Synthesis of orthogonally protected lanthionines

Synthetic approaches to the lantibiotics, a family of thioether-bridged antimicrobial peptides, require flexible synthetic routes to a variety of orthogonally protected derivatives of lanthionine 1. The most direct approaches to lanthionine involve the reaction of cysteine with an alanyl beta-cation equivalent. Several possibilities exist for the alanyl beta-cation equivalent, including direct activation of serine under Mitsunobu conditions: however, the low reactivity of sulfur nucleophiles in the Mitsunobu reaction has previously precluded its use in the synthesis of the lantibiotics. We report here a new approach to the synthesis of protected lanthionine, using a novel variant of the Mitsunobu reaction in which catalytic zinc tartrate is used to enhance the nucleophilicity of the thiol. In the course of these studies, we have also demonstrated that the synthesis of lanthionine from trityl-protected beta-iodoalanines is prone to rearrangement, via an aziridine, to give predominantly trityl-protected alpha-iodo-beta-alanines, and hence norlanthionines, as the major products.     

1-D infinite array of metalloporphyrin cages

The reaction of Co(II) with 5,15-dipyridyl-10,20-diphenylporphyrin (H(2)DPyP) produces the first metal-organic coordination polymer supported by a trans meso-bifunctional porphyrin ligand. Formulated empirically as [Co(3)(DPyP)(3)] x 4DMF, this compound exhibits a ribbonlike coordination network consisting of tetranuclear metalloporphyrin cages. The DMF guest molecules fill the intra-ribbon cages as well as the inter-ribbon space. Evacuation of [Co(3)(DPyP)(3)] x 4DMF at 130 degrees C generates [Co(3)(DPyP)(3)] that retains crystallinity, as shown by its powder X-ray diffraction pattern, which is consistent with that of [Co(3)(DPyP)(3)] x 4DMF.     

Synthesis, characterization, and energetic properties of diazido heteroaromatic high-nitrogen C-N compound

The synthesis, characterization, and energetic properties of diazido heteroaromatic high-nitrogen C-N compound, 3,6-diazido-1,2,4,5-tetrazine (DiAT), are reported. Its normalized heat of formation (NDeltaHf), experimentally determined using an additive method, is shown to be the highest positive NDeltaHf compared to all other organic molecules. The unexpected azido-tetrazolo tautomerizations and irreversible tetrazolo transformation of DiAT are remarkable compared to all other polyazido heteroaromatic high-nitrogen C-N compounds, for example, 2,4,6-triazido-1,3,5-triazine; 4,4',6,6'-tetra(azido)hydrazo-1,3,5-triazine; 4,4',6,6'-tetra(azido)azo-1,3,5-triazine; and 2,5,8-tri(azido)-1,3,4,6,7,9,9b-heptaazaphenalene (heptazine).     

A new one‐dimensional strontium vanadium tellurite,Sr7V4Te12O41

Vanadium tellurites display a rich structural chemistry with interesting physical properties, such as second harmonic generation (SHG). Tellurites, i.e. Te⁴⁺O_x, are often observed in unusual structures and form various structural motifs, including isolated clusters, chains, layers, and three‐dimensional networks. Similarly, vanadates, i.e. V⁵⁺O_x, show rich structural features, such as VO₄ tetrahedra, VO₅ square pyramids or trigonal bipyramids, and VO₆ octahedra. Strontium vanadium tellurite, Sr₇V₄Te₁₂O₄₁, was obtained from the melt of the solid‐state reaction of SrTeO₄ and VO₂ in a sealed quartz tube as it cooled from 973 K. The crystal structure exhibits a one‐dimensional latticework along the a axis comprised of paired Sr₃Te₃O_x units, namely Sr₆Te₆O_2x+1, with corner‐shared TeO₄ polyhedra – and specifically the Te lone‐pair electrons – facing outward in the bc plane. The Sr₆Te₆O_2x+1 latticework is helical and is layered in the b‐axis direction against sheets of corner‐shared VO₄ tetrahedra, and is linked in the c‐axis direction via individual corner‐shared SrO₈ square prisms.     

Facile synthesis of the tridecameric Al13 nanocluster Al13(mu3-OH)6(mu2-OH)18(H2O)24(NO3)15

Treatment of aluminum nitrate with an organic nitroso-containing compound yields the "flat", tridecameric nanocluster Al 13(mu 3-OH) 6(mu 2-OH) 18(H 2O) 24(NO 3) 15 ( Al 13 ) in good yield on a preparative scale under ambient conditions. Synthetic procedures yielding two different single-crystal forms of the Al 13 cation with two varying counterion compositions are described.     

A new sparteine surrogate for asymmetric deprotonation of N-Boc pyrrolidine

The s-BuLi complex of a cyclohexane-derived diamine is as efficient as s-BuLi/(-)-sparteine for the asymmetric deprotonation of N-Boc pyrrolidine. This is the first example of high enantioselectivity using a non-sparteine-like diamine in such reactions. The (S,S)-diamine is a useful (+)-sparteine surrogate and was utilized in short syntheses of (-)-indolizidine 167B and an intermediate for the synthesis of the CCK antagonist (+)-RP 66803.     

Room temperature benzene C-H activation by a new [PSiP]Ir pincer complex

The synthesis and reactivity of coordinatively unsaturated Rh and Ir complexes supported by the new bis(phosphino)silyl pincer ligand [kappa(3)-(2-Cy(2)PC(6)H(4))(2)SiMe](-) ([Cy-PSiP](-)) are reported, including the first example of facile, room temperature intermolecular arene C-H bond activation mediated by a silyl pincer complex.     

Efficient base catalyzed alkylation reactions with aziridine electrophiles

N-Mesitylene sulfonyl and N-tosyl aziridines have been identified as effective electrophiles in alkylation reactions of carbon acids catalyzed by the organic phosphorine base BEMP; yields of up to 99% for a range of pro-nucleophiles under mild reaction conditions are reported.     

Nanoparticle‐Based Imaging of Clinical Transplant Populations Encapsulated in Protective Polymer Matrices

A recent clinical trial proves that autologous olfactory mucosal cell (OMC) transplantation improves locomotion in dogs with naturally occurring spinal injuries comparable to human lesions. However, not all dogs respond to the treatment, likely due to the transplantation procedures involving injections of cell suspensions that are associated with cell death, uneven cell distribution, and cell washout. Encapsulating cells in protective hydrogel matrices offers a tissue engineering solution to safely achieve 3D growth of viable transplant cells for implantation into injury sites, to improve regenerative outcomes. It is shown for the first time that canine OMCs (cOMCs) can be propagated with high viability in 3D collagen matrices. Further, a method to incorporate cOMCs pre‐labeled with clinical‐grade iron oxide nanoparticles into the constructs is described. Intraconstruct labeled cells are visualized using magnetic resonance imaging, offering substantial promise for in vivo tracking of cOMCs delivered in protective matrices.