New ent-Verticillane Diterpenoids from the Japanese Liverwort Jackiella javanica

Three new ent-verticillane diterpenoids have been isolated from the Japanese liverwort Jackiella javanica, together with known sesqui- and diterpenoids. Their absolute configurations were established by X-ray crystallographic analysis and circular dichroism spectroscopy.     

Asymmetric synthesis of cyclic α-amino acid derivatives by the intramolecular reaction of magnesium carbenoid with an N-magnesio arylamine

The synthesis of pipecolic acid and homopipecolic acid derivatives was developed from ω-(2-aminophenyl)-1-chloroalkyl p-tolyl sulfoxides by treatment with i-PrMgCl. An intramolecular nucleophilic substitution reaction of a magnesium carbenoid with an N-magnesio arylamine is the key step of this reaction. Proline and pipecolic acid derivatives were also synthesized from ω-(arylamino)-1-chloroalkyl p-tolyl sulfoxides by the same chemistry. Starting from enantiomerically pure (1S,R_S)-1-chloro-3-[2-(N-methylamino)phenyl]propyl p-tolyl sulfoxide, enantiomerically pure (R)-pipecolic acid derivative was obtained. The intramolecular nucleophilic substitution reaction of the magnesium carbenoid with N-magnesio arylamine was proven to take place with inversion of the carbenoid carbon. The stereochemistry of these reactions is also discussed.     

New applications of multiply charged ionic probes as cleavable cross-linker and polymerization reagent

We have designed new cleavable cross-linkers for biomolecules containing the 2,6-bis(oxazolinyl)pyridine (pybox) lanthanum complex. These species can effectively donate multiple charges to afford cross-linker ions for target biomolecules. The cross-linkers are cleaved easily by adding water. Moreover, we were able to detect chain structures of target molecules, including biomolecules and carbon clusters, such as fullerene C₆₀, by the addition of some MS ionic probes. Cold-spray ionization mass spectrometry demonstrated the applications of multiply charged ionic probes as cleavable cross-linkers and polymerization reagents.     

A photoelectron spectroscopic observation of iron surfaces exposed to N2, N2O,NO, NO2 and air at 200 torr or 1 atm

Photoelectron spectra from core levels are presented for adsorption of nitrogen-containing gases at 200 torr or 1 atm on iron surfaces. Assignments of each band and the adsorption process are discussed. On the substrate at normal temperature, each gas forms nitride and nitrogen oxide groups (NO, NO₂ and NO₃) which appear at 398.6, 400.0, 404.5 and 407.1 eV, respectively. The relative intensifies of each species depend on the gases adsorbed. NO and NO₂ are considered to dissociate on the surface and the oxygen atom adsorb preferentially. The oxygen on the surface can be considered to contribute to the formation of each surface ligand.     

Reaction of beta-ethoxyvinyl lithiums generated from phenyltellanyl- and ethyltellanylacetaldehyde diethyl acetals with aldehydes and ketones and successive hydrations

Reactions of alpha-tellanyl-beta-ethoxyvinyl lithiums of aldehydes and ketones proceeded in good to high yields and the successive treatment with acids gave the alpha-tellanyl alpha,beta-unsaturated aldehydes. alpha-Tellanyl alpha,beta-unsaturated aldehydes easily transformed to more useful compounds.     

Synthesis of linear tripeptides for right-hand segments of complestatin

This paper concerns a synthetic study of the right-hand segment of complestatin, an inhibitor of gp120-CD4 receptor. The effective synthesis of four important precursors for the right-hand segment of complestatin is described. Two of them are the precursor tripeptides for macrolactamization to the right-hand segment of complestatin at the last step and the other two are the precursor tripeptides for ring-closing reaction using Suzuki and Stille coupling, respectively, to the right-hand segment of complestatin at the last step. These compounds and the synthetic procedure will serve for both the synthesis of the right-hand segment and total synthesis of complestatin in the near future. In addition, consideration of the smooth acidic isomerization of complestatin to chloropeptin was carried out by density functional theory (DFT) calculation.