When glucose and boric acid are heated in acetic acid a soluble compound forms from which, with acetic anhydride and catalytic amounts of sulfuric acid, a mixture consisting of >90% of the glucofuranose per-acetates (αâ¶Î² ratio 1â¶1.8) is obtained in high yield. In the absence of the sulfuric acid partial acetylation takes place and penta-O-acetyl-β-D-glucofuranose (αâ¶Î² ratio 1â¶52) is obtainable in good yield by removal of boric acid and completion of the esterification by addition of acetic anhydride and pyridine. A new, crystalline glucofuranose, penta-O-propanoyl-β-D-glucofuranose, is obtained in 58% yield in a âone-potâ procedure using boric acid.
The effects of boric acid on the acid-catalysed acetylation of other aldo-hexoses and -pentoses suggest that the synthesis of furanosyl per-esters could be successful with xylose and idose as well as with glucose.
p
当
葡萄糖和
硼酸在
醋酸中加热时,会形成一种可溶性化合物,从中通过
醋酐和少量的
硫酸催化,可以获得含有>90%的葡萄
呋喃糖全
乙酸酯(α∶β比率为1∶1.8)的高产率混合物。在没有
硫酸的情况下,会发生部分乙酰化,通过去除
硼酸并加入
醋酐和
吡啶完成酯化反应,可以以良好的产率获得五-O-乙酰基-β-D-葡萄
呋喃糖(α∶β比率为1∶52)。通过使用
硼酸的“一锅法”程序,可以以58%的产率获得一种新的结晶葡萄
呋喃糖,即五-O-
丙酸酰基-β-D-葡萄
呋喃糖。
硼酸对其他
己醛糖和
戊醛糖的酸催化乙酰化反应的影响表明,与
葡萄糖一样,
木糖和艾杜糖的
呋喃糖全酯合成也可能是成功的。