LETTER
One-Pot Diastereoselective Preparation of a,b-Unsaturated-g-Silylated-d-Lactones
139
Table Preparation of d-Lactones 1a-g. Diastereomeric Ratio
O
KF
O
H2, Pd/C
d.e.[%]a
R'
Yield [%]
78
Product
1
d
2
CH3
i-Pr
1ab
DMSO
C11H23
54% overall
74
8
1bb,c
79
90
O
>
>
96
96
KF, DMSO
76%
1cd
t-Bu
1e
3
9
O
C11H23
73
70
1dd
>96
>96
R
C H
5
1eb
1fb
11
HC
C
70
Scheme 5
>
96
60
1ge
>
96
In summary, this paper shows a simple and efficient gen-
eral access to diastereomerically pure a,b-unsaturated-g-
silylated-d-lactones 1. The two natural lactones 2 and 3
could be synthesized in overall yields of 70-90%. These
results also suggest that the enantiopure a,b-unsaturated-
g-silylated-d-lactones are interesting building blocks for
further 1,4-addition reactions on the a,b-unsaturated ester
moiety and electrophilic additions on the allylsilane skel-
eton.
1
a) Measured by H NMR. b) Purified as a white solid by recrystalli-
sation. c) ee = 93-99%. The enantiomeric excesses were measured
by chiral GC. They were checked to be equal to the starting vinylo-
xiranes’ees, proving that chirality is totally transferred through this
one-pot procedure. d) Purified by flash chromatography on silica
gel. e) Synthesized in a racemic form.
1
4
tuted-d-lactones 1a-g. This selectivity can be explained
1
2,13
by a Felkin model.
References and Notes
Other alkylating agents have been added to aldehydes 6.
In the case of methyllithium and methylcerium dichloride
(1) Davies-Coleman, M.T.; Rivett D.E.A. Fortschr. Chem. Org.
Naturst. 1989, 55, 1-35.
(
(
2) Ohloff, G. Fortschr. Chem. Org. Naturst. 1978, 35, 431-527.
3) Takano, S.; Kamikubo, T.; Sugihara, T.; Ogasawara, K.
Tetrahedron : Asymmetry 1992, 3, 853-856.
(
7
Scheme 4), the d-lactone 1a and the homoallylic alcohol
are isolated. The intermediate aldehyde 6 is also recov-
ered. Alcohol 7 could be conveniently cyclized to lactone
(
(
4) Grove, J. F. J. Chem. Soc. Perkin Trans. I 1985, 865-869.
5) Ley, S.V.; Armstrong, A.; Diez-Martin, D.; Ford, M.J.; Grice,
P.; Knight, J.G.; Kolb, H.C.; Madin, A.; Marby, C.A.;
Mukherjee, S.; Shaw, A.N.; Slawin, A.M.Z.; Vile, S.; White,
A.D.; Williams, D.J.; Woods, M. J. Chem. Soc. Perkin Trans.
I 1991, 667-692.
1
5
1
a by Otera’s procedure in 85% yield. Grignard reagents
led to higher yields of lactones probably due to magne-
sium-catalyzed transesterification.
Desilylation (Scheme 5) of lactones 1d and 1e was con-
ducted in dimethyl sulfoxide at room temperature with a
large excess of potassium fluoride. Lactone 1d leads to the
desilylated product 8, which was directly hydrogenated to
the pheromone 2; whereas 1e was directly transformed
into the natural product 3. Partial racemization of 1d and
(
6) Ikan, R.; Gottlieb, R.; Bergmann, E. D.; Ishay, J. J. Insect.
Physiol. 1969, 15, 1709-1712.
(7) (a) Mori, K. Agric. Biol. Chem. 1976, 40, 1617-1619
(b) Cavill, G. W. K.; Clark, D. V.; Whitfield, F. B. Aust. J.
Chem. 1968, 21, 2819-2823.
(
8) Murayama, T.; Sugiyama, T.; Yamashita, K. Agric. Biol.
Chem. 1986, 50, 2347-2351.
1
e during the desilylation process, led to less optical activ-
2
0
20
ity for 2 (aD 9.47(c 0.95, THF)) and 3 (a -28.7 (c 1.02,
CHCl )) than reported in litterature for 2 and 3. Isola-
D
(
9) (a) Kuo, Y.-H.; Shih, K.-S. Heterocycles 1990, 31, 1941-1949
1
6
17
3
(
(
b) Bacardit, R.; Moreno-Manas, M. Chem. Lett. 1982, 5-6
c) Pirkle, W. H.; Adams, P.E. J. Org. Chem. 1980, 45, 4117-
tion of the acidic form of the intermediate conjugated car-
boxylate 9 gave an explanation for the loss of
enantiomeric purity observed during the desilylation reac-
tion which is currently under study in our group.
4121 (d) Pirkle, W. H.; Adams, P.E. J. Org. Chem. 1979, 44,
2169-2175.
OH
O
1
) Pd(0)
H3C
TBDMS
+
H
+
5
1a
2) CH3M
CO2CH3
(~ 25%)
TBDMS
2
CO CH3
7
6 (~ 10%)
(~ 35%)
(
85%) 15
Scheme 4
Synlett 2001, No. 1, 138–140 ISSN 0936-5214 © Thieme Stuttgart · New York