Hereditarily Optimal Realizations of Consistent Metrics

One of the main problems in phylogenetics is to find good approximations of metrics by weighted trees. As an aid to solving this problem, it could be tempting to consider optimal realizations of metrics—the guiding principle being that, the (necessarily unique) optimal realization of a tree metric is the weighted tree that realizes this metric. And, although optimal realizations of arbitrary metrics are, in general, not trees, but rather weighted networks, one could still hope to obtain a phylogenetically informative representation of a given metric, maybe even more informative than the best approximating tree. However, optimal realizations are not only difficult to compute, they may also be non-unique. Here we focus on one possible way out of this dilemma: hereditarily optimal realizations. These are essentially unique, and can be described in a rather explicit way. In this paper, we recall what a hereditarily optimal realization of a metric is and how it is related to the 1-skeleton of the tight span of that metric, and we investigate under what conditions it coincides with this 1-skeleton. As a consequence, we will show that hereditarily optimal realizations for consistent metrics, a large class of phylogentically relevant metrics, can be computed in a straight-forward fashion. Received August 26, 2004     

Mesoporous silicabis(ethylsulfanyl)propane palladium catalysts for hydrogenation and one-pot two-step Suzuki cross-coupling followed by hydrogenation

The solid phase catalytic activity of mesoporous silicabis(ethylsulfanyl)propane palladium catalysts for hydrogenation and novel one-pot two-step Suzuki cross-coupling followed by hydrogenation is described. The efficiency of catalytic hydrogenation was measured for substrate nitrobenzene with 5, 7 and 14 nm average pore diameter materials. The 5 nm pore material performed best and was also very effective in the catalytic hydrogenation of alkene, nitrile and imine substrates. Novel one-pot two-step Suzuki cross-coupling and hydrogenation was demonstrated using bromonitro- and bromodinitrobenzene and phenylboronic acid as substrates with conversion to the corresponding coupled amino compounds. As a consequence of the high affinity of the sulfur ligands for palladium, none was detected in leaching tests and the catalyst is easily separated and recycled.     

Densely Functionalized 2-Methylideneazetidines: Evaluation as Antibacterials

Twenty-two novel, variously substituted nitroazetidines were designed as both sulfonamide and urethane vinylogs possibly endowed with antimicrobial activity. The compounds under study were obtained following a general procedure recently developed, starting from 4-nitropentadienoates deriving from a common β-nitrothiophenic precursor. While being devoid of any activity against fungi and Gram-negative bacteria, most of the title compounds performed as potent antibacterial agents on Gram-positive bacteria (E. faecalis and three strains of S. aureus), with the most potent congener being the 1-(4-chlorobenzyl)-3-nitro-4-(p-tolyl)azetidine 22, which displayed potency close to that of norfloxacin, the reference antibiotic (minimum inhibitory concentration values 4 and 1–2 μg/mL, respectively). Since 22 combines a relatively efficient activity against Gram-positive bacteria and a cytotoxicity on eucharyotic cells only at 4-times higher concentrations (inhibiting concentration on 50% of the cultured eukaryotic cells: 36 ± 10 μM, MIC: 8.6 μM), it may be considered as a promising hit compound for the development of a new series of antibacterials selectively active on Gram-positive pathogens. The relatively concise synthetic route described herein, based on widely available starting materials, could feed further structure–activity relationship studies, thus allowing for the fine investigation and optimization of the toxico-pharmacological profile.     

Über Pyrokondensationen in der aromatischen Reihe

Ohne Zusammenfassung     

Untersuchungen über die Veresterung unsymmetrischer zwei- und mehrbasischer Säuren

Ohne ZusammenfassungFür die Ausführung der hier mitgeteilten krystallographischen Untersuchungen sagen wir Herrn Hofrat Professor V. v. Lang ergebenen Dank.