c Burkholderia thailandensis contains three acyl-homoserine lactone quorum sensing circuits and has two additional LuxR homologs. To identify B. thailandensis quorum sensing-controlled genes, we carried out transcriptome sequencing (RNA-seq) analyses of quorum sensing mutants and their parent. The analyses were grounded in the fact that we identified genes coding for factors shown previously to be regulated by quorum sensing among a larger set of quorum-controlled genes. We also found that genes coding for contact-dependent inhibition were induced by quorum sensing and confirmed that specific quorum sensing mutants had a contact-dependent inhibition defect. Additional quorum-controlled genes included those for the production of numerous secondary metabolites, an uncharacterized exopolysaccharide, and a predicted chitin-binding protein. This study provides insights into the roles of the three quorum sensing circuits in the saprophytic lifestyle of B. thailandensis, and it provides a foundation on which to build an understanding of the roles of quorum sensing in the biology of B. thailandensis and the closely related pathogenic Burkholderia pseudomallei and Burkholderia mallei.

The ability to perform a dynamic kinetic asymmetric transformation (DYKAT) using the palladiumcatalyzed asymmetric allylic alkylation (AAA) is explored in the context of butadiene monoepoxide. The versatility of this commercially available, but racemic, four-carbon building block becomes significantly enhanced via conversion of both enantiomers into a single enantiomeric product. The concept is explored in the context of a synthesis of vinylglycinol with phthalimide as the nitrogen source. The success of the project required a new design of the ligand for palladium wherein additional conformational restraints were introduced. Thus, the phthalimide derivative of vinylglycinol was obtained in nearly quantitative yield and had an ee of 98% which, upon crystallization, was enhanced to >99%. This one-step synthesis of a protected form of vinylglycinol provided short practical syntheses of the title compounds. Vigabatrin requires only four steps, and ethambutol six. The intermediate to the existing synthesis of ethambutol is available in 87% yield in three steps. (R)-Serine derives from oxidative cleavage of the double bond. The reaction of phthalimide and isoprene monoepoxide demonstrates the remarkable ability of the chiral ligands to control both regioselectivity and enantioselectivity and demonstrates the effectiveness of this protocol in creating a quaternary center asymmetrically.While, in theory, there are many mechanisms for asymmetric induction with transition metal catalysts, in practice, the overwhelming mechanism comes down to the differentiation of enantiotopic faces of prochiral unsaturation (alkenes, carbonyl groups, etc.). 1 The metal-catalyzed allylic alkylation may employ a similar mechanism; however, in most cases, it involves some other enantiodiscriminating events such as discriminating between enantiotopic leaving groups or enantiotopic termini of π-allylmetal interemediates. 2 An unsymmetrical substrate such as 1 (Scheme 1) may lead preferentially to either complex 2 or 3 to give rise to an asymmetric alkylation. On the other hand, it may give a mixture of 2 and 3 which can equilibrate via a σ-complex. In this case, the enantiodiscrimination arises because of a rate differential between the reaction of the two diastereomeric complexes 2 and 3 and the nucleophile to give either enantiomeric product 4 or ent-4. In this latter scenario, employing the racemate 7 and ent-7 also may lead to asymmetric induction. This type of process, while frequently referred to as a kinetic resolution, is more properly referred to as a dynamic kinetic asymmetric transformation (DYKAT). Using the family of ligands being developed in these laboratories, 3 our mnemonic predicts the complex derived from ligand 5 and Pd(0) should favor path a; whereas, the complex derived from ligand 6 and Pd(0) should favor path b. The major problem with this series is the issue of regioselectivity since attack in such systems is normally favored at the primary carbon which generates an achiral product. 4

While great strides in asymmetric induction have been made in many types of transition metal catalyzed reactions exemplified by hydrogenation,1 epoxidation,2 dihydroxylation,3 cyclopropanation,4 and aziridination,5 progress in allylic alkylations with stabilized nucleophiles has been sporadic.6™11 The reason stems from the nature of the processes. Whereas in all of the areas first mentioned bond formation occurs within the coordination sphere of the metal and therefore within the asymmetric environment created by the chiral fragments, in allylic alkylation the crucial bond-making (or bond-breaking) event occurs on the face of the allyl fragment distal to the metal and therefore remote from the asymmetric environment created by the chiral ligands. Furthermore, for the case in which asymmetric induction involves nucleophilic attack on a prochiral (ir-allyl)palladium intermediate 1 as the enantiodiscriminating step as illustrated in eq 1, the nature of the nucleophile may have a profound effect. Early

Bleomycin (BLM) is an antitumor antibiotic that is used clinically. Its major cause of cytotoxicity is thought to be related to BLM's ability to cause double-strand (ds) DNA cleavage. A single molecule of BLM appears to cleave both strands of DNA in the presence of its required cofactors Fe(2+) and oxygen without dissociating from the helix. A mechanism for this process has been proposed based on a model structure of the hydroperoxide of Co(III)-BLM (CoBLM) bound sequence-specifically to an intact duplex containing a GTAC site, a hot spot for ds cleavage [Vanderwall, D. E., Lui, S. M., Wu, W., Turner, C. J., Kozarich, J. W., and Stubbe, J. (1997) Chem. Biol. 4, 373-387]. In this paper, we present a structural model for the second cleavage event. Two-dimensional NMR spectroscopy and molecular modeling were carried out to study CoBLM bound to d(CCAAAGXACTGGG).d(CCCAGTACTTTGG), where X represents a 3'-phosphoglycolate lesion next to a 5'-phosphate. Assignments of 729 NOEs, including 51 between the drug and the DNA and 126 within the BLM molecule, have been made. These NOEs in addition to 96 dihedral angle constraints have been used to obtain a well-defined structural model for this complex. The model reveals that the bithiazole tail is partially intercalated between the T19 and the A20 of the duplex and that the metal binding domain is poised for abstraction of the T19 H4' in the minor groove. The modeling further reveals that the predominant conformation of the bithiazole protons is trans. Two cis conformations of these protons are also observed, and ROESY experiments provide evidence for interconversion of all of these forms. The relationship of these observations to the model for ds cleavage is presented.

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