Intramolecular 1,3-dipolar nitrone and nitrile oxide cycloaddition of 2- and 4-O-allyl and propargyl glucose derivatives: a versatile approach to chiral cyclic ether fused isoxazolidines, isoxazolines and isoxazoles
作者:Subir Ghorai、Ranjan Mukhopadhyay、Asish P. Kundu、Anup Bhattacharjya
DOI:10.1016/j.tet.2005.01.119
日期:2005.3
demonstrated the preferred formation of a five-membered ring to that of six or seven-membered rings. The nitrile oxide generated from a 3,4,5,6,7-pentaallyloxy-1-nitroheptane derivative obtained from pentaallylglucose underwent diastereoselective cycloaddition to give an isoxazoline fused to a pyran ring. Enantiopure isoxazoles containing tetrahydrofuran and oxepane rings were also prepared in good
从容易获得的葡萄糖二硫缩醛制备2- O-和4- O-烯丙基和-炔丙基葡萄糖以及相应的肟衍生物。上述无环2- O-烯丙基葡萄糖衍生物的N-苄基和N-甲基硝酮的分子内1,3-偶极环加成导致并入有四氢呋喃环的手性异恶唑烷的非对映选择性形成。EI质谱显示与呋喃氧原子相邻的C-烷基的特征性裂解。对映体纯的三取代四氢呋喃是通过还原性裂解其中一个环加合物的异恶唑烷环而获得的。相反,2- O的一氧化氮环加成反应-烯丙基衍生物提供相应的二氢异恶唑啉的非对映异构体混合物,其立体化学是根据光学叠加原理初步确定的。由五烯丙基硝酮或一氧化二氮独家形成四氢呋喃环表明,五元环比六元或七元环更优选。将从五烯丙基葡萄糖获得的3,4,5,6,7-戊烯丙基氧基-1-硝基庚烷衍生物生成的腈氧化物进行非对映选择性环加成,得到与吡喃环稠合的异恶唑啉。通过2- O-和4- O-炔丙基衍生物的腈氧化环加成,也以高收率制备了含有四氢呋喃和氧杂环丁烷环的对映体纯的异恶唑。