Efficient and β-Stereoselective Synthesis of 4(5)-(β-<scp>d</scp>-Ribofuranosyl)- and 4(5)-(2-Deoxyribofuranosyl)imidazoles<sup>1</sup>
作者:Shinya Harusawa、Yoshihiko Murai、Hideki Moriyama、Tomonari Imazu、Hirofumi Ohishi、Ryuji Yoneda、Takushi Kurihara
DOI:10.1021/jo952136z
日期:1996.1.1
A synthetic route to 4(5)-(beta-D-ribofuranosyl)imidazole (1), starting from 2,3,5-tri-O-benzyl-D-ribose (5), was developed via a Mitsunobu cyclization. Reaction of 5 with the lithium salt of bis-protected imidazole afforded the corresponding 5-ribosylimidazole 7RS. Hydrolysis of 7RS gave a 1:1 mixture of diol isomers 8R and 8S having an unsubstituted imidazole. Mitsunobu cyclization of the mixture
通过Mitsunobu环化反应,从2,3,5-三-O-苄基-D-核糖(5)开始,合成了4(5)-(β-D-呋喃呋喃糖基)咪唑(1)。5与双保护的咪唑的锂盐反应,得到相应的5-核糖咪唑7RS。7RS的水解得到具有未取代的咪唑的二醇异构体8R和8S的1:1混合物。使用N,N,N',N'-四甲基偶氮二甲酰胺和Bu(3)P的混合物8RS的Mitsunobu环化以26.3的比率独家提供了苄基化的β-核呋喃呋喃糖基咪唑9beta,伴随有α-端基异构体9alpha: 1。通过乙氧基羰基衍生物10beta的X射线晶体学确定了9beta的构型。在Pd / C上进行了9beta的还原性脱苄基作用,并且从四个步骤开始从5开始获得1的合成,总产率为87%。这种合成方法扩展到4(5)-(2-deoxy-beta-D-rifurfuranosyl)imidazole(2)的合成。相应的二醇异构体14RS的1:1混合物的Mitsunobu环化以5