据报道,合成α-milbemycins所需的羟基丁烯内酯(-)-6和milbemycin G 7的总合成完成。经过初步研究,开发了由羟基酮38合成羟基丁烯内酯(-)-6的最佳方法,该方法涉及通过分离3-(O-氯乙酰基)-(S)-扁桃酸酯80和83拆分38的酯。酯80对应于所需的羟基酮38的对映异构体,从非对映异构酯80和83的混合物中结晶出来,经乙醇化后得到(-)-羟基酮(-)-38,总产率为47%(基于外消旋体38) 。将羟基酮(-)-38氧化为烯丙基二酮(-)-39,然后进行苯硒化和立体选择性还原,得到三羟基环己基硒化物(-)-43。然后通过使用三氯乙酸将4-羟基酯化以得到三氯乙酸酯(-)-69,将非共轭双键区域选择性地引入到六元环中。使用叔丁基过氧化氢从三氯乙酸盐中进行氧化消除反应具有很高的区域选择性,乙醇化三氯乙酸盐后,环内和环外烯烃(-)-44和(-)-46的比例为95:5。经由
Milbemycin derivaties: Modification at the C-5 position.
作者:SATORU NAITO、TOSHIHIKO NANBA、YUKA OWATARI、YASUO NAKADA、SHIGEKI MURAMATSU、JUNYA IDE
DOI:10.7164/antibiotics.47.233
日期:——
Protection of the hydroxyl group at the C-5 position of milbemycin A4 and D was carried out to investigate the influence of the C-5 hydroxyl group on the anthelmintic potency of these derivatives. Moreover, the hydroxyl group was converted into amide groups as bioisosters. Biological activities of these derivatives were measured against Nippostrongylus brasiliensis in vitro, and minimal concentrations which induce 100% immotility in worms were determined for each derivative. Biological testing revealed that the hydroxyl group at C-5 is a structural requirement for retaining anthelmintic activity.
Total synthesis of milbemycin G: assembly and completion of the synthesis
作者:Simon Bailey、Aphiwat Teerawutgulrag、Eric J. Thomas
DOI:10.1039/c39950002521
日期:——
The Wittig reaction between phosphonium salt 1 and the hydroxybutenolide 2 followed by deprotection, macrocyclisation, and reduction gives the 6-hydroxymilbemycin E 9 which by further cyclisation is converted into milbemycin G 11.
鏻盐 1 和羟基丁烯内酯 2 发生维蒂希反应,然后进行脱保护、大环化和还原反应,得到 6-羟基米尔贝霉素 E 9,进一步环化后可转化为米尔贝霉素 G 11。
A total synthesis of milbemycin G: approaches to the C(1)–C(10)-fragment and completion of the synthesis
作者:Simon Bailey、Madeleine Helliwell、Aphiwat Teerawutgulrag、Eric J. Thomas
DOI:10.1039/b508675b
日期:——
A synthesis of the hydroxybutenolide (-)-6 required for synthesis of alpha-milbemycins and the completion of a total synthesis of milbemycin G 7 is reported. Following preliminary studies, an optimised synthesis of the hydroxybutenolide (-)-6 from the hydroxyketone 38 was developed which involved the resolution of 38 by separation of the 3-(O-chloroacetyl)-(S)-mandelates 80 and 83. Ester 80, which
据报道,合成α-milbemycins所需的羟基丁烯内酯(-)-6和milbemycin G 7的总合成完成。经过初步研究,开发了由羟基酮38合成羟基丁烯内酯(-)-6的最佳方法,该方法涉及通过分离3-(O-氯乙酰基)-(S)-扁桃酸酯80和83拆分38的酯。酯80对应于所需的羟基酮38的对映异构体,从非对映异构酯80和83的混合物中结晶出来,经乙醇化后得到(-)-羟基酮(-)-38,总产率为47%(基于外消旋体38) 。将羟基酮(-)-38氧化为烯丙基二酮(-)-39,然后进行苯硒化和立体选择性还原,得到三羟基环己基硒化物(-)-43。然后通过使用三氯乙酸将4-羟基酯化以得到三氯乙酸酯(-)-69,将非共轭双键区域选择性地引入到六元环中。使用叔丁基过氧化氢从三氯乙酸盐中进行氧化消除反应具有很高的区域选择性,乙醇化三氯乙酸盐后,环内和环外烯烃(-)-44和(-)-46的比例为95:5。经由