General Synthesis of -1,4-Dialdehydes and Their Application in Ir-Catalyzed Asymmetric Tishchenko Reactions.

A practical synthesis of -1,4-dialdehydes based on the oxidative cleavage of cyclobutanediol derivatives using polymer-supported periodate was developed. The -1,4-dialdehydes were obtained in up to >99% yield and subsequently employed in Ir-catalyzed asymmetric Tishchenko reactions to give the corresponding chiral lactones, which are versatile synthetic intermediates, in good yield with moderate enantiomeric excess. The catalytically active species was identified by means of cold-spray ionization mass spectrometry and H NMR spectroscopy.

Catalytic enantioselective intramolecular Tishchenko reaction of -dialdehyde: synthesis of ()-cedarmycins.

The first successful example of a catalytic enantioselective intramolecular Tishchenko reaction of a -dialdehyde in the presence of a chiral iridium complex is described. Chiral lactones were obtained in good yields with up to 91% ee. The obtained enantioenriched lactones were utilized for the first synthesis of ()-cedarmycins A and B.

Using α- and β-Epimerizations of -2,3-Bis(hydroxymethyl)-γ-butyrolactone for the Synthesis of Both Enantiomers of Enterolactone.

In the context of asymmetric synthesis, epimerization is usually problematic. Here, we describe the use of the epimerization of -2,3-bis(hydroxymethyl)-γ-butyrolactone for the synthesis of enterolactones with anti-carcinogenic, anti-inflammatory, anti-angiogenic, and antioxidant activity. Selective α- or β-epimerization of a γ-butyrolactone was used to selectively synthesize both enantiomers of enterolactone.

Tetrahedral Copper(II) Complexes with a Labile Coordination Site Supported by a Tris-tetramethylguanidinato Ligand.

A new tridentate N ligand (TMGtach) consisting of cis,cis-1,3,5-triaminocyclohexane (tach) and three N,N,N',N'-tetramethylguanidino (TMG) groups has been developed to prepare copper complexes with a tetrahedral geometry and a labile coordination site. Treatment of the ligand with CuX (X = Cl and Br) gave copper(II)-halide complexes, [Cu(TMGtach)Cl] (2) and [Cu(TMGtach)Br] (2), the structures of which have been determined by X-ray crystallographic analysis. The complexes exhibit a four-coordinate structure with C symmetry, where the labile halide ligand (X) occupies a position on the trigonal axis.

Supramolecular Photochirogenesis with a Higher-Order Complex: Highly Accelerated Exclusively Head-to-Head Photocyclodimerization of 2-Anthracenecarboxylic Acid via 2:2 Complexation with Prolinol.

An unprecedented 2:2 complex was shown to intervene in the enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylic acid (A) mediated by a hydrogen-bonding template l-prolinol (P) to accelerate the formation of chiral anti-head-to-head and achiral syn-head-to-head cyclodimers in >99% combined yield with enhanced enantioselectivities of up to 72% ee for the former. The supramolecular complexation and photochirogenic behaviors, as well as the plausible structures, of intervening Am·Pn complexes (m, n = 1 or 2) were elucidated by combined theoretical and experimental spectroscopic, photophysical, and photochemical studies. Furthermore, the photochemical chiral amplification was achieved for the first time by utilizing the preferential 2:2 complexation of A with homochiral P to give normalized product enantioselectivities higher than those of the template used.

Cyclic mismatch binding ligand CMBL4 binds to the 5'-T-3'/5'-GG-3' site by inducing the flipping out of thymine base.

A newly designed cyclic bis-naphthyridine carbamate dimer CMBL4: with a limited conformational flexibility was synthesized and characterized. Absorption spectra revealed that two naphthyridines in CMBL4: were stacked on each other in aqueous solutions. The most efficient binding of CMBL4: to DNA was observed for the sequence 5'-T-3'/5'-GG-3' (T/GG) with the formation of a 1:1 complex, which is one of possible structural elements involved in the higher order structures of (TGG)n repeat DNA triggering the genome microdeletion.

A non-radioactive assay for selenophosphate synthetase activity using recombinant pyruvate pyrophosphate dikinase from Thermus thermophilus HB8.

Biosynthesis of selenocysteine-containing proteins requires monoselenophosphate, a selenium-donor intermediate generated by selenophosphate synthetase (Sephs). A non-radioactive assay was developed as an alternative to the standard [8-(14)C] AMP-quantifying assay. The product, AMP, was measured using a recombinant pyruvate pyrophosphate dikinase from Thermus thermophilus HB8.

A Model for the Active-Site Formation Process in DMSO Reductase Family Molybdenum Enzymes Involving Oxido-Alcoholato and Oxido-Thiolato Molybdenum(VI) Core Structures.

New bis(ene-1,2-dithiolato)-oxido-alcoholato molybdenum(VI) and -oxido-thiolato molybdenum(VI) anionic complexes, denoted as [Mo(VI)O(ER)L2](-) (E = O, S; L = dimethoxycarboxylate-1,2-ethylenedithiolate), were obtained from the reaction of the corresponding dioxido-molybdenum(VI) precursor complex with either an alcohol or a thiol in the presence of an organic acid (e.g., 10-camphorsulfonic acid) at low temperature.

One-Pot Catalysis Using a Chiral Iridium Complex/Brønsted Base: Catalytic Asymmetric Synthesis of Catalponol.

Tandem asymmetric hydrogen transfer oxidation/aldol condensation under relay catalysis of a chiral iridium complex/achiral Brønsted base binary system is described for the synthesis of α-benzylidene-γ-hydroxytetralones with high ee's. A two-step synthesis of catalponol was achieved using this sequential methodology together with regio- and stereoselective hydroboration.

Generation, Characterization, and Reactivity of a Cu(II)-Alkylperoxide/Anilino Radical Complex: Insight into the O-O Bond Cleavage Mechanism.

The reaction of [Cu(I)(TIPT3tren) (CH3CN)]ClO4 (1) and cumene hydroperoxide (C6H5C(CH3)2OOH, ROOH) at -60 °C in CH2Cl2 gave a Cu(II)-alkylperoxide/anilino radical complex 2, the formation of which was confirmed by UV-vis, resonance Raman, EPR, and CSI-mass spectroscopy. The mechanism of formation of 2, as well as its reactivity, has been explored.

cis-1,2-Aminohydroxylation of Alkenes Involving a Catalytic Cycle of Osmium(III) and Osmium(V) Centers: Os(V)(O)(NHTs) Active Oxidant with a Macrocyclic Tetradentate Ligand.

Catalytic activity of [Os(III)(OH)(H2O)(L-N4Me2)](PF6)2 (1: L-N4Me2 = N,N'-dimethyl-2,11-diaza-[3,3](2,6)pyridinophane) in 1,2-cis-aminohydroxylation of alkenes with sodium N-chloro-4-methylbenzenesulfonamide (chloramine-T) is explored. Simple alkenes as well as those containing several types of substituents are converted to the corresponding 1,2-aminoalcohols in modest to high yields. The aminoalcohol products have exclusively cis conformation with respect to the introduced -OH and -NHTs groups.

Oxo-carboxylato-molybdenum(VI) complexes possessing dithiolene ligands related to the active site of type II DMSOR family molybdoenzymes.

Spectroscopic and kinetic studies indicate that oxo-carboxylato-molybdenum(VI) bis-dithiolene complexes, (Mo(VI)O(p-X-OBz)L2), have been generated at low temperature as active site structural models for the type II class of pyranopterin molybdenum DMSOR family enzymes. A DFT analysis of low energy charge transfer bands shows that these complexes possess a Mo-S(dithiolene) π-bonding interaction between the Mo(d(xy)) redox active molecular orbital and a cis S(p(z)) donor orbital located on one of the dithiolene ligands.