Formation of enantiopure β-amino alcohols with a 3-oxa-2,7- diazabicyclo[3.3.0]octane framework

Article abstract of DOI:10.1016/S0040-4020(98)01117-X

N-Allylamino alcohols 11a-g were prepared from enantiopure (1S, 2S)-2- amino-1-phenylpropane-1,3-diol (8) by various reaction pathways. Selective Swern oxidation of the primary alcohol group of compounds 11 followed by treatment of the resulting aldehyde with N-alkylhydroxylamines afforded the corresponding nitrones that underwent an intramolecular 1,3-dipolar cycloaddition to give the bicyclic compounds 12 and 13. 12c and 13c (R³ = allyl) were deallylated providing compounds 12i and 13i, which could be methylated subsequently yielding 12k and 13k, respectively. X-ray analyses of 13a,c and 12g were performed indicating different conformations of 13a and c on the one hand and of 12g on the other hand. Conclusions concerning the conformation of the other compounds 12 and 13 were drawn from their ¹H NMR data. Compounds 12 and 13 act as chiral ligands in the enantioselective addition of diethylzinc to benzaldehyde, however, the enantiomeric excess of the 1-phenylpropane-1-ol is usually low, the best result (79% ee) was achieved with compound 12c.