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Issue 14, 2006
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Oxazinanones as chiral auxiliaries: synthesis and evaluation in enolate alkylations and aldol reactions

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Abstract

Homochiral β-amino esters (prepared on multigram scale by lithium amide conjugate addition) are readily transformed into oxazinanones. N-Acyl derivatives of oxazinanones undergo stereoselective enolate alkylation reactions, with higher stereoselectivities observed for the enolate alkylation of (R)-N-propanoyl-4-iso-propyl-6,6-dimethyl-oxazinan-2-one than the corresponding Evans oxazolidin-2-one. A C(4)-iso-propyl stereodirecting group within the oxazinanone conveys higher stereoselectivity than the analogous C(4)-phenyl substituent. gem-Dimethyl substitution at C(6) within the oxazinanone framework facilitates exclusive exocyclic cleavage upon hydrolysis to furnish α-substituted carboxylic acid derivatives and the parent oxazinanone in good yield. Asymmetric aldol reactions of a range of aromatic and aliphatic aldehydes with the chlorotitanium enolate of (R)-N-propanoyl-4-iso-propyl-6,6-dimethyl-oxazinan-2-one proceed with excellent diastereoselectivity. Hydrolysis of the aldol products affords homochiral α-methyl-β-hydroxy-carboxylic acids.

Graphical abstract: Oxazinanones as chiral auxiliaries: synthesis and evaluation in enolate alkylations and aldol reactions

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Publication details

The article was received on 20 Mar 2006, accepted on 17 May 2006 and first published on 13 Jun 2006


Article type: Paper
DOI: 10.1039/B604073J
Citation: Org. Biomol. Chem., 2006,4, 2753-2768
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    Oxazinanones as chiral auxiliaries: synthesis and evaluation in enolate alkylations and aldol reactions

    S. G. Davies, A. C. Garner, P. M. Roberts, A. D. Smith, M. J. Sweet and J. E. Thomson, Org. Biomol. Chem., 2006, 4, 2753
    DOI: 10.1039/B604073J

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