promising method for the versatile synthesis of chiral 2-amino alcohols is provided by the enantioselective functionalization of the olefinic moiety of the simple heterocycle, 2-oxazolone, involving a stereodefined introduction of easily replaceable groups followed by stepwise substitution. Versatility of this method is shown in chiral synthesis of unusual hydroxy amino acids such as statine and hydroxyglutamic
Methoxyselenylation and methoxybromination of chiral 3-acyl-2-oxazolones with PhSeCl/MeOH and Br2/MeC(OMe)3 smoothly proceed to result in highly stereoselective formation of chiral synthons for β-aminoalcohols, but with opposite π-facial selectivity.
The thermal reaction of 3-[(IS)-2-alkoxy-1-apocamphanecarbonyl]-2-oxazolones (21a-c) with dialkyl azodicarboxylates (9) results in exclusive formation of [4 + 2] type cycloadducts (22 and 23) with moderate levels of diastereofacial selection (up to 72% d.e.). The diastereomers thus obtained were readily purified and subsequent treatment with acidic methanol followed by removal of the auxiliary with LiBH4/MeOH (1:2) gave optically pure 4-methoxy-5-hydrazino-2-oxazolidinones (26 and 27), which serve as alpha-aminoaldehyde templates useful for the synthesis of a wide variety of optically active alpha-amino acids as well as 4-alkyl and 4-aryl-2-oxazolidinones. (C) 1997, Elsevier Science Ltd.