centers on carbocyclic rings by intramolecular asymmetric
alkylation, and open a new approach to the macrocyclic cembrane
diterpenes.
Table 2 Intramolecular asymmetric alkylation of bromo oxazolidi-
nones 15a,b
Notes and references
1 For reviews, see: (a) D. A. Evans, in Asymmetric Synthesis, ed. J. D.
Morrison, Academic Press, New York, 1983, vol. 3, ch. 1, p. 1; (b)
K. A. Lutomski and A. I. Meyers, in Asymmetric Synthesis, ed. J. D.
Morrison, Academic Press, New York, 1983, vol. 3, ch. 3, p. 213; (c)
A. Job, C. F. Janeck, W. Bettray, R. Peters and D. Enders, Tetrahedron,
2002, 58, 2253.
Entry
R
Base
T/uC
Yield (%)
dra
2 For selected highly effective auxiliaries see: (a) J. K. Whitesell and
M. A. Whitesell, J. Org. Chem., 1977, 42, 377; (b) G. Helmchen and
R. Wierzchowski, Angew. Chem., Int. Ed. Engl., 1984, 23, 60; (c)
W. Oppolzer, P. Dudfield, T. Stevenson and T. Gobel, Helv. Chim.
Acta, 1985, 68, 212; (d) S. Ikegami, H. Uchiyama, T. Hayama,
T. Katsuki and M. Yamaguchi, Tetrahedron, 1988, 44, 5333; (e)
A. G. Meyers, B. H. Yang, H. Chen, L. Mckinstry, D. J. Kopecky and
J. L. Gleason, J. Am. Chem. Soc., 1997, 119, 6496.
1
2
3
4
5
6
a
iPr
iPr
iPr
Bn
Bn
Bn
NaHMDS
NaHMDS
NaHMDS
NaHMDS
LiHMDS
LiN(iPr)2
23
50
43
43
41
45
46
93:7
95:5
97:3
97:3
98:2
98:2
278 A 23
278 A 0
278 A 23
278 A 23
278 A 23
By 1H NMR analysis after column chromatography
3 (a) W. A. Kleschick, M. W. Reed and J. Bordner, J. Org. Chem., 1987,
52, 3168; (b) A. Solladie´-Cavallo, L. M. Martin-Cabrejas, G. Caravatti
and M. Lang, Tetrahedron: Asymmetry, 2001, 12, 967; (c) T. Kawabata,
S. Kawakami and S. Majumdar, J. Am. Chem. Soc., 2003, 125, 13012;
(d) N. Vignola and B. List, J. Am. Chem. Soc., 2004, 126, 450.
4 R. M. Coates and M. W. Johnson, J. Org. Chem., 1980, 45, 2685.
5 (a) D. A. Evans, R. P. Polniaszek, K. M. DeVries, D. E. Guinn and
D. J. Mathre, J. Am. Chem. Soc., 1991, 113, 7613; (b) V. Guerlavais,
P. J. Carroll and M. M. Joullie´, Tetrahedron: Asymmetry, 2002, 13, 675.
6 (a) M. M. Ravn, Q. Jin and R. M. Coates, Eur. J. Org. Chem., 2000,
1401; (b) A. I. Meyers and E. W. Collington, J. Org. Chem., 1971, 36,
3044; (c) E. J. Corey, G. Luo and L. S. Lin, J. Am. Chem. Soc., 1997,
119, 9927.
7 D. A. Evans, K. T. Chapman and J. Bisaha, J. Am. Chem. Soc., 1988,
110, 1238.
8 D. A. Evans, T. C. Britton and J. A. Ellman, Tetrahedron Lett., 1987,
28, 6141.
9 L. Piovetti, G. Combaut and A. Diara, Phytochemistry, 1980, 19, 2117.
10 E. von Rudloff, Can. J. Chem., 1961, 39, 1860.
11 For cembrene A see: (a) V. D. Patil, U. R. Nayak and S. Dev,
Tetrahedron, 1973, 29, 341; (b) C.-Y. Duh, S.-K. Wang, Y.-L. Weng,
M. Y. Chiang and C.-F. Dai, J. Nat. Prod., 1999, 62, 1518; For
nephthenol see: (c) F. J. Schmitz, D. J. Vanderah and L. S. Ciereszko,
J. Chem. Soc., Chem. Commun., 1974, 407; (d) Y.-P. Shi, A. D. Rodr´ıguez
and O. L. Padilla, J. Nat. Prod., 2001, 64, 1439.
12 For a review see: M. A. Tius, Chem. Rev., 1988, 88, 719.
13 (a) R. Schwabe, I. Farkas and H. Pfander, Helv. Chim. Acta, 1988, 71,
292; (b) I. Farkas and H. Pfander, Helv. Chim. Acta, 1990, 73, 1980; (c)
X.-J. Yue and Y.-L. Li, Synthesis, 1996, 736; (d) K. Ishihara,
H. Nakamura and H. Yamamoto, Synlett, 2001, 1113.
14 (a) R. P. Hanzlik, Org. Synth., 1988, Coll. Vol. VI, 560; (b) S. Handa,
P. S. Nair and G. Pattenden, Helv. Chim. Acta, 2000, 83, 2629; (c)
E. J. Corey and W.-C. Shieh, Tetrahedron Lett., 1992, 33, 6435.
15 E. J. Corey and R. S. Kania, J. Am. Chem. Soc., 1996, 118, 1229.
16 M. Kodama, Y. Matsuki and S. Ito, Tetrahedron Lett., 1975, 16,
3065.
Scheme 4
The structures and absolute configurations of cyclic products 16
were confirmed by conversion to the natural diterpene (+)-
nephthenol (18), [a]D23 +48 (c 1.24, CHCl3), for ent-18, lit.13b [a]589
243.0 (c 0.72, CHCl3), and by comparisons with the reported
spectral data (Scheme 4).11c,13a,b The (2)-antipode ent-18 [a]2D3
246.3 (c 1.20, CHCl3) was also synthesized using the enantiomeric
bromo oxazolidinone bearing the (S)-Xv auxiliary. Dehydration of
(2)-nephthenol to (2)-cembrene A (ent-19) with SOCl2–pyridine
has been reported.13a,b,16
The cyclizations of bromo oxazolidinones 5 and 15 provide a
promising precedent for enantioselective construction of tertiary
2904 | Chem. Commun., 2006, 2902–2904
This journal is ß The Royal Society of Chemistry 2006