Synthesis of heliannuol D, an allelochemical from Helianthus annus

A synthesis of heliannuol D 1 is described involving regioselective oxidation of the benzoxabicyclo[3.2.1]octanone 20 followed by hydrogenolysis to generate the benzoxepane ring system of 1.     

A short, rapid synthesis of heliannuol D, an allelochemical from Helianthus annus employing ring-closing metathesis

A facile, very short synthesis of the allelochemical heliannuol D is described involving the application of ring-closing metathesis to generate the benzoxepane ring system of 1.     

Analysis of benzoxazinone derivatives in plant tissues and their degradation products in agricultural soils

Plant allelopathy may be considered an additional means of weed control in modern agriculture, but its means of action are not well understood and knowledge of specific allelochemicals involved in allelopathy is required.Benzoxazinoids are a chemical family with the most active allelopathic compounds in some crops (e.g., wheat, rye or maize). The analysis of these analytes has been based mainly on gas chromatography coupled to mass spectrometry (MS) and liquid chromatography (LC) coupled to ultraviolet detection. To improve the sensitivity and selectivity, new methodologies (e.g., LC coupled to MS and tandem MS) are being developed. Less information is available on the analytical strategies to determine their degradation products in soil samples.This article presents an overview of recent advanced analysis of benzoxazinone derivatives in plant tissues and their degradation products in agricultural soils.     

Stereoselective synthesis of β-glycosyl esters of cis-cinnamic acid and its derivatives using unprotected glycosyl donors

The β-glycosyl esters of cis-cinnamic acid were synthesized directly using Hannesian’s unprotected glycosyl donor and the carboxylic acid in toluene. This protocol does not require protecting groups on the glycosyl donors, and high stereoselectivity was achieved. The first synthesis of a potent allelochemical, 1-O-cis-cinnamoyl-β-d-glucopyranose, is also described.     

The synthesis of heliannuol C, an allelochemical from Helianthus annuus

The synthesis of the allelochemical heliannuol C 1 is described by employing a Bargellini condensation and a Claisen rearrangement to install the gem-dimethyl and vinyl functionalities, respectively. A Dieckmann cyclisation of diester 11 enabled the generation of the benzoxepane ring system enshrined in 1.     

Synthesis of heliannuols A and K, allelochemicals from cultivar sunflowers and the marine metabolite helianane, unusual sesquiterpenes containing a benzoxocane ring system

Synthesis of the allelochemicals heliannuols A and K, and the sesquiterpene helianane is described. A regioselective cleavage of a benzo-fused oxabicyclo(5.1.0)octane system under hydrogenation as well as radical induced condition was developed to generate the basic benzoxocane ring system of these unusual sesquiterpenes.     

Synthesis and absolute configuration of annuionone A

Synthesis of both enantiomers of annuionone A (1), an allelopathic agent isolated from Helianthus annuus (sunflower), was accomplished. The absolute configuration of the naturally occurring 1 was determined to be 1S,5R,8R.