Stereoselective Michael Addition of Thiophenols, Amino Acids and Hydrazoic Acid to (2S)-Hydroxymethyl-dihydropyridone as a Convenient Route to Novel Azasugar Derivatives

The outcome and stereochemical aspects of 1,4-conjugate addition of thiophenols, α-aminoacid derivatives and hydrazoic acid to chiral (2S)-hydroxymethyl-dihydropyridone 3 is presented. Subsequent reduction with NaBH4 provided predominantly the kinetically favored axial 3-piperidinol adducts. The stereochemistry of the products, which depends on electrostatic interaction and steric hindrance, was revealed by 1H NMR and 2D NOESY spectroscopic analysis.