An alternative synthetic approach for the introduction of chirality in β-carboline moiety through in situ reduction of N-acyliminium ion intermediates generated from imine 2 and chloroformate of 8-phenylmenthyl as chiral auxiliary was achieved. The method applied microwave-assisted irradiation and used PdCl2/Et3SiH protocol as a mild reducing agent, which decreased reaction times to minutes when compared
通过原位还原由亚胺2和8-苯基薄荷基的氯甲酸酯作为手性助剂生成的N-酰基亚胺离子中间体,实现了另一种在β-咔啉部分中引入手性的合成方法。该方法采用微波辅助辐射,并使用PdCl 2 / Et 3 SiH协议作为温和的还原剂,与常规的热反应相比,该方法将反应时间缩短至数分钟。还原产生的R-胺的非对映选择性(4-12:1),与从Noyori不对称氢化催化剂获得的产物相比,在手性辅助去除和光谱数据后将其分配。
Inverted Binding of Non-natural Substrates in Strictosidine Synthase Leads to a Switch of Stereochemical Outcome in Enzyme-Catalyzed Pictet–Spengler Reactions
作者:Elisabeth Eger、Adam Simon、Mahima Sharma、Song Yang、Willem B. Breukelaar、Gideon Grogan、K. N. Houk、Wolfgang Kroutil
DOI:10.1021/jacs.9b08704
日期:2020.1.15
The Pictet–Spenglerreaction is a valuable route to 1,2,3,4-tetrahydro-β-carboline (THBC) and isoquinoline scaffolds found in many important pharmaceuticals. Strictosidine synthase (STR) catalyzes the Pictet–Spengler condensation of tryptamine and the aldehyde secologanin to give (S)-strictosidine as a key intermediate in indole alkaloid biosynthesis. STRs also accept short-chain aliphatic aldehydes
Bifunctional thiosquaramide catalyzed asymmetric reduction of dihydro-β-carbolines and enantioselective synthesis of (−)-coerulescine and (−)-horsfiline by oxidative rearrangement
作者:Manda Sathish、Fabiane M. Nachtigall、Leonardo S. Santos
DOI:10.1039/d0ra07705d
日期:——
(up to 88%). Moreover, the chiral thiosquaramide used also afforded exceptional catalyst activity in the syntheses of (−)-coerulescine (5) and (−)-horsfiline (6) with excellent enantioselectivities up to 98% and 93% ee, respectively, via an enantioselective oxidativerearrangement approach.
Novel Supramolecular Palladium Catalyst for the Asymmetric Reduction of Imines in Aqueous Media
作者:Wender A. da Silva、Manoel T. Rodrigues、N. Shankaraiah、Renan B. Ferreira、Carlos Kleber Z. Andrade、Ronaldo A. Pilli、Leonardo S. Santos
DOI:10.1021/ol9011772
日期:2009.8.6
A novel approach to the asymmetric reduction of dihydro-β-carboline derivatives to the corresponding tetrahydro-β-carbolines is described based on the supramolecular lyophilized complex formed from β-cyclodextrin/imines as an enzyme mimetic and palladium hydride as the reducing agent. The methodology allowed us to develop a short and efficient preparation of (R)-harmicine and (R)-deplancheine alkaloids
Asymmetric Transfer Hydrogenation of Imines in Water by Varying the Ratio of Formic Acid to Triethylamine
作者:Vaishali S. Shende、Sudhindra H. Deshpande、Savita K. Shingote、Anu Joseph、Ashutosh A. Kelkar
DOI:10.1021/acs.orglett.5b00889
日期:2015.6.19
Asymmetrictransferhydrogenation (ATH) of imines has been performed with variation in formic acid (F) and triethylamine (T) molar ratios in water. The F/T ratio is shown to affect both the reduction rate and enantioselectivity, with the optimum ratio being 1.1 in the ATH of imines with the Rh-(1S,2S)-TsDPEN catalyst. Use of methanol as a cosolvent enhanced reduction activity. A variety of imine substrates