525-40-6Relevant articles and documents
Bifunctional thiosquaramide catalyzed asymmetric reduction of dihydro-β-carbolines and enantioselective synthesis of (-)-coerulescine and (-)-horsfiline by oxidative rearrangement
Nachtigall, Fabiane M.,Santos, Leonardo S.,Sathish, Manda
, p. 38672 - 38677 (2020/11/05)
Tetrahydro-β-carboline (THBC) is a tricyclic ring system that can be found in a large number of bioactive alkaloids. Herein, we report a simple and efficient method for the synthesis of enantiopure THBCs through a chiral thiosquaramide (11b) catalyzed imine reduction of dihydro-β-carbolines (17a-f). The in situ generated Pd-H employed as hydride source in the reaction of differently substituted chiral THBCs (18a-f) afforded high selectivities (R isomers, up to 96% ee) and good isolated yields (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 oxidative rearrangement approach.
Asymmetric Synthesis of (R)-1-Alkyl-Substituted Tetrahydro-?-carbolines Catalyzed by Strictosidine Synthases
Pressnitz, Desiree,Fischereder, Eva-Maria,Pletz, Jakob,Kofler, Christina,Hammerer, Lucas,Hiebler, Katharina,Lechner, Horst,Richter, Nina,Eger, Elisabeth,Kroutil, Wolfgang
supporting information, p. 10683 - 10687 (2018/08/17)
Stereoselective methods for the synthesis of tetrahydro-?-carbolines are of significant interest due to the broad spectrum of biological activity of the target molecules. In the plant kingdom, strictosidine synthases catalyze the C?C coupling through a Pictet–Spengler reaction of tryptamine and secologanin to exclusively form the (S)-configured tetrahydro-?-carboline (S)-strictosidine. Investigating the biocatalytic Pictet–Spengler reaction of tryptamine with small-molecular-weight aliphatic aldehydes revealed that the strictosidine synthases give unexpectedly access to the (R)-configured product. Developing an efficient expression method for the enzyme allowed the preparative transformation of various aldehydes, giving the products with up to >98 % ee. With this tool in hand, a chemoenzymatic two-step synthesis of (R)-harmicine was achieved, giving (R)-harmicine in 67 % overall yield in optically pure form.
Sequence-Based In-silico Discovery, Characterisation, and Biocatalytic Application of a Set of Imine Reductases
Velikogne, Stefan,Resch, Verena,Dertnig, Carina,Schrittwieser, Joerg H.,Kroutil, Wolfgang
, p. 3236 - 3246 (2018/08/03)
Imine reductases (IREDs) have recently become a primary focus of research in biocatalysis, complementing other classes of amine-forming enzymes such as transaminases and amine dehydrogenases. Following in the footsteps of other research groups, we have established a set of IRED biocatalysts by sequence-based in silico enzyme discovery. In this study, we present basic characterisation data for these novel IREDs and explore their activity and stereoselectivity using a panel of structurally diverse cyclic imines as substrates. Specific activities of >1 U/mg and excellent stereoselectivities (ee>99 %) were observed in many cases, and the enzymes proved surprisingly tolerant towards elevated substrate loadings. Co-expression of the IREDs with an alcohol dehydrogenase for cofactor regeneration led to whole-cell biocatalysts capable of efficiently reducing imines at 100 mM initial concentration with no need for the addition of extracellular nicotinamide cofactor. Preparative biotransformations on gram scale using these ‘designer cells’ afforded chiral amines in good yield and excellent optical purity.
