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Issue 10, 2004
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Asymmetric synthesis of (4R,5R)-cytoxazone and (4R,5S)-epi-cytoxazone

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(4R,5R)-Cytoxazone has been prepared in four steps and in 61% overall yield and >98% ee. Conjugate addition of lithium (R)-N-benzyl-N-α-methylbenzylamide to tert-butyl (E)-3-(p-methoxyphenyl)prop-2-enoate and subsequent in situ diastereoselective enolate oxidation with (+)-(camphorsulfonyl)oxaziridine gave tert-butyl (2R,3RR)-2-hydroxy-3-(p-methoxyphenyl)-3-(N-benzyl-N-α-methylbenzylamino)propanoate in >98% de. Subsequent N-benzyl deprotection to the primary β-amino ester via hydrogenolysis, oxazolidinone formation with C(2)-retention by treatment with diphosgene and chemoselective ester reduction furnishes (4R,5R)-cytoxazone. The synthesis of the C(5)-epimer, (4R,5S)-epi-cytoxazone in 44% overall yield, has also been completed via a protocol involving N-Boc protection of the primary β-amino ester, utilization of the N-Boc group to facilitate simultaneous C(2)-inversion and oxazolidinone formation, and subsequent reduction.

Graphical abstract: Asymmetric synthesis of (4R,5R)-cytoxazone and (4R,5S)-epi-cytoxazone

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Publication details

The article was received on 18 Feb 2004, accepted on 30 Mar 2004 and first published on 27 Apr 2004

Article type: Paper
DOI: 10.1039/B402437K
Citation: Org. Biomol. Chem., 2004,2, 1549-1553
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    Asymmetric synthesis of (4R,5R)-cytoxazone and (4R,5S)-epi-cytoxazone

    S. G. Davies, D. G. Hughes, R. L. Nicholson, A. D. Smith and A. J. Wright, Org. Biomol. Chem., 2004, 2, 1549
    DOI: 10.1039/B402437K

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