Synthetic studies on thiostrepton family of peptide antibiotics: synthesis of the dihydroquinoline portion of thiostrepton, the siomycins, and the thiopeptins

Synthesis of the dihydroquinoline portion of thiostrepton, the siomycins, and the thiopeptins, members of the thiostrepton family of peptide antibiotics, has been achieved featuring the one-pot olefination via the Matsumura-Boekelheide rearrangement “using trifluoromethanesulfonic anhydride and triethylamine” and the stereoselective addition reaction controlled by the stereocenter of the peri-position.     

2-D electron spin transient nutation spectroscopy of Lanthanoid ion Eu2+(8S7/2) in a CaF2 single crystal on the basis of FT-pulsed electron spin resonance spectroscopy: Transition moment spectroscopy

This work demonstrates the usefulness of pulsed electron spin resonance (ESR)-based two-dimensional electron spin transient nutation (2-D ESN) spectroscopy for complete assignments of complicated fine-structure hyperfine ESR spectra including hyperfine forbidden transitions from electronic and nuclear high-spin systems. The 2-D ESN spectroscopy is termed transition moment spectroscopy as spectra are acquired as a function of transition moment instead of transition energy used in conventional spectroscopy. We have applied the novel spectroscopic technique to Eu²⁺ ion (S=7/2,I=5/2), which has two isotopes (¹⁵¹Eu [47.9%] and¹⁵³Eu [52.1%]), in a CaF₂ single crystal as a model system. We have completely identified the complicated fine-structure hyperfine ESR spectra by invoking the spectral simulation of the 2-D ESN spectra on the basis of transition moment analyses. The analyses are based on exact numerical calculations of the transition moments as well as a perturbation-based analytical approach combined with reduced rotation matrices for the nuclear part of the transition moment. This is the first example of the spectral simulation for 2-D ESN spectra including the hyperfine allowed and forbidden transitions in high-spin systems. In addition, we have made simulation of the fine-structure forbidden transitions, which reproduces the angular variations of the observed spectra at liquid helium temperatures.     

Synthetic studies on oligomycins. Enantiospecific synthesis of the oligomycin B spiroketal portion and establishment of the absolute stereochemistry of oligomycin B

The enantiospecific synthesis of the oligomycin B degradation product 2, corresponding to the C19–C34 spiroketal portion, has been achieved by sequential coupling of the C19–C21, C22–C27, and C28–C34 subunits, establishing the absolute stereochemistry of oligomycin B.     

The structure of the CT complex between 5,7,12,14-tetramethoxydibenzo[b,i]thianthrene with TCNQ

The structure of 1,4-dithiines obtained from orthodihalogeno heterocycles with thiocarbonyl compounds was determined by X-ray structure analysis of the intermolecular charge-transfer complex between 5,7,12,14-tetramethoxydibenzo[b,i]thianthrene and TCNQ. The formation of the thiazole ring has already been reported but the products were confirmed to be 1,4-dithiines by X-ray structure analysis and the previously reported results.     

The structure of arugomycin,a new anthracycline antibiotic part I. structural elucidation of degradation products,AG1, AG2 and AG3.

Based on ¹H- and ¹³C-NMR and mass spectral analysis and chemical degradation, the structures of degradation products of arugomycin (arugorol, AG1, AG2 and AG3) have been determined as shown in Fig. 1.     

Phenylselenenyl chloride in acetonitrile-water : A highly convenient reagent for hydroxyselenation of olefins and preparation of cyclic ethers from dienes

The reaction of phenylselenenyl chloride with olefins in aqueous acetonitrile affords β-hydroxyalkyl phenyl selenides in excellent yields, providing the most convenient method for hydroxyselenation of olefins so far reported. When the reaction was applied to conjugated dienes, monohydroxyselenated products were obtained in good to excellent yields. From non-conjugated dienes, on the other hand, cyclic ethers containing two phenylseleno groups were produced in good to excellent yields, the first step of this reaction being the hydroxyselenation of one double bond.     

Studies on vocal fold injection and changes in pitch associated with alcohol intake

The current study was carried out with particular emphasis on the association between phonetic function tests and alterations in the appearance of the hypopharyngeal and laryngeal mucosa, such as capillary dilatation, edema, and vocal fold injection after alcohol intake. The results demonstrated the occurrence of previously unrecognized pathophysiological changes associated with synchronous phonetic functions in the vocal pathway after alcohol intake. Serum ethanol and aldehyde concentration levels were evaluated hourly for 2.5 h after ingestion of alcohol. When an electronystagmogram showed the typical pattern of alcohol intake, the study was initiated. Occasionally, rhinography was performed on subjects complaining of a stuffy nose after alcohol intake.     

Transition moment directions of some important in-plane vibrations of uracil,thymine and cytosine. A fixed partial charge model calculation

Transition moment directions for the double-bond region vibrations of uracil, thymine and cytosine are calculated using the fixed partial charge model approximation. The coupling between the two carbonyl bonds and the carbon—carbon double bond in uracil and thymine is sensitive to the choice of the corresponding stretching force constants. The transition moment directions are correspondingly changed, thus, in principle, enabling the quantitative determination of coupling between the vibrations from linear dichroism measurements.