Organofluorine Compounds and Fluorinating Agents, Part 33:Regioselective Chlorodifluoromethylations in the 1-Position of 1,2-Unsaturated Monosaccharide Derivatives
作者:Ralf Miethchen、Anita Wegert、Martin Hein、Helmut Reinke
DOI:10.1055/s-2005-865361
日期:——
The dithionite-mediated chlorodifluoromethylations of 3,4-di-O-acetyl-1,5-anhydro-2,6-dideoxy-l-arabino-hex-1-enitol (1), 1,5-anhydro-2,3,4-tri-O-pivaloyl-d-erythro-pent-1-enitol (13), 2,3,4-tri-O-acetyl-1,5-anhydro-6-deoxy-l-lyxo-hex-1-enitol (15), and 2,3,4,6-tetra-O-acetyl-1,5-anhydro-d-arabino-hex-1-enitol (18) with CBrClF2 in acetonitrile-water and methanol, respectively, are described. Sodium dithionite serves as radical initiator and reducing reagent. Whereas, starting with 1, the chlorodifluoromethyl group was predominantly introduced into position 2, the 1-chlorodifluoromethyl substituted C-glycosides 1,5-anhydro-1-(S)-chlorodifluoromethyl-2,3,4-tri-O-pivaloyl-d-ribitol (14), 2,3,4-tri-O-acetyl-1,5-anhydro-1-(R)-chlorodifluoromethyl-6-deoxy-l-galactitol (16), and 2,3,4,6-tetra-O-acetyl-1,5-anhydro-1-(S)-chlorodifluoromethyl-d-glucitol (19) could be synthesized in moderate to good yields from 13, 15, and 18, respectively. X-ray analyses are given for the products 3,4-di-O-acetyl-1,5-anhydro-2-chlorodifluoromethyl-2,6-dideoxy-l-glucitol, 1,3,4-tri-O-acetyl-2-chlorodifluoromethyl-2,6-dideoxy-α-l-mannopyranose, 1,5-anhydro-1-(S)-chlorodifluoromethyl-2,3,4-tri-O-pivaloyl-d-ribitol, and 2,3,4,6-tetra-O-acetyl-1,5-anhydro-1-(S)-chlorodifluoromethyl-d-glucitol.
在
亚硫酸氢盐介导下,3,4-二-O-乙酰基-1,5-脱
水-2,6-二脱氧-阿拉比诺-己-1-烯糖醇 (1)、1,5-脱
水-2,3,4-三-O-特戊酰基-赤式-戊-1-烯糖醇 (13)、2,3、描述了在
乙腈-
水和
甲醇中分别用
CBrClF2 和 与 1,5-脱
水-2,3,4-三-O-新戊酰-d-赤式-1-烯糖醇 (13)、2,3,4-三-O-乙酰基-1,5-脱
水-6-脱氧-l-来苏-己-1-烯糖醇 (15) 和 2,3,4,6-四-O-乙酰基-1,5-脱
水-d-阿拉伯-己-1-烯糖醇 (18) 反应的过程。
连二亚硫酸钠既是自由基
引发剂,又是还原试剂。从 1 开始,
氯二
氟甲基主要被引入位置 2,而 1-
氯二
氟甲基取代的 C-糖苷 1,5-anhydro-1-(S)-chlorodifluoromethyl-2,3,4-tri-O-pivaloyl-d-ribitol (14)、2,3、可分别从 13、15 和 18 合成 2,3,4,6-O-三乙酰基-1,5-脱
水-1-(R)-
氯二
氟甲基-6-脱氧-l-半
乳糖醇 (16) 和 2,3,4,6-O-四乙酰基-1,5-脱
水-1-(S)-
氯二
氟甲基-d-
葡萄糖醇 (19),收率中等至良好。X 射线分析给出了产物 3,4-二-O-乙酰基-1,5-脱
水-2-
氯二
氟甲基-2,6-二脱氧-l-
葡萄糖醇、1,3,4-三-O-乙酰基-2-
氯二
氟甲基-2、6-二脱氧-δ-l-
吡喃
甘露糖、1,5-脱
水-1-(S)-
氯二
氟甲基-2,3,4-三-O-特戊酰基-d-
核糖醇,以及 2,3,4,6-O-四乙酰基-1,5-脱
水-1-(S)-
氯二
氟甲基-d-
葡萄糖醇。