Synthetic Study Using a New Active Reaction Species, Nitrosoketene

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Previously, we reported that heating of isonitroso Meldrum's acid with ketones in a aprotic solvent to give cyclic nitrones. This reaction involves the 1,3-cycloaddition of ketone with nitrosoketene derived from isonitroso Meldrum's acid. In this research project, we synthesized chiral cyclic nitrones from the reaction of nitrosoketene with various chiral ketones, and achieved the asymmetric synthesis of modified amino acids via asymmetric 1,3-dipolar cycloaddition of the nitrones. Thus, reaction of nitrosoketene with (+)-nopinone or (+)-camphenilone gave a chiral nitrone as a single isomer whereas l-menthone reacted with nitrosokene to give two isomers of chiral nitrones. One of these isomers was used for the EPC synthesis of modified amino acids such as allylglycine and cyclopentenylglycine. Furthermore, we first succeeded the detection of nitrosoketene using FT-IR spectroscopy under collaboration with American researchers. Thus, we found that nitrosoketene was gradually generated from isonitroso Meldrum's acid above 80ﾟC and then decomposed about 160ﾟC,and that life time of nitrosoketene was 4 h at 90ﾟC.