Ichiyanagi Tsuyoshi, Yamasaki Ryohei
Department of Biochemistry and Biotechnology, Tottori University, Tottori 680-8553, Japan.
Carbohydr Res. 2005 Dec 12;340(17):2682-7. doi: 10.1016/j.carres.2005.09.002. Epub 2005 Sep 29.
To develop a convenient method for the preparation of an alpha-Kdo derivative carrying a functional spacer at the reducing end, we examined anomeric O-acylation using Kdo and halogenated alkyl/aryl isocyanates as nucleophile and electrophiles, respectively. Reaction of a Kdo derivative with 2-chloroethyl isocyanate in the presence of DMAP gave an alpha-spiro product (82%) and an alpha-Kdo derivative of a dimeric isocyanate adduct (10%). Similar reaction with 4-(chloromethyl)phenyl isocyanate gave only the corresponding alpha-spiro product (81%). The NMR data show that the pyranose rings of both the alkyl and aryl spiro products adopt the 5C2 conformation. Thus, we accomplished alpha-selective anomeric O-acylation by coupling the Kdo derivative with alkyl and aryl isocyanates.
为开发一种简便的方法来制备在还原端带有功能性间隔基的α-Kdo衍生物，我们分别使用Kdo和卤代烷基/芳基异氰酸酯作为亲核试剂和亲电试剂，研究了异头碳O-酰化反应。在DMAP存在下，Kdo衍生物与2-氯乙基异氰酸酯反应，得到α-螺环产物（82%）和二聚异氰酸酯加合物的α-Kdo衍生物（10%）。与4-(氯甲基)苯基异氰酸酯的类似反应仅得到相应的α-螺环产物（81%）。核磁共振数据表明，烷基和芳基螺环产物的吡喃糖环均采用5C2构象。因此，我们通过将Kdo衍生物与烷基和芳基异氰酸酯偶联，实现了α-选择性异头碳O-酰化。
