The use of and search for drugs and dietary supplements derived from plants have accelerated in recent years. Ethnopharmacologists, botanists, microbiologists, and natural-products chemists are combing the Earth for phytochemicals and “leads” which could be developed for treatment of infectious diseases. While 25 to 50% of current pharmaceuticals are derived from plants, none are used as antimicrobials. Traditional healers have long used plants to prevent or cure infectious conditions; Western medicine is trying to duplicate their successes. Plants are rich in a wide variety of secondary metabolites, such as tannins, terpenoids, alkaloids, and flavonoids, which have been found in vitro to have antimicrobial properties. This review attempts to summarize the current status of botanical screening efforts, as well as in vivo studies of their effectiveness and toxicity. The structure and antimicrobial properties of phytochemicals are also addressed. Since many of these compounds are currently available as unregulated botanical preparations and their use by the public is increasing rapidly, clinicians need to consider the consequences of patients self-medicating with these preparations.

Plant Products as Antimicrobial Agents

BODIPY dyes and their derivatives: syntheses and spectroscopic properties.

The world of organic luminophores has been confined for a long time to fairly standard biological labeling applications and to certain analytical tests. Recently, however, the field has undergone a major change of direction, driven by the dual needs to develop novel organic electronic materials and to fuel the rapidly emerging nanotechnologies. Among the many diverse fluorescent molecules, the Bodipy family, first developed as luminescent tags and laser dyes, has become a cornerstone for these new applications. The near future looks extremely bright for "porphyrin's little sister".

The Chemistry of Fluorescent Bodipy Dyes: Versatility Unsurpassed

9.2. Protein-Based Hg(II) Detectors 3467 9.3. Oligonucleotide-Based Hg(II) Detector 3467 9.4. DNAzyme-Based Hg(II) Detectors 3469 9.5. Antibody-Based Hg(II) Detector 3469 10. Mercury Detectors Based on Materials 3469 10.1. Soluble and Fluorescent Polymers 3469 10.2. Membranes, Films, and Fibers 3471 10.3. Micelles 3473 10.4. Nanoparticles 3473 11. Perspectives 3474 12. Addendum 3475 12.1. Small Molecules 3475 12.2. Biomolecules 3477 12.3. Materials 3477 13. List of Abbreviations 3477 14. Acknowledgments 3478 15. References 3478

Tools and tactics for the optical detection of mercuric ion.

The increasing demand to produce enantiomerically pure pharmaceuticals, agrochemicals, flavors, and other fine chemicals has advanced the field of asymmetric catalytic technologies.1,2 Among all asymmetric catalytic methods, asymmetric hydrogenation utilizing molecular hydrogen to reduce prochiral olefins, ketones, and imines, have become one of the most efficient methods for constructing chiral compounds.3 The development of homogeneous asymmetric hydrogenation was initiated by Knowles4a and Horner4b in the late 1960s, after the discovery of Wilkinson’s homogeneous hydrogenation catalyst [RhCl(PPh3)3]. By replacing triphenylphosphine of the Wilkinson’s catalystwithresolvedchiralmonophosphines,6Knowles and Horner reported the earliest examples of enantioselective hydrogenation, albeit with poor enantioselectivity. Further exploration by Knowles with an improved monophosphine CAMP provided 88% ee in hydrogenation of dehydroamino acids.7 Later, two breakthroughs were made in asymmetric hydrogenation by Kagan and Knowles, respectively. Kagan reported the first bisphosphine ligand, DIOP, for Rhcatalyzed asymmetric hydrogenation.8 The successful application of DIOP resulted in several significant directions for ligand design in asymmetric hydrogenation. Chelating bisphosphorus ligands could lead to superior enantioselectivity compared to monodentate phosphines. Additionally, P-chiral phosphorus ligands were not necessary for achieving high enantioselectivity, and ligands with backbone chirality could also provide excellent ee’s in asymmetric hydrogenation. Furthermore, C2 symmetry was an important structural feature for developing new efficient chiral ligands. Kagan’s seminal work immediately led to the rapid development of chiral bisphosphorus ligands. Knowles made his significant discovery of a C2-symmetric chelating bisphosphine ligand, DIPAMP.9 Due to its high catalytic efficiency in Rh-catalyzed asymmetric hydrogenation of dehydroamino acids, DIPAMP was quickly employed in the industrial production of L-DOPA.10 The success of practical synthesis of L-DOPA via asymmetric hydrogenation constituted a milestone work and for this work Knowles was awarded the Nobel Prize in 2001.3k This work has enlightened chemists to realize * Corresponding author. 3029 Chem. Rev. 2003, 103, 3029−3069

New Chiral Phosphorus Ligands for Enantioselective Hydrogenation

Synthesis and spectroscopic properties of a new 4-bora-3a,4a-diaza-s-indacene (BODIPY®) dye

Phosphine oxazoline ligands la-j were converted to the corresponding [Ir(cod)(phosphine oxazoline)]+ complexes 2a-j. X-ray diffraction analyses of complexes 2b, 2h, 2i, and 2j were performed. The tert-butyl-, 1,1-diphenylethyl-, and phenyl-oxazoline complexes (2b, 2h, and 2i, respectively) had typical square planar metal environments with chair-like metallocyclic rings. However, the 3,5-di-tert-butylphenyl oxazoline complex 2j was distorted toward a tetrahedral metal geometry. This library of complexes was tested in asymmetric hydrogenations of several arylalkenes. High enantioselectivities and conversions were observed for some substrates. A possible special role for the HPh2C-oxazoline substituent in asymmetric hydrogenations was identified and is discussed. In attempts to rationalize why high enantioselectivities were not observed for some alkenes, a series of deuterium labeling experiments were performed to probe for competing reactions that occurred prior to the hydrogenation step. Double bond migrations were inferred for several substrates, and this is a significant complication in asymmetric hydrogenations of arylalkenes that had not been discussed prior to this study. A mechanistic rationale is proposed involving competing double bond migration for some but not all substrates. Appreciation of this complication will be valuable in further studies aimed at optimization of enantioselection in asymmetric hydrogenations of unfunctionalized alkenes.

Enantioselective Hydrogenations of Arylalkenes Mediated by [Ir(cod)(JM-Phos)]+ Complexes

Three different syntheses of the phosphine oxazoline systems 1 are presented. Two of these approaches are divergent routes designed to involve an advanced intermediate that can be transformed into several different end-products. The third is a shorter route specifically designed to facilitate preparations of these systems on a larger scale using minimal functional group protection. Overall, eight different phosphine oxazolines were prepared. These were screened in several palladium-mediated allylation reactions. They proved to be most useful for asymmetric alkylation of 3-acetoxy-1,3-diphenylpropene and less suitable/effective for the more challenging substrates (a pentenyl derivative and a cyclohexenyl system). X-ray crystallographic analysis of the complex [(η3-PhCHCHCHPh)Pd(1a)][PF6] led to the conclusion that the origins of asymmetric induction in these systems might be indirectly attributed to interaction of the oxazoline-phenyl substituent with the palladium and with an allyl-phenyl substituent. Fin...

New, optically active phosphine oxazoline (JM-Phos) ligands: syntheses and applications in allylation reactions.

The reaction of benzeneseleninic anhydride and hexamethyldisilazane gives a reactive intermediate namely oligomeric (RSeN) 4 which oxidizes a phenol to the selenoiminoquinone 1. Both spectroscopic and crystallographic studies showed that the oxygen atom of the carbonyl group in the (phenylselenoimino)quinone 2 is involved in an attractive interaction with the selenium atom. The carbon atom of the phenyl ring is also found to be in the same plane as the O-C-C-N-Se plane. Theoretical studies of these systems clearly show a strong dependence of the Se-O interactions on the substituent on the selenium atom

Joseph H. Reibenspies

Papers

Synthesis and spectroscopic properties of a new 4-bora-3a,4a-diaza-s-indacene (BODIPY®) dye

Enantioselective Hydrogenations of Arylalkenes Mediated by [Ir(cod)(JM-Phos)]+ Complexes

New, optically active phosphine oxazoline (JM-Phos) ligands: syntheses and applications in allylation reactions.

Unusual attractive interactions between selenium and oxygen in selenoiminoquinones

Studies of Ligand Exchange in N-Heterocyclic Carbene Silver(I) Complexes