Crystal structures of seven mixed-valence gold compounds of the form [( P)Au][Au ] ( = -butyl or isopropyl, = S or Se, and = Cl or Br).

During our studies of the oxidation of gold(I) complexes of tri-alkyl-phosphane chalcogenides, general formula PAu, ( = -butyl or isopropyl, = S or Se, = Cl or Br) with PhICl or elemental bromine, we have isolated a set of seven mixed-valence by-products, the bis-(tri-alkyl-phosphane chalcogenido)gold(I) tetra-halogenidoaurates(III) [( P)Au][Au ]. These corres-pond to the addition of one halogen atom per gold atom of the Au precursor. Com-pound , bis-(triiso-propyl-phosphane sulfide)-gold(I) tetra-chlorido-aur-ate(III), [Au(CHPS)][AuCl] or [( PrPS)Au][AuCl], crystallizes in space group 2/ with = 4; the gold(I) atoms of the two cations lie on twofold rotation axes, and the gold(III) atoms of the two anions lie on inversion centres.

(2,4)-5-Fluoroleucine, (2,4)-5-Fluoroleucine, and 5,5'-Difluoroleucine in PpiB: Protein Production, F NMR, and Ligand Sensing Enhanced by the γ-Gauche Effect.

Global substitution of leucine for analogues containing CHF instead of methyl groups delivers proteins with multiple sites for monitoring by F nuclear magnetic resonance (NMR) spectroscopy. The 19 kDa peptidyl-prolyl isomerase B (PpiB) was prepared with uniform high-level substitution of leucine by (2,4)-5-fluoroleucine, (2,4)-5-fluoroleucine, or 5,5'-difluoroleucine. The stability of the samples toward thermal denaturation was little altered compared to the wild-type protein.

Conformational Preferences of the Non-Canonical Amino Acids (2,4)-5-Fluoroleucine, (2,4)-5-Fluoroleucine, and 5,5'-Difluoroleucine in a Protein.

Proteins produced with leucine analogues, where CHF groups substitute specific methyl groups, can readily be probed by F NMR spectroscopy. As CF and CH groups are similar in hydrophobicity and size, fluorinated leucines are expected to cause minimal structural perturbation, but the impact of fluorine on the rotational freedom of CHF groups is unclear. We present high-resolution crystal structures of peptidyl-prolyl - isomerase B (PpiB) prepared with uniform high-level substitution of leucine by (2,4)-5-fluoroleucine, (2,4)-5-fluoroleucine, or 5,5'-difluoroleucine.

Crystal structures of fourteen halochalcogenylphos-pho-nium tetra-halogenidoaurates(III).

The structures of fourteen halochalcogenyl-phospho-nium tetra-halogen-ido-aurates(III), phosphane chalcogenide derivatives with general formula [ P][Au ] ( = -butyl; = isopropyl; = 0 to 3; = S or Se; = Cl or Br) are presented. The eight possible chlorido derivatives are: , = 3, = S; , = 2, = S; , = 1, = S; , = 0, = S; , = 3, = Se; , = 2, = Se; , = 1, = Se; and , = 0, = Se, and the corresponding bromido derivatives are - in the same order. Structures were obtained for all compounds except for the tri--butyl derivatives and .

Crystal structures of ten phosphane chalcogenide complexes of gold(III) chloride and bromide.

The structures of ten phosphane chalcogenide complexes of gold(III) halides, with general formula PAu ( = -butyl; = -propyl; = 0 to 3; = S or Se; = Cl or Br) are presented. The eight possible chlorido derivatives are: , = 3, = S; , = 2, = S; , = 1, = S; , = 0, = S; , = 3, = Se; , = 2, = Se; , = 1, = Se; and , = 0, = Se, and the corresponding bromido derivatives are - in the same order. Structures were obtained for , (and a second polymorph ), (and its deutero-chloro-form monosolvate ), (as its di-chloro-methane monosolvate), , (as its deutero-chloro-form monosolvate , in which the solvent mol-ecule is disordered over two positions), , , and .

Crystal structures of sixteen phosphane chalcogenide complexes of gold(I) chloride, bromide and iodide.

The structures of 16 phosphane chalcogenide complexes of gold(I) halides, with the general formula PAu ( = -butyl; = isopropyl; = 0 to 3; = S or Se; = Cl, Br or I), are presented. The eight possible chlorido derivatives are: , = 3, = S; , = 2, = S; , = 1, = S; , = 0, = S; , = 3, = Se; , = 2, = Se; , = 1, = Se; and , = 0, = Se, and the corresponding bromido derivatives are - in the same order. However, and were badly disordered and was not obtained.

Selective thiazoline peptide cyclisation compatible with mRNA display and efficient synthesis.

Peptide display technologies are a powerful method for discovery of new bioactive sequences, but linear sequences are often very unstable in a biological setting. Macrocyclisation of such peptides is beneficial for target affinity, selectivity, stability, and cell permeability. However, macrocyclisation of a linear hit is unreliable and requires extensive structural knowledge.

A tandem Mannich addition-palladium catalyzed ring-closing route toward 4-substituted-3(2H)-furanones.

A facile route towards highly functionalized 3(2H)-furanones via a sequential Mannich addition-palladium catalyzed ring closing has been elaborated. The reaction of 4-chloroacetoacetate esters with imines derived from aliphatic and aromatic aldehydes under palladium catalysis afforded 4-substituted furanones in good to excellent yields. 4-Hydrazino-3(2H)-furanones could also be synthesized from diazo esters in excellent yields by utilising the developed strategy.

The Paternò-Büchi reaction: importance of triplet states in the excited-state reaction pathway.

The Paternò-Büchi (PB) reaction between an excited carbonyl compound and an alkene has been widely studied, but so far little is known about the excited-state dynamics of the reaction. In this investigation, we used a compound in which a formyl and a vinyl group are attached to a [2.2]paracyclophane in order to obtain a model system in pre-reactive conformation for the PB reaction.