Methyl 2,3,4-Tri-O-benzyl-α-D-glucopyranosyl-derived γ-silyloxy allylic stannanes as reagents for SE2′ additions to aldehydes

Article abstract of DOI:10.1021/jo9601627

The methyl α-D-glucopyranoside allylic stannanes 3.1 and 3.2 were prepared from the 3-(5-pyranosyl)-2-propenal 2.1 and the cuprate Bu₃Sn(Bu)CuCNLi₂, followed by trapping of the derived enolate with TBSCl. The major stannane, 3.1, underwent BF₃-promoted addition to 2-nonynal to afford a single syn adduct 4.1 in 70-90% yield. The minor stannane, 3.2, gave rise to a 70:30 mixture of adduct 4.1 and the diastereomeric syn adduct 5.1 under these conditions. The stereochemistry of the adduct 4.1 was proven by degradation of the bis-TES derivative 4.2 to aldehyde 4.3, prepared independently from the (R,Z)-γ-OTBS crotyl stannane 4.4 and 2-nonynal along similar lines. Analogous degradation of the adducts 4.1 and 5.1 led to a ca. 65:35 mixture of aldehydes 4.3 and its enantiomer. Accordingly, it can be surmised that the addition of stannane 3.2 to 2-nonynal takes place mainly by a syn S_E2′ pathway. BF₃-promoted additions to enal 6.1 proceeded as expected. Stannane 3.1 afforded the syn adduct 6.2 in 87-97% yield, and stannane 3.2 gave rise to a 9:1 mixture of syn and anti adducts 7.1 and 7.4 in 70-80% yield.

Full text of DOI:10.1021/jo9601627

J . Org. Chem. 1996, 61, 4611-4616
4611
Meth yl 2,3,4-Tr i-O-ben zyl-r-D-glu cop yr a n osyl-Der ived γ-Silyloxy
Allylic Sta n n a n es a s Rea gen ts for SE2′ Ad d ition s to Ald eh yd es†
J ames A. Marshall* and L. Michelle Elliott
Department of Chemistry, University of Virginia, Charlottesville, Virginia 22901
Received J anuary 24, 1996X
The methyl R-D-glucopyranoside allylic stannanes 3.1 and 3.2 were prepared from the 3-(5-
pyranosyl)-2-propenal 2.1 and the cuprate Bu3Sn(Bu)CuCNLi2, followed by trapping of the derived
enolate with TBSCl. The major stannane, 3.1, underwent BF3-promoted addition to 2-nonynal to
afford a single syn adduct 4.1 in 70-90% yield. The minor stannane, 3.2, gave rise to a 70:30
mixture of adduct 4.1 and the diastereomeric syn adduct 5.1 under these conditions. The
stereochemistry of the adduct 4.1 was proven by degradation of the bis-TBS derivative 4.2 to
aldehyde 4.3, prepared independently from the (R,Z)-γ-OTBS crotyl stannane 4.4 and 2-nonynal
along similar lines. Analogous degradation of the adducts 4.1 and 5.1 led to a ca. 65:35 mixture
of aldehydes 4.3 and its enantiomer. Accordingly, it can be surmised that the addition of stannane
3.2 to 2-nonynal takes place mainly by a syn SE2′ pathway. BF3-promoted additions to enal 6.1
proceeded as expected. Stannane 3.1 afforded the syn adduct 6.2 in 87-97% yield, and stannane
3.2 gave rise to a 9:1 mixture of syn and anti adducts 7.1 and 7.4 in 70-80% yield.
In the past several years we have developed a synthetic
approach to carbohydrates through additions of nonra-
cemic γ-alkoxy and silyloxy allylic stannanes, and related
metallo species, to aldehydes.1 The approach has proven
successful for differentially protected precursors of the
diastereomeric hexoses as well as higher sugars, such as
lincosamine and destomic acid.2 Studies to date have
employed relatively simple stannanes derived from cro-
tonaldehyde. It was of interest to investigate the syn-
thesis and use of more complex γ-alkoxyallylic stannanes
as possible reagents for the preparation of higher carbo-
hydrates and C-disaccharides.3
Several years ago J arosz and Fraser-Reid described the
preparation of stannane 1.5 from the protected glucose
derivative 1.1 (eq 1).4 Attempts to effect addition to 3-O-
benzyl-1,2-O-isopropylidene-R-D-xylo-pentadialdo-1,4-fura-
nose (glyCHO), in the presence of ZnCl2, led to 1,4-
elimination affording diene 1.7 as the only product.
When TiCl4 was employed as the Lewis acid promoter,
the adduct 1.6 was secured in 55% yield as a ca. 80:20
mixture of anti and syn diastereomers.
For the present studies we employed enal 2.1, obtained
from allylic alcohol 1.3 by Swern oxidation, as the
stannane precursor. It was our intent to prepare the
diastereomeric γ-silyloxy allylic stannanes 2.6, in the
usual way, through addition of Bu3SnLi to enal 2.1
followed by in situ oxidation to the acylstannane 2.3 then
reduction with (S)- or (R)-BINAL-H and silylation of the
resulting (R)- or (S)-R-hydroxy stannane 2.4. Subsequent
1,3-isomerization with one of several possible Lewis acids
Enal 2.1 proved surprisingly unreactive toward Bu3SnLi
under the usual conditions. Only traces of adducts 2.2
could be isolated along with considerable unreacted enal.
Attempts to facilitate the addition through use of the
cerium reagent and through alternative methodology for
preparation of the Bu3SnLi reagent were unsuccessful.
We therefore explored an alternative route involving 1,4-
addition of Bu3Sn(Bu)CuCNLi2 to enal 2.1 followed by
trapping of the derived enolate with TBSCl.5 This
approach proved successful. The silyloxy stannanes 3.1
and 3.2 were obtained as a separable 2.5:1 mixture in
up to 80% yield.
would afford the (Z)-γ-silyloxy allylic stannanes 2.6.1
† Dedicated to Clayton H. Heathcock on the occasion of his 60th
birthday.
X Abstract published in Advance ACS Abstracts, J une 1, 1996.
(1) For recent reviews, see (a) Marshall, J . A. Chemtracts-Org. Chem.
1992, 5, 75. (b) Marshall, J . A. Chem. Rev. 1996, 96, 31.
(2) (a) Marshall, J . A.; Beaudoin, S.; Lewinski, K. J . Org. Chem.
1993, 58, 5876. (b) Marshall, J . A.; Seletsky, B. M.; Luke G. P. J . Org.
Chem. 1994, 59, 3413. (c) Marshall, J . A.; Beaudoin, S. J . Org. Chem.
1994, 59, 6614. (d) Marshall, J . A.; Hinkle, K. W. J . Org. Chem. 1996,
61, 105. (e) Marshall, J . A.; Beaudoin, S. J . Org. Chem. 1996, 61, 581.
(3) For possible applications, see Armstrong, R. W.; Sutherlin, D.
P. Tetrahedron Lett. 1994, 35, 7743.
(4) J arosz, S.; Fraser-Reid, B. J . Org. Chem. 1989, 54, 4011. For a
related approach to disaccharides, see Roush, W. R.; VanNieuwenhze,
M. S. J . Am. Chem. Soc. 1994, 116, 8536.
(5) Marshall, J . A.; Welmaker, G. S. J . Org. Chem. 1992, 57, 7158.
S0022-3263(96)00162-4 CCC: $12.00 © 1996 American Chemical Society

4612 J . Org. Chem., Vol. 61, No. 14, 1996
Marshall and Elliott
expected from past experience.9 The optical rotation of
the derived aldehyde 4.3, [R]D 5.9, is in close agreement
with that expected from a 65:35 mixture of (R,S) and
(S,R) enantiomers based on the value measured for 4.3
([R]D 18.9) secured from adduct 4.1 (see eq 4).
Unexpectedly, these stannanes failed to react with
crotonaldehyde and related conjugate aldehydes under
our standard conditions with BF3‚OEt2 as the promoter.1
In all cases the stannanes were recovered unchanged.
Attempts to effect MgBr2-promoted addition to 2-(ben-
zyloxy)propanal were also unsuccessful.6 In that case, a
small amount of elimination product (see eq 1) was
isolated along with recovered stannane.
Success was finally realized with a more reactive
aldehyde, 2-nonynal. Addition of stannane 3.17 led to a
single product in up to 90% yield. Retrospectively7 we
would expect stannane 3.1 to afford the (S,S)-adduct 4.1
based on transition state considerations.1 Confirmation
of this expectation was secured through a two-step
oxidative cleavage of the double bond of the bis-TBS ether
4.2 to give aldehyde 4.3. An authentic sample of this
aldehyde was prepared by a parallel cleavage of the bis-
TBS ether 4.6, derived from the adduct 4.5 of stannane
4.4 and 2-nonynal (eq 4).8
As added support for the foregoing conclusion, we
1
compared the H NMR spectrum of an authentic sample
of the anti-bis-OTBS aldehyde 5.3 with that of 4.3.9,10 As
expected, the two spectra were clearly different.
On the basis of exclusive formation of adduct 4.1 from
stannane 3.1 and 2-nonynal and mechanistic consider-
ations,1 we can assign the (R) configuration to the allylic
stereocenter of 3.1. However, the anomalous behavior
of stannane 3.2 weakens the arguments for this assign-
ment. For this reason, and as a prelude to synthetic
applications in the higher sugar and C-disaccharide
areas, we examined additions to aldehyde 6.1, prepared
by selective ozonolysis of ethyl sorbate.11
The addition of stannane 3.1 proceeded smoothly under
the usual BF3 conditions affording a single adduct 6.2 in
high yield. Evidence for the expected (S) configuration
at the carbinyl stereocenter was secured through 1H
NMR analysis of the (R)- and (S)-O-methyl mandelates
6.3 and 6.4.12 The vinylic protons, especially Ha, showed
the expected shielding in the (R)-mandelate 6.3 (eq 6).
Addition of stannane 3.2 to 2-nonynal proceeded more
rapidly than that of 3.1 under comparable conditions. The
product, obtained in 70-80% yield, consisted of a 70:30
mixture, presumably stereoisomers, according to analysis
1
of the H and 13C NMR spectra. Remarkably, the major
isomer showed spectral characteristics identical to those
of 4.1, the adduct of stannane 3.1 and 2-nonynal! The
derived mixture of bis-TBS ethers likewise displayed the
predominant spectral characteristics of 4.2 derived from
stannane 3.1. Oxidative cleavage of this mixture, as
before, afforded what appeared to be a single aldehyde
according to NMR analysis. Futhermore, the spectra
were identical to those of aldehyde 4.3. Thus the addition
of stannane 3.2 to 2-nonynal would appear to have
produced the diastereomeric syn adducts 4.1 and 5.1
rather than a syn:anti mixture as might have been
(6) Marshall, J . A; J ablonowski, J . A.; Luke, G. P. J . Org. Chem.
1994, 59, 7825.
(7) At this point the configuration was not known. For clarity of the
discussion we will show the configurations that were later proved.
(8) The configuration of the analogous 2-heptynal adduct has been
shown to be (S,S).5
(9) To achieve economy of the space the adducts are shown in a
hairpin projection rather than the usual zig-zag arrangement. It is
the latter form from which the terms “syn” and “anti” are derived. We
apologize for any confusion resulting from this presentation.
(10) Marshall, J . A.; Hinkle, K. W. J . Org. Chem. 1995, 60, 1920.
We are indebted to Albert Garofalo for a sample of this material.

Methyl R-D-Glucopyranosyl Allylic Stannanes
J . Org. Chem., Vol. 61, No. 14, 1996 4613
Stannane 3.2 afforded an 85:15 mixture of two adducts
upon addition to aldehyde 6.1. These were identified as
syn/ anti diastereomers through oxidation to a single
ketone 7.5.13 This ketone showed distinct spectral dif-
ferences from its epimer 7.6, secured through oxidation
of alcohol 6.2. The expected (R) configuration at the
carbinyl center was confirmed by analysis of the O-
methyl mandelates 7.2 and 7.3. In this case the vinylic
proton Ha of the (S)-mandelate 7.3 was profoundly
shielded (eq 7).
F igu r e 1. Yamamoto transition states leading to syn adducts.
Nonetheless, given the intrinsically lower reactivity of
γ-oxygenated allylic stannanes compared to their non-
oxygenated counterparts,18 and in consideration of previ-
ous results (eq 1),4 it is remarkable that the stereochem-
ically homogeneous adducts 4.1 and 6.2 can be obtained
in 90% or higher yield. The latter adducts, and appropri-
ate analogues of the former, represent potentially useful
precursors of complex unnatural higher sugars and
C-disaccharides.19
Exp er im en ta l Section 20
En a l 2.1. To a stirring solution of 2.8 mL (32 mmol) of
oxalyl chloride in 100 mL of dry CH2Cl2 cooled to -78 °C was
added 3.0 mL (43 mmol) of DMSO. The mixture was stirred
at -78 °C for 20 min, and a solution of 10.4 g (21.3 mmol) of
allylic alcohol 1.34 in 25 mL of dry CH2Cl2 was slowly added.
The reaction mixture was stirred at -78 °C for 30 min, and
then 12.0 mL (85.1 mmol) of Et3N was added. The mixture
was warmed to 0 °C for 20 min, and then diluted with Et2O
and washed with 10% HCl, saturated aqueous NaHCO3, and
brine. The organic extract was dried over MgSO4, filtered, and
concentrated under reduced pressure to afford 10.7 g of a thick
yellow syrup. Chromatography on silica gel with 20% EtOAc-
hexanes as the eluant afforded 8.99 g (86%) of aldehyde 2.1
as a cloudy, colorless syrup. [R]D 112.7 (c 2.3, THF). 1H-NMR
(CDCl3, 400 MHz) δ 9.33(d, J ) 8.0 Hz, 1H), 7.34-7.26(m,
15H), 6.65(dd, J ) 15.8, 4.1 Hz, 1H), 6.28(m, 1H), 4.98, 4.83-
(ABq, J AB ) 10.9 Hz, 2H), 4.87, 4.54(ABq, J AB ) 11.3 Hz, 2H),
4.80, 4.66(ABq, J AB ) 12.6 Hz, 2H), 4.60(d, J ) 3.6 Hz, 1H),
4.31(m, 1H), 4.03(dd(apparent t), J ) 9.2 Hz, 1H), 3.51(dd, J
) 9.7, 3.6 Hz, 1H), 3.34(s, 3H), 3.25(dd(apparent t), J ) 9.5
Hz, 1H). 13C-NMR (CDCl3, 75 MHz) δ 193.1, 152.3, 138.4,
137.8, 137.4, 131.7, 128.5, 128.4, 128.3, 128.2, 128.1, 128.0,
127.9, 127.6, 98.1, 82.0, 80.8, 79.7, 75.9, 75.3, 73.5, 69.0, 55.5.
IR(neat) 3085, 3029, 2907, 2730, 1952, 1874, 1811, 1692, 1495,
1452, 1097.
Meth yl 2,3,4-Tr i-O-ben zyl-6-d eoxy-6-(tr i-n -bu tylsta n -
n yl)-6-[(E)-2-(ter t- bu tyld im eth ylsilyloxy)vin yl]-r-D-glu -
cop yr a n osid e (3.1 a n d 3.2). To a stirred suspension of 1.75
g (19.6 mmol) of CuCN in 100 mL of dry THF cooled to -78
°C was added 15.0 mL (38.9 mmol) of 2.59 M n-BuLi in
hexanes. The reaction mixture was warmed slightly until a
faint yellow color appeared and the suspension dissolved. The
mixture was again cooled to -78 °C, and 10.4 mL (38.6 mmol)
of Bu3SnH was added. The resulting bright yellow solution
was stirred at -78 °C for 25 min. A solution of 8.58 g (17.6
mmol) of conjugated aldehyde 2.1 in 50 mL of dry THF was
slowly added, and the mixture was stirred for 30 min before
10.6 g (70.2 mmol) of TBSCl was added. After stirring at -78
°C for 30 min, the reaction mixture was quenched and diluted
Aldehyde 6.1 thus displays typical matched-mis-
matched characteristics with stannanes 3.1 and 3.2. In
view of previous findings with (E)-γ-silyloxy allylic stan-
nanes,5,14 it seems safe to assume that adducts 6.2 and
7.1 are syn diastereomers.9
The unprecedented BF3-promoted syn SE2′ addition of
stannane 3.2 to 2-nonynal15 as a major reaction pathway
is not readily explained. Assuming Yamamoto acyclic
transition states, as depicted in Figure 1,16 it is unclear
why the arrangement represented by C should not be
preferred for this addition, particularly since A ad-
equately accounts for the exclusive formation of adducts
4.1 and 6.2 from stannane 3.1 and the appropriate
aldehydes. Even though the glycoside substituent of
these stannanes would appear to be relatively remote
from the reaction center, it obviously could play a role.
A priori we might expect it to influence both the preferred
orientation of the allylic stannane with respect to the
glycoside appendage (rotation about the C5/C6 bond) and
the facial approach to the π system of the stannane by
the aldehyde. The apparent preference for B over C by
2-nonynal may reflect these factors. However it is quite
surprising that enal 6.1 is not similarly influenced, as
apparently little or no product from it and stannane 3.2
is formed via B.17
(11) Veysoglu, T.; Mitscher, L. A.; Swayze, J . K. Synthesis 1980, 807.
(12) Trost, B. M.; Belletire, J . L.; Godleski, S.; McDougal, P. G.;
Balkovec, J . M.; Baldwin, J . J .; Christy, M. E.; Ponticello, G. S.; Varga,
S. L.; Springer, J . P. J . Org. Chem. 1986, 51, 2370.
(13) Dess, D. B.; Martin, J . C. J . Org. Chem. 1983, 48, 4155. Ireland,
R. E.; Liu, L. J . Org. Chem. 1993, 58, 2899.
(14) Marshall, J . A.; J ablonowski, J . A.; Elliott, L. M. J . Org. Chem.
1995, 60, 2662.
(15) Fortes, C. C.; Garrote, C. F. D. Synth. Commun. 1993, 23, 2869.
(16) Yamamoto, Y.; Yatagai, H.; Ishihara, Y.; Norihika, M.; Maruya-
ma, K. Tetrahedron 1984, 40, 2239. For a recent review, see Yamamoto,
Y.; Shida, N. Advances in Detailed Reaction Mechanisms; J AI Press:
Greenwich, CT, 1994; Vol. 3, pp 1-44.
(17) The glycoside substituent may not be the crucial factor in this
addition as we have found that the reaction of (R,E)-3-[(tri-n-butyl-
stannyl)-1-(tert-butyldimethylsilyl)oxy]-1-propene to 2-heptynal affords
the syn adduct of only 20% ee. In contrast, addition of this stannane
to (E)-2-heptenal gives the syn adduct of >95% ee.14
(18) Marshall, J . A.; J ablonowski, J . A.; Welmaker, G. S. J . Org.
Chem. 1996, 61, 2904.
(19) For a preliminary disclosure of some of these results, see ref
14.
(20) For typical experimental protocols, see Marshall, J . A.; Wang,
X-j. J . Org. Chem. 1991, 56, 960.

4614 J . Org. Chem., Vol. 61, No. 14, 1996
Marshall and Elliott
with a 1:1 solution of 3% NH4OH and saturated NH4Cl. The
mixture was warmed to ambient temperature and diluted with
Et2O, and the layers were separated. The aqueous layer was
extracted with Et2O, and the combined organic extracts were
washed with brine, dried over MgSO4, filtered, and concen-
trated under reduced pressure to afford 25.7 g of a pale yellow
oil. Chromatography on silica gel first with hexanes to remove
Bu6Sn2, then 5% EtOAc-hexanes afforded 7.99 g (51%) of
stannane 3.1 and 3.69 g (24%) of stannane 3.2 as clear,
colorless oils.
lutidine followed by 0.270 mL (1.18 mmol) of TBSOTf. The
reaction mixture was stirred for 25 min, quenched with H2O,
and extracted with Et2O. The combined organic extracts were
washed with brine, dried over MgSO4, and filtered, and the
solvent was removed by distillation under reduced pressure
to afford 0.282 g of a light yellow oil. Chromatography on silica
gel with 10% EtOAc-hexanes as the eluant afforded 0.255 g
(91%) of the TBS ether 4.2 as a pale yellow oil. [R]D 6.4 (c 2.2,
CHCl3). 1H-NMR (CDCl3, 400 MHz) δ 7.35-7.25 (m, 15H),
6.08 (dd, J ) 15.6, 4.2 Hz, 1H), 5.85 (dd, J ) 16.1, 5.2 Hz,
1H), 4.92, 4.79 (ABq, J AB ) 10.8 Hz, 2H), 4.78, 4.66 (ABq, J AB
) 12.2 Hz, 2H), 4.73, 4.67 (ABq, J AB ) 10.7 Hz, 2H), 4.60 (d,
J ) 3.6 Hz, 1H), 4.18-4.08 (m, 3H), 3.96 (dd(apparent t), J )
9.3 Hz, 1H), 3.51 (dd, J ) 9.7, 3.6 Hz, 1H), 3.35 (s, 3H), 3.23
(dd(apparent t), J ) 9.3 Hz, 1H), 2.04 (m, 2H), 1.41-1.19 (m,
11H), 0.90-0.83 (m, 18H), 0.09-0.00 (m, 12H). 13C-NMR
(CDCl3, 75 MHz) δ 138.7, 138.2, 138.2, 132.4, 128.7, 128.3,
128.2, 128.2, 127.9, 127.9, 127.9, 127.7, 127.7, 127.4, 97.8, 86.5,
82.6, 81.8, 79.9, 79.4, 76.0, 75.8, 74.9, 73.3, 70.2, 67.9, 54.9,
31.4, 28.6, 26.0, 22.6, 18.9, 18.5, 18.3, 14.2, -4.3, -4.4, -4.5,
-4.6. Anal. Calcd for C51H76O7Si2: C, 71.45; H, 8.94.
Found: C, 71.37; H, 8.99.
Sta n n a n e 3.1: [R]D -3.7 (c 1.1, CHCl3). 1H-NMR (CDCl3,
400 MHz) δ 7.29 (m, 15 H), 6.05 (d, J ) 12.0 Hz, 1H), 5.15
(dd(apparent t), J ) 12.0 Hz, 1H), 4.94, 4.75 (ABq, J AB ) 10.8
Hz, 2H), 4.88, 4.66 (ABq, J AB ) 11.6 Hz, 2H), 4.77, 4.66 (ABq,
J AB ) 12.1 Hz, 2H), 4.54 (d, J ) 3.5 Hz, 1H), 3.94 (dd(apparent
t), J ) 9.4 Hz, 1H), 3.76 (dd, J ) 9.4, 2.1 Hz, 1H), 3.53 (dd-
(apparent t), J ) 9.2 Hz, 1H), 3.44 (dd, J ) 3.5, 6.3 Hz, 1H),
3.38 (s, 3H), 2.51 (dd, J ) 9.7, 2.2 Hz, 1H). 13C-NMR (CDCl3,
125 MHz) δ 139.1, 139.0, 138.5, 138.4, 128.4, 128.4, 128.0,
127.9, 127.8, 127.5, 127.5, 127.4, 127.4, 110.3, 98.8, 82.0, 80.4,
80.0, 75.6, 74.7, 73.4, 73.3, 65.8, 56.3, 29.3, 29.2, 29.1, 27.8,
27.5, 27.2, 26.2, 25.8, 18.3, 15.3, 13.7, 10.9, 10.9, 9.4, 7.9, 7.9,
-5.0, -5.2. Anal. Calcd for C48H74O6SiSn: C, 64.50; H, 8.34.
Found: C, 64.64; H, 8.37.
The above procedure was employed with 430 mg (0.579
mmol) of adducts 4.1/5.1, from stannane 3.2, 12 mL of dry CH2-
Cl2, 0.236 mL (2.03 mmol) of 2,6-lutidine, and 0.466 mL (2.03
mmol) of TBSOTf affording the bis-TBS ethers 4.2/5.2 (418
mg) in 84% yield.
Sta n n a n e 3.2: [R]D 23.5 (c 1.4, CHCl3). 1H-NMR (CDCl3,
400 MHz) δ 7.29 (m, 15H), 6.11 (d, J ) 11.8 Hz, 1H), 5.20 (dd-
(apparent t), J ) 11.6 Hz, 1H), 4.94, 4.76 (ABq, J AB ) 11.2
Hz, 2H), 4.87, 4.61 (ABq, J AB ) 11.9 Hz, 2H), 4.76, 4.64 (ABq,
J AB ) 11.8 Hz, 2H), 4.44 (d, J ) 3.5 Hz, 1H), 3.93 (dd(apparent
t), J ) 9.3 Hz, 1H), 3.78 (dd, J ) 9.6, 2.4 Hz, 1H), 3.44 (dd, J
) 6.2, 3.6 Hz, 1H), 3.36 (s, 3H), 3.07 (dd(apparent t), J ) 9.3
Hz, 1H), 2.36 (dd, J ) 11.3, 2.4 Hz, 1H). 13C-NMR (CDCl3,
125 MHz) δ 138.9, 138.6, 138.2, 137.3, 128.4, 128.4, 128.3,
128.2, 128.1, 128.0, 127.9, 127.8, 127.6, 128.5, 113.6, 97.7, 82.6,
82.1, 80.3, 75.7, 75.1, 74.6, 73.3, 55.3, 30.5, 29.4, 29.3, 29.2,
27.8, 27.5, 27.2, 25.7, 18.3, 13.7, 11.7, 10.2, 8.7, -5.1, -5.2.
Anal. Calcd for C48H74O6SiSn: C, 64.50; H, 8.34. Found: C,
64.68; H, 8.37.
2-Non yn a l Ad d u ct 4.1 A. F r om Sta n n a n e 3.1. To a
solution of 0.017 g (0.12 mmol) of 2-nonynal15 in 1 mL of dry
CH2Cl2 cooled to -78 °C was added 0.021 mL (0.168 mmol) of
BF3‚OEt2 with stirring. After 10 min, a solution of 0.057 g
(0.063 mmol) of stannane 3.1 in 1 mL of dry CH2Cl2 was slowly
added. The reaction mixture was stirred at -78 °C for 1.5 h,
then quenched with saturated aqueous NaHCO3. The mixture
was warmed to ambient temperature and extracted with
CH2Cl2. The combined organic extracts were dried over
MgSO4, filtered, and concentrated under reduced pressure to
afford 0.068 g of a pale yellow oil. Chromatography on silica
gel with 20% EtOAc-hexanes as the eluant afforded 0.018 g
(27%) of recovered stannane and 0.027 g (77%) of the adduct
4.1 as a pale yellow syrup. [R]D 11.9 (c 4.8, CHCl3). 1H-NMR
(CDCl3, 300 MHz) δ 7.36-7.25 (m, 15H), 5.86 (m, 2H), 4.94,
4.79 (ABq, J AB ) 10.9 Hz, 2H), 4.78, 4.66 (ABq, J AB ) 12.3
Hz, 2H), 4.78, 4.61 (ABq, J AB ) 10.8 Hz, 2H), 4.58 (d, J ) 3.6
Hz, 1H), 4.12-4.05 (m, 3H), 3.97 (dd(apparent t), J ) 9.3 Hz,
1H), 3.51 (dd, J ) 9.7, 3.6 Hz, 1H), 3.34 (s, 3H), 3.21
(dd(apparent t), J ) 9.4 Hz, 1H), 2.53 (d, J ) 5.3 Hz, 1H),
2.13 (m, 2H), 1.49-1.21 (m, 11H), 0.87 (s, 9H), 0.08 (s, 3H),
0.02 (s, 3H). 13C-NMR (CDCl3, 100 MHz) δ 138.8, 138.2, 131.5,
129.8, 128.4, 128.4, 128.1, 128.0, 127.9, 127.8, 127.7, 126.6,
97.9, 86.7, 82.4, 81.9, 79.9, 78.4, 76.5, 75.8, 75.0, 73.4, 69.7,
66.5, 55.0, 31.3, 28.6, 28.5, 25.8, 22.5, 18.8, 18.2, 14.0, -4.1,
-4.8. IR (neat) 3472, 3030, 2929, 2226, 1453. Anal. Calcd
for C45H62O7Si: C, 72.72; H, 8.41. Found: C, 72.82; H, 8.42.
B. F r om Sta n n a n e 3.2. The above procedure was followed
with 0.093 g (0.67 mmol) of 2-nonynal,15 0.085 mL (0.69 mmol)
of BF3‚OEt2, and 0.474 g (0.530 mmol) of stannane 3.2.
Chromatography on silica gel with 20% EtOAc-hexanes as
the eluant afforded 0.314 g (80%) of a 70:30 mixture of adducts
4.1/5.1 as a pale yellow syrup, [R]D 12.3 (c 0.62, CHCl3).
Recovered stannanes from this and the previous experiment
were unchanged.
(+)- (2R,3S)-2,3-Bis-[(ter t-Bu tyld im eth ylsilyl)oxy-4-u n -
d ecyn a l (4.3). To a stirring solution of 0.233 g (0.272 mmol)
of olefin 4.2 (from stannane 3.1) in 7.0 mL of a 9:2:1 solution
of acetone, t-BuOH, and H2O at room temperature were added
0.166 g (1.42 mmol) of NMO and 0.495 mL (0.046 mmol) of
2.5% OsO4 in t-BuOH. The reaction mixture was stirred at
room temperature for 44 h and quenched with saturated
aqueous NaHSO3. The mixture was diluted and extracted
with EtOAc. The combined organic extracts were washed with
brine, dried over MgSO4, and filtered, and the solvent was
removed by distillation under reduced pressure to afford 0.251
g of a brown syrup. Chromatography on silica gel with 15%
EtOAc-hexanes as the eluant afforded 0.100 g (0.112 mmol,
41%) of the diol product as a pale yellow oil. This oil was
dissolved in 3.0 mL of THF and treated with 0.080 g (0.351
mmol) of H5IO6 with stirring. The reaction mixture, which
quickly formed a white precipitate, was quenched after 7 min
with H2O, diluted, and extracted with Et2O. The combined
organic extracts were dried over MgSO4, filtered, and concen-
trated under reduced pressure to afford 0.093 g of a yellow
oil. Chromatography on silica gel with 15% EtOAc-hexanes
as the eluant afforded 0.020 g (42%) of the bis-TBS aldehyde
4.3 as a clear, colorless oil. [R]D +18.9 (c 2.0, THF). 1H-NMR
(CDCl3, 300 MHz) δ 9.67 (d, J ) 1.7 Hz, 1H), 4.54 (m, 1H),
3.95 (dd, J ) 7.0, 2.1 Hz, 1H), 2.16 (m, 2H) 1.55-1.19 (m, 11H),
0.90-0.85 (m, 18H), 0.12 (s, 3H), 0.08 (s, 3H), 0.07 (s, 3H),
0.07 (s, 3H). 13C-NMR (CDCl3, 100 MHz) δ 201.7, 88.0, 80.6,
78.0, 64.9, 31.3, 29.7, 28.5, 28.3, 25.7, 22.5, 18.7, 18.3, 18.1,
14.0, -4.5, -4.8, -4.8, -4.9.
The above procedure was employed with 392 mg (0.457
mmol) of olefins 4.2/5.2 derived from stannane 3.2, 12 mL of
a 9:2:1 solution of acetone, t-BuOH, and H2O, 165 mg (1.41
mmol) of NMO, and 0.480 mL (0.045 mmol) of 2.5% OsO4 in
t-BuOH, affording 129 mg of diol in 32% yield. This oil was
treated with 0.101 g (0.444 mmol) of H5IO6 as described above,
affording 0.046 g (84%) of aldehyde 4.3 of 30% ee as a pale
yellow oil. [R]D 5.9 (c 4.6, THF).
B. F r om Ad d u ct 4.5. The above procedure was followed
with 0.249 g (0.567 mmol) of olefin 4.6, affording 0.106 g (40%)
of the tetraol as a pale yellow oil after chromatography. This
oil was treated with 0.070 g of H5IO6 as described above,
affording 0.059 g (61%) of aldehyde 4.3 as a pale yellow oil.
[R]D 18.5 (c 1.7, THF).
(E)- (4S,5S)-4-[(ter t-Bu tyldim eth ylsilyl)oxy]-2-tr idecen -
6-yn -5-ol (4.5). To a stirring solution of 0.087 g (0.63 mmol)
of 2-nonynal15 in 5.0 mL of dry CH2Cl2 cooled to -78 °C was
added 0.076 mL (0.62 mmol) of BF3‚OEt2. The reaction
mixture was stirred at -78 °C for 15 min, and then a solution
of 0.246 g (0.521 mmol) of stannane 4.45 in 4.0 mL of dry
Bis-TBS Eth er 4.2. To a stirring solution of 0.242 g (0.326
mmol) of alcohol 4.1 (from stannane 3.1) in 7.0 mL of dry
CH2Cl2 cooled to 0 °C was added 0.140 mL (1.20 mmol) of 2,6-

Methyl R-D-Glucopyranosyl Allylic Stannanes
J . Org. Chem., Vol. 61, No. 14, 1996 4615
CH2Cl2 was added. The reaction mixture was stirred at -78
°C for 5 min and then quenched with saturated aqueous
NaHCO3 and warmed to rt. The mixture was extracted with
CH2Cl2, dried over MgSO4, filtered, and concentrated under
reduced pressure to afford 0.352 g of a pale yellow oil.
Chromatography on silica gel with 5% EtOAc-hexanes as the
eluant afforded 0.137 (81%) of the alcohol 4.5 as a pale yellow
oil. [R]D 1.1 (c 1.8, CHCl3). 1H-NMR (CDCl3, 400 MHz) δ
5.72-5.64 (m, 1H), 5.48-5.42 (m, 1H), 4.09-4.05 (m, 1H), 4.01
(dd, J ) 6.5 Hz, 1H), 2.56 (d, 1H), 2.19-2.15 (m, 2H), 1.68
(dd, J ) 6.5, 1.5 Hz, 3H), 1.50-1.23 (m, 11H), 0.91-0.72 (m,
9H), 0.07 (s, 3H), 0.03 (s, 3H). 13C-NMR (CDCl3, 100 MHz) δ
130.1, 128.6, 86.2, 78.4, 76.5, 66.5, 31.1, 28.3, 27.6, 26.6, 25.6,
22.3, 18.5, 17.9, 17.5, 17.3, 13.8, 13.5, -4.3, -5.0. IR (neat)
3455, 2958, 2929, 2230, 1671. Anal. Calcd for C19H36O2Si: C,
70.31; H, 11.18. Found: C, 70.57; H, 11.19.
(E)- (4S,5S)-4,5-Bis-[(ter t-Bu t yld im et h ylsilyl)oxy]-2-
tr id ecen -6-yn e (4.6). The procedure described for TBS ether
4.2 was followed with 0.217 g (0.669 mmol) of alcohol 4.5, 0.094
mL of 2,6 lutidine, and 0.184 mL of TBSOTf to afford 0.286 g
of a pale yellow oil. Chromatography on silica gel with 10%
EtOAc-hexanes as eluant afforded 0.249 g (85%) of the TBS
ether 4.6 as a pale yellow oil. [R]D 13.2 (c 3.1, CHCl3). 1H-
NMR (CDCl3, 400 MHz) δ 5.67-5.50 (m, 2H), 4.16-4.14 (m,
1H), 3.96 (dd(apparent t), J ) 6.3 Hz, 1H), 2.17-2.13 (m, 2H),
1.68 (d, J ) 6.3 Hz, 3H), 1.53-1.23 (m, 11H), 0.90-0.84 (m,
18H), 0.10-0.00 (m, 12H). 13C-NMR (CDCl3, 100 MHz) δ
130.8, 127.7, 86.3, 79.8, 68.2, 31.6, 28.8, 28.7, 26.1, 22.8, 19.0,
18.6, 18.4, 18.0, 14.2, -4.6, -4.7, -4.8, -4.9. Anal. Calcd for
C25H50O2Si2: C, 68.42; H, 11.48. Found: C, 68.30; H, 11.47.
Ad d u ct 6.2. The procedure for the preparation of alcohol
4.1 was employed with 0.200 g (1.56 mmol) of aldehyde 6.1,11
45 mL of dry CH2Cl2, 0.575 mL (4.68 mmol) of BF3‚OEt2, and
0.927 g (1.04 mmol) of stannane 3.1, affording 0.042 g (4.5%)
of recovered stannane 3.1 and 0.553 g (73%) of adduct 6.2 as
a clear, colorless syrup. [R]D 22.5 (c 1.1, CHCl3). 1H-NMR
(CDCl3, 400 MHz) δ 7.36-7.24 (m, 15H), 6.86 (m, 1H), 6.08
(m, 1H), 5.80 (m, 2H), 4.96-4.54 (m, 7H), 4.15-4.02 (m, 3H),
3.99-3.94 (m, 1H), 3.51 (dd, J ) 9.7, 3.6 Hz, 1H), 3.34 (s, 3H),
3.21 (dd(apparent t), J ) 9.4 Hz, 1H), 2.59 (d, J ) 5.5 Hz,
1H), 2.15 (s, 3H), 1.23 (t, 3H), 0.83 (s, 9H), 0.04 (s, 3H), 0.00
(s, 3H). 13C-NMR (CDCl3, 75 MHz) δ 166.0, 146.2, 138.6, 138.1,
138.0, 130.5, 130.4, 128.3, 128.2, 128.0, 127.8, 127.6, 127.5,
127.4, 122.0, 97.9, 82.4, 81.9, 79.8, 76.2, 75.7, 75.0, 74.1, 73.4,
69.2, 60.4, 60.3, 55.0, 31.6, 25.8, 22.7, 18.2, 14.3, 14.3, 14.2,
-3.9, -4.7. IR (neat) 3479, 2927, 1718, 1656, 1452. Anal.
Calcd for C42H56O9Si: C, 68.82; H, 7.70. Found: C, 68.91; H,
7.73.
Ad d u ct 7.1. The above procedure was followed with 0.053
g (0.43 mmol) of aldehyde 6.1, 0.105 mL (0.0854 mmol) of
BF3‚OEt2, and 0.258 g (0.289 mmol) of stannane 3.2 to afford
0.123 g (70%) of the adducts 7.1/7.4 as a clear, colorless syrup
after chromatography on silica gel. [R]D 23.4 (c 2.7, CHCl3).
1H-NMR (CDCl3, 400 MHz) δ 7.36-7.26 (m, 15H), 6.87 (dd, J
) 15.7, 3.9 Hz, 1H), 6.05 (dd, J ) 15.7, 1.7 Hz, 1H), 5.81 (dd-
(apparent t), J ) 3.6 Hz, 2H), 4.84-4.56 (m, 7H), 4.17-4.03
(m, 5H), 3.98 (dd(apparent t), J ) 9.3 Hz, 1H), 3.52 (dd, J )
9.7, 3.6 Hz, 1H), 3.35 (s, 3H), 3.20 (dd(apparent t), J ) 9.3
Hz, 1H), 2.48 (d, J ) 5.5 Hz, 1H), 1.24 (t, 3H), 0.86 (s, 9H),
0.03 (s, 3H), 0.01 (s, 3H). 13C-NMR (CDCl3, 75 MHz) δ 166.0,
146.3, 138.5, 138.1, 138.0, 131.4, 130.2, 128.3, 128.3, 128.0,
127.9, 127.9, 127.8, 127.6, 127.5, 121.9, 97.9, 82.2, 81.8, 79.9,
75.9, 75.8, 74.9, 74.0, 73.4, 69.9, 60.3, 55.2, 25.9, 18.2, 14.3,
-3.9, -4.7. IR (neat) 3478, 3062, 2924, 2361, 2340, 1716, 1657,
1454. Anal. Calcd for C42H56O9Si: C, 68.82; H, 7.70. Found:
C, 68.66; H, 7.79.
(R)-Ma n d ela te 6.3. To a stirring solution of 0.051 g (0.070
mmol) of alcohol 6.2 in 1.0 mL of dry CH2Cl2 at rt was added
0.017 g (0.082 mmol) of DCC, 0.027 g (0.16 mmol) of (R)- (-)-
R-methoxyphenylacetic acid, and a catalytic amount of DMAP.
The reaction mixture was stirred at rt for 3 days, and then
hexane was added and the mixture filtered to remove the white
precipitate that formed. The filtrate was washed with 10%
HCl, saturated aqueous NaHCO3, and brine. The organic
layer was dried over MgSO4, filtered, and concentrated to
afford 0.055 g of a clear, colorless oil. Chromatography on
silica gel with 20% EtOAc-hexanes as the eluant afforded
0.045 g (74%) of the mandelate 6.3 as a clear, colorless oil.
[R]D -8.7 (c 3.5, CHCl3). 1H-NMR (CDCl3, 300 MHz) δ 7.43-
7.25 (m, 20H), 6.71 (dd, J ) 15.8, 4.6 Hz, 1H), 5.79 (m, 2H),
5.37 (m, 1H), 5.30 (dd, J ) 15.8, 1.5 Hz, 1H), 4.98-4.56 (m,
8H), 4.23 (dd(apparent t), J ) 6.0 Hz, 1H), 4.14-3.95 (m, 4H),
3.53 (dd, J ) 9.6, 3.5 Hz, 1H), 3.38 (s, 3H), 3.35 (s, 3H), 3.19
(dd(apparent t), J ) 9.4 Hz, 1H), 1.29-1.17 (m, 3H), 0.99-
0.78 (m, 9H), 0.08 (s, 3H), 0.01 (s, 3H). 13C-NMR (CDCl3, 75
MHz) δ 169.2, 165.2, 141.2, 138.6, 138.1, 135.7, 130.4, 129.5,
128.9, 128.7, 128.3, 128.2, 128.2, 128.0, 127.8, 127.5, 127.4,
127.4, 127.2, 122.5, 97.8, 82.4, 81.9, 79.8, 75.7, 75.5, 74.9, 73.4,
69.2, 60.3, 57.3, 55.0, 25.8, 18.1, 14.2, -4.3, -4.8.
(S)-Ma n d ela t e 6.4. The above procedure was employed
with 50 mg (0.068 mmol) of alcohol 6.2, 1 mL of CH2Cl2, 21
mg (0.10 mmol) of DCC, 23 mg (0.14 mmol) of (S)- (+)-R-
methoxyphenylacetic acid, and a catalytic amount of DMAP.
Chromatography on silica gel with 20% EtOAc-hexanes as
the eluant afforded 47 mg (80%) of mandelate 6.4 as a pale
yellow oil. [R]D 7.4 (c 4.9, CHCl3). 1H-NMR (CDCl3, 300 MHz)
δ 7.44-7.25 (m, 20H), 6.87 (dd, J ) 15.8, 5.0 Hz, 1H), 5.90
(dd, J ) 15.8, 1.9 Hz, 1H), 5.66-5.37 (m, 3H), 4.97-4.51 (m,
8H), 4.16-3.89 (m, 5H), 3.48 (dd, J ) 9.6, 3.5 Hz, 1H), 3.40 (s,
3H), 3.31 (s, 3H), 3.09 (dd(apparent t), J ) 9.2 Hz, 1H), 1.24
(t, J ) 7.1 Hz, 3H), 0.82 (s, 9H), -0.01 (s, 3H), -0.07 (s, 3H).
13C-NMR (CDCl3, 75 MHz) δ 169.3, 165.4, 141.6, 138.6, 138.2,
138.1, 135.8, 129.7, 129.6, 128.7, 128.6, 128.4, 128.2, 128.2,
128.0, 127.8, 127.4, 127.1, 123.1, 97.7, 82.4, 82.2, 81.9, 79.7,
75.7, 75.6, 74.7, 73.3, 72.7, 69.2, 60.5, 57.4, 55.0, 25.8, 18.1,
14.3, -4.4, -4.9.
(R)-Ma n d ela te 7.2. The above procedure was employed
with 62 mg (0.085 mmol) of alcohol 7.1, 1 mL of CH2Cl2, 27
mg (0.13 mmol) of DCC, 24 mg (0.14 mmol) of (R)- (-)-R-
methoxyphenylacetic acid, and a catalytic amount of DMAP
affording 68 mg (91%) of mandelate 7.2 as a clear, colorless
oil. [R]D 21.6 (c 5.8, CHCl3). 1H-NMR (CDCl3, 300 MHz) δ
7.41-7.24 (m, 20H), 6.90 (dd, J ) 15.8, 4.6 Hz, 1H), 5.91 (dd,
J ) 15.8, 1.5 Hz, 1H), 5.64-5.33 (m, 3H), 4.97-4.47 (m, 8H),
4.23-3.89 (m, 5H), 3.50 (dd, J ) 9.6, 3.5 Hz, 1H), 3.38 (s, 3H),
3.33 (s, 3H), 3.08 (dd(apparent t), J ) 9.4 Hz, 1H), 1.23 (t, J )
7.1 Hz, 3H), 0.85 (s, 9H), 0.02 (s, 3H), -0.03 (s, 3H). 13C-NMR
(CDCl3, 75 MHz) δ 169.4, 165.4, 141.2, 138.6, 138.1, 135.8,
129.9, 129.2, 128.8, 128.6, 128.4, 128.2, 128.0, 127.9, 127.6,
127.5, 127.2, 123.0, 97.8, 82.8, 82.3, 81.8, 79.8, 75.8, 75.4, 75.0,
73.4, 72.3, 69.6, 60.5, 57.4, 55.1, 25.8, 18.1, 14.2, -4.4, -4.9.
(S)-Ma n d ela t e 7.3. The above procedure was employed
with 60 mg (0.082 mmol) of alcohol 7.1, 1 mL of CH2Cl2, 28
mg (0.14 mmol) of DCC, 24 mg (0.14 mmol) of (S)- (+)-R-
methoxyphenylacetic acid, and a catalytic amount of DMAP
affording 66 mg (92%) of mandelate 7.3 as a clear, colorless
oil. [R]D 43.2 (c 5.9, CHCl3). 1H-NMR (CDCl3, 300 MHz) δ
7.37-7.25 (m, 20H), 6.74 (dd, J ) 16.0, 4.4 Hz, 1H), 5.93-
5.70 (m, 2H), 5.39-5.33 (m, 2H), 4.98-4.55 (m, 8H), 4.30 (dd-
(apparent t), J ) 5.4 Hz,), 4.14-3.96 (m, 5H), 3.54 (dd, J )
9.6, 3.5 Hz, 1H), 3.38 (s, 3H), 3.35 (s, 3H), 3.17 (dd(apparent
t), J ) 9.2 Hz, 1H), 1.19 (t, J ) 7.1 Hz, 3H), 0.89 (s, 9H), 0.09
(s, 3H), 0.04 (s, 3H). 13C-NMR (CDCl3, 75 MHz) δ 169.2, 165.3,
141.0, 138.6, 138.1, 138.0, 135.7, 130.1, 129.5, 128.9, 128.7,
128.6, 128.4, 128.3, 128.2, 128.0, 127.8, 127.8, 127.6, 127.5,
127.1, 122.6, 97.9, 82.8, 82.3, 81.8, 79.9, 75.8, 75.4, 75.1, 73.4,
72.7, 69.7, 60.3, 57.2, 55.1, 25.8, 18.2, 14.3, 14.1, -4.4, -4.7.
Keton e 7.6. To a stirring solution of 0.102 g (0.139 mmol)
of alcohol 6.2 in 1.2 mL of dry CH2Cl2 at rt was added 0.116
g (0.274 mmol) of Dess-Martin periodinane reagent.13 The
reaction mixture, which quickly turned a pale, milky green
color, was stirred at rt for 1 h. To this stirring mixture was
added a solution of 0.180 g (1.14 mmol) of Na2S2O3 in saturated
aqueous NaHCO3. The mixture was stirred at rt until two
clear layers were formed. The reaction mixture was diluted
with Et2O, and the layers were separated. The aqueous layer
was extracted with Et2O. The combined organic extracts were
dried over MgSO4, filtered, and concentrated under reduced
pressure to afford 0.116 g of a pale yellow oil. Chromatography
on silica gel with 20% EtOAc-hexanes as the eluant afforded
0.79 g (77%) of ketone 7.6 as a clear yellow syrup. [R]D -10.6
(c 0.46, CHCl3). 1H-NMR (CDCl3, 300 MHz) δ 7.45 (d, J )

4616 J . Org. Chem., Vol. 61, No. 14, 1996
Marshall and Elliott
15.8 Hz, 1H), 7.38-7.21 (m, 15H), 6.74 (d, J ) 16.2 Hz, 1H),
6.14-5.85 (m, 2H), 4.98-4.53 (m, 9H), 4.26-4.14 (m, 3H), 3.99
(dd(apparent t), J ) 9.2 Hz, 1H), 3.53 (dd, J ) 9.6, 3.5 Hz,
1H), 3.37 (s, 3H), 3.22 (dd(apparent t), J ) 9.4 Hz, 1H), 1.28
(t, J ) 7.1 Hz, 3H), 0.90 (s, 9H), 0.06 (s, 3H), 0.05 (s, 3H). 13C-
NMR (CDCl3, 75 MHz) δ 198.2, 165.7, 139.3, 138.7, 138.6,
135.0, 132.8, 130.9, 129.2, 129.0, 128.9, 128.8, 128.6, 128.4,
128.1, 128.1, 128.0, 98.6, 82.9, 82.3, 80.3, 79.4, 78.0, 75.5, 73.9,
70.5, 61.7, 55.8, 26.3, 18.7, 14.6, -4.2, -4.5. IR (neat) 3029,
2929, 2858, 1718, 1621, 1493, 1453.
Keton e 7.5. The above procedure was employed with 0.046
g (0.063 mmol) of alcohols 7.1/7.4, 0.057 g (0.13 mmol) of Dess-
Martin periodinane reagent,13 2.5 mL of dry CH2Cl2, and 0.070
g of Na2S2O3. Chromatography on silica gel with 20% EtOAc-
hexanes as the eluant afforded 0.038 g (83%) of ketone 7.5 as
a clear yellow syrup. [R]D +59.5 (c 3.6, CHCl3). 1H-NMR
(CDCl3, 300 MHz) δ 7.47 (d, J ) 15.8 Hz, 1H), 7.35-7.23 (m,
15H), 6.77 (d, J ) 15.8 Hz, 1H), 6.09-5.81 (m, 2H), 4.98-4.51
(m, 9H), 4.23-4.12 (m, 3H), 3.98 (dd(apparent t), J ) 9.2 Hz,
1H), 3.52 (dd, J ) 9.4, 3.7 Hz, 1H), 3.36 (s, 3H), 3.19
(dd(apparent t), J ) 9.4 Hz, 1H), 1.27 (t, J ) 7.1 Hz, 3H), 0.91
(s, 9H), 0.05 (s, 3H), 0.04 (s, 3H). 13C-NMR (CDCl3, 75 MHz)
δ 197.5, 165.0, 138.6, 138.0, 137.9, 134.4, 132.2, 132.1, 130.4,
128.7, 128.7, 128.4, 128.3, 128.0, 127.8, 127.6, 127.5, 127.3,
98.0, 82.5, 82.5, 81.6, 81.5, 79.8, 79.7, 79.1, 77.4, 77.3, 76.6,
76.5, 75.8, 75.7, 75.2, 73.4, 70.2, 61.2, 61.1, 55.3, 55.2, 25.7,
25.7, 18.2, 14.1, -4.7, -4.9.
Ack n ow led gm en t. This research was supported by
a grant from the National Institute of Allergy and
Infectious Disease (NIH 2ROI-AI31422).
Su p p or tin g In for m a tion Ava ila ble: 1H NMR spectra for
key intermediates (20 pages). This material is contained in
libraries on microfiche, immediately follows this article in the
microfilm version of the journal, and can be ordered from the
ACS; see any current masthead page for ordering information.
J O9601627