Asymmetric Synthesis of Substituted Prolines by 1,3-Dipolar Cycloadditions of Azomethine Ylides from Chiral 6-Isopropyl-5-phenylmorpholin-2-ones

Chiral saturated alanine- and glycine-derived 6-isopropyl-5-phenylmorpholin-2-ones 11 and 12 have been prepared and employed for the generation of carboxy-stabilized ylides in asymmetric 1,3-dipolar cycloaddition reactions under thermal conditions, with electron-deficient dipolarophiles bearing double and triple bonds. The cycloadducts are obtained with high stereocontrol and mainly with endo selectivity, and can be used for the synthesis of highly substituted enantiomerically pure prolines.