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DOI: 10.1055/s-0031-1289543
An Ireland-Claisen Rearrangement/Lactonisation Cascade as a Key Step in Studies Towards the Synthesis of (-)-Euonyminol:
Publikationsverlauf
Publikationsdatum:
19. Oktober 2011 (online)
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Abstract
Progress towards the asymmetric total synthesis of (-)-euonyminol is described with the focus on the installation of the oxygenation pattern on the lower rim of the molecule. An Ireland-Claisen rearrangement/lactonisation cascade has been developed and studies towards further elaboration have uncovered an intriguing tunable diastereoselective α-bromination of the resulting γ-lactone.
Key words
Ireland-Claisen - Celastraceae - bromination - euonyminol - sesquiterpene
- Supporting Information for this article is available online:
- Supporting Information
- Supporting Information
- For reviews, see
-
1a
Spivey AC.Weston M.Woodhead S. Chem. Soc. Rev. 2002, 31: 43 -
1b
Brinker AM.Ma J.Lipsky PE.Raskin I. Phytochemistry 2007, 68: 732 - For selected recent examples, see:
-
2a
Zhou G.Gao X.Li WZ.Li Y. Tetrahedron Lett. 2001, 42: 3101 -
2b
Li WZ.Zhou G.Gao X.Li Y. Tetrahedron Lett. 2001, 42: 4649 -
2c
Mehta G.Kumaran RS. Tetrahedron Lett. 2003, 44: 7055 -
2d
Lee CA.Floreancig PE. Tetrahedron Lett. 2004, 45: 7193 -
2e
Siwicka A.Cuperly D.Tedeschi L.Le Vézouet R.White AJP.Barrett AGM. Tetrahedron 2007, 63: 5903 - 3
Spivey AC.Woodhead SJ.Weston M.Andrews BI. Angew. Chem. Int. Ed. 2001, 40: 769 - 4
Beroza M. J. Am. Chem. Soc. 1953, 75: 44 - 5
Duan H.Takaishi Y.Imakura Y.Jia Y.Li D.Cosentino LM.Lee K.-H. J. Nat. Prod. 2000, 63: 357 - 6
Duan H.Takaishi Y.Bando M.Kido M.Imakura Y.Lee KH. Tetrahedron Lett. 1999, 40: 2969 - 7
Horiuch M.Murakami C.Fukamiya N.Yu D.Chen T.-H.Bastow KF.Zhang D.-C.Takaishi Y.Imakura Y.Lee KH. J. Nat. Prod. 2006, 69: 1271 - 8
White JD.Shin H.Kim T.-S.Cutshall NS. J. Am. Chem. Soc. 1997, 119: 2404 - 9
Ireland RE.Mueller RH. J. Am. Chem. Soc. 1972, 94: 5897 - 10
Hutchison JM.Hong S.-P.McIntosh MC. J. Org. Chem. 2004, 69: 4185 - 11
Oh K.Parsons PJ.Cheshire D. Synlett 2004, 2771 - 12
Thompson AL.Watkin DJ. Tetrahedron: Asymmetry 2009, 20: 712 - This selectivity is in contrast to other examples of cis-fused γ-lactone α-brominations that we are aware of in the literature, all of which are reported to give products resulting from approach of the electrophile from the least hindered convex face, see:
-
13a
Greene AE.Edgar MT. J. Org. Chem. 1989, 54: 1468 -
13b
Greene AE.Muller J.-C.Ourisson G. Tetrahedron Lett. 1972, 2489 -
13c
Greene AE.Muller J.-C.Ourisson G. J. Org. Chem. 1974, 39: 186 -
13d
Alberto Marco J.Carda M. Tetrahedron 1987, 43: 2523 -
13e
Shimoma F.Kusaka H.Azami H.Wada K.Suzuki T.Hagiwara H.Ando M. J. Org. Chem. 1998, 63: 3758 -
13f
Huguchi Y.Shimoma F.Ando M. J. Nat. Prod. 2003, 66: 810 -
13g
Crow JR.Thomson RJ.Mander LN. Org. Biomol. Chem. 2006, 4: 2532 -
13h
Ando M.Wada T.Isogai K. J. Org. Chem. 1991, 56: 6235 -
13i
The example most similar to ours involves the α-bromination of an α-(-)-santonin derivative (compound 19, see Supporting Information) for which the stereochemistry of the product was assigned by NOE (see ref. 13h). We repeated this reaction under both their conditions (LiCPh3, BrCH2CH2Br, 37% yield) and ours (TMSCl, LDA, NBS, 80% yield), obtained the same product 20 they report for both reactions, and confirmed the reported stereochemistry by a single crystal X-ray structure determination (see Supporting Information). Oxidation of lactone 19 also proceeded on the convex face to give α-hydroxylactone 21 (LDA, MoOPD, 62% yield; cf. Scheme [4] ; see Supporting Information).
- 15
Anderson JC.Smith SC. Synlett 1990, 107 - 16
Vedejs E. J. Am. Chem. Soc. 1974, 96: 5944 - 17
Osamu H.Takizawa J.-I.Yamatake T.Makino K.Hamada Y. Tetrahedron Lett. 1999, 40: 7787 - 18
Shi Y.-J.Hughes DL.McNamara JM. Tetrahedron Lett. 2003, 44: 3609
References and Notes
Stereochemical assignments were made based upon NMR spectroscopic comparisons with bromolactones 9a and 15b for which X-ray structural data were obtained (see Supporting Information).
19Product 18 was not fully characterised due to lack of material and this line of investigation has not been pursued further to allow verification of the stereochemistry at C-11.