T.-P. Loh, P.-L. Lye / Tetrahedron Letters 42 (2001) 3511–3514
Table 2. Allylation reaction with four different aldehydes
3513
Aldehydea
Ratio a:b
b
Total yield (a+b%)
c
Entry
1
2
3
4
Nonyl aldehyde
Cyclohexanecarboxaldehyde
Benzaldehyde
(7a:7b) (53:47)
(8a:8b) (64:36)
(9a:9b) (35:65)
(10a:10b) (15:85)
34d
95
77
3-Methoxybenzaldehyde
60
a
All reactions were performed under neat conditions at room temperature for 3 days.
Product ratios (a:b) were determined based on isolated yields.
Overall purified yield for a and b.
b
c
d
Reaction not optimized.
1
13
Scheme 3. The H and C NMR data for compounds 6a, 11 and 1 are given in Ref. 12.
In conclusion, we have developed a short and efficient
route for the synthesis of (±)-methylenolactocin 1.
Especially noteworthy is that both the diastereomers
obtained from indium-mediated allylation of allylic
3. (a) Heathcock, C. H.; Graham, S. L.; Pirrung, M. C.;
Plavac, F.; White, C. T. In J. ApSimon: The Total
Synthesis of Natural Products, Vol. 5: The Total Synthesis
of Sesquiterpenes 1970–1979; Wiley: New York, 1983; (b)
Grieco, P. A.; Ohfune, Y.; Majetich, G. F. J. Org. Chem.
1983, 48, 360; (c) Tanaka, A.; Yamashita, K. Agric. Biol.
Chem. 1980, 44, 199 and references cited therein.
(
Z)-4a with hexanal can be converted to (±)-1 in just
five steps.
Furthermore, this method allows easy access to a wide
variety of analogues. The synthesis and biological eval-
uation of various analogues are currently in progress.
4. (a) Saicic, R. N.; Zard, S. Z. Chem. Commun. 1996, 1631;
(b) Takahata, H.; Uchida, Y.; Momose, T. J. Org. Chem.
1995, 60, 5628; (c) Vaupel, A.; Knochel, P. Tetrahedron
Lett. 1995, 26, 231; (d) Honda, T.; Kimura, N. J. Chem.
Soc., Chem. Commun. 1994, 77; (e) de Azevedo, M. B.
M.; Murta, M. M.; Greene, A. E. J. Org. Chem. 1992, 57,
Acknowledgements
4567 and references cited therein.
5. Mahato, S. B.; Siddiqui, K. I. A.; Bhattacharya, G.;
Ghosai, T. J. Nat. Prod. 1987, 50, 245.
This research was assisted financially by grants from
the National University of Singapore.
6
. (a) Paquette, L. A. In Green Chemistry, Frontiers in
Benign Chemical Syntheses and Processes; Anantas, P.;
Williamson, T. C., Eds.; Oxford University Press: New
York, 1998; (b) Li, C. J.; Chan, T. H. Tetrahedron Lett.
1999, 55, 11149; (c) Araki, S.; Shimizu, T.; Johar, P. S. J.
Org. Chem. 1991, 56, 2538; (d) Loh, T. P.; Diana, S. C.
H.; Sim, K. Y. Synlett 1996, 263; (e) Loh, T. P.; Cao, G.
Q.; Pei, J. Tetrahedron Lett. 1998, 39, 1457.
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