| Abstract
| - Diastereoselective alkylation of ethyl 2-methyl- and/or 2-ethylacetoacetates using the (S,S)-cyclohexane-1,2-diol as an acetal chiral auxiliary afforded enol ethers (2a−f and 5a−f) of 92−>95%de in 31−70% yields. Removal of the cyclohexane-1,2-diol with BF3−OEt2 afforded β-keto esters (3and 6) bearing a chiral quaternary carbon. The β-keto esters could be easily converted into opticallyactive α-methylated and/or α-ethylated α,α-disubstituted amino acids (12 and 13) in 21−99% yieldsusing Schmidt rearrangement.
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