Preparation of aminosaccharides using ester-imine condensations: syntheses of methyl N-benzoylacosaminide and methyl N-[oxo(phenylmethoxy) acetyl)daunosaminide from (S)-ethyl 3-hydroxybutyrate

The dianion of (S)-ethyl β-hydroxybutyrate (1) was treated with N-trimethylsilyl Imine 2 to afford β-lactam 4. The same dianion reacted with N-ary1 imine 10 to give β-lactams 11, 12, and 13. A three-step sequence was used to convert 4 into the β-lactam-pyran hybrid 9 while a five-step sequence was developed to transform 11 and 12 into 9. Application of the carboxyinversion reaction to derivatives of 9 afforded protected analogs of the amino-saccharldes daunosamlne (5) and acosamine (6).