Total Synthesis of Tabernanthine and Ibogaline: Rapid Access to Nosyl Tryptamines
作者:Alexander J. Hughes、Steven D. Townsend
DOI:10.1002/ejoc.202400442
日期:2024.8.12
The total syntheses of tabernanthine and ibogaline were enabled by application of a thermal coupling of nosyl aziridine and indoles in eight steps each, 10 and 14 % yield respectively. A Friedel-Crafts type macrocyclization facilitated key C−C bond formation. Regio- and diastereoselective hydroboration-oxidation of the resultant macrocyclic alkene enabled C−N bond formation and furnished the completed
Hypoxia occurs in various diseases, including cancer, ischemia, and acute and chronic vascular diseases. Here we describe the design and synthesis of the first hypoxia-sensitive MRI contrast agents, SAGds. SAGds showed a pH-dependent r(1) relaxivity change associated with intramolecular chelation of the nitrogen atom of the sulfonamide moiety to the Gd3+ center. There was a correlation between the pK(a) of the r(1) relaxivity change and the sum of the Hammett sigma constants of substituents on the aromatic ring. Among the synthesized compounds, 4NO(2)2MeOSAGd was selectively reduced to the amine by rat liver microsomes under hypoxic conditions, resulting in a 1.8-fold increment of the r(1) relaxivity owing to the change in pK(a) of the arylsulfonamide moiety. This enhancement of the r(1) relaxivity could be clearly detected in T-1-weighted MR images. Thus, 4NO(2)2MeOSAGd is a 'smart' MRI contrast agent for the detection of hypoxia under physiological conditions. (C) 2012 Elsevier Ltd. All rights reserved.