SYNTHESIS OF CHIRAL SPIRO 3-OXAZOLIN-5-ONE 3-OXIDES (CHIRAL NITRONES) VIA A NITROSOKETENE INTERMEDIATE AND THEIR ASYMMETRIC 1,3-DIPOLAR CYCLOADDITION REACTIONS LEADING TO THE EPC SYNTHESIS OF MODIFIED AMINO ACIDS

摘要

Cycloaddition of chiral cyclic ketones such as (-)-menthone, (+)-nopinone, and (+)-camphenilone to nitrosoketene generated by thermolysis of 5-hydroxyimino-2,2-dimethyl-1,3-dioxane-4,6-dione gave the corresponding chiral spiro 3-oxazolin-5-one 3-oxides (chiral cyclic nitrones). These nitrones underwent asymmetric 1,3-dipolar cycloaddition reactions with electron rich olefins to give the corresponding oxazolidine derivatives with high diastereoselectivity, which were converted to optically pure amino acids. (C) 1997 Elsevier Science Ltd. [References: 23]