The structure of itesmol and its C-24 congenor.
Abstract Structures 1 and 2 respectively have been assigned to itesmol and its minor congener isolated from a cactus indigenous to Mexico.
Stereoselective synthesis of 24-alkyl-22-hydroxysterols based on chelation-controlled radical reactions
We have shown that the diastereoselectivity in the radical-mediated reactions of steroidal 24-methylene-22-oxy-25-oic acid esters 6–11 with alkyl iodides performed in the presence of Lewis acid MgBr2·OEt2 depends on the bulk of the alkyl iodides, the oxy groups at C-22 and the configuration at C-22. The ethylation of 9 afforded the syn-adduct exclusively and the methylation of 6 and 7, ethylation of 10 and isopropylation of 9 gave syn-adducts with high selectivities (syn–anti = 8.8–5.1∶1). Other combinations, except for the tert-butyl radical addition to 6, 7 and 10 predominantly yielding anti-adducts, showed lower syn-selectivities.
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...