Tetracyclic diterpenoids with a new carbon skeleton forming products of the cyclization of labdane diterpenoids
From the product of the cyclization of a mixture of isomeric ent-copalols (i) [i] with a mixture of formic and concentrated acids, we have isolated an oxygen-containing fraction (yield 47%) consisting of a mixture of five alcohols and their formates. Three of the alcohols proved to be known: isoagath-12-en-15-ols epimeric at Cz4 [2] and 14~-hibanol [3]. For the other two alcohols, with the composition C2oH3~O, structures (2) and (3) were shown, these being based on a new carbon skeleton [4].
Chiroptical studies. Part LXXXIX. An empirical analysis of the circular dichroism of hexahydroindanones, bicyclo[4.2.0]octan-7-ones, and their polycyclic analogues
An empirical analysis of c.d. data for five-membered ring ketones of the hexahydroindanone type, including androstan-15-ones, -16-ones, and -17-ones and similar compounds, has established the main features of the relationships between Cotton effects and structural and conformational types in this series. The analysis has been extended to a few compounds of steroid-like structure which include a cyclobutanone ring (bicyclo[4.2.0]octan-7-ones). Five stereochemical types of hexahydroindanone are recognised, three for hexahydroindan-1-ones and two for hexahydroindan-2-ones.In the first stage of the analysis, estimates of c.d. contributions (δΔIµ) are obtained from experimental data for the following units: (a) the bicyclic systems, (b) angular methyl groups, and (c)‘third rings’. Estimates of the contribution of the ‘second’(cyclohexane) ring to the total value of ΔIµ for each of the bicyclic systems are then obtained by regarding the effects of individual bonds of the ‘second’ ring as equivalent to those of C–Me bonds at ‘α’ or ‘β’ positions of the cyclopentanone ring. The δΔIµ values obtained in this way for ‘second’ rings are used to derive δΔIµ values for the chiral cyclopentanone rings themselves. The values confirm earlier suggestions that the sign and magnitude of the Cotton effect is controlled largely by the chirality of the cyclopentanone ring itself, although other major contributions may come from any ‘α’-quasi-axial substituents present at the ring junction. Effects of alkyl substituents elsewhere on the cyclopentanone ring are discussed briefly.
Identification of Dihydroxy Aromatic Compounds in a Low-Temperature Pyrolysis Coal Tar by Gas Chromatography−Mass Spectrometry (GC−MS) and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS)
Dihydroxy aromatics in coal tar undergo rapid coupling reactions with each other and with some coal-derived species during coal pyrolysis and liquefaction. However, only limited information on the structure of dihydroxy aromatics is known. In this study, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and gas chromatography−mass spectrometry (GC−MS) were used to characterize the dihydroxy aromatics in a low-temperature pyrolyzed coal tar and its distillate and residue fractions. Negative-ion electrospray ionization (ESI) FT-ICR MS spectra of coal-tar-derived samples had low molecular masses and narrow mass ranges. Negative-ion ESI is extremely selective for the dihydroxy aromatics present in coal tar. The O2 class species had the highest ion intensity among the species in the negative-ion FT-ICR mass spectrum for each sample. Dihydroxy compounds with an aromatic core structure of benzene, indan, biphenyl (and/or acenaphthene), and naphthalene were identified in the distillate fract...