Ring-opening polymerization of <em>rac</em>-lactide and ε-caprolactone using zinc and calcium salicylaldiminato complexes

Tridentate Schiff base complexes of zinc and calcium were prepared and tested in the ring-opening polymerization of ε-caprolactone and rac-lactide to generate biodegradable polymeric materials from biocompatible metals. Alteration of the pendant donor arm attached to the imine backbone provides some control over catalyst composition and polymerization activity. Complexes of the formula [ONN]ZnN(SiMe3)2, where [ONN] = 2-(N-donor arm-imine)[4,6-di(tert-butyl)phenoxide], were isolated with ethyldimethylamine, ethylpiperidine, and ethylmorpholine substituents, while disproportionation led to the isolation of [ONN]2Zn complexes with methylpyridine, quinoline, and ethyldiisopropylamine derivatives, two of which were crystallographically characterized. Calcium complexes were more stable and novel [ONN]CaN(SiMe3)2 complexes with ethylpiperidine and ethyldiisopropylamine substituents were reported. Zinc and calcium catalysts coordinated to a single tridentate ligand were effective at initiating the polymerization of ε-caprolactone, but did not control the polymerizations, whereas the bis(ligand) complexes produced no polymer. These catalysts were effective at controlling the polymerization of rac-lactide. Coordinatively saturated complexes inhibit the polymerization, while initiation from either the amido or ligand alkoxide functionalities produces poly(lactic acid) with low polydispersities. </jats:p

Ethyl 6-methyl-4-[2-(4,4,5,5-tetra­methyl-1,3,2-dioxaborolan-2-yl)thio­phen-3-yl]-2-thioxo-1,2,3,4-tetra­hydro­pyrimidine-5-carboxyl­ate

A new Biginelli compound, C18H25BN2O4S2, containing a boronate ester group was synthesized from a lithium bromide-catalysed reaction. The compound crystallizes with two independent mol­ecules in the asymmetric unit that differ mainly in the conformation of the ester functionality. The crystal structure is stabilized by inter­molecular N—H⋯O and N—H⋯S hydrogen bonds involving the 3,4-dihydro­pyrimidine-2(1H)-thione NH groups as donors and the carbonyl O and thio­phene S atoms as acceptors

IL-4 receptor-alpha-dependent control of Cryptococcus neoformans in the early phase of pulmonary infection

Cryptococcus neoformans is an opportunistic fungal pathogen that causes lung inflammation and meningoencephalitis in immunocompromised people. Previously we showed that mice succumb to intranasal infection by induction of pulmonary interleukin (IL)-4Rα-dependent type 2 immune responses, whereas IL-12-dependent type 1 responses confer resistance. In the experiments presented here, IL-4Rα −/− mice unexpectedly show decreased fungal control early upon infection with C. neoformans , whereas wild-type mice are able to control fungal growth accompanied by enhanced macrophage and dendritic cell recruitment to the site of infection. Lower pulmonary recruitment of macrophages and dendritic cells in IL-4Rα −/− mice is associated with reduced pulmonary expression of CCL2 and CCL20 chemokines. Moreover, IFN-γ and nitric oxide production are diminished in IL-4Rα −/− mice compared to wild-type mice. To directly study the potential mechanism(s) responsible for reduced production of IFN-γ, conventional dendritic cells were stimulated with C. neoformans in the presence of IL-4 which results in increased IL-12 production and reduced IL-10 production. Together, a beneficial role of early IL-4Rα signaling is demonstrated in pulmonary cryptococcosis, which contrasts with the well-known IL-4Rα-mediated detrimental effects in the late phase

catena-Poly[bis[dimethyl(pyridine-&#954;N)indium(III)]-&#956;4-benzene-1,3-diolato-bis[dimethylindium(III)]-&#956;4-benzene-1,3-diolato]

The title compound, [In2(CH3)4(C6H4O2)(C5H5N)] or [{(CH3)2In}(1,3-O2C6H4){In(CH3)2(py)}]n, (py = pyridine) contains two crystallographically unique InIII ions which are in distorted tetrahedral C2O2 and distorted trigonal-bipyramidal C2O2N coordination environments. The InIII coordination centers are bridged head-to-head via In&#8212;O bonds, yielding four-membered In2O2 rings and zigzag polymeric chains along [001]

Synthesis, characterization, and reactivity of a novel thallium arylspiroboronate ester

Addition of 3,5-di-tert-butylcatechol (butcat) to solutions of H 3B·SMe2 gave the novel diboron species B 2(butcat)3 (2) in moderate to high yields. Compound 2 reacts with Tl(acac) to give butcatB(acac) (4) and Tl(Bbutcat2) (5). Attempts to abstract the chlorides from [(dppb)Rh(μ-Cl)]2 (where dppb = 1,4-bis(diphenylphosphino)buthane) using 5 led to the unusual dimer [(dppb)Rh(μ-Cl)2(μ-Tl)Rh(dppb)][Bbutcat2] (6), which contains an unsymmetrical Rh-Tl-Rh bridge