Underappreciated in the realm of palladium catalyzed cross-coupling chemistry is the formation of phosphorous–carbon bonds. This tutorial review summarises a collection of important contributions in the area, providing a flavour of the many types of phosphorus species that are participants in palladium catalyzed phosphorus–carbon bond formation. Recent developments include the usage of the cross-coupling reaction for preparation of phosphine ligands and the involvement of low molecular weight phosphinic acid derivatives for the synthesis of unsaturated phosphinic and phosphonic acid derivatives. Mechanistic cycles are offered in some instances. Stereochemical issues are addressed where applicable. The literature is covered to mid 2003.
A comprehensive review of recent chemistry of sulfenate anions is presented. Compound structure, methods of generation and reaction of sulfenates are all addressed. Topical areas including asymmetric alkylation, sulfinyl zinc species and bio-organic mechanisms are covered.
Finger millet is an ancient African cereal crop, domesticated 7000 years ago in Ethiopia, reaching India at 3000 BC. Finger millet is reported to be resistant to various fungal pathogens including Fusarium sp. We hypothesized that finger millet may host beneficial endophytes (plant-colonizing microbes) that contribute to the antifungal activity. Here we report the first isolation of endophyte(s) from finger millet. Five distinct fungal species were isolated from roots and predicted taxonomically based on 18S rDNA sequencing. Extracts from three putative endophytes inhibited growth of F. graminearum and three other pathogenic Fusarium species. The most potent anti-Fusarium strain (WF4, predicted to be a Phoma sp.) was confirmed to behave as an endophyte using pathogenicity and confocal microscopy experiments. Bioassay-guided fractionation of the WF4 extract identified four anti-fungal compounds, viridicatol, tenuazonic acid, alternariol and alternariol monomethyl ether. All the purified compounds caused dramatic breakage of F. graminearum hyphae in vitro. These compounds have not previously been reported to have anti-Fusarium activity. None of the compounds, except for tenuazonic acid, have previously been reported to be produced by Phoma. We conclude that the ancient, disease-tolerant crop, finger millet, is a novel source of endophytic anti-fungal natural products. This paper suggests the value of the crops grown by subsistence farmers as sources of endophytes and their natural products. Application of these natural chemicals to solve real world problems will require further validation.