V. K. Nyavanandi et al. / Tetrahedron Letters 47 (2006) 6667–6672
6671
Maeda, H.; Uenishi, J.-I.; Yonemitsu, O. Chem. Pharm.
Bull. 1998, 46, 1335; (h) Matsushima, T.; Horita, K.;
Nakajima, N.; Yonemitsu, O. Tetrahedron Lett. 1996, 37,
385.
At this stage the primary hydroxyl group of (ꢀ)-25 was
oxidized (TEMPO) to give the corresponding aldehyde
which was reacted with the crotyl borane reagent to
install the other two chiral centers (C-10, C-11) as
present in the target fragment 5. However, several
attempts using this reaction gave unacceptably low
yields of the expected fragment. The failure of the crotyl
boration led us to follow an alternative approach and
completion of the synthesis of fragment 5 was straight-
forward as described in Scheme 5.
5. (a) Taylor, R. E.; Hearn, B. R.; Ciavarri, J. P. Org. Lett.
2002, 4, 2953; (b) Taylor, R. E.; Ciavarri, J. P.; Hearn, B.
R. Tetrahedron Lett. 1998, 39, 9361. For the synthesis of
the myriaporones, a related class of natural products, see:
Fleming, K. N.; Taylor, R. E. Angew. Chem., Int. Ed.
2004, 43, 1728.
6. (a) Smith, A. B.; Adams, C. M.; Barbosa, S. A. L.;
Degnan, A. P. Proc. Natl. Acad. Sci. U.S.A. 2004, 101,
12042; (b) Smith, A. B.; Adams, C. M.; Barbosa, S. A. L.;
Degnan, A. P. J. Am. Chem. Soc. 2003, 125, 350; (c)
Smith, A. B.; Lodise, S. A. Org. Lett. 1999, 1, 1249.
7. (a) Jung, M. E.; Lee, C. P. Org. Lett. 2001, 3, 333; (b)
Jung, M. E.; Lee, C. P. Tetrahedron Lett. 2000, 41, 9719;
(c) Jung, M. E.; Marquez, R. Org. Lett. 2000, 2, 1669; (d)
Jung, M. E.; Marquez, R. Tetrahedron Lett. 1999, 40,
3129.
Thus, Evans aldol reaction between chiral auxiliary 8
and aldehyde 26 gave the desired adduct17 which upon
reduction with NaBH4 yielded (ꢀ)-27. The C-11 PMB
protection was carried out by cyclic acetal formation
with anisaldehyde dimethyl acetal followed by regio-
selective opening with DIBAL-H (90%, two steps)
to give (ꢀ)-28. Finally oxidation of alcohol 28 with
TEMPO followed by a Wittig reaction on the resulting
aldehyde with Ph3P = CH2 and n-BuLi in THF afforded
the target C(8)–C(17) segment 524 in 75% yield.
8. (a) Loh, T.-P.; Feng, L.-C. Tetrahedron Lett. 2001, 42,
6001; (b) Loh, T.-P.; Feng, L.-C. Tetrahedron Lett. 2001,
42, 3223.
9. (a) Julian, L. D.; Newcom, J. S.; Roush, W. R. J. Am.
Chem. Soc. 2005, 127, 6186; (b) Roush, W. R.; Newcom, J.
S. Org. Lett. 2002, 4, 4739; (c) Roush, W. R.; Lane, G. C.
Org. Lett. 1999, 1, 95.
10. Liu, J.-F.; Abiko, A.; Pei, Z. H.; Buske, D. C.; Masamune,
S. Tetrahedron Lett. 1998, 39, 1873.
11. (a) Ehrlich, G.; Kalesse, M. Synlett 2005, 655; (b)
Hassfeld, J.; Kalesse, M. Synlett 2002, 2007.
12. Iwata, Y.; Tanino, K.; Miyashita, M. Org. Lett. 2005, 7,
2341.
In summary, we have carried out a highly stereoselective
synthesis of the C(8)–C(17) segment of tedanolide where
all six stereogenic centers were generated using the
Evans chiral auxiliary in an iterative fashion. Continued
advancement of this intermediate toward tedanolide (1)
will be reported in due course.
13. The 230th ACS National Meeting, Washington, DC,
August 28–September 1, 2005.
Acknowledgements
14. (a) Hu, T.; Schaus, J. V.; Lam, K.; Palfreyman, M. G.;
Wuonola, M.; Gustafson, G.; Panek, J. S. J. Org. Chem.
1998, 63, 2401–2406; (b) Hall, D. G.; Caille, S.; Drouin,
M.; Lamothe, S.; Muller, R.; Deslongchamps, P. Synthesis
1995, 1081–1088.
We thank Dr. Reddy’s Laboratories Ltd., for support-
ing this research work.
15. Evans, D. A.; Bartroli, J.; Shih, T. L. J. Am. Chem. Soc.
1981, 103, 2127.
References and notes
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17. The other diastereomer was not observed in the crude
NMR.
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The other diastereomer was observed in the next step of
the first aldol reaction. (97.3:2.7).
1. Schmitz, F. J.; Gunasekera, S. P.; Yalamanchili, G.;
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23.
OBn
14
16
14
16
Hb
H
H
O
O
OTBS
O
O
PMP
(-) -22
H
Ha
H
OMe
Ha – Hb = 2.4 Hz
Ha – H14 = 8.8 Hz