Cephalosporolide B Serving as a Versatile Synthetic Precursor: Asymmetric Biomimetic Total Syntheses of Cephalosporolides C, E, F, G, and (4-OMe-)G
摘要:
Cephalosporolide B (Ces-B) was efficiently synthesized and exploited for the first time as a versatile biomimetic synthetic precursor for the chemical syntheses of not only cephalosporolides C, G, and (4-OMe-) G via a challenging diastereoselective oxa-Michael addition but also the structurally unprecedented cephalosporolides E and F via a novel biomimetic ring-contraction rearrangement. These findings provide the first direct chemical evidence that Ces-B may be the true biosynthetic precursor of cephalosporolides.
Cephalosporolide B Serving as a Versatile Synthetic Precursor: Asymmetric Biomimetic Total Syntheses of Cephalosporolides C, E, F, G, and (4-OMe-)G
摘要:
Cephalosporolide B (Ces-B) was efficiently synthesized and exploited for the first time as a versatile biomimetic synthetic precursor for the chemical syntheses of not only cephalosporolides C, G, and (4-OMe-) G via a challenging diastereoselective oxa-Michael addition but also the structurally unprecedented cephalosporolides E and F via a novel biomimetic ring-contraction rearrangement. These findings provide the first direct chemical evidence that Ces-B may be the true biosynthetic precursor of cephalosporolides.
Regioselective and Stereospecific Copper-Catalyzed Deoxygenation of Epoxides to Alkenes
作者:Jingxun Yu、Yu Zhou、Zhenyang Lin、Rongbiao Tong
DOI:10.1021/acs.orglett.6b02405
日期:2016.9.16
diazo malonate for chemo-/regioselective and stereospecificdeoxygenation of various epoxides with tolerance of common functional groups (alkene, ketone, ester, p-methoxybenzyl, benzyl, tert-butyldimethylsilyl, and triisopropylsilyl). In particular, the unprecedented regioselectivity allowed for the first time monodeoxygenation of diepoxides to alkenyl epoxides. Density functional theory mechanistic studies
两种铜盐(Cu(CF 3 CO 2)2和IMesCuCl)被鉴定为是地球上丰富的,廉价的但有效的金属催化剂,与重氮丙二酸酯一起用于各种环氧化物的化学/区域选择性和立体定向脱氧反应,并具有常见的官能团耐受性(烯烃,酮,酯,对甲氧基苄基,苄基,叔丁基二甲基甲硅烷基和三异丙基甲硅烷基)。特别是,空前的区域选择性使二环氧化物首次单脱氧为烯基环氧化物。密度泛函理论的机理研究表明,脱氧是通过折叠游离的叶立德而发生的,不利于通过可能的氧杂环丁烷的环还原而产生的直观途径。
Concise Enantioselective Synthesis of the Ten-Membered Lactone Cephalosporolide G and Its C-3 Epimer
作者:Silvia Barradas、Antonio Urbano、M.â Carmen Carreño
DOI:10.1002/chem.200901735
日期:2009.9.21
One, two, three selective oxidations are the key steps in the atom‐economic first total synthesis of the natural ten‐membered lactone cephalosporolide G and its C‐3 epimer (see scheme). They have been synthesised in only seven or eight steps starting from the natural phenol (R)‐rhododendrol, which contains all the carbon atoms present in the final targets.