4880
E. Quesada et al. / Tetrahedron Letters 45 (2004) 4877–4881
synthesis. Further studies towards the total synthesis of
more members of the Preussomerin family as well as
asymmetric approaches are currently under investiga-
tion and will be reported in due course.
Acknowledgeꢁents
The authors thank Professor K. Krohn (University of
Paderborn) for providing authentic comparison samples
of Preussomerins K and L. Dr. A. C. Whitwood is
acknowledged for assistance with the X-ray study.
Fꢂgꢀre 2. ORTEP drawing of compound 15 (50% probability thermal
ellipsoids).
20
References and notes
1
2
3
. For a recent review, see Krohn, K. In Progress in the
Chemistry of Organic Natural Products; Herz, W., Falk,
H., Kirby, G. W., Eds.; Springer: Wien, 2003; Vol. 85, p 1.
. (a) Bode, H. B.; Wegner, B.; Zeeck, A. J. Antibiot. 2000,
compound 18, which was easily separated and isolated
in 54% yield under the optimised conditions. Unfortu-
nately, attempted deprotection of 18 (9-I-BBN,
bromochatecolborane, etc.) resulted in extensive de-
gradation. We circumvented this limitation by using
excess boron tribromide, which provided the interme-
diate bromohydrin 19. The epoxide was regenerated by
basic treatment of 19 affording Preussomerin K 20
5
5
3, 153; (b) Bode, H. B.; Zeeck, A. Phytochemistry 2000,
5, 311.
. (a) Ohkanda, J.; Knowles, D. B.; Blaskovich, M. A.; Sebti,
S. M.; Hamilton, A. D. Curr. Top. Med. Chem. 2002, 2,
303–323; (b) Leonard, D. M. J. Med. Chem. 1997, 40,
2971.
(
Scheme 4). The data from the synthetic samples of
4. (a) Schlingmann, G.; West, R. R.; Milne, L.; Pearce, C. J.;
Carter, G. T. Tetrahedron Lett. 1993, 34, 7225; (b)
Schlingmann, G.; Matile, S.; Berova, N.; Nakanishi, K.;
Carter, G. T. Tetrahedron 1996, 52, 435.
Preussomerin K and L matched those found by analy-
sing authentic samples of the natural compounds kindly
provided by Professor K. Krohn.
5
. (a) Krohn, K.; Michel, A.; Florke, U.; Aust, H. J.;
Draeger, S.; Schulz, B. Liebigs Ann. Chem. 1994, 1099; (b)
Krohn, K.; Michel, A.; Florke, U.; Aust, H. J.; Draeger,
S.; Schulz, B. Liebigs Ann. Chem. 1994, 1093; (c) Krohn,
K.; Beckmann, K.; Florke, U.; Aust, H. J.; Draeger, S.;
Schulz, B.; Busemanna, S.; Bringmann, G. Tetrahedron
In summary, we have successfully synthesised the race-
mic natural products Preussomerin K and L (4% overall
yields in both cases) from inexpensive building blocks
through the application of a novel non-biomimetic
strategy with the functionalisation of a 2-arylacetal
anion, one-pot Friedel–Crafts cyclisation–deprotection
and reductive opening of epoxides as the key steps of the
1
997, 53, 3101.
6. McDonald, L. A.; Abbanat, D. R.; Barbieri, L. R.;
Bernan, V. S.; Discafani, C. M.; Greenstein, M.; Janota,
O
OMe
O
O
OMe
O
O
OMe
O
(
PhSe)2
O
NaBH4
0.9 equiv)
O
(
HO
O
O
O
O
+
O
O
+
14
+
15
AcOH
EtOH
(
18%) (17%)
OH
O
0 ºC to rt, 1 h
O
O
O
O
1
4
17 (11%)
18 (54%)
O
OH
O
OH
O
Br
t-BuOK
EtOH
O
BBr3
DCM
HO
1
8
O
O
O
O O
rt, 45 min
-
78 ºC
OH
OH
(50%)
then, rt
O
O
1
9
Preussomerin K 20
Scheꢁe 4. Synthesis of Preussomerin K 20.