64 糖縮合イソキサゾリン類とスピロ糖イソキサゾリジン類の合成(ポスター発表の部)

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Recently, cosiderable attention has been given to many unnatural nucleosides since the appearance of some unnatural nucleosides as potential antiviral agents.^1 Thus, in connection with our study directed towards the synthesis of unnatural nucleosides, we present herein the first synthesis of sugar condensed isoxazolines and spiro sugar isoxazolidines. [1] Synthesis of Sugar Condensed Isoxazolines The oxidation of protected D-ribose oxime 1 with aqueous NaOCl solution gave the corresponding hydroximolactone 5, which was then allowed to react with dimethyl acetylenedicarboxylate (DMAD) in the presence of triethylamine, giving a 3:1 mixture of diastereoisomeric sugar condensed isoxazoline derivatives 7a and 8a in 85% yield. Their separation and deprotection were carried out by t.l.c. purification and HCl-MeOH treatment, respectively. The structures of 7a and 8a were determined mainly by NOESY measurement.^2 Further, D-deoxyribose, D-glucose, and D-galactose underwent the similar reaction to give the corresponding sugar condensed isoxazoline derivatives. [2] Synthesis of Spiro Sugar Isoxazolidines A mixture of D-ribose hydroximolactone 5, methyl acrylate, and dry toluene was heated in sealed tube to give the corresponding spiro sugar isoxazolidine derivative 22a in 85% yield. The tandem Michael addition-1,3-dipolar cycloaddition reaction gives 22a in a regio- and stereoselective manner because the ribose functions as a chiral template. Reduction of 22a with Raney nickel gave the corresponding pyrrolidone derivative 23, which was then changed into the corresponding pyrrolidine derivative 24 using LiAlH_4.^7 The structure of spiro sugar isoxazolidine 25 derived from methyl vinyl ketone was determined by single crystal X-ray diffraction. D-Glucose also underwent the similar reaction to give the corresponding spiro sugar isoxazolidine derivatives.
天然有機化合物討論会の論文
1990-09-25

64 糖縮合イソキサゾリン類とスピロ糖イソキサゾリジン類の合成(ポスター発表の部)

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