Cinchona alkaloid-based polymer-bound phase-transfer catalysts: Efficient enantioselective alkylation of benzophenone imine of glycine esters

Summary Cross-linked polystyrene-bound and poly(ethylene glycol)-bound phase-transfer catalysts as well as homopolymers of cinchona alkaloid derivatives have been synthesised. Both soluble and insoluble polymers have been investigated. The enantioselective alkylation of N-diphenyl methylene glycine t-butyl ester has been successfully carried out in heterogeneous and homogeneous systems. High enantioselectivities (up to 96%) have been obtained. The polymer-bound catalysts have been easily recovered and conditions for efficient recycling have been studied.     

Alkaloid and phenolic compounds of Galanthus caucasicus, Magnolia obovata, Cocculus laurifolius, and Veratrum lobelianum grown in Georgia

A collection of plants from the country of Georgia (Galanthus caucasicus, Magnolia obovata, Cocculus laurifolius, and Veratrum lobelianum) has been studied for their alkaloid content. Our studies led to the isolation and identification of 24 alkaloids, three of which are being identified and reported for the first time.     

Stereoselective syntheses of (+)-α- and (−)-β-conhydrine from L-aspartic acid

An efficient synthesis of (+)-α-conhydrine 1 and (−)-β-conhydrine 2 has been achieved by diastereoselective alkylation of an amino aldehyde derivative 7 with ethylmagnesium bromide or diethylzinc.     

Expedient Construction of the Hexacycle of Franchetine

Franchetine, a unique 7,17‐seco type of norditerpenoid alkaloid, possesses a highly congested polycyclic architecture coupled with nine stereogenic centers. Here we present an efficient synthetic approach for the intact hexacyclic framework of franchetine from the known tricyle 16 in 20 steps. The synthesis features a diastereoselective 6‐exo‐tet radical cyclization for construction of ring A and a unique oxidative Wagner–Meerwein‐type rearrangement to realize the functionalized [3.2.1] bridging ring CD.     

Isolation and structure determination of a new diketopiperazine dimer from marine-derived fungus Aspergillus sp. SF-5280

A new diketopiperazine dimer designated as SF5280-415 (1) was isolated from an EtOAc extract of the marine-derived fungus Aspergillus sp. SF-5280 by various chromatographic methods. The structure of 1 was mainly determined by analysis of the NMR spectroscopic data and MS data, along with Marfey’s method. This compound is a new diastereoisomer of known bispyrrolidinoindoline diketopiperazine alkaloid WIN 64745, which possesses unique architecture biosynthetically derived from an indole oxidation reaction of tryptophan.     

A new denudatine type C20-diterpenoid alkaloid from Aconitum sinchiangense W. T. Wang

A new denudatine-type C₂₀-diterpenoid alkaloid, designated as sinchianine (1), together with eight known diterpenoid alkaloids, 12-acetyl-12-epi-napelline (2), 12-epi-napelline (3), neoline (4), talatisamine (5), 14-O-acetylsenbusine A (6) and benzoylaconine (7), songorine (8) and aconitine (9), were isolated from the whole herb of Aconitum sinchiangense W. T. Wang. Their structures were elucidated on the basis of extensive spectroscopic analyses (NMR and HR-ESI-MS) and comparison with data reported in the literature.     

Targeted profiling and relative quantification of benzoyl diterpene alkaloids in Aconitum roots by using LC–MS/MS with precursor ion scan

Benzoyl aconite alkaloids have myocardial protective effects at a low dose and produce toxic effects at high dose. Due to lack of enough reference compounds, most of the benzoyl alkaloids had few concerns, except the typical ones, i.e. aconitine, mesaconitine, and hypaconitine. To rapidly screen out and quantify benzoyl alkaloids, a high performance liquid chromatography combined with tandem mass spectrometry was proposed based on precursor ion scanning mode. First, a diagnostic ion at m/z 105 corresponding to benzoyl group was observed by using tandem mass spectrometry, which could be used for the rapid identification of benzoyl alkaloids. The targeted screening of these alkaloids was then conducted by using precursor ion scan of characteristic ion at m/z 105. Shengfuzi (the lateral root of A. carmichaelii) was taken as example, and 24 benzoyl‐containing alkaloids were identified. The six major alkaloids including aconitine, mesaconitine, hypaconitine, benzoylaconine, benzoylmesaconine, and benzoylhypaconine were determined in the precursor ion scan mode by the standard curve method. Reliable linearity, sensitivity, precision, accuracy, and repeatability were obtained and validated. Then the relative response factors between these six analytes were calculated, which were not more than two times using any alkaloid as reference. Thus, the other 18 alkaloids lacking reference compounds were relatively quantified. This approach provides a useful tool for rapid identification and quantitative analysis of toxic benzoyl alkaloids, and also an efficient method for the safety assessment of Aconitum roots.