Synthesis and assignment of the absolute configuration of the anti-Helicobacter pylori agents CJ-12,954 and CJ-13,014
作者:Margaret A. Brimble、Christina J. Bryant
DOI:10.1039/b709932k
日期:——
The synthesis of the spiroacetal-containing anti-Helicobacter pylori agents (3S,2″S,5″S,7″S)-1a (ent-CJ-12,954) and (3S,2″S,5″R,7″S)-2a (ent-CJ-13,014) has been carried out based on the convergent union of a 1 : 1 mixture of heterocycle-activated spiroacetal sulfones6 and 7 with (3S)-phthalide aldehyde5a. The synthesis of the (3R)-diastereomers (3R,2″S,5″S,7″S)-1b and (3R,2″S,5″R,7″S)-2b was also undertaken in a similar manner by union of (3R)-phthalide aldehyde5b with a 1 : 1 mixture of spiroacetal sulfones6 and 7. Comparison of the 1H and 13C NMR data, optical rotations and HPLC retention times of the synthetic compounds (3S,2″S,5″S,7″S)-1a and (3S,2″S,5″R,7″S)-2a and the (3R)-diastereomers (3R,2″S,5″S,7″S)-1b and (3R,2″S,5″R,7″S)-2b, with the naturally occurring compounds, established that the synthetic isomers 1a and 2a were in fact enantiomeric to the natural products CJ-12,954 and CJ-13,014. The (2S,8S)-stereochemistry in protected dihydroxyketone 21, the precursor to the mixture of spiroacetal sulfones6 and 7 was established via union of readily available (S)-acetylene 18 with aldehyde17 in which the (4S)-stereochemistry was established via asymmetric allylation. Deprotection and cyclization of protected dihydroxyketone 21 afforded an inseparable 1 : 1 mixture of spiroacetal alcohols24 and 25 that were converted into a 1 : 1 inseparable mixture of spiroacetal sulfones6 and 7. Phthalide-aldehyde 3a was prepared via intramolecular acylation of bromocarbamate 11 in which the (3S)-stereochemistry was established via asymmetric CBS reduction of ketone8.
含螺缩醛的抗幽门螺旋杆菌药物(3S,2″S,5″S,7″S)-1a (ent-CJ-12,954)和(3S,2″S,5″R,7″S)-2a (ent-CJ-13,014)的合成是基于杂环激活的螺缩醛砜6和7与(3S)-邻苯二甲醛5a的1:1混合物的会聚结合。(3R)-非对映异构体(3R,2″S,5″S,7″S)-1b 和(3R,2″S,5″R,7″S)-2b 的合成也以类似的方法进行,即(3R)-邻苯二甲醛 5b 与螺醛类砜 6 和 7 的 1 : 1 混合物结合。比较了合成化合物(3S,2″S,5″S,7″S)-1a 和(3S,2″S,5″R,7″S)-2a 以及(3R)-非对映异构体(3R,2″S,5″S、7″S)-1b 和 (3R,2″S,5″R,7″S)-2b,确定合成异构体 1a 和 2a 事实上是天然产物 CJ-12,954 和 CJ-13,014 的对映体。受保护的二羟基酮 21(螺醛砜混合物 6 和 7 的前体)中的(2S,8S)-立体化学是通过现成的(S)-乙炔 18 与醛 17 结合而建立的,其中的(4S)-立体化学是通过不对称烯丙基化建立的。对受保护的二羟基酮 21 进行脱保护和环化,可得到 1 : 1 不可分离的螺醛醇混合物24 和 25,并将其转化为 1 : 1 不可分离的螺醛砜混合物6 和 7。酞醛 3a 是通过溴代氨基甲酸酯 11 的分子内酰化反应制备的,其中的 (3S)- 立体化学结构是通过酮的不对称 CBS 还原8 建立的。