Synthese de l'acide (dihydroxy-5,7 dioxo-9,25ethyl-16 heptamethyl-2,4,6,12,18,22,24 methoxy-3) hexacosatriene-12,16,20oique par copulation de 3 synthons希罗
Substrate-Directed Diastereoselective Hydroformylation: Key Step for the Assembly of Polypropionate Subunits
摘要:
Stereoselective hydroformylation of methallylic alcohols of types 3 and 4, that employed the substrate-bound catalyst-directing ortho-diphenyl-phosphanylbenzoyl (o-DPPB) group, was used as a key step for the construction of bifunctionalized stereotriads, which ale central building blocks of polyketide natural products. The required diastereomerically pure syn- and anti- starting methallylic alcohol systems 3 and 4 were obtained either by Cram-selective carbonyl reduction, Frater alkylation, or by chelation-controlled carbonyl reduction. Enantiomerically pure stereotriad building blocks were derived from a combination of an Evans aldol addition and subsequent o-DPPB-directed stereoselective hydroformylation (-->24). A crystal structure analysis for steretriad building block 24 confirmed the relative and absolute configuration of the stereogenic centers. Additionally, it provided evidence for a previously postulated preferred conformation of the catalyst-directing o-DPPB group as well as of the polyketide main chain.
Synthesis and Conformational Analysis of Geodiamolide Analogues
作者:Srinivasa Marimganti、Ralph Wieneke、Armin Geyer、Martin E. Maier
DOI:10.1002/ejoc.200700024
日期:2007.6
ω-hydroxy and ω-amino acid derivatives 13 and 21, the two closely related geodiamolide analogs 32 and 35, respectively, were prepared. Compared to the natural cyclodepsipeptide geodiamolide (1), the macrocycles 32 and 35 have a smaller ring size (17- vs. 18-membered). Conformationalanalysis by ROESY spectroscopy and molecular dynamics simulation revealed that the reduced ring size causes the polypropionate
Asymmetric Total Synthesis of Pre-schisanartanin C
作者:Yan-Long Jiang、Hai-Xin Yu、Yong Li、Pei Qu、Yi-Xin Han、Jia-Hua Chen、Zhen Yang
DOI:10.1021/jacs.9b11872
日期:2020.1.8
Pre-schisanartanin C belongs to the family of Schisandra nortriterpenoids with potent antihepatitis, antitumor, and anti-HIV activities. This paper presents the enantioselective total synthesis of pre-schisanartanin C (1). An important step in the total synthesis of 1 is gold-catalyzed intramolecular cyclopropanation of an 1,8-enyne substrates bearing a secondary ester group at the propargylic position
五味子素前体 C 属于五味子降三萜类化合物家族,具有有效的抗肝炎、抗肿瘤和抗 HIV 活性。本文介绍了前五味子素 C (1) 的对映选择性全合成。1 的全合成中的一个重要步骤是金催化的分子内环丙烷化,在炔丙基位置带有仲酯基的 1,8-烯炔底物制备双环 [6.1.0] 壬烷核。其他亮点包括 i) 不对称 Diels-Alder 反应以安装 1 的初始 C5 立体中心,以及 ii) 顺序 Pd 催化的 Stille 偶联、区域和立体选择性 Sharpless 不对称二羟基化,以及随后的分子内内酯化以构建1的侧链
Stereoselective Hydroformylation: Key Step for the Assembly of Polypropionate Subunits
作者:Bernhard Breit、Stephan K. Zahn
DOI:10.1021/jo015634i
日期:2001.7.1
achieved. The basis of this result was a careful substrate design making use of a syn-pentane interaction as the decisive stereochemical control element. Confirmation of this working hypothesis came from conformational analysis studies on alkenic substrate 16 employing 2DNOESY experiments in solution and MACROMODEL/MM3 calculations. This stereoselective, transition metal-catalyzed, C-C bond-forming
Stereocontrol in intramolecular hydrosilylation of allyl and homoallyl alcohols: a new approach to the stereoselective synthesis of 1,3-diol skeletons
作者:Kohei. Tamao、Takashi. Nakajima、Ritsuo. Sumiya、Hitoshi. Arai、Noriko. Higuchi、Yoshihiko. Ito
DOI:10.1021/ja00279a097
日期:1986.9
31.30; H, 5.22; N, 36.52. Found: C, 31.34; H, 5.25; N, 36.70. Low-resolution mass spectral analysis showed the expected molecular ion at m / e 345. The infrared spectrum contained a cyano stretching peak at 2180 cm-'. The 31P NMR spectrum consisted of a singlet at -7.8 ppm. Crystals suitable for X-ray analysis were grown by slow evaporation of a solution of 2 in hexane. The structure of 2 is illustrated
Four possible diastereomers having three consective chiralcenters, R-CHMe-CHOH-CHMe-R′, have been synthesized stereoselectivelybased on the stereoselectivereduction of acyclicketones.