Synthesis of a novel C-6 nigrogen-substituted carbapenem from 6-aminopenicillanic acid

Synthesis of optically active 6-phthalimidocarbapenems from 6-aminopenicillanic acid is described.     

Modulation frequency dependence of actively mode-locked oscillation of A He-Ne 3.39 μm laser

The dependence of mode-locked oscillation of homogeneous lasers on the modulation frequency of locking signal is studied. An experiment using a He-Ne 3.39 μm laser and applying intracavity phase (FM) modulation was performed on the frequency range of 40 MHz to 1.20 GHz. The oscillation bandwidth was observed to be nearly proportion to $\text{√}\text{?}{}_{\mathrm{m}}$ and ?_m (?_m: modulation frequency) for the modulation frequency range of ?_m<Δ? and ?_m>Δ? (Δ?: linewidth), respectively. The possibility to generate ultra-short pulses by using larger modulation frequency than the linewidth is also discussed. For 1.20 GHz modulation frequency, the pulsewidth was estimated to be about 70 ps from the observed power spectrum, while the reciprocal of the linewidth was about 3 ns.     

Interpretation of electronic spectra by configuration analysis MO theoretical interpretation of the spectral changes caused by substitution in naphthalene

The spectral changes caused by the introduction of a substituent into naphthalene are mainly dependent on the position of the introduced substituent but are almost independent of the electron-donating or the electron-accepting nature of the substituent. An attempt was made to analyze this using the MO theoretical interpretation of the spectral changes in substituted naphthalenes based on the method of configuration analysis. It was found empirically that the magnitudes of the spectral shifts are determined primarily by the extent of charge-transfer contributions. From the analysis of the contribution of charge-transfer configurations, the spectral behavior characteristic of the substituted naphthalenes is satisfactorily interpreted by the pairing properties of naphthalene molecular orbitals.     

Nickel-catalyzed reaction of butadiene with strained ring olefins: Formation of a four-membered cyclic compound

Reaction of butadiene with strained ring olefins such as norbornene, dicyclopentadiene etc. Gives an exo-methylene- and methyl-substituted four-membered cyclic compound (II). The effective catalysts are (n-Bu₃P)₂NiBr₂/NaBH₄ or /alkoxide $\text{1}\text{1}$ syn-π-crotylbis(triethyl phosphite)nickel hexafluorophosphate (IV), and tetrakis(triethyl phosphite)nickel/CF₃COOH $\text{1}\text{1}$. π-Crotyl complex IV reacts with the strained ring olefins to give the corresponding product similarly. It is concluded that the active species for this catalytic reaction is a nickel hydride and that this reaction proceeds through π-crotyl intermediate.