Imino-Sugars by Stereoselective Processes Employing Pyrroline N-Oxides

Hydroxylated pyrroline-N-oxides provide a general entry to the synthesis of polyhydroxylated pyrrolizidine and indolizidine alkaloids. Their use appears attractive for many aspects that are a major topic in modern organic synthesis. They allow a high “atom economy” in the overall process as all the skeleton atoms are kept intact from reagents to products. All the key steps occur by simple thermal induction without any need of added catalyst. This feature allow to carry out several steps in one pot as a domino process, another appealing aspect for environmentally friendly syntheses. Finally, the described methodology allows the multiplication of stereogenic centers in the indolizidine skeleton, with complete control of enantiomeric and diastereomeric relations, starting from the same stereogenic nitrone precursor.