1984
C. Song et al.
LETTER
CO2Me
The diacetonide 10 can be converted to the pentaacetate of
carba- -D-altropyranose 3 following known literature
procedures by stereoselective hydrogenation, DIBAL-H
reduction, removal of the isopropylidene group and sub-
sequent acetylation.14
CO2Me
CO2H
i, ii
iii
OH
OSO2CF3
O
O
HO
OH
O
O
OH
(−)-Shikimic acid
Following a sequence of reactions similar to that of diol 8,
the diol 9 was also transformed into carbasugar 4 in an
overall yield of 73% (Scheme 3).
6
5
CO2Me
CO2Me
OH
HO CO2Me
HO
iv
v
+
HO CO2Me
O
HO
OH
OH
OH
O
O
O
HO
O
O
O
HO
HO
O
O
O
i, ii
iii
8
9
7
O
OH
O
Scheme 1 Reagents and condtions: i, CSA, MeOH, reflux, 10 h,
96%; ii, CMe2(OMe)2, CSA, r.t., 2 h, 95%; iii, Tf2O, DMAP, pyridi-
ne, CH2Cl2, 20 ºC, 40 min, 98%; iv, CsOAc, DMF, r.t., 2 h, 81%; v,
OsO4, NMO, t-BuOH H2O (10:1), 20 ºC, 8 h, 38% for 8, 35% for 9.
9
4
13
Scheme 3 Reagents and condtions: i, CMe2(OMe)2, CSA, r.t., 10 h,
82%; ii, DIBAL–H, THF, 10 ºC, 1 h, 99%; iii, TFA-H2O (6:1), r.t.,
1 h, 90%.
Gabosine K had previously been assigned the structure 2,
which is from a family of carbasugars produced by Strep-
tomyces.22 However, the spectral properties of a racemic
2, synthesised by Metha and Lakshminath,11 were found
to be different from that of gabosine K. To investigate
this, alcohol 11 was treated with acetic anhydride in pyri-
dine to give the acetate 12 (93%), [ ]D +43.1 (c 1.16 in
CHCl3). Selective removal of the isopropylidene groups
in 12 proved to be difficult under a range of reaction con-
ditions, such as 50% aq. TFA, I2 in methanol, Amberlyst
in THF–water, which all produced a mixture of ( )-
MK7607 (1) and compound 2. It was later found that
treatment of 12 with 80% aqueous acetic acid could selec-
tively take off the isopropylidene groups to give the tetrol
2, the spectral properties of which are identical with that
of the synthesised racemate.11 Therefore, our synthesis
confirmed that gabosine K was incorrectly assigned the
structure 2.
In summary, using ( )-shikimic acid as chiral template we
have synthesised the antipode of the naturally occuring
herbicide MK 7607 and some other carbasugars. Works
are under way to further elaborate the diene 7 into other
synthetic targets.
Acknowledgement
We thank Dr Fred Huntley and Prof. Bruce Ganem (Baker Labora-
tory, Cornell University) for information of diene 7, Prof. Gover-
dhan Mehta (Indian Institute of Sciences, Bangalore) for his
comments on compound 2, and the EPSRC for access to the mass
spectrometry service at the University of Wales, Swansea (Director,
Prof. D. E. Games).
References
(1) McCasland, G. E.; Furuta, S.; Durham, L. J. J. Org. Chem.
1966, 31, 1516.
CO2Me
CO2Me
OH
OH
(2) For reviews, see: (a) Ogawa, S. J. Synth. Org. Chem., Jpn.
1985, 43, 26. (b) Suami, T. Pure Appl. Chem. 1987, 59,
1509. (c) Suami, T.; Ogawa, S. Adv. Carbohydr. Chem.
Biochem. 1990, 48, 21. (d) Suami, T. Top. Curr. Chem.
1990, 154, 257. (e) Ogawa, S. In Studies in Natural
Products Chemistry, Vol. 13; Rahman, A.-U., Ed.; Elsevier
Sciences: New York, 1993, 187.
O
O
ii
i
O
O
OH
O
O
O
O
O
O
10
8
11
(3) For reviews, see: (a) Ogawa, S. In Carbohydrates in Drug
Design; Witczak, Z. J.; Nieforth, K. A., Eds.; Marcel
Dekker: New York, 1997, 433. (b) Ogawa, S. In
Carbohydrate Mimics: Concepts and Methods; Chapleur,
Y., Ed.; Wiley-VCH: Weinheim, 1998, 87. (c) Berecibar,
A.; Grandjean, C.; Siriwardena, A. Chem. Rev. 1999, 99,
779.
(4) Miller, T. W.; Arison, B. H.; Albers-Schönberg, G.
Biotechnol. Bioeng. 1973, 15, 1075.
(5) Isogai, A.; Sakuda, S.; Nakayama, J.; Watanabe, S.; Suzuki,
S. Agric. Biol. Chem. 1987, 51, 2277.
iii
iv
OAc
OH
OAc
OH
O
OH
OH
v
O
O
HO
HO
OH
O
OH
(1)
OH
2
12
(−)-MK7607
(6) Jolad, S. D.; Hoffman, J. J.; Schram, K. H.; Cole, J. R.;
Tempesta, M. S.; Bates, R. B. J. Org. Chem. 1981, 46, 4267.
(7) Schulte, G. R.; Ganem, B.; Chantrapromma, K.; Kodpinid,
M.; Sudsuansri, K. Tetrahedron Lett. 1982, 23, 289.
Scheme 2 Reagents and condtions: i, CMe2(OMe)2, CSA, r.t., 3 h,
98%; ii, DIBAL-H, THF, 10 ºC, 1.5 h, 99%; iii, TFA–H2O (6:1), r.t.,
2 h, 92%; iv, Ac2O, DMAP, pyridine, r.t., 2.5 h, 93%; v, aq. HOAc
(80%), 60 ºC, 4.5 h, 66%.
Synlett 2001, No. 12, 1983–1985 ISSN 0936-5214 © Thieme Stuttgart · New York