ABSTRACT
Sulfuric acid in the atmosphere can participate in acid-catalyzed and acid-driven reactions, including those within secondary organic aerosols (SOA). Previous studies have observed enhanced absorption at visible wavelengths and significant changes in the chemical composition when SOA was exposed to sulfuric acid. However, the specific chromophores responsible for these changes could not be identified. The goals of this study are to identify the chromophores and determine the mechanism of browning in highly acidified α-pinene SOA by following the behavior of specific common α-pinene oxidation products, namely, cis-pinonic acid and cis-pinonaldehyde, when they are exposed to highly acidic conditions. The products of these reactions were analyzed with ultra-performance liquid chromatography coupled with photodiode array spectrophotometry and high-resolution mass spectrometry, UV-vis spectrophotometry, and nuclear magnetic resonance spectroscopy. cis-Pinonic acid (2) was found to form homoterpenyl methyl ketone (4), which does not absorb visible radiation, while cis-pinonaldehyde (3) formed weakly absorbing 1-(4-(propan-2-ylidene)cyclopent-1-en-1-yl)ethan-1-one (5) and 1-(4-isopropylcyclopenta-1,3-dien-1-yl)ethan-1-one (6) via an acid-catalyzed aldol condensation. This chemistry could be relevant for environments characterized by high sulfuric acid concentrations, for example, during the transport of organic compounds from the lower to the upper atmosphere by fast updrafts.
ABSTRACT
We report the first total syntheses of strasseriolide A and B. Strasseriolide B shows potent activity against the wild-type malaria parasite Plasmodium falciparum and good activity against a chloroquine-resistant strain. A convergent strategy was envisioned with an aldehyde-acid fragment and a vinyl iodide-alcohol fragment. Both fragments were prepared using chiral pool starting materials. They were combined with a Yamaguchi esterification and cyclized with a Nozaki-Hiyama-Kishi reaction. Strasseriolide B was assembled in a 16-step LLS.
Subject(s)
Antimalarials , Biological Products , Macrolides , Plasmodium falciparum , Antimalarials/chemical synthesis , Antimalarials/chemistry , Antimalarials/pharmacology , Biological Products/chemical synthesis , Biological Products/chemistry , Biological Products/pharmacology , Macrolides/chemical synthesis , Macrolides/chemistry , Macrolides/pharmacology , Molecular Conformation , Parasitic Sensitivity Tests , Plasmodium falciparum/drug effectsABSTRACT
An operationally simple protocol has been discovered that couples primary or secondary amines with N-aryl-substituted lactams to deliver differentiated diamines in moderate to high yields. The process allows for the partial reduction of a lactam in the presence of Cp2ZrHCl (Schwartz's reagent), followed by a reductive amination between the resulting hemiaminal and primary or secondary amine. These reactions can be telescoped in a one-pot fashion to significantly simplify the operation. The scope of amines and substituted lactams of various ring sizes was demonstrated through the formation of a range of differentiated diamine products. Furthermore, this methodology was expanded to include N-aryl pyrrolidinone substrates with an enantiopure ester group at the 5-position, and α-amino piperidinones were prepared with complete retention of stereochemical information. The development of this chemistry has enabled the consideration of lactams as useful synthons.