Synthesis of the insect antifeedant CDE molecular fragment of 12-ketoepoxyazadiradione and related compounds

A diastereoselective synthesis of the model insect antifeedant 29 a CDE molecular fragment of 12-ketoepoxyazadiradione has been achieved in ten steps from indenone 9 in 44% overall yield. Several of the compounds obtained along the synthesis related to model compound 29 show significant antifeedant activity against Spodoptera littoralis and Spodoptera frugiperda.     

Two New C‐seco Limonoids from the Fruit of Melia azedarach

A phytochemical investigation of the fruits of Melia azedarach led to the isolation of two new C‐seco‐nimbolinin‐type limonoids, 3α‐acetoxy‐1α,7α‐dihydroxy‐12α‐methoxynimbolinin ( 1 ) and 3α‐acetoxy‐1α,12α‐dihydroxy‐7α‐(2‐methylprop‐2‐enoyl)nimbolinin ( 2 ), together with eleven known compounds, 3 – 13 . Their structures were elucidated on the basis of extensive spectroscopic analysis, including ¹H‐ and ¹³C‐NMR, HMQC, HMBC, NOESY, and HR‐FAB‐MS.     

Eight new limonoids from Turraea pubescens

Eight new ring B-seco limonoids, turrapubesic acids A-C (1-3) and turrapubesins C-G (4-8), along with turraflorin E and isoazadironolide were isolated from the twigs and leaves of Turraea pubescens. Turrapubesic acids A-C (1-3) are a group of ring B-seco limonoid 17-carboxylic acids with a new C₂₃ skeleton, and turrapubesin C (4) incorporates an unprecedented 1,30-oxygen bridge. The structures including absolute stereochemistry of 1-8 were established on the basis of extensive NMR spectroscopic analysis and CD study. The cytotoxicity of the isolates against the P-388 and A-549 cells was evaluated.     

Synthesis of limonoid CDE fragments related to limonin and nimbinim

A practical, brief and selective synthesis of limonoid CDE fragments from a readily available starting diketone is described. The key step is a cationic electrocyclization promoted by strong acids. In general the methodology has been demonstrated for compounds with sensitive furane and thiophene substituents to obtain diverse substituted indenones. Several of the compounds obtained show significant antifeedant activity against Spodoptera littoralis.     

Stereoselective synthesis of a 12-acetoxyazadiradione analogue

The synthesis of the 12-acetoxy enone 15 related to the limonoid azadiradione has been achieved in 12 steps (16% overall yield) starting from tricyclic diester 1. The key steps involve intramolecular 1,3-dipolar cycloaddition of a nitrile oxide and a Stille coupling reaction of a vinyl iodide with a stannylfuran.     

An unusual 9,11-seco limonoid from Toona ciliata

An unusual 9,11-seco limonoid, toonasecone A (1), had been isolated from the bark of Toona ciliata. The structure was elucidated on the basis of extensive spectroscopic data analysis. This is the first time the 9,11-seco limonoid has been isolated from the Meliaceae family.     

New Limonoids from the Seeds of Xylocarpus granatum

Three novel limonoids, 2,3‐dideacetylxyloccensin S ( 1 ), 30‐deacetylxyloccensin W ( 2 ), and 7‐hydroxy‐21β‐methoxy‐3‐oxo‐24,25,26,27‐tetranortirucalla‐1,14‐diene‐23(21)‐lactone ( 3 ), were isolated from the seeds of the Chinese mangrove, Xylocarpus granatum. The structures were elucidated on the basis of 1D‐ and 2D‐NMR (including ¹H‐ and ¹³C‐NMR, DEPT, ¹H,¹H‐COSY, HSQC, HMBC, and NOESY) data and confirmed by HR‐MS.     

Determination of limonoate and nomilinoate A-ring lactones in citrus juices by liquid chromatography-electrospray ionization mass spectrometry

The development of delayed bitterness in citrus products is a major problem to citrus producers and juice processors worldwide. A rapid and sensitive liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) method has been developed to quantify the recognized precursors of limonoid derived delayed bitterness, limonoate and nomilinoate A-ring lactones, in a wide variety of citrus juices. The limonoid A-ring lactones were isolated by solid-phase extraction from juice samples, analyzed by negative ion LC-ESI-MS and quantified utilizing the standard addition method.     

Two new limonoids from Melia toosendan

Two new limonoid-type triterpenoids, named 12-o-ethyl-l-deacetylnimbolinin B and 1-o-tigloyl-1-o-debenzoylohchinal, have been isolated from the fruit of Melia toosendan Sieb. et Zucc. Their structures were elucidated by spectral methods, including 2D-NMR spectra.