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Cyclic Imines and Their Salts as Universal Precursors in the Synthesis of Nitrogen-Containing Alkaloids.
Int J Mol Sci
December 2024
Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, Arbuzov Str., 8, Kazan 420088, Russia.
Alkaloids are predominantly nitrogen-containing heterocyclic compounds that are usually isolated from plants, and sometimes from insects or animals. Alkaloids are one of the most important types of natural products due to their diverse biological activities and potential applications in modern medicine. Cyclic imines were chosen as starting compounds for the synthesis of alkaloids due to their high synthetic potential.
View Article and Find Full Text PDFThe Effect of Alkyl Substituents on the Formation and Structure of Homochiral (*,*)-[RGa(-OCH(Me)COR')] Species-Towards the Factors Controlling the Stereoselectivity of Dialkylgallium Alkoxides in the Ring-Opening Polymerization of -Lactide.
Molecules
January 2025
Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland.
Building on our previous studies, which have demonstrated that homochiral propagating species-(*,*)-[MeGa(-OCH(Me)COR)]-were crucial for the heteroselectivity of [MeGa(-OCH(Me)COMe)] in the ring-opening polymerization (ROP) of racemic lactide (-LA), we have investigated the effect of alkyl groups on the structure and catalytic properties of dialkylgallium alkoxides in the ROP of -LA. Therefore, we have isolated and characterized the -[RGa(-OCH(Me)COMe] (R = Et (), Pr () and -[RGa(-OCH(Me)CHN] (R = Et (), Pr ()) complexes, to demonstrate the effect of alkyl groups on the chiral recognition induced the formation of the respective homochiaral species-(*,*)-[RGa(-OCH(Me)COMe)] and (*,*)-[RGa(-OCH(Me)CHN]. Moreover, we have investigated the structure of (,)-[RGa(-OCH(Me)COMe] (R = Et ((,)-, R = Pr ((,)-,) and their catalytic activity in the ROP of -LA.
View Article and Find Full Text PDFThe Relationship between Substrate Structure and Selectivity of Ketoreduction in Multimodular Polyketide Synthases: A Comparative Study of A-Type Ketoreductases from Late Modules Using Complex Precursor Analogues.
ACS Chem Biol
January 2025
Professur Organische Chemie IV, Fakultät für Biologie, Chemie und Geowissenschaften, Department of Chemistry, Universität Bayreuth, 95447 Bayreuth, Germany.
Ketoreductases (KRs) are domains in the reductive loops of type I polyketide synthases (PKSs) and are responsible for the majority of stereocenters in reduced polyketides. Although the highly stereoselective reduction of ACP-bound β-ketothioester intermediates by KRs is crucial for the overall functioning of PKSs, the substrate-dependent stereoselectivity of KRs is a factor that is not yet fully understood, especially for KR domains in late PKS modules that act on biosynthetic precursors with complex polyketidic moieties. We present studies on the three KR domains FosKR7, PlmKR6, and EryKR6 from the biosynthetic pathways of fostriecin, phoslactomycin, and erythromycin by in vitro assays using close surrogates of the octaketidic FosKR7 biosynthetic precursor, complex derivatives and a diketide in the form of their biomimetic -acetylcysteamine thioesters.
View Article and Find Full Text PDFSesquiterpene enantiomers from Alismatis Rhizoma.
Phytochemistry
April 2025
Institute of Chinese Materia Medica, China Academy of Chinese Medical Sciences, Beijing, 100700, PR China. Electronic address:
A pair of dinor-sesquiterpene enantiomers (1a/1b), eight pairs of guaiane-type sesquiterpenes enantiomers (2a/2b, 3a/3b, 4a/4b, 5a/5b, 6a/6b, 7a/7b, 8a/8b, 9a/9b) and two guaiane-type sesquiterpenes (10, 11), including eleven undescribed ones (1a, 1b, 2a, 2b, 3a, 3b, 4a, 5b, 6a, 10, and 11), were isolated from the aqueous extract of Alismatis Rhizoma. The structures were elucidated by combining 1D and 2D NMR and HRESIMS spectroscopic data. The absolute configurations were determined by experimental and calculated ECD spectra, [Mo(OAc)]-induced ECD spectral analysis, and comparison of the experimental ECD spectra with those of similar analogs.
View Article and Find Full Text PDFA Quantitative Study of the Halogenophilic Nucleophilic Substitution (S2X) Reaction and Chalcogenophilic Nucleophilic Substitution (S2Ch) Reaction.
J Am Chem Soc
December 2024
School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore.
Halogenophilic nucleophilic substitution (S2X) has a distinctly different reaction pathway compared to the bimolecular nucleophilic substitution reaction (S2), but they can lead to the same reaction product. However, their differences can be distinguished by studying stereoselective reactions in which both reaction pathways are possible. Herein, we utilize the stereospecific nature of S2 and the presence of a pro-chiral anion intermediate in S2X to conduct a quantitative study in which both S2 and S2X reactions exist.
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