1,3-Dipolar Cycloaddition Of Chiral Cyclic α-Alkoxycarbonylnitrones And Synthesis Of N-terminal Amino Acid Component Of Nikkomycin B

From a single chiral source, camphorquinone, two new chiral geometry-fixed a-alkoxycarbonylnitrones 29 and 34 were prepared. Nitrone 29 was prepared from tricycloiminolactone through hydrogenation and oxidation. Condensation of hydroxyamine derived from camphorquinone with glyoxylic acid and in situ cyclization of the intermediate gave the nitrone 34.These two nitrones reacted with a wide range of alkenes in high yield and with high stereoselectivity. Furthermore, to remove the camphor-derived auxiliary group of the cycloadducts, the chemical transformations of the cycloadducts were also examined.The asymmetric chemistry of nitrone was also reviewed.On the other hand, the N-terminal amino acid componet of nikkomycin B was investigated. 1, 3-dipolar cycloaddition between chiral nitrile oxide 1 and alkene 2 gave two isoxazolines 7a, b. Subsequent LAH reduction afforded the 1, 3-amino alcohol 9a, b, which was transformed to lactone 12a, b. The relative configuration 12a, b was the C-2 epimer of narural N-terminal amino acid componet. The synthesis of the N-terminal moiety was also reviewed.