Synthesis and characterization of TiL2 complexes with tridentate (ONO) (S)-NOBIN Schiff-base ligands

Tridentate (ONO) C[subscript 1]-symmetric Schiff base ligands were synthesized by the condensation of (S)-2-amino-2'-hydroxy-1,1'-binaphthyalene with 4-hydroxy-3-phenanthrenecarboxaldehyde or 1-hydroxybenz[a]anthracene-2-carboxaldehyde. C[subscript 2]-symmetric titanium(IV) Schiff base complexes, TiL[subscript 2], were synthesized and characterized with these ligands. The complex with the benz[a]anthryl unit crystallizes in a facial coordination mode, OC-6-1'3'-C, whereas complex with phenanthryl unit crystallizes in a meridional mode, OC-6-22'-A. A comparison between the complexes and the ligands were done in solution using circular dichroism spectroscopy. Preliminary catalytic studies showed that these complexes can catalyze asymmetric carbonyl-ene addition reactions of 2-methoxypropene with aromatic aldehydes with moderate selectivity. The ligands and complexes were characterized by NMR, HRMS, single crystal X-ray diffraction and CD spectroscopy

Altering physical properties of pharmaceutical co-crystals in a systematic manner

Systematic structure-property studies on a series of co-crystals of potential cancer drugs with aliphatic dicarboxylic acids were undertaken. This study reveals that systematic changes to the molecular nature of the co-crystallizing agent combined with control over the way individual building blocks are organized within the crystalline lattice makes it possible to establish predictable links between molecular structure and macroscopic physical properties, such as melting behaviour and aqueous solubility. However, it is not possible to find any notable correlation between physical properties-chemical compositions in the absence of structural consistency

A Mutagenetic Tree Hidden Markov Model for Longitudinal Clonal HIV Sequence Data

RNA viruses provide prominent examples of measurably evolving populations. In HIV infection, the development of drug resistance is of particular interest, because precise predictions of the outcome of this evolutionary process are a prerequisite for the rational design of antiretroviral treatment protocols. We present a mutagenetic tree hidden Markov model for the analysis of longitudinal clonal sequence data. Using HIV mutation data from clinical trials, we estimate the order and rate of occurrence of seven amino acid changes that are associated with resistance to the reverse transcriptase inhibitor efavirenz.Comment: 20 pages, 6 figure

Supramolecular Hierarchy among Halogen-Bond Donors

Through a combination of structural chemistry, vibrational spectroscopy, and theory, we have systematically examined the relative structure-directing importance of a series of ditopic halogen-bond (XB) donors. The molecular electrostatic potential surfaces of six XB donors were evaluated, which allowed for a charge-based ranking. Each molecule was then co-crystallized with 21 XB acceptors and the results have made it possible to map out the supramolecular landscape describing the competition between I/Br-ethynyl donors, perfluorinated I/Br donors, and I/Br-phenyl based donors. The results offer practical guidelines for synthetic crystal engineering driven by robust and directional halogen bonds. Copyright 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

The quest for a molecular capsule assembled via halogen bonds

A halogen-bonded capsule is obtained via directed assembly of a rigid tetra(3-pyridyl) cavitand and a flexible tetra(4-iodotetrafluorophenyl) calix[4]arene. The pyridyl nitrogen atoms from one cavitand molecule interact with the iodine atoms of a single calixarene molecule through short and directional I…N halogen bonds. The flexibility of the ethylenedioxy moieties on the calixarene platform results in positional flexibility of the iodotetrafluorobenzene sites which, coupled with a supramolecular chelating effect, allow for an effective partner-induced geometric fitting between four nitrogen atoms on the cavitand and four iodine atoms on the calixarene

Advanced composite elevator for Boeing 727 aircraft. Volume 1: Technical summary

The design, development, analysis, and testing activities and results that were required to produce five and one-half shipsets of advanced composite elevators for Boeing 727 aircraft are summarized. During the preliminary design period, alternative concepts were developed. After selection of the best design, detail design and basic configuration improvements were evaluated. Five and one-half shipsets were manufactured. All program goals (except competitive cost demonstration) were accomplished when our design met or exceeded all requirements, criteria, and objectives

Syntheses of 3-[(Alkylamino)methylene]-6-methyl-1Hpyridine-2,4-diones, Fluorescence Probes 3-Substituted 7-Methyl-6H-pyrano[3,2-c]pyridine-2,5-diones, and Tetrahydro-6H-2,10-dioxa-9-azaanthracen-1-ones

Various condensation and ring-closing reactions were used for the syntheses of 3-[(alkylamino)methylene]-6-methylpyridine-2,4(1H,3H)-diones, bicyclic pyridinones, and tricyclic morpholinopyrones. For instance, 3-[(dialkylamino)methylene]-6-methylpyridine-2,4(1H,3H)-diones were synthesized from the condensation of dialkylamines and 3-formyl-4-hydroxy-6-methylpyridin-2(1H)-one. 3-Formyl-4-hydroxy-6-methylpyridin-2(1H)-one, derived from 3-formyl-4-hydroxy-6-methylpyridin-2(1H)-one, was used to construct a number of bicyclic pyridinones via a one-pot Knoevenagal and intramolecular lactonization reaction. Tricyclic morpholinopyrones were assembled from a dialkylation reaction involving a dinucleophile, 3-amino-4-hydroxy-6-methyl-2H-pyran-2-one, and a dielectrophile, trans-3,6-dibromocyclohexene. Depending on the reaction conditions, isomers of the tricyclic molecules can be selectively produced, and their chemical structures were unequivocally determined using single-crystal X-ray analyses and 2D COSY spectroscopy. The fluorescently active bicyclic pyridinone compounds show longer absorption (368–430 nm; maximum) and emission wavelengths (450–467 nm) than those of 7-amino-4-methylcoumarin (AMC; λ[subscript abs,max] = 350 nm; λ[subscript em] = 430 nm) suggesting these molecules, such as 3-(2-aminoacetyl)-7-methyl-2H-pyrano[3,2-c]pyridine-2,5(6H)-dione, can be employed as fluorescence activity based probes for tracing biological pathways