Chemically Reactive Immunogens Lead to Functional Convergence of the Immune Response

MnO2 as a terminal oxidant in Wacker oxidation of homoallyl alcohols and terminal olefins

Efficient and mild reaction conditions for Wacker-type oxidation of terminal olefins of less explored homoallyl alcohols to β-hydroxy-methyl ketones have been developed by using a Pd(ii) catalyst and MnO2 as a co-oxidant. The method involves mild reaction conditions and shows good functional group compatibility along with high regio- and chemoselectivity. While our earlier system of PdCl2/CrO3/HCl produced α,β-unsaturated ketones from homoallyl alcohols, the present method provided orthogonally the β-hydroxy-methyl ketones. No overoxidation or elimination of benzylic and/or β-hydroxy groups was observed. The method could be extended to the oxidation of simple terminal olefins as well, to methyl ketones, displaying its versatility. An application to the regioselective synthesis of gingerol is demonstrated.

A new fluorescence/PET probe for targeting intracellular human telomerase reverse transcriptase (hTERT) using Tat peptide-conjugated IgM

Despite an increasing need for methods to visualize intracellular proteins in vivo, the majority of antibody-based imaging methods available can only detect membrane proteins. The human telomerase reverse transcriptase (hTERT) is an intracellular target of great interest because of its high expression in several types of cancer. In this study, we developed a new probe for hTERT using the Tat peptide. An hTERT antibody (IgG or IgM) was conjugated with the Tat peptide, a fluorescence dye and (64)Cu. HT29 (hTERT+) and U2OS (hTERT-) were used to visualize the intracellular hTERT. The hTERT was detected by RT-PCR and western blot. Fluorescence signals for hTERT were obtained by confocal microscopy, live cell imaging, and analyzed by Tissue-FAXS. In nude mice, tumors were visualized using the fluorescence imaging devices Maestro™ and PETBOX. In RT-PCR and western blot, the expression of hTERT was detected in HT29 cells, but not in U2OS cells. Fluorescence signals were clearly observed in HT29 cells and in U2OS cells after 1 h of treatment, but signals were only detected in HT29 cells after 24 h. Confocal microscopy showed that 9.65% of U2OS and 78.54% of HT29 cells had positive hTERT signals. 3D animation images showed that the probe could target intranuclear hTERT in the nucleus. In mice models, fluorescence and PET imaging showed that hTERT in HT29 tumors could be efficiently visualized. In summary, we developed a new method to visualize intracellular and intranuclear proteins both in vitro and in vivo.

Lycojapodine A, a novel alkaloid from Lycopodium japonicum

Lycojapodine A, a novel C(16)N-type Lycopodium alkaloid with an unprecedented 6/6/6/7 tetracyclic ring system, was isolated from the club moss Lycopodium japonicum. The structure and relative stereochemistry were elucidated on the basis of spectroscopic data and were further confirmed by X-ray analysis. A possible biosynthetic pathway for 1 was proposed. Its inhibitory activity on acetylcholinestrease and anti-HIV-1 activity were also evaluated.

Ti-catalyzed reformatsky-type coupling between alpha-halo ketones and aldehydes

We describe the first Ti-catalyzed Reformatsky-type coupling between alpha-halo ketones and aldehydes. The reaction affords beta-hydroxy ketones under mild, neutral conditions compatible with ketones and other electrophiles. The catalytic cycle possibly proceeds via bis(cyclopentadienyl)titanium enolates.

Dual mechanism of zinc-proline catalyzed aldol reactions in water

The aldol reaction of acetone with aldehydes in aqueous medium under catalysis by zinc-proline (Zn(L-Pro)2) and secondary amines such as proline, (2S,4R)-4-hydroxyproline (Hyp) and (S)-(+)-1-(2-pyrrolidinomethyl)pyrrolidine (PMP) is shown to proceed by an enamine mechanism, as evidenced by reductive trapping of the iminium intermediate, while the aldol reaction of dihydroxyacetone (DHA) under catalysis by zinc-proline and by general bases such as N-methylmorpholine (NMM) is shown to occur under rate-limiting deprotonation of the alpha-carbon and formation of an enolate intermediate.

Highly efficient antibody-catalyzed deuteration of carbonyl compounds

Antibody 38C2 efficiently catalyzes deuterium-exchange reactions at the alpha position of a variety of ketones and aldehydes, including substrates that have a variety of sensitive functional groups. In addition to the regio- and chemoselectivity of these reactions, the catalytic rates (kcat) and rate-enhancement values (kcat/kun) are among the highest values ever observed with catalytic antibodies. Comparison of the substrate range of the catalytic antibody with highly evolved aldolase enzymes, such as rabbit-muscle aldolase, highlights the much broader practical scope of the antibody, which accepts a wide range of substrates. The hydrogen-exchange reaction was used for calibration and mapping of the antibody active site. Isotope-exchange experiments with cycloheptanone reveal that the formation of the Schiff base species (as concluded from the 16O/18O exchange rate at the carbonyl oxygen) is much faster than the formation of the enamine intermediate (as concluded from the H/D exchange rate), and both steps are faster than the antibody-catalyzed aldol addition reaction.

Biocatalytic synthesis of hydroxylated natural products using aldolases and related enzymes

Synthetic building blocks bearing hydroxylated chiral centers are important targets for biocatalysis. Many C-C bond forming enzymes have recently been investigated for new applications and new strategies towards the synthesis of natural products and related oxygenated compounds. Several old catalysts have been studied to increase our functional knowledge of natural aldolase-type enzymes, and new mutated catalysts or catalytic antibodies have been tested for their synthetic utility.