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Vinyl substituted (1 R ,2 S )-amino alcohols 5 were obtained by addition of vinyl magnesium bromide to the corresponding cyanohydrin O -trimethylsilyl ethers (R)- 2 . The O - and N -protected vinyl amino alcohols 6 were ozonized at −78°C in methanol yielding (1 R ,2 S )-2-amino-1,3-diols 7 in high enantiomeric and diastereomeric excesses. For purification, compounds 7 in some cases were acetylated to give the derivatives (1R,2S)- 8 . Racemic 6a was converted by oxidative ozonolysis at −78°C in methanolic NaOH solution to the corresponding methyl N -acetyl-β-hydroxy propanoate 9a . The configuration of (1R,2S)- 8a was confirmed by x-ray crystallographic analysis. |
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