7
Because of their bicyclic structure levoglucosenone (1)1
and isolevoglucosenone (2)2 are attractive templates for
the convergent and stereoselective construction of disac-
charide mimetics,3 including C-disaccharides.4-8 For in-
stance, the conjugate addition of a nucleophile Nu-M+ to
enones 1 and 2 occurs on their less sterically hindered
face9 leading to enolate intermediates 3 and 4, respective-
ly. These species can add to sugar-derived carbaldehydes
of type 5 to generate aldols 610 and 7,5,8 respectively, that
are precursors of C(1Æ3)-disaccharides (Scheme 1). Al-
ternatively, enolates 3 and 4 can be trapped as their triflu-
oromethanesulfonates 8 and 9, respectively that undergo
Nozaki-Kishi couplings6 with aldehydes 5 giving adducts
10 and 11 that can be transformed into the corresponding
C(1Æ2) and C(1Æ4)-disaccharides, respectively
(Scheme 2).7
C(1→3)disaccharides
Scheme 1
O
O
3
4
O
O
TfO
OTf
Nu
Nu
8
9
CrCl2, NiCl2
CrCl2, NiCl2
+ RCHO O2))), 25 °C
DMF
+ RCHO O2))), 25 °C
DMF
O
O
O
During the development of this chemistry we encountered
some difficulties in the conversion of 1,6-anhydropyra-
nose moieties into the corresponding C-pyranosides. To
circumvent this problem, we proposed the substitution of
templates 1 and 2 by monocyclic enones. We set out to
synthesize enone 16 and explore its potential as a precur-
sor to C-disaccharides.11,12 We view the allenyl group as a
masked carbaldehyde, which opens up the possibility of
an iterative method for the assembly of oligomers contain-
ing C-glycosidic linkages.
O
OH
HO
Nu
Nu
R
R
10
11
C(1→2)disaccharides
C(1→4)disaccharides
Scheme 2
Synlett 2001, No. 1, 82–86 ISSN 0936-5214 © Thieme Stuttgart · New York

LETTER
Synthesis of a (2R,6R)-2-(Hydroxymethyl)-6-propa-1,2-dienyl-2H-pyran-3(6H)-one Derivative
83
n-hexanal to give a 1:1 mixture of aldols 20a and 20b
(Oshima’s reaction,20 Scheme 4) in 50-60% yield. Trap-
ping enolate 19 with aldehyde 21 led to a mixture of aldols
22 and 23 that were separated by column chromatography
on silica gel and isolated in 15% and 29% yield, respec-
tively (Scheme 5). Reduction of the major aldol 23 with
NaBH4 in MeOH/THF was highly stereoselective and
provided the C-disaccharide 24 in 77% yield.21
H
6
OAc
H
OR1
O
SiMe3
5
H
O
OAc
1
4
H
Me3SiOSO2CF3
MeCN, 0oC
AcO
R2O
13 R1 = R2 = Ac
14 R1 = R2 = H
15 R1 = (t-Bu)Ph2Si =
TBDPS, R2 = H
(67% from 12)
12
K2CO3, MeOH
(t-Bu)Ph2SiCl, pyr., DMAP
1'
OTBDPS
2
O
OR'
OR'
Dess-Martin
(71%)
6
1''
O
O
O
PhS
Et3N
+
4
16 + PhSH
O
O
3''
CHCl3
16
20 °C
SPh
17 (26%)
18 (55%)
Scheme 3
OR'
O
PhS
CH2Cl2
-78 C, 1 h
Me2AlO
16 + PhSAlMe2
C-Glycosidation of tri-O-acetyl glucal (12) with
allylsilane13 and trimethylsilylmethylacetylenes14 are well
known processes.15,16 We have found that the dropwise
addition of Me3SiOSO2CF3 to a 1:1.5 mixture of 12 and
propargyltrimethylsilane in CH3CN at 0 °C gives the a-C-
allenyl derivative 13. This a-C-allenation of glucal 12 was
well precedented13,15 and the outcome supported by the
absence of a NOE between the anomeric proton H-1
(dH = 4.82 ppm) and H-5 (dH = 3.78 ppm) and the observa-
tion of weak NOE's between the signals of H-1 (dH = 4.82
ppm), H-4 (dH = 5.25 ppm) and H-6 (dH = 4.16, 3.78 ppm).
Methanolysis of the acetates (MeOH, K2CO3) provided
diol 14 in 83% yield. Subsequent selective silylation of its
primary alcohol with (t-Bu)(Ph)2SiCl/pyridine/4-dimeth-
ylaminopyridine furnished 15 (64%), an unstable com-
pound that was decomposed with silica gel. Hence, the
above three successive reactions were performed without
purification providing 15 in 67% based on glucal 12.
Dess-Martin periodinane oxidation17 of 15 gave enone
1618 in 71% yield (Scheme 3).
°
19
OR'
O
+ C5H11CHO
PhS
O
-78 °C, 3 h
HO
C5H11
20a,b
Scheme 4
OR'
OR'
O
O
1. PhSAIMe2
PhS
PhS
O
O
+
16
CH2Cl2
-78 °C, 1 h
OH
O
HO
H
O
O
OMe
2. +
O
OMe
OMe
O
O
-78 °C
3 h
O
O
O
O
3. HCl/H2O
22 (15%)
23 (29%)
Our goal being to generate C-pyranosides and C-disac-
charides by conjugate additions to enone 16, we examined
first the possibility to introduce a protected hydroxy group
following the method we had used with the bicyclic
enones 1 and 2 (Scheme 1, 2). Contrary to levoglucose-
none (1)10 and isolevoglucosenone (2)5 that underwent
smooth addition of all kind of alcohols (including benzyl
alcohol) giving the corresponding b-alkoxyketones with
high exo-stereoselectivity, the treatment of monocyclic
enone 16 with benzyl alcohol (Et3N, 20 °C, no solvent)
did not lead to any detectable adduct. With sodium benzy-
late (THF, DMF, -50 to -20 °C) 16 was transformed into
an untractable mixture. Since phenylthio ethers can be
converted into ketones by oxidation first into the corre-
sponding sulfoxides, followed by Pummerer rearrange-
ments,19 we studied the conjugate additions of thiophenol
and thiophenolates to enone 16.
21
9
OR'
8
HO
7
O
NaBH4
PhS
4
R' = (t-Bu)Me2Si
23
6
MeOH/THF
2
1
3
5
5'
4'
OH
O
1'
OMe
O
3'
2'
O
24
Scheme 5
Coupling constants between vicinal protons and the 2-D-
1
NOESY H NMR spectrum of 24 established the a-con-
figuration of the C-glycoside linkage. The trans diaxial
relationship between H-4/H-5, H-5/H-6 and H-6/H-7 pro-
ton pairs was established by the vicinal coupling constants
3J(H-4,H-5) = 10.2 Hz, J(H-5,H-6) = 3J(H-6,H-7) = 9.5
3
In the presence of an excess of thiophenol and one equiv-
alent of Et3N (CHCl3, 20 °C) 16 gave a 1:2 mixture of ad-
ducts 17 and 18. With Me2AlSPh in CH2Cl2 16 (-78 °C)
generated a single aluminum enolate 19 that reacted with
Hz.
Synlett 2001, No. 1, 82–86 ISSN 0936-5214 © Thieme Stuttgart · New York

84
Y.-H. Zhu, P. Vogel
LETTER
It is well known that trialkylsilyl groups can be considered (-15 ∞C, 4 h), the resulting aldol-borate was oxidized with
as masked hydroxy groups (Tamao oxidation).22 Fleming 35% H2O2 (pH 7, phosphate buffer) giving adduct 28 iso-
and co-workers23,24 have developed efficient nucleophilic lated in 24%, together with 30% of recovered 25 (Scheme
silyl reagents for their conjugate additions to enones. 6). The retro-aldol reaction appears to be a problem during
When reacted with PhMe2SiZnMe2Li24 in THF at -78 °C the work-up of these reactions. Stereoselective reduction
30
16 gave a single adduct 25 in 87% yield. The trans relative of aldol 28 with Me4NBH(AcO)3 afforded diol 29 in
configuration of the 4-allenyl and 5-(dimethyl)phenylsilyl 59% yield.31 The D-altro-configuration of its C-pyranosyl
substituents, as well as the conformation proposed for 25 unit was established by its 1H NMR spectrum that showed
1
3
3
(Scheme 6) were given by its H NMR data (3J(Haxial- 3J(H-4, H-5) = 10.8 Hz, J(H-5, H-6) = 12.1 Hz, J(H-6,
3
5,Haxial-6) = 9.5 Hz). With the hope to equilibrate 25 H-7) = 5.0 Hz, J(H-7, H-8) = 5.2 Hz. Reduction of the
with a diastereomer we attempted a Lewis acid promoted boron-aldolate obtained from 25+27+(c-Hex)2BCl/Et3N
heterolysis of its tetrahydropyranosyl moiety. Because of with LiBH4 (-30∞C)32 provided 30 as major product the
1
the assistance by the 4-allenyl (p-conjugation) and the structure of which was given by its H NMR and 2D-
5-silyl substituent (b-silyl effect25) the O-C(4) s-bond of NOESY-1H NMR spectra (3J(H-4, H-5) = 9.2 Hz, 3J(H-5,
25 is likely to undergo SN1 heterolysis. We thus treated 25 H-6) = 12.2 Hz, 3J(H-6, H-7) = 9.2 Hz,3J(H-7, H-8) = 2.2
with BF3◊Et2O in MeCN at -30 °C. A quick reaction oc- Hz). The 1'S configuration of aldol 28 was not established
curred with b-elimination of the (dimethyl)phenylsilyl unambigously. It is proposed to be as such by analogy
group giving trienone 2626 in 59% yield (Scheme 6). The with other cross-adol reactions of boron enolates known
heterolytical process, apparently, does not allow for to adopt closed transition structures (Zimmerman-Traxler
s-bond rotations and internal return: the elimination is too model).33
easy (b-silyl electrofugal group).
The new enone template 16 has been derived readily from
tri-O-acetylglucal. Conjugate addition to 16 followed by
cross-aldol reaction with sugar-derived carbaldehydes
generate C-disaccharide precursors with high diastereose-
OR'
9
1. THF, -78
°
C
lectivity. The systems so obtained are expected to be use-
ful for the construction of C-glycosides of
C-disaccharides and of C,C-trisaccharides.
4
2
3
8
16 + PhMe2SiZnMe2Li
1
O
2. NH4Cl/H2O
SiMe2Ph
6
7
3. HCl, H2O, 20
°
C
5
O
25
BF3·Et2O/MeCN
-30
°
C
Acknowledgement
OH
OTBS
O
TBSO
TBSO
O
We thank the Swiss National Science Foundation, the Fonds Her-
bette (Lausanne) and the "Office Fédéral de l'Education et de la Sci-
ence" (COST D13/0001/99 project) for financial support. We are
grateful also to Mr. Martial Rey and Francisco Sepulveda for their
technical help.
H
(t-Bu)(Ph)2SiO
O
OTBS
27
26
OR'
O
OTBS
O
TBSO
TBSO
1. (c-Hex)2BCl
Et3N
SiMe2Ph
25
O
References and Notes
1'
H
2. + 27
(1) Levoglucosenone and Levoglucosans; Chemistry and
Applications, Witczak, Z.J., Ed., ATL Press, Inc. Science
Publishers, Mount Prospect, IL, USA, 1994; Taniguchi, T.;
Nakamura, K.; Ogasawara, K. Synlett 1996, 971.
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3783; see also: Furneaux, R.H.; Gainsford, G.J.; Shafizadeh,
F.; Stevenson, T.T. Carbohydr. Res. 1986, 146, 113.
(3) Witczak, Z.J.; Chhabra, R.; Xie, X. Carbohydr. Res. 1997,
301, 167.
OH
28
OTBS
OR'
O
9
4
2
3
8
1
X
OTBS
TBSO7'
Me4NBH(OAc)3
MeCN/AcOH
(59%)
SiMe2Ph
25
6
7
H5
5'
6'
O
Y
2'
TBSO
1'
3'
4'
OH
OTBS
29 X = H, Y = OH
30 X = OH, Y = H
LiBH4
(4) Witczak, Z.J.; Chhabra, R.; Chojnacki J. Tetrahedron Lett.
1997, 38, 2215.
28
(5) a) Zhu,Y.-H.; Vogel, P. Tetrahedron Lett. 1998, 39, 31;
b) Zhu,Y.-H.; Vogel, P. J. Org. Chem. 1999, 64, 666.
(6) Takai, K.; Tagashira, M.; Kuroda, T.; Oshima, K.; Vtimoto,
K.; Nozaki, H. J. Am. Chem. Soc. 1986, 108, 6048;
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169.
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1873.
(8) Zhu, Y.H.; Demange, R.; Vogel, P. Tetrahedron: Asymmetry
2000, 11, 263.
Scheme 6
Treatment of ketone 25 with (Me3Si)2NLi(THF,-78∞C)
gave an enolate that did not react with b-C-galactopyrano-
sylformaldehyde derivative 27.27 Zincation of the lithium
enolate of 25 with ZnCl2 followed by addition of aldehyde
27 failed to give the expected aldol. Better results were
obtained with the boron enolate28 prepared by treatment of
25 with dicyclohexylboron chloride and Et3N at -15 ∞C.29
After the addition of 27 to the boron enolate of 25
Synlett 2001, No. 1, 82–86 ISSN 0936-5214 © Thieme Stuttgart · New York

LETTER
Synthesis of a (2R,6R)-2-(Hydroxymethyl)-6-propa-1,2-dienyl-2H-pyran-3(6H)-one Derivative
85
(9) Shafizadeh, F; Furneaux, R.H.; Pang, D.; Stevenson, T.T.
Carbohydr. Res. 1982, 100, 303; Samet, A.V.; Niyazymbetov,
M.E.; Semenov, V.V.; Laikhter, A.L.; Evans, D.H. J. Org.
Chem. 1996, 61, 8786; Rao, B.; Chan, J.B.; Moskowitz, N.;
Fraser-Reid, B. Bull. Soc. Chim. Fr. 1993, 130, 428; see also:
Blake, A.J.; Cook, T.A.; Forsyth, A.C.; Gould, R.O.; Paton,
R.M. Tetrahedron 1992, 48, 8053.
1H, 3J(H-4',H-5') = 3J(H-5',OH) = 9.2 Hz,3J(H-3,H-5') = 3.5
Hz, H-5'), 4.78 (ddd, 1H, 2J = 11.1 Hz, 4J(H-3,H-1a) = 6.7 Hz,
5J(H-4,H-1a) = 2.2 Hz, H-1a), 4.73 (ddd, 1H, 2J = 11.1 Hz,
4J(H-3,H-1b) = 6.7 Hz, 5J(H-4,H-1b) = 2.2 Hz, H-1b), 4.56
(d, 1H, 3J(H-1',H-2') = 3.8 Hz, H-2'), 4.46 (dd, 1H, 3J(H-4',H-
5') = 8.9 Hz, 3J(H-3',H-4') = 3.2 Hz, H-4'), 4.36 (ddd, 1H,
3J(H-6,H-7) = 9.5 Hz, 3J(H-7,H-8) = 4.8 Hz, 4J(H-7,H-
9) = 1.6 Hz, H-7), 4.13-4.06 (m, 3H, H-4,8,9), 3.95 (d, 1H,
3J(H-3',H-4') = 3.2 Hz, H-3'), 3.83 (m, 1H, H-9), 3.52 (d, 1H,
3J(H-5',OH) = 9.2 Hz, OH), 3.46 (s, 3H, OMe), 3.45 (dd, 1H,
3J(H-4,H-5) = 10.2 Hz, 3J(H-5,H-6) = 9.5 Hz, H-5), 2.34 (td,
1H, 3J(H-5,H-6) = 3J(H-6,H-7) = 9.5 Hz, 3J(H-6,H-5') = 3.5
(10) Marquis, C. Ph.D. thesis, University of Lausanne, 1999.
(11) To our knowledge this type of nona-4,7,8-trieno-5-ulose
derivative have never been reported. Related to it, (2R,6R)-
2[dimethyl-(1,1,2-trimethylpropyl)silanoxymethyl]-6-
propyl-2H-pyran-3(6H)-one has been described recently:
Ponten, F.; Magnusson, G. J. Org. Chem. 1997, 62, 7972.
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Ireland, R.E.; Daub, J.P. J. Org. Chem. 1981, 46, 479, Ireland,
R.E.; Daub, J.P. J. Org. Chem. 1983, 48, 1303; Cheng, J.C-Y.;
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Uriel, C.; Egron, M.-J.; Santarromana, M.; Scherman, D.;
Antonakis, K.; Herscovici, J. Bioorg. Med. Chem. 1996, 4,
2081.
Hz, H-6), 1.51, 1.34 (2s, 6H, Me2Si), 1.04 (s, 9H, t-Bu); 13
C
NMR (100.6 Hz, CDCl3): dc 209.1, 171.1, 135.5, 133.8, 134.4,
132.2, 130.0, 128.6, 127.4, 111.7, 105.4, 91.1, 84.7, 80.9,
80.6, 74.3, 72.2, 70.3, 68.2, 62.3, 60.3, 58.0, 49.1, 46.5, 27.0,
26.7, 26.3, 21.0, 19.0, 14.1.
(22) Buncel, E.; Davies, A.G. J. Chem. Soc. 1958, 1550; Tamao, K,
In "Organosilicon and Bioorganosilicon Chemistry", Sakurai,
H. Ed. Ellis Horwood, Chichester, 1985, p. 231, Fleming, I.
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Chem. 1982, 239, 115; Colvin, E.W. in Comprehensive
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B.; Maiti, S.B. Carbohydr. Res. 1999, 321, 1
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Trans 1 1981, 2520; see also: Sharma, S.; Oehschlager, A.C.
Tetrahedron 1991, 47, 1177.
(24) Crump, R.A.N.C.; Fleming, I.; Urch, C.J. J.Chem. Soc. Perkin
Trans. 1 1994, 701.
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Pergamon, Elsevier Science Ltd., Oxford, U.K. 1995;
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(25) Eaborn, C.; Feichtmayr, F.; Horn, M.; Murrell, J.N. J. Org.
Chem. 1974, 77, 39; Pople, J.A.; Apeloig, Y.; Schleyer, P. v.
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Tetrahedron Lett. 1986, 42, 4211; Lambert, J.B.; Wang, G.-t.;
Teramura, D. H. J. Org. Chem. 1988, 53, 5422.
(26) Data for 26: colorless oil; 1H NMR (400MHz, CDCl3): dH
7.70-7.59 (m, 4H), 7.49-7.34 (m, 6H), 5.94 (dd, 1H, 3J(H-5,H-
6) = 15.4 Hz, 3J(H-6,H-7) = 10.2 Hz, H-6), 5.84 (dt, 1H, 3J(H-
6,H-7) = 10.2 Hz, 4J(H-7,H-9) = 6.6 Hz, H-7), 5.73 (dt, 1H,
3J(H-5,H-6) = 15.4 Hz, 3J(H-4,H-5) = 6.9 Hz, H-5), 4.93
(br.d, 2H, 4J(H-7,H-9) = 6.6 Hz, H-9), 4.27 (dt, 1H, 3J(H-
2,OH) = 6.0 Hz, 3J(H-1a,H-2) = 3J(H-1b,H-2) = 3.3 Hz, H-2),
4.03 (dd, 1H, 2J = 11.0 Hz, 3J(H-1a,H-2) = 3.3 Hz, H-1a),
3.92 (dd, 1H, 2J = 11.0 Hz, 3J(H-1b,H-2) = 3.3 Hz, H-1b),
3.65 (d, 1H, 3J(H-2,OH) = 6.0 Hz, OH), 3.43 (dd, 1H,
2J = 17.6 Hz, 3J(H-4a,H-5) = 6.9 Hz, H-4a), 3.31 (dd, 1H,
2J = 17.6 Hz, 3J(H-4b,H-5) = 6.9 Hz, H-4b), 1.05 (s, 9H, t-
Bu).
(16) See also: Toshima, K.; Ishizuka, T; Matsuo, G.; Nakata, M.
Tetrahedron Lett. 1994, 35, 5673; Hoberg J.O. Carbohydr.
Res. 1997, 300, 365.
(17) Dess, D.B.; Martin, J.C. J. Org. Chem. 1983, 48, 4155.
(18) Data for 16: colorless oil; 1H NMR (400MHz, CDCl3) dH 7.70
(m, 4H), 7.41 (m, 6H), 7.04 (dd, 1H, 3J(H-4,H-5) = 10.3 Hz,
3J(H-5,H-6) = 3.0 Hz, H-5), 6.18 (dd, 1H, 3J(H-4,H-5) = 10.3
Hz, 4J(H-4,H-6) = 1.8 Hz, H-4), 5.36 (q, 1H, 3J(H-6,H-
1") = 4J(H-1",H-3a") = 4J(H-1",H-3"b) = 6.4 Hz, H-1'), 5.46
(m, 1H, H-6), 4.94 (ddd, 1H, 2J = 11.5 Hz, 4J(H-1",H-
3"a) = 6.4 Hz, 5J(H-6,H-3"a) = 2.7 Hz, H-3"a), 4.89 (ddd, 1H,
2J = 11.5 Hz, 4J(H-1",H-3"b) = 6.4 Hz, 5J(H-6,H-3"b) = 2.7
Hz, H-3"b), 4.34 (dd, 1H, 3J(H-1'a,H-2) = 4.5 Hz, 3J(H-1'b,H-
2) = 3.0 Hz, H-2), 4.10 (dd, 1H, 2J = 11.2 Hz, 3J(H-1'a,H-
2) = 4.5 Hz, H-1'a), 4.06 (dd, 1H, 2J = 11.2 Hz, 3J(H-1'b,H-
(27) Zhu, Y-H.; Vogel, P. Synlett 2001, 79.
(28) Swiss, K.A.; Choi, W.-B.; Liotta, D.C.; Abdel-Magid, A.F.;
Maryanoff, C.A. J. Org. Chem. 1991, 56, 5978.
(29) Evans, D.A.; Ng, H.P.; Clark, J.S.; Rieger, D.L. Tetrahedron
1992, 48, 2127.
(30) Evans, D.A.; Chapman, K.T.; Carreira, E.M. J. Am. Chem.
Soc. 1988, 110, 3560.
2) = 3.0 Hz, H-1'b), 1.09 (s, 3H, Me), 1.03 (s, 6H, 2Me); 13
C
NMR (100.6 MHz, CDCl3): dC 209.1, 194.6, 135.7, 135.6,
(31) Data for 29: colorless oil; 1H NMR (400MHz, CDCl3): dH
7.75-7.65 (m, 4H), 7.59-7.53 (m, 2H), 7.40-7.28 (m, 9H), 5.31
(td, 1H, 4J(H-1a,H-3) = 4J(H-1b,H-3) = 6.6 Hz, 3J(H-3,H-
4) = 5.8 Hz, H-3), 4.83, 4.76 (2ddd, 2H, 2J = 10.6 Hz, 4J(H-
1,H-3) = 6.6 Hz, 5J(H-1,H-4) = 2.2 Hz, H-1), 4.72 (m, 1H, H-
4), 4.28 (m, 1H, H-7), 4.14 (dd, 1H, 3J(H-5',H-6') = 6.6 Hz,
3J(H-6',H-7') = 2.5 Hz, H-6'), 4.12 (dd, 1H, 3J(H-2',H-
3') = 12.4 Hz, 3J(H-3',H-4') = 9.5 Hz, H-3'), 3.94 (m, 1H, H-
5'), 3.92 (dd, 1H, 2J = 11.7 Hz, 3J(H-8,H-9a) = 7.7 Hz, H-9a),
3.82 (m, 1H, H-8), 3.81 (dd, 1H, 2J = 11.7 Hz, 3J(H-8,H-
9b) = 2.6 Hz, H-9b), 3.80 (m, 1H, H-4'), 3.71 (m, 1H, H-1'),
3.66 (d, 1H, 3J(H-2',H-3') = 12.4 Hz, H-2'), 3.65 (dd, 1H,
134.8, 129.7, 129.6, 127.7, 126.9, 88.8, 78.5, 77.7, 69.8, 64.5,
26.7, 19.2.
(19) De Lucchi, O.; Miotta, U.; Modena, G. Org. Reactions 1991,
40, 157.
(20) Itoh, A.; Ozawa, S.; Oshima, K.; Nozaki, H. Tetrahedron Lett.
1980, 21, 361; Itoh, A.; Ozawa, S.; Oshima, K.; Nozaki, H.
Bull. Chem. Soc. Jpn. 1981, 54, 274.
(21) Data for 24: colorless oil; 1H NMR (400MHz, CDCl3): dH
7.68-7.63 (m,4H), 7.51-7.37 (m, 8H), 7.26-7.20 (m, 3H), 5.81
(d, 1H, 3J(H-1',H-2') = 3.8 Hz, H-1'), 5.13 (q, 1H, 4J(H-3,H-
1a) = 4J(H-3,H-1b) = 3J (H-3,H-4) = 6.7 Hz, H-3), 4.85 (td,
Synlett 2001, No. 1, 82–86 ISSN 0936-5214 © Thieme Stuttgart · New York

86
Y.-H. Zhu, P. Vogel
LETTER
2J = 4.1 Hz, 3J(H-6’,H-7’a) = 2.5 Hz, H-7’a), 3.33 (d, 1H,
2J = 4.1 Hz, H-7’b), 1.92 (dd, 1H, 3J(H-5,H-6) = 12.1 Hz,
3J(H-6,H-7)) = 5.0 Hz, H-6), 1.68 (dd, 1H, 3J(H-5,H-6) = 12.1
Hz, 3J(H-4,H-5) = 10.6 Hz, H-5), 1.04, 0.92, 0.88, 0.83, 0.70
(5s, 45H), 0.39, 0.29, 0.08, 0.06, 0.05, 0.03, 0.00, -0.01, -0.09,
-0.10 (10s, 30H, 5 Me2Si); 13C NMR (100.6 MHz, CDCl3): dC
209.2, 138.9, 135.7, 135.6, 133.9, 129.3, 129.2, 127.7, 127.5,
94.1, 79.6, 73.7, 72.8, 72.3, 72.2, 67.1, 66.6, 66.3, 64.8, 58.6,
48.4, 26.8, 26.0, 25.9, 25.8, 25.7, 23.6, 19.3, 18.1, 18.0, 17.9,
-1.2, -1.8, -3.4, -4.4, -4.6, -4.7, -4.8, -5.1, -5.3, -5.4.
(32) Paterson, I.; Perkins, M.V. Tetrahedron Lett. 1992, 33, 801.
(33) Zimmerman, H.E.; Traxler, M.D. J. Am. Chem. Soc. 1957, 59,
1920.
Article Identifier:
1437-2096,E;2001,0,01,0082,0086,ftx,en;G20400ST.pdf
Synlett 2001, No. 1, 82–86 ISSN 0936-5214 © Thieme Stuttgart · New York