Synthesis of cyclic hydrocarbons via intramolecular coupling of bis-pentadienyl iron tricarbonyl cations

A general synthesis for the preparation of medium sized cycloalkanes having 1,2-butadienyl substituents is described. The reaction sequence involved acylation of butadiene-iron tricarbonyl with a diacid chloride, reduction of the resultant diketone to a diol derivative and conversion with HBF₄ to an acyclic bis-pentadienyl Fe(C0)₃ dicationic complex. Upon treatment with zinc the dication undergoes intramolecular ring closure to afford the bis-Fe(C0)₃ complex of the 1,2-dibutadienyl cycloalkane. Five-, six- and ten-membered cyclolalkene derivatives have been prepared in this manner.     

Field ionization mass spectrometry—II: Benzyloxycarbonyl and t-butyloxycarbonyl derivatives of some simple peptides

A brief discussion is given of some factors that merit consideration in the analysis of peptides by mass spectrometry, with emphasis on sequence determination. The first systematic study of simple peptides by field ionization (FI) is described, and comparison made with the corresponding electron-impact (EI) ionization spectra, both at low resolution (approx. 1500). The substances examined were either benzyloxycarbonyl or t-butyloxycarbonyl derivatives of di-through pentapeptide methyl esters, containing the amino acids glycine, alanine, leucine, serine, threonine, proline and tyrosine. The incidences of sequence-characteristic cleavage peaks and rearrangement ion peaks were both slightly lower in the FI than the EI spectra, although the peak relative intensities generally were higher under FI conditions.     

Narrow band quantitative and multivariate electroencephalogram analysis of peri-adolescent period

ABSTRACT: BACKGROUND: The peri-adolescent period is a crucial developmental moment of transition from childhood to emergent adulthood. The present report analyses the differences in Power Spectrum (PS) of the Electroencephalogram (EEG) between late childhood (24 children between 8 and 13 years old) and young adulthood (24 young adults between 18 and 23 years old). RESULTS: The narrow band analysis of the Electroencephalogram was computed in the frequency range of 0--20 Hz. The analysis of mean and variance suggested that six frequency ranges presented a different rate of maturation at these ages, namely: low delta, delta-theta, low alpha, high alpha, low beta and high beta. For most of these bands the maturation seems to occur later in anterior sites than posterior sites. Correlational analysis showed a lower pattern of correlation between different frequencies in children than in young adults, suggesting a certain asynchrony in the maturation of different rhythms. The topographical analysis revealed similar topographies of the different rhythms in children and young adults. Principal Component Analysis (PCA) demonstrated the same internal structure for the Electroencephalogram of both age groups. Principal Component Analysis allowed to separate four subcomponents in the alpha range. All these subcomponents peaked at a lower frequency in children than in young adults. CONCLUSIONS: The present approaches complement and solve some of the incertitudes when the classical brain broad rhythm analysis is applied. Children have a higher absolute power than young adults for frequency ranges between 0-20 Hz, the correlation of Power Spectrum (PS) with age and the variance age comparison showed that there are six ranges of frequencies that can distinguish the level of EEG maturation in children and adults. The establishment of maturational order of different frequencies and its possible maturational interdependence would require a complete series including all the different ages.