C5′-Alkyl Substitution Effects on Digitoxigenin α-l-Glycoside Cancer Cytotoxicity
摘要:
A highly regio- and stereoselective asymmetric synthesis of various CS'-alkyl side chains of rhamnosyl- and amicetosyl-digitoxigenin analogues has been established via palladium-catalyzed glycosylation with postglycosylated dihydroxylation or diimide reduction. The C5'-methyl group in both alpha-L-rhamnose and cc-L-amicetose digitoxin analogues displayed a steric directed apoptosis induction and tumor growth inhibition against nonsmall cell human lung cancer cells (NCI-H460). The antitumor activity is significantly reduced when the steric hindrance is increased at the C5'-stereocenter.
Chiral 2-(2-hydroxyaryl)alcohols (HAROLs) with a 1,4-diol scaffold as a new family of ligands and organocatalysts
作者:Ömer Dilek、Mustafa A. Tezeren、Tahir Tilki、Erkan Ertürk
DOI:10.1016/j.tet.2017.11.054
日期:2018.1
Efficient and modular syntheses of chiral 2-(2-hydroxyaryl)alcohols (HAROLs), novel 1,4-diols carrying one phenolic and one alcohol hydroxyl group, have been developed which led to generation of a small library of structurally diverse HAROLs in enantiomerically pure form. Of the different HAROLs examined, a HAROL based on the indan backbone exhibited the highest activity and enantioselectivity in the
高效和模块化的手性2-(2-羟基芳基)醇(HAROLs)的合成,带有一个酚和一个醇羟基的新型1,4-二醇已被开发出来,这导致在对映异构体中生成结构多样的HAROLS小文库纯形式。在考察的不同HAROL中,基于茚满骨架的HAROL在Ti(O i Pr)4(y高达97%, 88%ee)并在三田膦的促进下在Morita-Baylis-Hillman反应中作为氢键供体有机催化剂发挥作用。
Switching of Enantioselectivity in the Catalytic Addition of Diethylzinc to Aldehydes by Regioisomeric Chiral 1,3-Amino Sulfonamide Ligands
作者:Takuji Hirose、Kazuyuki Sugawara、Koichi Kodama
DOI:10.1021/jo200834n
日期:2011.7.1
Twenty chiral 1,3-amino sulfonamides of two classes (2a–i and 3a–k) have been prepared from (−)-cis-2-benzamidocyclohexanecarboxylic acid (1) and studied as ligands for catalytic enantioselectiveaddition of Et2Zn to a variety of aromatic and aliphatic aldehydes. The ligands 2 and 3 are regioisomers in which the position of the amine and sulfonamide groups is exchanged. Each class of ligands with the
d-Penicillamine derived thiazolidine ligands were prepared in a two-step synthetic sequence and used in the enantioselective alkylation of a variety of aromatic aldehydes with diethylzinc at room temperature. Excellent ee, up to >99%, and nearly complete conversions were observed. Structurally analogous l-cysteine derived thiazolidine ligands were also synthesized and tested for comparative purposes
groups and ethylzinc carboxamidates from these ligands as catalysts for Et2Zn additions to aldehydes were reported. Excellent yields were obtained with moderate ee′s in Et2Zn additions to benzaldehyde derivatives, implying effectiveness of our newly designed catalytic structures as well as mediocre stereocontrol by these chiral ligands. Possible transition states were suggested based on the crystal structures
The first catalytic asymmetric addition of diethylzinc to aldehyde promoted by chiral thiourea
作者:Zhi Guo Qiao、Tian Hua Shen、Zhen Fang Fu、Jun Qi Li、Hong Wang、Qing Bao Song
DOI:10.1016/j.cclet.2011.07.015
日期:2011.11
Abstract A series of C2 -symmetric and asymmetricchiral thiourea derivatives were synthesized from commercial l -phenylalanine. All of the new compounds have been fully characterized by IR, 1 H NMR, 13 C NMR, MS spectra and elemental analyses. The chiral thioureas were used as chiralligands in the catalytic enantioselective ethylation of aldehydes with diethylzinc, the corresponding sec-alcohols
摘要从商品化的1-苯丙氨酸合成了一系列C 2对称和不对称的手性硫脲衍生物。所有新化合物均已通过IR,1 H NMR,13 C NMR,MS光谱和元素分析进行了全面表征。在条件优化后,手性硫脲被用作醛与二乙基锌催化醛的对映选择性乙基化的手性配体,获得了相应的仲醇,具有优异的对映选择性(最高87.1%ee)和高收率(最高76.7%)。